1
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Webb TA, Tamanna AN, Ding X, Verma N, Xu J, Krusin-Elbaum L, Dean CR, Basov DN, Pasupathy AN. Tunable Magnetic Domains in Ferrimagnetic MnSb 2Te 4. Nano Lett 2024; 24:4393-4399. [PMID: 38569084 DOI: 10.1021/acs.nanolett.3c05058] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/05/2024]
Abstract
Highly tunable properties make Mn(Bi,Sb)2Te4 a rich playground for exploring the interplay between band topology and magnetism: On one end, MnBi2Te4 is an antiferromagnetic topological insulator, while the magnetic structure of MnSb2Te4 (MST) can be tuned between antiferromagnetic and ferrimagnetic. Motivated to control electronic properties through real-space magnetic textures, we use magnetic force microscopy (MFM) to image the domains of ferrimagnetic MST. We find that magnetic field tunes between stripe and bubble domain morphologies, raising the possibility of topological spin textures. Moreover, we combine in situ transport with domain manipulation and imaging to both write MST device properties and directly measure the scaling of the Hall response with the domain area. This work demonstrates measurement of the local anomalous Hall response using MFM and opens the door to reconfigurable domain-based devices in the M(B,S)T family.
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Affiliation(s)
- Tatiana A Webb
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Afrin N Tamanna
- Department of Physics, The City College of New York, New York, New York 10027, United States
| | - Xiaxin Ding
- Department of Physics, The City College of New York, New York, New York 10027, United States
| | - Nishchhal Verma
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Jikai Xu
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Lia Krusin-Elbaum
- Department of Physics, The City College of New York, New York, New York 10027, United States
| | - Cory R Dean
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Dmitri N Basov
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Abhay N Pasupathy
- Department of Physics, Columbia University, New York, New York 10027, United States
- Condensed Matter Physics and Materials Science Division, Brookhaven National Laboratory, Upton, New York 11973, United States
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2
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Fu M, Xu S, Zhang S, Ruta FL, Pack J, Mayer RA, Chen X, Moore SL, Rizzo DJ, Jessen BS, Cothrine M, Mandrus DG, Watanabe K, Taniguchi T, Dean CR, Pasupathy AN, Bisogni V, Schuck PJ, Millis AJ, Liu M, Basov DN. Accelerated Nano-Optical Imaging through Sparse Sampling. Nano Lett 2024; 24:2149-2156. [PMID: 38329715 DOI: 10.1021/acs.nanolett.3c03733] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/09/2024]
Abstract
The integration time and signal-to-noise ratio are inextricably linked when performing scanning probe microscopy based on raster scanning. This often yields a large lower bound on the measurement time, for example, in nano-optical imaging experiments performed using a scanning near-field optical microscope (SNOM). Here, we utilize sparse scanning augmented with Gaussian process regression to bypass the time constraint. We apply this approach to image charge-transfer polaritons in graphene residing on ruthenium trichloride (α-RuCl3) and obtain key features such as polariton damping and dispersion. Critically, nano-optical SNOM imaging data obtained via sparse sampling are in good agreement with those extracted from traditional raster scans but require 11 times fewer sampled points. As a result, Gaussian process-aided sparse spiral scans offer a major decrease in scanning time.
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Affiliation(s)
- Matthew Fu
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Suheng Xu
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Shuai Zhang
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Francesco L Ruta
- Department of Physics, Columbia University, New York, New York 10027, United States
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, United States
| | - Jordan Pack
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Rafael A Mayer
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794, United States
| | - Xinzhong Chen
- Department of Physics, Columbia University, New York, New York 10027, United States
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794, United States
| | - Samuel L Moore
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Daniel J Rizzo
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Bjarke S Jessen
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Matthew Cothrine
- Department of Material Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - David G Mandrus
- Material Science & Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
- Department of Material Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Kenji Watanabe
- Research Center for Electronic and Optical Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Cory R Dean
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Abhay N Pasupathy
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Valentina Bisogni
- National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, New York 11973, United States
| | - P James Schuck
- Department of Mechanical Engineering, Columbia University, New York, New York 10027, United States
| | - Andrew J Millis
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Mengkun Liu
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794, United States
- National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, New York 11973, United States
| | - D N Basov
- Department of Physics, Columbia University, New York, New York 10027, United States
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3
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Handa T, Holbrook M, Olsen N, Holtzman LN, Huber L, Wang HI, Bonn M, Barmak K, Hone JC, Pasupathy AN, Zhu X. Spontaneous exciton dissociation in transition metal dichalcogenide monolayers. Sci Adv 2024; 10:eadj4060. [PMID: 38295176 PMCID: PMC10830119 DOI: 10.1126/sciadv.adj4060] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2023] [Accepted: 12/28/2023] [Indexed: 02/02/2024]
Abstract
Since the seminal work on MoS2, photoexcitation in atomically thin transition metal dichalcogenides (TMDCs) has been assumed to result in excitons, with binding energies order of magnitude larger than thermal energy at room temperature. Here, we reexamine this foundational assumption and show that photoexcitation of TMDC monolayers can result in a substantial population of free charges. Performing ultrafast terahertz spectroscopy on large-area, single-crystal TMDC monolayers, we find that up to ~10% of excitons spontaneously dissociate into charge carriers with lifetimes exceeding 0.2 ns. Scanning tunneling microscopy reveals that photocarrier generation is intimately related to mid-gap defects, likely via trap-mediated Auger scattering. Only in state-of-the-art quality monolayers, with mid-gap trap densities as low as 109 cm-2, does intrinsic exciton physics start to dominate the terahertz response. Our findings reveal the necessity of knowing the defect density in understanding photophysics of TMDCs.
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Affiliation(s)
- Taketo Handa
- Department of Chemistry, Columbia University, New York, NY 10027, USA
| | - Madisen Holbrook
- Department of Physics, Columbia University, New York, NY 10027, USA
| | - Nicholas Olsen
- Department of Chemistry, Columbia University, New York, NY 10027, USA
| | - Luke N. Holtzman
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, NY 10027, USA
| | - Lucas Huber
- Department of Chemistry, Columbia University, New York, NY 10027, USA
| | - Hai I. Wang
- Max Planck Institute for Polymer Research, Mainz 55128, Germany
| | - Mischa Bonn
- Max Planck Institute for Polymer Research, Mainz 55128, Germany
| | - Katayun Barmak
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, NY 10027, USA
| | - James C. Hone
- Department of Mechanical Engineering, Columbia University, New York, NY 10027, USA
| | | | - Xiaoyang Zhu
- Department of Chemistry, Columbia University, New York, NY 10027, USA
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4
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Posey VA, Turkel S, Rezaee M, Devarakonda A, Kundu AK, Ong CS, Thinel M, Chica DG, Vitalone RA, Jing R, Xu S, Needell DR, Meirzadeh E, Feuer ML, Jindal A, Cui X, Valla T, Thunström P, Yilmaz T, Vescovo E, Graf D, Zhu X, Scheie A, May AF, Eriksson O, Basov DN, Dean CR, Rubio A, Kim P, Ziebel ME, Millis AJ, Pasupathy AN, Roy X. Two-dimensional heavy fermions in the van der Waals metal CeSiI. Nature 2024; 625:483-488. [PMID: 38233620 DOI: 10.1038/s41586-023-06868-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Accepted: 11/14/2023] [Indexed: 01/19/2024]
Abstract
Heavy-fermion metals are prototype systems for observing emergent quantum phases driven by electronic interactions1-6. A long-standing aspiration is the dimensional reduction of these materials to exert control over their quantum phases7-11, which remains a significant challenge because traditional intermetallic heavy-fermion compounds have three-dimensional atomic and electronic structures. Here we report comprehensive thermodynamic and spectroscopic evidence of an antiferromagnetically ordered heavy-fermion ground state in CeSiI, an intermetallic comprising two-dimensional (2D) metallic sheets held together by weak interlayer van der Waals (vdW) interactions. Owing to its vdW nature, CeSiI has a quasi-2D electronic structure, and we can control its physical dimension through exfoliation. The emergence of coherent hybridization of f and conduction electrons at low temperature is supported by the temperature evolution of angle-resolved photoemission and scanning tunnelling spectra near the Fermi level and by heat capacity measurements. Electrical transport measurements on few-layer flakes reveal heavy-fermion behaviour and magnetic order down to the ultra-thin regime. Our work establishes CeSiI and related materials as a unique platform for studying dimensionally confined heavy fermions in bulk crystals and employing 2D device fabrication techniques and vdW heterostructures12 to manipulate the interplay between Kondo screening, magnetic order and proximity effects.
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Affiliation(s)
| | - Simon Turkel
- Physics Department, Columbia University, New York, NY, USA
- Condensed Matter Physics and Materials Science Division, Brookhaven National Laboratory, Upton, NY, USA
| | - Mehdi Rezaee
- Physics Department, Harvard University, Cambridge, MA, USA
| | | | - Asish K Kundu
- Condensed Matter Physics and Materials Science Division, Brookhaven National Laboratory, Upton, NY, USA
| | - Chin Shen Ong
- Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden
| | - Morgan Thinel
- Chemistry Department, Columbia University, New York, NY, USA
- Physics Department, Columbia University, New York, NY, USA
| | - Daniel G Chica
- Chemistry Department, Columbia University, New York, NY, USA
| | | | - Ran Jing
- Physics Department, Columbia University, New York, NY, USA
| | - Suheng Xu
- Physics Department, Columbia University, New York, NY, USA
| | - David R Needell
- Chemistry Department, Columbia University, New York, NY, USA
| | - Elena Meirzadeh
- Chemistry Department, Columbia University, New York, NY, USA
| | | | - Apoorv Jindal
- Physics Department, Columbia University, New York, NY, USA
| | - Xiaomeng Cui
- Physics Department, Harvard University, Cambridge, MA, USA
| | - Tonica Valla
- Condensed Matter Physics and Materials Science Division, Brookhaven National Laboratory, Upton, NY, USA
- Donostia International Physics Center (DIPC), Donostia-San Sebastián, Spain
| | - Patrik Thunström
- Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden
| | - Turgut Yilmaz
- National Synchrotron Light Source II, Brookhaven National Lab, Upton, NY, USA
| | - Elio Vescovo
- National Synchrotron Light Source II, Brookhaven National Lab, Upton, NY, USA
| | - David Graf
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL, USA
| | - Xiaoyang Zhu
- Chemistry Department, Columbia University, New York, NY, USA
| | - Allen Scheie
- Neutron Scattering Division, Oak Ridge National Lab, Oak Ridge, TN, USA
- MPA-Q, Los Alamos National Lab, Los Alamos, NM, USA
| | - Andrew F May
- Materials Science and Technology Division, Oak Ridge National Lab, Oak Ridge, TN, USA
| | - Olle Eriksson
- Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden
- Wallenberg Initiative Materials Science for Sustainability, Uppsala University, Uppsala, Sweden
| | - D N Basov
- Physics Department, Columbia University, New York, NY, USA
| | - Cory R Dean
- Physics Department, Columbia University, New York, NY, USA
| | - Angel Rubio
- Max Planck Institute for the Structure and Dynamics of Matter, Center for Free-Electron Laser Science and Department of Physics, Hamburg, Germany.
- Nano-Bio Spectroscopy Group and European Theoretical Spectroscopy Facility (ETSF), Departmento de Polímeros y Materiales Avanzados: Física, Química y Tecnología, Universidad del País Vasco (UPV/EHU), San Sebastián, Spain.
- Center for Computational Quantum Physics, Flatiron Institute, New York, NY, USA.
| | - Philip Kim
- Physics Department, Harvard University, Cambridge, MA, USA
| | | | - Andrew J Millis
- Physics Department, Columbia University, New York, NY, USA.
- Center for Computational Quantum Physics, Flatiron Institute, New York, NY, USA.
| | - Abhay N Pasupathy
- Physics Department, Columbia University, New York, NY, USA.
- Condensed Matter Physics and Materials Science Division, Brookhaven National Laboratory, Upton, NY, USA.
| | - Xavier Roy
- Chemistry Department, Columbia University, New York, NY, USA.
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5
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Xu K, Holbrook M, Holtzman LN, Pasupathy AN, Barmak K, Hone JC, Rosenberger MR. Validating the Use of Conductive Atomic Force Microscopy for Defect Quantification in 2D Materials. ACS Nano 2023; 17:24743-24752. [PMID: 38095969 DOI: 10.1021/acsnano.3c05056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2023]
Abstract
Defects significantly affect the electronic, chemical, mechanical, and optical properties of two-dimensional (2D) materials. Thus, it is critical to develop a method for convenient and reliable defect quantification. Scanning transmission electron microscopy (STEM) and scanning tunneling microscopy (STM) possess the required atomic resolution but have practical disadvantages. Here, we benchmark conductive atomic force microscopy (CAFM) by a direct comparison with STM in the characterization of transition metal dichalcogenides (TMDs). The results conclusively demonstrate that CAFM and STM image identical defects, giving results that are equivalent both qualitatively (defect appearance) and quantitatively (defect density). Further, we confirm that CAFM can achieve single-atom resolution, similar to that of STM, on both bulk and monolayer samples. The validation of CAFM as a facile and accurate tool for defect quantification provides a routine and reliable measurement that can complement other standard characterization techniques.
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Affiliation(s)
- Kaikui Xu
- Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Madisen Holbrook
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Luke N Holtzman
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, United States
| | - Abhay N Pasupathy
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Katayun Barmak
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, United States
| | - James C Hone
- Department of Mechanical Engineering, Columbia University, New York, New York 10027, United States
| | - Matthew R Rosenberger
- Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, Indiana 46556, United States
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6
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Gerber E, Torrisi SB, Shabani S, Seewald E, Pack J, Hoffman JE, Dean CR, Pasupathy AN, Kim EA. High-throughput ab initio design of atomic interfaces using InterMatch. Nat Commun 2023; 14:7921. [PMID: 38040714 PMCID: PMC10692083 DOI: 10.1038/s41467-023-43496-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Accepted: 11/10/2023] [Indexed: 12/03/2023] Open
Abstract
Forming a hetero-interface is a materials-design strategy that can access an astronomically large phase space. However, the immense phase space necessitates a high-throughput approach for an optimal interface design. Here we introduce a high-throughput computational framework, InterMatch, for efficiently predicting charge transfer, strain, and superlattice structure of an interface by leveraging the databases of individual bulk materials. Specifically, the algorithm reads in the lattice vectors, density of states, and the stiffness tensors for each material in their isolated form from the Materials Project. From these bulk properties, InterMatch estimates the interfacial properties. We benchmark InterMatch predictions for the charge transfer against experimental measurements and supercell density-functional theory calculations. We then use InterMatch to predict promising interface candidates for doping transition metal dichalcogenide MoSe2. Finally, we explain experimental observation of factor of 10 variation in the supercell periodicity within a few microns in graphene/α-RuCl3 by exploring low energy superlattice structures as a function of twist angle using InterMatch. We anticipate our open-source InterMatch algorithm accelerating and guiding ever-growing interfacial design efforts. Moreover, the interface database resulting from the InterMatch searches presented in this paper can be readily accessed online.
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Affiliation(s)
- Eli Gerber
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY, 14853, USA.
| | - Steven B Torrisi
- Department of Physics, Harvard University, Cambridge, MA, 02138, USA
- Energy & Materials Division, Toyota Research Institute, Los Altos, CA, 94022, USA
| | - Sara Shabani
- Department of Physics, Columbia University, New York, NY, USA
| | - Eric Seewald
- Department of Physics, Columbia University, New York, NY, USA
| | - Jordan Pack
- Department of Physics, Columbia University, New York, NY, USA
| | - Jennifer E Hoffman
- Department of Physics, Harvard University, Cambridge, MA, 02138, USA
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, 02138, USA
| | - Cory R Dean
- Department of Physics, Columbia University, New York, NY, USA
| | | | - Eun-Ah Kim
- Department of Physics, Cornell University, Ithaca, NY, 14853, USA
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7
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Han SY, Telford EJ, Kundu AK, Bintrim SJ, Turkel S, Wiscons RA, Zangiabadi A, Choi ES, Li TD, Steigerwald ML, Berkelbach TC, Pasupathy AN, Dean CR, Nuckolls C, Roy X. Interplay between Local Moment and Itinerant Magnetism in the Layered Metallic Antiferromagnet TaFe 1.14Te 3. Nano Lett 2023; 23:10449-10457. [PMID: 37934894 DOI: 10.1021/acs.nanolett.3c03112] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2023]
Abstract
Two-dimensional antiferromagnets have garnered considerable interest for the next generation of functional spintronics. However, many bulk materials from which two-dimensional antiferromagnets are isolated are limited by their air sensitivity, low ordering temperatures, and insulating transport properties. TaFe1+yTe3 aims to address these challenges with increased air stability, metallic transport, and robust antiferromagnetism. Here, we synthesize TaFe1+yTe3 (y = 0.14), identify its structural, magnetic, and electronic properties, and elucidate the relationships between them. Axial-dependent high-field magnetization measurements on TaFe1.14Te3 reveal saturation magnetic fields ranging between 27 and 30 T with saturation magnetic moments of 2.05-2.12 μB. Magnetotransport measurements confirm that TaFe1.14Te3 is metallic with strong coupling between magnetic order and electronic transport. Angle-resolved photoemission spectroscopy measurements across the magnetic transition uncover a complex interplay between itinerant electrons and local magnetic moments that drives the magnetic transition. We demonstrate the ability to isolate few-layer sheets of TaFe1.14Te3, establishing TaFe1.14Te3 as a potential platform for two-dimensional spintronics.
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Affiliation(s)
- Sae Young Han
- Department of Chemistry, Columbia University, 3000 Broadway, New York, New York 10027, United States
| | - Evan J Telford
- Department of Chemistry, Columbia University, 3000 Broadway, New York, New York 10027, United States
- Department of Physics, Columbia University, 538 West 120th Street, New York, New York 10027, United States
| | - Asish K Kundu
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, PO Box 5000, Upton, New York 11973, United States
| | - Sylvia J Bintrim
- Department of Chemistry, Columbia University, 3000 Broadway, New York, New York 10027, United States
| | - Simon Turkel
- Department of Physics, Columbia University, 538 West 120th Street, New York, New York 10027, United States
| | - Ren A Wiscons
- Department of Chemistry, Columbia University, 3000 Broadway, New York, New York 10027, United States
| | - Amirali Zangiabadi
- Department of Applied Physics and Applied Mathematics, Columbia University, 500 W 120th St, New York, New York 10027, United States
| | - Eun-Sang Choi
- National High Magnetic Field Laboratory, 1800 E Paul Dirac Dr, Tallahassee, Florida 32310, United States
| | - Tai-De Li
- Nanoscience Initiative at Advanced Science Research Center, Graduate Center of the City University of New York, 85 St. Nicholas Terrace, New York, New York 10031, United States
- Department of Physics, The City College of New York, 160 Convent Avenue, New York, New York 10031, United States
| | - Michael L Steigerwald
- Department of Chemistry, Columbia University, 3000 Broadway, New York, New York 10027, United States
| | - Timothy C Berkelbach
- Department of Chemistry, Columbia University, 3000 Broadway, New York, New York 10027, United States
| | - Abhay N Pasupathy
- Department of Physics, Columbia University, 538 West 120th Street, New York, New York 10027, United States
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, PO Box 5000, Upton, New York 11973, United States
| | - Cory R Dean
- Department of Physics, Columbia University, 538 West 120th Street, New York, New York 10027, United States
| | - Colin Nuckolls
- Department of Chemistry, Columbia University, 3000 Broadway, New York, New York 10027, United States
| | - Xavier Roy
- Department of Chemistry, Columbia University, 3000 Broadway, New York, New York 10027, United States
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8
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Zhang S, Liu Y, Sun Z, Chen X, Li B, Moore SL, Liu S, Wang Z, Rossi SE, Jing R, Fonseca J, Yang B, Shao Y, Huang CY, Handa T, Xiong L, Fu M, Pan TC, Halbertal D, Xu X, Zheng W, Schuck PJ, Pasupathy AN, Dean CR, Zhu X, Cobden DH, Xu X, Liu M, Fogler MM, Hone JC, Basov DN. Visualizing moiré ferroelectricity via plasmons and nano-photocurrent in graphene/twisted-WSe 2 structures. Nat Commun 2023; 14:6200. [PMID: 37794007 PMCID: PMC10550968 DOI: 10.1038/s41467-023-41773-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2023] [Accepted: 09/15/2023] [Indexed: 10/06/2023] Open
Abstract
Ferroelectricity, a spontaneous and reversible electric polarization, is found in certain classes of van der Waals (vdW) materials. The discovery of ferroelectricity in twisted vdW layers provides new opportunities to engineer spatially dependent electric and optical properties associated with the configuration of moiré superlattice domains and the network of domain walls. Here, we employ near-field infrared nano-imaging and nano-photocurrent measurements to study ferroelectricity in minimally twisted WSe2. The ferroelectric domains are visualized through the imaging of the plasmonic response in a graphene monolayer adjacent to the moiré WSe2 bilayers. Specifically, we find that the ferroelectric polarization in moiré domains is imprinted on the plasmonic response of the graphene. Complementary nano-photocurrent measurements demonstrate that the optoelectronic properties of graphene are also modulated by the proximal ferroelectric domains. Our approach represents an alternative strategy for studying moiré ferroelectricity at native length scales and opens promising prospects for (opto)electronic devices.
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Affiliation(s)
- Shuai Zhang
- Department of Physics, Columbia University, New York, NY, 10027, USA.
| | - Yang Liu
- Department of Mechanical Engineering, Columbia University, New York, NY, 10027, USA
| | - Zhiyuan Sun
- Department of Physics, Harvard University, Cambridge, MA, 02138, USA
- State Key Laboratory of Low-Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing, 100084, P.R. China
| | - Xinzhong Chen
- Department of Physics, Columbia University, New York, NY, 10027, USA
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, 11794, USA
| | - Baichang Li
- Department of Mechanical Engineering, Columbia University, New York, NY, 10027, USA
| | - S L Moore
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Song Liu
- Department of Mechanical Engineering, Columbia University, New York, NY, 10027, USA
| | - Zhiying Wang
- Department of Mechanical Engineering, Columbia University, New York, NY, 10027, USA
| | - S E Rossi
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Ran Jing
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Jordan Fonseca
- Department of Physics, University of Washington, Seattle, WA, 98195, USA
| | - Birui Yang
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Yinming Shao
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Chun-Ying Huang
- Department of Chemistry, Columbia University, New York, NY, 10027, USA
| | - Taketo Handa
- Department of Chemistry, Columbia University, New York, NY, 10027, USA
| | - Lin Xiong
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Matthew Fu
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Tsai-Chun Pan
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Dorri Halbertal
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Xinyi Xu
- Department of Mechanical Engineering, Columbia University, New York, NY, 10027, USA
| | - Wenjun Zheng
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, 11794, USA
| | - P J Schuck
- Department of Mechanical Engineering, Columbia University, New York, NY, 10027, USA
| | - A N Pasupathy
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - C R Dean
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Xiaoyang Zhu
- Department of Chemistry, Columbia University, New York, NY, 10027, USA
| | - David H Cobden
- Department of Physics, University of Washington, Seattle, WA, 98195, USA
| | - Xiaodong Xu
- Department of Physics, University of Washington, Seattle, WA, 98195, USA
| | - Mengkun Liu
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, 11794, USA
| | - M M Fogler
- Department of Physics, University of California, San Diego, La Jolla, CA, 92093, USA
| | - James C Hone
- Department of Mechanical Engineering, Columbia University, New York, NY, 10027, USA
| | - D N Basov
- Department of Physics, Columbia University, New York, NY, 10027, USA.
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9
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Rizzo DJ, Zhang J, Jessen BS, Ruta FL, Cothrine M, Yan J, Mandrus DG, Nagler SE, Taniguchi T, Watanabe K, Fogler MM, Pasupathy AN, Millis AJ, Rubio A, Hone JC, Dean CR, Basov DN. Polaritonic Probe of an Emergent 2D Dipole Interface. Nano Lett 2023; 23:8426-8435. [PMID: 37494638 DOI: 10.1021/acs.nanolett.3c01611] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/28/2023]
Abstract
The use of work-function-mediated charge transfer has recently emerged as a reliable route toward nanoscale electrostatic control of individual atomic layers. Using α-RuCl3 as a 2D electron acceptor, we are able to induce emergent nano-optical behavior in hexagonal boron nitride (hBN) that arises due to interlayer charge polarization. Using scattering-type scanning near-field optical microscopy (s-SNOM), we find that a thin layer of α-RuCl3 adjacent to an hBN slab reduces the propagation length of hBN phonon polaritons (PhPs) in significant excess of what can be attributed to intrinsic optical losses. Concomitant nano-optical spectroscopy experiments reveal a novel resonance that aligns energetically with the region of excess PhP losses. These experimental observations are elucidated by first-principles density-functional theory and near-field model calculations, which show that the formation of a large interfacial dipole suppresses out-of-plane PhP propagation. Our results demonstrate the potential utility of charge-transfer heterostructures for tailoring optoelectronic properties of 2D insulators.
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Affiliation(s)
- Daniel J Rizzo
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Jin Zhang
- Theory Department, Max Planck Institute for Structure and Dynamics of Matter and Center for Free-Electron Laser Science, 22761 Hamburg, Germany
| | - Bjarke S Jessen
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Francesco L Ruta
- Department of Physics, Columbia University, New York, New York 10027, United States
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, United States
| | - Matthew Cothrine
- Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Jiaqiang Yan
- Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996, United States
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - David G Mandrus
- Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996, United States
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Stephen E Nagler
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
- Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Takashi Taniguchi
- Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Kenji Watanabe
- Research Center for Electronic and Optical Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Michael M Fogler
- Department of Physics, University of California San Diego, La Jolla, California 92093, United States
| | - Abhay N Pasupathy
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Andrew J Millis
- Department of Physics, Columbia University, New York, New York 10027, United States
- Center for Computational Quantum Physics, Flatiron Institute, New York, New York 10010, United States
| | - Angel Rubio
- Theory Department, Max Planck Institute for Structure and Dynamics of Matter and Center for Free-Electron Laser Science, 22761 Hamburg, Germany
- Center for Computational Quantum Physics, Flatiron Institute, New York, New York 10010, United States
- Nano-Bio Spectroscopy Group, Universidad del País Vasco UPV/EHU, San Sebastián 20018, Spain
| | - James C Hone
- Department of Mechanical Engineering, Columbia University, New York, New York 10027, United States
| | - Cory R Dean
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - D N Basov
- Department of Physics, Columbia University, New York, New York 10027, United States
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10
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Liu S, Liu Y, Holtzman L, Li B, Holbrook M, Pack J, Taniguchi T, Watanabe K, Dean CR, Pasupathy AN, Barmak K, Rhodes DA, Hone J. Two-Step Flux Synthesis of Ultrapure Transition-Metal Dichalcogenides. ACS Nano 2023; 17:16587-16596. [PMID: 37610237 DOI: 10.1021/acsnano.3c02511] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/24/2023]
Abstract
Two-dimensional transition-metal dichalcogenides (TMDs) have attracted tremendous interest due to the unusual electronic and optoelectronic properties of isolated monolayers and the ability to assemble diverse monolayers into complex heterostructures. To understand the intrinsic properties of TMDs and fully realize their potential in applications and fundamental studies, high-purity materials are required. Here, we describe the synthesis of TMD crystals using a two-step flux growth method that eliminates a major potential source of contamination. Detailed characterization of TMDs grown by this two-step method reveals charged and isovalent defects with densities an order of magnitude lower than those in TMDs grown by a single-step flux technique. For WSe2, we show that increasing the Se/W ratio during growth reduces point defect density, with crystals grown at 100:1 ratio achieving charged and isovalent defect densities below 1010 and 1011 cm-2, respectively. Initial temperature-dependent electrical transport measurements of monolayer WSe2 yield room-temperature hole mobility above 840 cm2/(V s) and low-temperature disorder-limited mobility above 44,000 cm2/(V s). Electrical transport measurements of graphene-WSe2 heterostructures fabricated from the two-step flux grown WSe2 also show superior performance: higher graphene mobility, lower charged impurity density, and well-resolved integer quantum Hall states. Finally, we demonstrate that the two-step flux technique can be used to synthesize other TMDs with similar defect densities, including semiconducting 2H-MoSe2 and 2H-MoTe2 and semimetallic Td-WTe2 and 1T'-MoTe2.
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Affiliation(s)
- Song Liu
- Department of Mechanical Engineering, Columbia University, New York, New York 10027, United States
| | - Yang Liu
- Department of Mechanical Engineering, Columbia University, New York, New York 10027, United States
| | - Luke Holtzman
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, United States
| | - Baichang Li
- Department of Mechanical Engineering, Columbia University, New York, New York 10027, United States
| | - Madisen Holbrook
- Department of Mechanical Engineering, Columbia University, New York, New York 10027, United States
| | - Jordan Pack
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Takashi Taniguchi
- National Institute for Materials Science, Tsukuba, Ibaraki 305-0044, Japan
| | - Kenji Watanabe
- National Institute for Materials Science, Tsukuba, Ibaraki 305-0044, Japan
| | - Cory R Dean
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Abhay N Pasupathy
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Katayun Barmak
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, United States
| | - Daniel A Rhodes
- Department of Mechanical Engineering, Columbia University, New York, New York 10027, United States
| | - James Hone
- Department of Mechanical Engineering, Columbia University, New York, New York 10027, United States
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11
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Sobral JA, Obernauer S, Turkel S, Pasupathy AN, Scheurer MS. Machine learning the microscopic form of nematic order in twisted double-bilayer graphene. Nat Commun 2023; 14:5012. [PMID: 37591848 PMCID: PMC10435506 DOI: 10.1038/s41467-023-40684-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Accepted: 08/01/2023] [Indexed: 08/19/2023] Open
Abstract
Modern scanning probe techniques, such as scanning tunneling microscopy, provide access to a large amount of data encoding the underlying physics of quantum matter. In this work, we show how convolutional neural networks can be used to learn effective theoretical models from scanning tunneling microscopy data on correlated moiré superlattices. Moiré systems are particularly well suited for this task as their increased lattice constant provides access to intra-unit-cell physics, while their tunability allows for the collection of high-dimensional data sets from a single sample. Using electronic nematic order in twisted double-bilayer graphene as an example, we show that incorporating correlations between the local density of states at different energies allows convolutional neural networks not only to learn the microscopic nematic order parameter, but also to distinguish it from heterostrain. These results demonstrate that neural networks are a powerful method for investigating the microscopic details of correlated phenomena in moiré systems and beyond.
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Affiliation(s)
- João Augusto Sobral
- Institute for Theoretical Physics III, University of Stuttgart, 70550, Stuttgart, Germany.
- Institute for Theoretical Physics, University of Innsbruck, A-6020, Innsbruck, Austria.
| | - Stefan Obernauer
- Institute for Theoretical Physics, University of Innsbruck, A-6020, Innsbruck, Austria
| | - Simon Turkel
- Department of Physics, Columbia University, 10027, New York, NY, USA
| | - Abhay N Pasupathy
- Department of Physics, Columbia University, 10027, New York, NY, USA
- Condensed Matter Physics and Materials Science Division, Brookhaven National Laboratory, 11973, Upton, NY, USA
| | - Mathias S Scheurer
- Institute for Theoretical Physics III, University of Stuttgart, 70550, Stuttgart, Germany
- Institute for Theoretical Physics, University of Innsbruck, A-6020, Innsbruck, Austria
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12
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Chen H, Zhao B, Mutch J, Jung GY, Ren G, Shabani S, Seewald E, Niu S, Wu J, Wang N, Surendran M, Singh S, Luo J, Ohtomo S, Goh G, Chakoumakos BC, Teat SJ, Melot B, Wang H, Pasupathy AN, Mishra R, Chu JH, Ravichandran J. Charge Density Wave Order and Electronic Phase Transitions in a Dilute d-Band Semiconductor. Adv Mater 2023:e2303283. [PMID: 37540897 DOI: 10.1002/adma.202303283] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2023] [Revised: 07/31/2023] [Indexed: 08/06/2023]
Abstract
As one of the most fundamental physical phenomena, charge density wave (CDW) order predominantly occurs in metallic systems such as quasi-1D metals, doped cuprates, and transition metal dichalcogenides, where it is well understood in terms of Fermi surface nesting and electron-phonon coupling mechanisms. On the other hand, CDW phenomena in semiconducting systems, particularly at the low carrier concentration limit, are less common and feature intricate characteristics, which often necessitate the exploration of novel mechanisms, such as electron-hole coupling or Mott physics, to explain. In this study, an approach combining electrical transport, synchrotron X-ray diffraction, and density-functional theory calculations is used to investigate CDW order and a series of hysteretic phase transitions in a dilute d-band semiconductor, BaTiS3 . These experimental and theoretical findings suggest that the observed CDW order and phase transitions in BaTiS3 may be attributed to both electron-phonon coupling and non-negligible electron-electron interactions in the system. This work highlights BaTiS3 as a unique platform to explore CDW physics and novel electronic phases in the dilute filling limit and opens new opportunities for developing novel electronic devices.
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Affiliation(s)
- Huandong Chen
- Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, CA, 90089, USA
| | - Boyang Zhao
- Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, CA, 90089, USA
| | - Josh Mutch
- Department of Physics, University of Washington, Seattle, WA, 98195, USA
| | - Gwan Yeong Jung
- Department of Mechanical Engineering and Materials Science, Washington University in St. Louis, St. Louis, MO, 63130, USA
| | - Guodong Ren
- Institute of Materials Science and Engineering, Washington University in St. Louis, St. Louis, MO, 63130, USA
| | - Sara Shabani
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Eric Seewald
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Shanyuan Niu
- Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, CA, 90089, USA
| | - Jiangbin Wu
- Ming Hsieh Department of Electrical and Computer Engineering, University of Southern California, Los Angeles, CA, 90089, USA
| | - Nan Wang
- Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, CA, 90089, USA
| | - Mythili Surendran
- Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, CA, 90089, USA
- Core Center for Excellence in Nano Imaging, University of Southern California, Los Angeles, CA, 90089, USA
| | - Shantanu Singh
- Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, CA, 90089, USA
| | - Jiang Luo
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO, 63130, USA
| | - Sanae Ohtomo
- Department of Physics, University of Washington, Seattle, WA, 98195, USA
| | - Gemma Goh
- Department of Chemistry, University of Southern California, Los Angeles, CA, 90089, USA
| | - Bryan C Chakoumakos
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Simon J Teat
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Brent Melot
- Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, CA, 90089, USA
- Department of Chemistry, University of Southern California, Los Angeles, CA, 90089, USA
| | - Han Wang
- Ming Hsieh Department of Electrical and Computer Engineering, University of Southern California, Los Angeles, CA, 90089, USA
| | - Abhay N Pasupathy
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Rohan Mishra
- Department of Mechanical Engineering and Materials Science, Washington University in St. Louis, St. Louis, MO, 63130, USA
- Institute of Materials Science and Engineering, Washington University in St. Louis, St. Louis, MO, 63130, USA
| | - Jiun-Haw Chu
- Department of Physics, University of Washington, Seattle, WA, 98195, USA
| | - Jayakanth Ravichandran
- Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, CA, 90089, USA
- Ming Hsieh Department of Electrical and Computer Engineering, University of Southern California, Los Angeles, CA, 90089, USA
- Core Center for Excellence in Nano Imaging, University of Southern California, Los Angeles, CA, 90089, USA
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13
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Chen X, Xu S, Shabani S, Zhao Y, Fu M, Millis AJ, Fogler MM, Pasupathy AN, Liu M, Basov DN. Machine Learning for Optical Scanning Probe Nanoscopy. Adv Mater 2023; 35:e2109171. [PMID: 36333118 DOI: 10.1002/adma.202109171] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Revised: 07/09/2022] [Indexed: 06/16/2023]
Abstract
The ability to perform nanometer-scale optical imaging and spectroscopy is key to deciphering the low-energy effects in quantum materials, as well as vibrational fingerprints in planetary and extraterrestrial particles, catalytic substances, and aqueous biological samples. These tasks can be accomplished by the scattering-type scanning near-field optical microscopy (s-SNOM) technique that has recently spread to many research fields and enabled notable discoveries. Herein, it is shown that the s-SNOM, together with scanning probe research in general, can benefit in many ways from artificial-intelligence (AI) and machine-learning (ML) algorithms. Augmented with AI- and ML-enhanced data acquisition and analysis, scanning probe optical nanoscopy is poised to become more efficient, accurate, and intelligent.
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Affiliation(s)
- Xinzhong Chen
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, 11794, USA
| | - Suheng Xu
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Sara Shabani
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Yueqi Zhao
- Department of Physics, University of California at San Diego, La Jolla, CA, 92093-0319, USA
| | - Matthew Fu
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Andrew J Millis
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Michael M Fogler
- Department of Physics, University of California at San Diego, La Jolla, CA, 92093-0319, USA
| | - Abhay N Pasupathy
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Mengkun Liu
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, 11794, USA
- National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - D N Basov
- Department of Physics, Columbia University, New York, NY, 10027, USA
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14
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Zhao H, Blackwell R, Thinel M, Handa T, Ishida S, Zhu X, Iyo A, Eisaki H, Pasupathy AN, Fujita K. Smectic pair-density-wave order in EuRbFe 4As 4. Nature 2023; 618:940-945. [PMID: 37380689 DOI: 10.1038/s41586-023-06103-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2022] [Accepted: 04/20/2023] [Indexed: 06/30/2023]
Abstract
The pair density wave (PDW) is a superconducting state in which Cooper pairs carry centre-of-mass momentum in equilibrium, leading to the breaking of translational symmetry1-4. Experimental evidence for such a state exists in high magnetic field5-8 and in some materials that feature density-wave orders that explicitly break translational symmetry9-13. However, evidence for a zero-field PDW state that exists independent of other spatially ordered states has so far been elusive. Here we show that such a state exists in the iron pnictide superconductor EuRbFe4As4, a material that features co-existing superconductivity (superconducting transition temperature (Tc) ≈ 37 kelvin) and magnetism (magnetic transition temperature (Tm) ≈ 15 kelvin)14,15. Using spectroscopic imaging scanning tunnelling microscopy (SI-STM) measurements, we show that the superconducting gap at low temperature has long-range, unidirectional spatial modulations with an incommensurate period of about eight unit cells. Upon increasing the temperature above Tm, the modulated superconductor disappears, but a uniform superconducting gap survives to Tc. When an external magnetic field is applied, gap modulations disappear inside the vortex halo. The SI-STM and bulk measurements show the absence of other density-wave orders, indicating that the PDW state is a primary, zero-field superconducting state in this compound. Both four-fold rotational symmetry and translation symmetry are recovered above Tm, indicating that the PDW is a smectic order.
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Affiliation(s)
- He Zhao
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY, USA
| | - Raymond Blackwell
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY, USA
| | - Morgan Thinel
- Department of Physics, Columbia University, New York, NY, USA
- Department of Chemistry, Columbia University, New York, NY, USA
| | - Taketo Handa
- Department of Chemistry, Columbia University, New York, NY, USA
| | - Shigeyuki Ishida
- Research Institute for Advanced Electronics and Photonics, National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan
| | - Xiaoyang Zhu
- Department of Chemistry, Columbia University, New York, NY, USA
| | - Akira Iyo
- Research Institute for Advanced Electronics and Photonics, National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan
| | - Hiroshi Eisaki
- Research Institute for Advanced Electronics and Photonics, National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan
| | - Abhay N Pasupathy
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY, USA.
- Department of Physics, Columbia University, New York, NY, USA.
| | - Kazuhiro Fujita
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY, USA.
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15
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Sternbach AJ, Vitalone RA, Shabani S, Zhang J, Darlington TP, Moore SL, Chae SH, Seewald E, Xu X, Dean CR, Zhu X, Rubio A, Hone J, Pasupathy AN, Schuck PJ, Basov DN. Quenched Excitons in WSe 2/α-RuCl 3 Heterostructures Revealed by Multimessenger Nanoscopy. Nano Lett 2023. [PMID: 37195262 DOI: 10.1021/acs.nanolett.3c00974] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
We investigate heterostructures composed of monolayer WSe2 stacked on α-RuCl3 using a combination of Terahertz (THz) and infrared (IR) nanospectroscopy and imaging, scanning tunneling spectroscopy (STS), and photoluminescence (PL). Our observations reveal itinerant carriers in the heterostructure prompted by charge transfer across the WSe2/α-RuCl3 interface. Local STS measurements show the Fermi level is shifted to the valence band edge of WSe2 which is consistent with p-type doping and verified by density functional theory (DFT) calculations. We observe prominent resonances in near-IR nano-optical and PL spectra, which are associated with the A-exciton of WSe2. We identify a concomitant, near total, quenching of the A-exciton resonance in the WSe2/α-RuCl3 heterostructure. Our nano-optical measurements show that the charge-transfer doping vanishes while excitonic resonances exhibit near-total recovery in "nanobubbles", where WSe2 and α-RuCl3 are separated by nanometer distances. Our broadband nanoinfrared inquiry elucidates local electrodynamics of excitons and an electron-hole plasma in the WSe2/α-RuCl3 system.
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Affiliation(s)
- Aaron J Sternbach
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Rocco A Vitalone
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Sara Shabani
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Jin Zhang
- Max Planck Institute for the Structure and Dynamics of Matter, Luruper Chaussee 149, 22761 Hamburg, Germany
| | - Thomas P Darlington
- Department of Mechanical Engineering, Columbia University, New York, New York 10027, United States
| | - Samuel L Moore
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Sang Hoon Chae
- Department of Mechanical Engineering, Columbia University, New York, New York 10027, United States
| | - Eric Seewald
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Xiaodong Xu
- Department of Physics, University of Washington, Seattle, Washington 98195, United States
| | - Cory R Dean
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Xiaoyang Zhu
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Angel Rubio
- Max Planck Institute for the Structure and Dynamics of Matter, Luruper Chaussee 149, 22761 Hamburg, Germany
- Center for Computational Quantum Physics (CCQ), Flatiron Institute, 162 Fifth Avenue, New York, New York 10010, United States
| | - James Hone
- Department of Mechanical Engineering, Columbia University, New York, New York 10027, United States
| | - Abhay N Pasupathy
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - P James Schuck
- Department of Mechanical Engineering, Columbia University, New York, New York 10027, United States
| | - D N Basov
- Department of Physics, Columbia University, New York, New York 10027, United States
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16
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Halbertal D, Turkel S, Ciccarino CJ, Profe JB, Finney N, Hsieh V, Watanabe K, Taniguchi T, Hone J, Dean C, Narang P, Pasupathy AN, Kennes DM, Basov DN. Unconventional non-local relaxation dynamics in a twisted trilayer graphene moiré superlattice. Nat Commun 2022; 13:7587. [PMID: 36481831 PMCID: PMC9731949 DOI: 10.1038/s41467-022-35213-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Accepted: 11/18/2022] [Indexed: 12/13/2022] Open
Abstract
The electronic and structural properties of atomically thin materials can be controllably tuned by assembling them with an interlayer twist. During this process, constituent layers spontaneously rearrange themselves in search of a lowest energy configuration. Such relaxation phenomena can lead to unexpected and novel material properties. Here, we study twisted double trilayer graphene (TDTG) using nano-optical and tunneling spectroscopy tools. We reveal a surprising optical and electronic contrast, as well as a stacking energy imbalance emerging between the moiré domains. We attribute this contrast to an unconventional form of lattice relaxation in which an entire graphene layer spontaneously shifts position during assembly, resulting in domains of ABABAB and BCBACA stacking. We analyze the energetics of this transition and demonstrate that it is the result of a non-local relaxation process, in which an energy gain in one domain of the moiré lattice is paid for by a relaxation that occurs in the other.
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Affiliation(s)
- Dorri Halbertal
- Department of Physics, Columbia University, New York, NY, 10027, USA.
| | - Simon Turkel
- Department of Physics, Columbia University, New York, NY, 10027, USA
- Condensed Matter Physics and Materials Science Division, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - Christopher J Ciccarino
- Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, 02138, USA
| | - Jonas B Profe
- Institute for Theory of Statistical Physics, RWTH Aachen University, and JARA Fundamentals of Future Information Technology, 52062, Aachen, Germany
| | - Nathan Finney
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Valerie Hsieh
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - James Hone
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Cory Dean
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Prineha Narang
- Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, 02138, USA
| | - Abhay N Pasupathy
- Department of Physics, Columbia University, New York, NY, 10027, USA
- Condensed Matter Physics and Materials Science Division, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - Dante M Kennes
- Institute for Theory of Statistical Physics, RWTH Aachen University, and JARA Fundamentals of Future Information Technology, 52062, Aachen, Germany
- Max Planck Institute for the Structure and Dynamics of Matter, Center for Free Electron Laser Science, Hamburg, Germany
| | - D N Basov
- Department of Physics, Columbia University, New York, NY, 10027, USA
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17
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Shabani S, Darlington TP, Gordon C, Wu W, Yanev E, Hone J, Zhu X, Dreyer CE, Schuck PJ, Pasupathy AN. Ultralocalized Optoelectronic Properties of Nanobubbles in 2D Semiconductors. Nano Lett 2022; 22:7401-7407. [PMID: 36122409 DOI: 10.1021/acs.nanolett.2c02265] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
The optical properties of transition-metal dichalcogenides have previously been modified at the nanoscale by using mechanical and electrical nanostructuring. However, a clear experimental picture relating the local electronic structure with emission properties in such structures has so far been lacking. Here, we use a combination of scanning tunneling microscopy (STM) and near-field photoluminescence (nano-PL) to probe the electronic and optical properties of single nanobubbles in bilayer heterostructures of WSe2 on MoSe2. We show from tunneling spectroscopy that there are electronic states deeply localized in the gap at the edge of such bubbles, which are independent of the presence of chemical defects in the layers. We also show a significant change in the local band gap on the bubble, with a continuous evolution to the edge of the bubble over a length scale of ∼20 nm. Nano-PL measurements observe a continuous redshift of the interlayer exciton on entering the bubble, in agreement with the band-to-band transitions measured by STM. We use self-consistent Schrödinger-Poisson simulations to capture the essence of the experimental results and find that strong doping in the bubble region is a key ingredient to achieving the observed localized states, together with mechanical strain.
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Affiliation(s)
- Sara Shabani
- Department of Physics, Columbia University, New York 10027, New York, United States
| | - Thomas P Darlington
- Department of Mechanical Engineering, Columbia University, New York 10027, New York, United States
| | - Colin Gordon
- Department of Physics and Astronomy, Stony Brook University, Stony Brook 11790, New York, United States
| | - Wenjing Wu
- Department of Chemistry, Columbia University, New York 10027, New York, United States
| | - Emanuil Yanev
- Department of Mechanical Engineering, Columbia University, New York 10027, New York, United States
| | - James Hone
- Department of Mechanical Engineering, Columbia University, New York 10027, New York, United States
| | - Xiaoyang Zhu
- Department of Chemistry, Columbia University, New York 10027, New York, United States
| | - Cyrus E Dreyer
- Center for Computational Quantum Physics, Flatiron Institute, New York 10010, New York, United States
| | - P James Schuck
- Department of Mechanical Engineering, Columbia University, New York 10027, New York, United States
| | - Abhay N Pasupathy
- Department of Physics, Columbia University, New York 10027, New York, United States
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18
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Telford EJ, Dismukes AH, Lee K, Cheng M, Wieteska A, Bartholomew AK, Chen YS, Xu X, Pasupathy AN, Zhu X, Dean CR, Roy X. Layered Antiferromagnetism Induces Large Negative Magnetoresistance in the van der Waals Semiconductor CrSBr. Adv Mater 2022; 34:e2205639. [PMID: 36047736 DOI: 10.1002/adma.202205639] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
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19
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Vitalone RA, Sternbach AJ, Foutty BA, McLeod AS, Sow C, Golez D, Nakamura F, Maeno Y, Pasupathy AN, Georges A, Millis AJ, Basov DN. Nanoscale Femtosecond Dynamics of Mott Insulator (Ca 0.99Sr 0.01) 2RuO 4. Nano Lett 2022; 22:5689-5697. [PMID: 35839312 DOI: 10.1021/acs.nanolett.2c00581] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Ca2RuO4 is a transition-metal oxide that exhibits a Mott insulator-metal transition (IMT) concurrent with a symmetry-preserving Jahn-Teller distortion (JT) at 350 K. The coincidence of these two transitions demonstrates a high level of coupling between the electronic and structural degrees of freedom in Ca2RuO4. Using spectroscopic measurements with nanoscale spatial resolution, we interrogate the interplay of the JT and IMT through the temperature-driven transition. Then, we introduce photoexcitation with subpicosecond temporal resolution to explore the coupling of the JT and IMT via electron-hole injection under ambient conditions. Through the temperature-driven IMT, we observe phase coexistence in the form of a stripe phase existing at the domain wall between macroscopic insulating and metallic domains. Through ultrafast carrier injection, we observe the formation of midgap states via enhanced optical absorption. We propose that these midgap states become trapped by lattice polarons originating from the local perturbation of the JT.
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Affiliation(s)
- Rocco A Vitalone
- Department of Physics, Columbia University, 1150 Amsterdam Avenue, New York, New York 10027, United States
| | - Aaron J Sternbach
- Department of Physics, Columbia University, 1150 Amsterdam Avenue, New York, New York 10027, United States
| | - Benjamin A Foutty
- Department of Physics, Columbia University, 1150 Amsterdam Avenue, New York, New York 10027, United States
- Department of Physics, Stanford University, 450 Serra Mall, Stanford, California 94305m United States
| | - Alexander S McLeod
- Department of Physics, Columbia University, 1150 Amsterdam Avenue, New York, New York 10027, United States
- School of Physics and Astronomy, University of Minnesota Twin Cities, 115 Union Street SE, Minneapolis, Minnesota 55455, United States
| | - Chanchal Sow
- Deparment of Physics, Kyoto University, Yoshidahonmachi, Sakyo Ward, Kyoto 606-8501, Japan
- Department of Physics, IIT Kanpur, Kalyanpur Kanpur, Uttar Pradesh, India 209016
| | - Denis Golez
- Center for Computational Physics, Flatiron Institute, 162 Fifth Avenue, New York, New York 10010, United States
- Jozef Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia
- Faculty of Mathematics and Physics, University of Ljubljana, Jandranska 19, 1000 Ljubljana, Slovenia
| | - Fumihiko Nakamura
- Department of Education and Creation Engineering, Kurume Institute of Technology, Kurume, Fukuoka 830-0052, Japan
| | - Yoshiteru Maeno
- Deparment of Physics, Kyoto University, Yoshidahonmachi, Sakyo Ward, Kyoto 606-8501, Japan
| | - Abhay N Pasupathy
- Department of Physics, Columbia University, 1150 Amsterdam Avenue, New York, New York 10027, United States
| | - Antoine Georges
- Center for Computational Physics, Flatiron Institute, 162 Fifth Avenue, New York, New York 10010, United States
- Department of Physics, College of France, 11Pl. Marcelin, Berthelot, Paris, France FR 75231
- CPHT, CNRS, Polytechnic Institute of Paris, Ecole Polytechnique Palaiseau, Paris, France FR 91128
- DQMP, Universite de Geneve, 24 Quai Ernest Ansermet, Geneve CH-1211, Switzerland
| | - Andrew J Millis
- Department of Physics, Columbia University, 1150 Amsterdam Avenue, New York, New York 10027, United States
- Center for Computational Physics, Flatiron Institute, 162 Fifth Avenue, New York, New York 10010, United States
| | - D N Basov
- Department of Physics, Columbia University, 1150 Amsterdam Avenue, New York, New York 10027, United States
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20
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Telford EJ, Dismukes AH, Dudley RL, Wiscons RA, Lee K, Chica DG, Ziebel ME, Han MG, Yu J, Shabani S, Scheie A, Watanabe K, Taniguchi T, Xiao D, Zhu Y, Pasupathy AN, Nuckolls C, Zhu X, Dean CR, Roy X. Coupling between magnetic order and charge transport in a two-dimensional magnetic semiconductor. Nat Mater 2022; 21:754-760. [PMID: 35513502 DOI: 10.1038/s41563-022-01245-x] [Citation(s) in RCA: 32] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Accepted: 03/29/2022] [Indexed: 06/14/2023]
Abstract
Semiconductors, featuring tunable electrical transport, and magnets, featuring tunable spin configurations, form the basis of many information technologies. A long-standing challenge has been to realize materials that integrate and connect these two distinct properties. Two-dimensional (2D) materials offer a platform to realize this concept, but known 2D magnetic semiconductors are electrically insulating in their magnetic phase. Here we demonstrate tunable electron transport within the magnetic phase of the 2D semiconductor CrSBr and reveal strong coupling between its magnetic order and charge transport. This provides an opportunity to characterize the layer-dependent magnetic order of CrSBr down to the monolayer via magnetotransport. Exploiting the sensitivity of magnetoresistance to magnetic order, we uncover a second regime characterized by coupling between charge carriers and magnetic defects. The magnetoresistance within this regime can be dynamically and reversibly tuned by varying the carrier concentration using an electrostatic gate, providing a mechanism for controlling charge transport in 2D magnets.
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Affiliation(s)
- Evan J Telford
- Department of Chemistry, Columbia University, New York, NY, USA
- Department of Physics, Columbia University, New York, NY, USA
| | | | | | - Ren A Wiscons
- Department of Chemistry, Columbia University, New York, NY, USA
| | - Kihong Lee
- Department of Chemistry, Columbia University, New York, NY, USA
| | - Daniel G Chica
- Department of Chemistry, Columbia University, New York, NY, USA
| | | | - Myung-Geun Han
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY, USA
| | - Jessica Yu
- Department of Chemistry, Columbia University, New York, NY, USA
| | - Sara Shabani
- Department of Physics, Columbia University, New York, NY, USA
| | - Allen Scheie
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Japan
| | - Di Xiao
- Department of Materials Science and Engineering, University of Washington, Seattle, WA, USA
- Department of Physics, University of Washington, Seattle, WA, USA
| | - Yimei Zhu
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY, USA
| | - Abhay N Pasupathy
- Department of Physics, Columbia University, New York, NY, USA
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY, USA
| | - Colin Nuckolls
- Department of Chemistry, Columbia University, New York, NY, USA
| | - Xiaoyang Zhu
- Department of Chemistry, Columbia University, New York, NY, USA
| | - Cory R Dean
- Department of Physics, Columbia University, New York, NY, USA.
| | - Xavier Roy
- Department of Chemistry, Columbia University, New York, NY, USA.
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21
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Rizzo DJ, McLeod AS, Carnahan C, Telford EJ, Dismukes AH, Wiscons RA, Dong Y, Nuckolls C, Dean CR, Pasupathy AN, Roy X, Xiao D, Basov DN. Visualizing Atomically Layered Magnetism in CrSBr. Adv Mater 2022; 34:e2201000. [PMID: 35504841 DOI: 10.1002/adma.202201000] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2022] [Revised: 04/22/2022] [Indexed: 06/14/2023]
Abstract
2D materials can host long-range magnetic order in the presence of underlying magnetic anisotropy. The ability to realize the full potential of 2D magnets necessitates systematic investigation of the role of individual atomic layers and nanoscale inhomogeneity (i.e., strain) on the emergence of stable magnetic phases. Here, spatially dependent magnetism in few-layer CrSBr is revealed using magnetic force microscopy (MFM) and Monte Carlo-based simulations. Nanoscale visualization of the magnetic sheet susceptibility is extracted from MFM data and force-distance curves, revealing a characteristic onset of both intra- and interlayer magnetic correlations as a function of temperature and layer-thickness. These results demonstrate that the presence of a single uncompensated layer in odd-layer terraces significantly reduces the stability of the low-temperature antiferromagnetic (AFM) phase and gives rise to multiple coexisting magnetic ground states at temperatures close to the bulk Néel temperature (TN ). Furthermore, the AFM phase can be reliably suppressed using modest fields (≈16 mT) from the MFM probe, behaving as a nanoscale magnetic switch. This prototypical study of few-layer CrSBr demonstrates the critical role of layer parity on field-tunable 2D magnetism and validates MFM for use in nanomagnetometry of 2D materials (despite the ubiquitous absence of bulk zero-field magnetism in magnetized sheets).
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Affiliation(s)
- Daniel J Rizzo
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | | | - Caitlin Carnahan
- Department of Physics, Carnegie Mellon University, Pittsburgh, PA, 15213, USA
| | - Evan J Telford
- Department of Physics, Columbia University, New York, NY, 10027, USA
- Department of Chemistry, Columbia University, New York, NY, 10027, USA
| | - Avalon H Dismukes
- Department of Chemistry, Columbia University, New York, NY, 10027, USA
| | - Ren A Wiscons
- Department of Chemistry, Columbia University, New York, NY, 10027, USA
| | - Yinan Dong
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Colin Nuckolls
- Department of Chemistry, Columbia University, New York, NY, 10027, USA
| | - Cory R Dean
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Abhay N Pasupathy
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Xavier Roy
- Department of Chemistry, Columbia University, New York, NY, 10027, USA
| | - Di Xiao
- Department of Material Science and Engineering, University of Washington, Seattle, WA, 98195, USA
- Department of Physics, University of Washington, Seattle, WA, 98195, USA
| | - D N Basov
- Department of Physics, Columbia University, New York, NY, 10027, USA
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22
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Turkel S, Swann J, Zhu Z, Christos M, Watanabe K, Taniguchi T, Sachdev S, Scheurer MS, Kaxiras E, Dean CR, Pasupathy AN. Orderly disorder in magic-angle twisted trilayer graphene. Science 2022; 376:193-199. [PMID: 35389784 DOI: 10.1126/science.abk1895] [Citation(s) in RCA: 26] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Magic-angle twisted trilayer graphene (TTG) has recently emerged as a platform to engineer strongly correlated flat bands. We reveal the normal-state structural and electronic properties of TTG using low-temperature scanning tunneling microscopy at twist angles for which superconductivity has been observed. Real trilayer samples undergo a strong reconstruction of the moiré lattice, which locks layers into near-magic-angle, mirror symmetric domains comparable in size with the superconducting coherence length. This relaxation introduces an array of localized twist-angle faults, termed twistons and moiré solitons, whose electronic structure deviates strongly from the background regions, leading to a doping-dependent, spatially granular electronic landscape. The Fermi-level density of states is maximally uniform at dopings for which superconductivity has been observed in transport measurements.
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Affiliation(s)
- Simon Turkel
- Department of Physics, Columbia University, New York, NY 10027, USA
| | - Joshua Swann
- Department of Physics, Columbia University, New York, NY 10027, USA
| | - Ziyan Zhu
- Department of Physics, Harvard University, Cambridge, MA 02138, USA
| | - Maine Christos
- Department of Physics, Harvard University, Cambridge, MA 02138, USA
| | - K Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - T Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Subir Sachdev
- Department of Physics, Harvard University, Cambridge, MA 02138, USA.,School of Natural Sciences, Institute for Advanced Study, Princeton, NJ 08540, USA
| | - Mathias S Scheurer
- Institute for Theoretical Physics, University of Innsbruck, A-6020 Innsbruck, Austria
| | - Efthimios Kaxiras
- Department of Physics, Harvard University, Cambridge, MA 02138, USA.,John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA
| | - Cory R Dean
- Department of Physics, Columbia University, New York, NY 10027, USA
| | - Abhay N Pasupathy
- Department of Physics, Columbia University, New York, NY 10027, USA.,Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY 11973, USA
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23
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Rizzo D, Shabani S, Jessen BS, Zhang J, McLeod AS, Rubio-Verdú C, Ruta FL, Cothrine M, Yan J, Mandrus DG, Nagler SE, Rubio A, Hone JC, Dean CR, Pasupathy AN, Basov DN. Nanometer-Scale Lateral p-n Junctions in Graphene/α-RuCl 3 Heterostructures. Nano Lett 2022; 22:1946-1953. [PMID: 35226804 PMCID: PMC8915251 DOI: 10.1021/acs.nanolett.1c04579] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
The ability to create nanometer-scale lateral p-n junctions is essential for the next generation of two-dimensional (2D) devices. Using the charge-transfer heterostructure graphene/α-RuCl3, we realize nanoscale lateral p-n junctions in the vicinity of graphene nanobubbles. Our multipronged experimental approach incorporates scanning tunneling microscopy (STM) and spectroscopy (STS) and scattering-type scanning near-field optical microscopy (s-SNOM) to simultaneously probe the electronic and optical responses of nanobubble p-n junctions. Our STM/STS results reveal that p-n junctions with a band offset of ∼0.6 eV can be achieved with widths of ∼3 nm, giving rise to electric fields of order 108 V/m. Concurrent s-SNOM measurements validate a point-scatterer formalism for modeling the interaction of surface plasmon polaritons (SPPs) with nanobubbles. Ab initio density functional theory (DFT) calculations corroborate our experimental data and reveal the dependence of charge transfer on layer separation. Our study provides experimental and conceptual foundations for generating p-n nanojunctions in 2D materials.
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Affiliation(s)
- Daniel
J. Rizzo
- Department
of Physics, Columbia University, New York, New York 10027, United States
| | - Sara Shabani
- Department
of Physics, Columbia University, New York, New York 10027, United States
| | - Bjarke S. Jessen
- Department
of Physics, Columbia University, New York, New York 10027, United States
- Department
of Mechanical Engineering, Columbia University, New York, New York 10027, United States
| | - Jin Zhang
- Theory
Department, Max Planck Institute for Structure
and Dynamics of Matter and Center for Free-Electron Laser Science, 22761 Hamburg, Germany
| | - Alexander S. McLeod
- Department
of Physics, Columbia University, New York, New York 10027, United States
| | - Carmen Rubio-Verdú
- Department
of Physics, Columbia University, New York, New York 10027, United States
| | - Francesco L. Ruta
- Department
of Physics, Columbia University, New York, New York 10027, United States
- Department
of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, United States
| | - Matthew Cothrine
- Department
of Materials Science and Engineering, University
of Tennessee, Knoxville, Tennessee 37996, United States
| | - Jiaqiang Yan
- Department
of Materials Science and Engineering, University
of Tennessee, Knoxville, Tennessee 37996, United States
- Materials
Science and Technology Division, Oak Ridge
National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - David G. Mandrus
- Department
of Materials Science and Engineering, University
of Tennessee, Knoxville, Tennessee 37996, United States
- Materials
Science and Technology Division, Oak Ridge
National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Stephen E. Nagler
- Neutron
Scattering Division, Oak Ridge National
Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Angel Rubio
- Theory
Department, Max Planck Institute for Structure
and Dynamics of Matter and Center for Free-Electron Laser Science, 22761 Hamburg, Germany
- Center
for Computational Quantum Physics, Flatiron
Institute, New York, New York 10010, United
States
- Nano-Bio
Spectroscopy Group, Universidad del País
Vasco UPV/EHU, San Sebastián 20018, Spain
| | - James C. Hone
- Department
of Mechanical Engineering, Columbia University, New York, New York 10027, United States
| | - Cory R. Dean
- Department
of Physics, Columbia University, New York, New York 10027, United States
| | - Abhay N. Pasupathy
- Department
of Physics, Columbia University, New York, New York 10027, United States
- Condensed
Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, United States
| | - D. N. Basov
- Department
of Physics, Columbia University, New York, New York 10027, United States
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24
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Zhang S, Li B, Chen X, Ruta FL, Shao Y, Sternbach AJ, McLeod AS, Sun Z, Xiong L, Moore SL, Xu X, Wu W, Shabani S, Zhou L, Wang Z, Mooshammer F, Ray E, Wilson N, Schuck PJ, Dean CR, Pasupathy AN, Lipson M, Xu X, Zhu X, Millis AJ, Liu M, Hone JC, Basov DN. Nano-spectroscopy of excitons in atomically thin transition metal dichalcogenides. Nat Commun 2022; 13:542. [PMID: 35087038 PMCID: PMC8795359 DOI: 10.1038/s41467-022-28117-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2021] [Accepted: 01/06/2022] [Indexed: 11/21/2022] Open
Abstract
Excitons play a dominant role in the optoelectronic properties of atomically thin van der Waals (vdW) semiconductors. These excitons are amenable to on-demand engineering with diverse control knobs, including dielectric screening, interlayer hybridization, and moiré potentials. However, external stimuli frequently yield heterogeneous excitonic responses at the nano- and meso-scales, making their spatial characterization with conventional diffraction-limited optics a formidable task. Here, we use a scattering-type scanning near-field optical microscope (s-SNOM) to acquire exciton spectra in atomically thin transition metal dichalcogenide microcrystals with previously unattainable 20 nm resolution. Our nano-optical data revealed material- and stacking-dependent exciton spectra of MoSe2, WSe2, and their heterostructures. Furthermore, we extracted the complex dielectric function of these prototypical vdW semiconductors. s-SNOM hyperspectral images uncovered how the dielectric screening modifies excitons at length scales as short as few nanometers. This work paves the way towards understanding and manipulation of excitons in atomically thin layers at the nanoscale.
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Affiliation(s)
- Shuai Zhang
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Baichang Li
- Department of Mechanical Engineering, Columbia University, New York, NY, 10027, USA
| | - Xinzhong Chen
- National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY, 11973, USA
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, 11794, USA
| | - Francesco L Ruta
- Department of Physics, Columbia University, New York, NY, 10027, USA
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, NY, 10027, USA
| | - Yinming Shao
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Aaron J Sternbach
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - A S McLeod
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Zhiyuan Sun
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Lin Xiong
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - S L Moore
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Xinyi Xu
- Department of Mechanical Engineering, Columbia University, New York, NY, 10027, USA
| | - Wenjing Wu
- Department of Chemistry, Columbia University, New York, NY, 10027, USA
| | - Sara Shabani
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Lin Zhou
- Department of Chemistry, Columbia University, New York, NY, 10027, USA
| | - Zhiying Wang
- Department of Mechanical Engineering, Columbia University, New York, NY, 10027, USA
| | - Fabian Mooshammer
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Essance Ray
- Department of Physics, University of Washington, Seattle, WA, 98195, USA
| | - Nathan Wilson
- Department of Physics, University of Washington, Seattle, WA, 98195, USA
| | - P J Schuck
- Department of Mechanical Engineering, Columbia University, New York, NY, 10027, USA
| | - C R Dean
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - A N Pasupathy
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Michal Lipson
- Department of Electrical Engineering, Columbia University, New York, NY, 10027, USA
| | - Xiaodong Xu
- Department of Physics, University of Washington, Seattle, WA, 98195, USA
| | - Xiaoyang Zhu
- Department of Chemistry, Columbia University, New York, NY, 10027, USA
| | - A J Millis
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Mengkun Liu
- National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY, 11973, USA
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, 11794, USA
| | - James C Hone
- Department of Mechanical Engineering, Columbia University, New York, NY, 10027, USA
| | - D N Basov
- Department of Physics, Columbia University, New York, NY, 10027, USA.
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25
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Xu S, McLeod AS, Chen X, Rizzo DJ, Jessen BS, Yao Z, Wang Z, Sun Z, Shabani S, Pasupathy AN, Millis AJ, Dean CR, Hone JC, Liu M, Basov DN. Deep Learning Analysis of Polaritonic Wave Images. ACS Nano 2021; 15:18182-18191. [PMID: 34714043 DOI: 10.1021/acsnano.1c07011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Deep learning (DL) is an emerging analysis tool across the sciences and engineering. Encouraged by the successes of DL in revealing quantitative trends in massive imaging data, we applied this approach to nanoscale deeply subdiffractional images of propagating polaritonic waves in complex materials. Utilizing the convolutional neural network (CNN), we developed a practical protocol for the rapid regression of images that quantifies the wavelength and the quality factor of polaritonic waves. Using simulated near-field images as training data, the CNN can be made to simultaneously extract polaritonic characteristics and material parameters in a time scale that is at least 3 orders of magnitude faster than common fitting/processing procedures. The CNN-based analysis was validated by examining the experimental near-field images of charge-transfer plasmon polaritons at graphene/α-RuCl3 interfaces. Our work provides a general framework for extracting quantitative information from images generated with a variety of scanning probe methods.
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Affiliation(s)
- Suheng Xu
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Alexander S McLeod
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Xinzhong Chen
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794, United States
| | - Daniel J Rizzo
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Bjarke S Jessen
- Department of Physics, Columbia University, New York, New York 10027, United States
- Department of Mechanical Engineering, Columbia University, New York, New York 10027, United States
| | - Ziheng Yao
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794, United States
| | - Zhicai Wang
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794, United States
| | - Zhiyuan Sun
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Sara Shabani
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Abhay N Pasupathy
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Andrew J Millis
- Department of Physics, Columbia University, New York, New York 10027, United States
- Center for Computational Quantum Physics, Flatiron Institute, New York, New York 10010, United States
| | - Cory R Dean
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - James C Hone
- Department of Mechanical Engineering, Columbia University, New York, New York 10027, United States
| | - Mengkun Liu
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794, United States
- National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, New York 11973, United States
| | - D N Basov
- Department of Physics, Columbia University, New York, New York 10027, United States
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26
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Wang D, Telford EJ, Benyamini A, Jesudasan J, Raychaudhuri P, Watanabe K, Taniguchi T, Hone J, Dean CR, Pasupathy AN. Andreev Reflections in NbN/Graphene Junctions under Large Magnetic Fields. Nano Lett 2021; 21:8229-8235. [PMID: 34569787 DOI: 10.1021/acs.nanolett.1c02020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Hybrid superconductor/graphene (SC/g) junctions are excellent candidates for investigating correlations between Cooper pairs and quantum Hall (QH) edge modes. Experimental studies are challenging as Andreev reflections are extremely sensitive to junction disorder, and high magnetic fields are required to form QH edge states. We fabricated low-resistance SC/g interfaces, composed of graphene edge contacted with NbN with a barrier strength of Z ≈ 0.4, that remain superconducting under magnetic fields larger than 18 T. We establish the role of graphene's Dirac band structure on zero-field Andreev reflections and demonstrate dynamic tunability of the Andreev reflection spectrum by moving the boundary between specular and retro Andreev reflections with parallel magnetic fields. Through the application of perpendicular magnetic fields, we observe an oscillatory suppression of the 2-probe conductance in the ν = 4 Landau level attributed to the reduced efficiency of Andreev processes at the NbN/g interface, consistent with theoretical predictions.
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Affiliation(s)
- Da Wang
- Department of Physics, Columbia University, New York, New York 10027, United States
- Department of Mechanical Engineering, Columbia University, New York, New York 10027, United States
| | - Evan J Telford
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Avishai Benyamini
- Department of Physics, Columbia University, New York, New York 10027, United States
- Department of Mechanical Engineering, Columbia University, New York, New York 10027, United States
| | - John Jesudasan
- Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400 005, India
| | - Pratap Raychaudhuri
- Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400 005, India
| | - Kenji Watanabe
- National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - James Hone
- Department of Mechanical Engineering, Columbia University, New York, New York 10027, United States
| | - Cory R Dean
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Abhay N Pasupathy
- Department of Physics, Columbia University, New York, New York 10027, United States
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, United States
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27
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Moore SL, Ciccarino CJ, Halbertal D, McGilly LJ, Finney NR, Yao K, Shao Y, Ni G, Sternbach A, Telford EJ, Kim BS, Rossi SE, Watanabe K, Taniguchi T, Pasupathy AN, Dean CR, Hone J, Schuck PJ, Narang P, Basov DN. Nanoscale lattice dynamics in hexagonal boron nitride moiré superlattices. Nat Commun 2021; 12:5741. [PMID: 34593793 PMCID: PMC8484559 DOI: 10.1038/s41467-021-26072-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2021] [Accepted: 09/02/2021] [Indexed: 11/12/2022] Open
Abstract
Twisted two-dimensional van der Waals (vdW) heterostructures have unlocked a new means for manipulating the properties of quantum materials. The resulting mesoscopic moiré superlattices are accessible to a wide variety of scanning probes. To date, spatially-resolved techniques have prioritized electronic structure visualization, with lattice response experiments only in their infancy. Here, we therefore investigate lattice dynamics in twisted layers of hexagonal boron nitride (hBN), formed by a minute twist angle between two hBN monolayers assembled on a graphite substrate. Nano-infrared (nano-IR) spectroscopy reveals systematic variations of the in-plane optical phonon frequencies amongst the triangular domains and domain walls in the hBN moiré superlattices. Our first-principles calculations unveil a local and stacking-dependent interaction with the underlying graphite, prompting symmetry-breaking between the otherwise identical neighboring moiré domains of twisted hBN. Here, the authors investigate the lattice dynamics of twisted hexagonal boron nitride layers via nano-infrared spectroscopy, showing local and stacking-dependent variations of the optical phonon frequencies associated to the interaction with the graphite substrate.
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Affiliation(s)
- S L Moore
- Department of Physics, Columbia University, New York, NY, USA.
| | - C J Ciccarino
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
| | - D Halbertal
- Department of Physics, Columbia University, New York, NY, USA
| | - L J McGilly
- Department of Physics, Columbia University, New York, NY, USA
| | - N R Finney
- Department of Mechanical Engineering, Columbia University, New York, NY, USA
| | - K Yao
- Department of Mechanical Engineering, Columbia University, New York, NY, USA
| | - Y Shao
- Department of Physics, Columbia University, New York, NY, USA
| | - G Ni
- Department of Physics, Columbia University, New York, NY, USA
| | - A Sternbach
- Department of Physics, Columbia University, New York, NY, USA
| | - E J Telford
- Department of Physics, Columbia University, New York, NY, USA
| | - B S Kim
- Department of Mechanical Engineering, Columbia University, New York, NY, USA
| | - S E Rossi
- Department of Physics, Columbia University, New York, NY, USA
| | - K Watanabe
- National Institute for Materials Science, 1-1 Namiki, Tsukuba, Japan
| | - T Taniguchi
- National Institute for Materials Science, 1-1 Namiki, Tsukuba, Japan
| | - A N Pasupathy
- Department of Physics, Columbia University, New York, NY, USA
| | - C R Dean
- Department of Physics, Columbia University, New York, NY, USA
| | - J Hone
- Department of Mechanical Engineering, Columbia University, New York, NY, USA
| | - P J Schuck
- Department of Mechanical Engineering, Columbia University, New York, NY, USA
| | - P Narang
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
| | - D N Basov
- Department of Physics, Columbia University, New York, NY, USA
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28
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Rhodes DA, Jindal A, Yuan NFQ, Jung Y, Antony A, Wang H, Kim B, Chiu YC, Taniguchi T, Watanabe K, Barmak K, Balicas L, Dean CR, Qian X, Fu L, Pasupathy AN, Hone J. Enhanced Superconductivity in Monolayer Td-MoTe 2. Nano Lett 2021; 21:2505-2511. [PMID: 33689385 DOI: 10.1021/acs.nanolett.0c04935] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Crystalline two-dimensional (2D) superconductors (SCs) with low carrier density are an exciting new class of materials in which electrostatic gating can tune superconductivity, electronic interactions play a prominent role, and electrical transport properties may directly reflect the topology of the Fermi surface. Here, we report the dramatic enhancement of superconductivity with decreasing thickness in semimetallic Td-MoTe2, with critical temperature (Tc) increasing up to 7.6 K for monolayers, a 60-fold increase with respect to the bulk Tc. We show that monolayers possess a similar electronic structure and density of states (DOS) as the bulk, implying that electronic interactions play a strong role in the enhanced superconductivity. Reflecting the low carrier density, the critical temperature, magnetic field, and current density are all tunable by an applied gate voltage. The response to high in-plane magnetic fields is distinct from that of other 2D SCs and reflects the canted spin texture of the electron pockets.
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Affiliation(s)
- Daniel A Rhodes
- Department of Mechanical Engineering, Columbia University, New York, New York 10027, United States
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Apoorv Jindal
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Noah F Q Yuan
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02142, United States
| | - Younghun Jung
- Department of Mechanical Engineering, Columbia University, New York, New York 10027, United States
| | - Abhinandan Antony
- Department of Mechanical Engineering, Columbia University, New York, New York 10027, United States
| | - Hua Wang
- Department of Materials Science and Engineering, Texas A&M University, College Station, Texas 77840, United States
| | - Bumho Kim
- Department of Mechanical Engineering, Columbia University, New York, New York 10027, United States
| | - Yu-Che Chiu
- Department of Physics and National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32306, United States
| | - Takashi Taniguchi
- National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Kenji Watanabe
- National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Katayun Barmak
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, United States
| | - Luis Balicas
- Department of Physics and National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32306, United States
| | - Cory R Dean
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Xiaofeng Qian
- Department of Materials Science and Engineering, Texas A&M University, College Station, Texas 77840, United States
| | - Liang Fu
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02142, United States
| | - Abhay N Pasupathy
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - James Hone
- Department of Physics, Columbia University, New York, New York 10027, United States
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29
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Kerelsky A, Rubio-Verdú C, Xian L, Kennes DM, Halbertal D, Finney N, Song L, Turkel S, Wang L, Watanabe K, Taniguchi T, Hone J, Dean C, Basov DN, Rubio A, Pasupathy AN. Moiréless correlations in ABCA graphene. Proc Natl Acad Sci U S A 2021; 118:e2017366118. [PMID: 33468646 PMCID: PMC7848726 DOI: 10.1073/pnas.2017366118] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
Atomically thin van der Waals materials stacked with an interlayer twist have proven to be an excellent platform toward achieving gate-tunable correlated phenomena linked to the formation of flat electronic bands. In this work we demonstrate the formation of emergent correlated phases in multilayer rhombohedral graphene--a simple material that also exhibits a flat electronic band edge but without the need of having a moiré superlattice induced by twisted van der Waals layers. We show that two layers of bilayer graphene that are twisted by an arbitrary tiny angle host large (micrometer-scale) regions of uniform rhombohedral four-layer (ABCA) graphene that can be independently studied. Scanning tunneling spectroscopy reveals that ABCA graphene hosts an unprecedentedly sharp van Hove singularity of 3-5-meV half-width. We demonstrate that when this van Hove singularity straddles the Fermi level, a correlated many-body gap emerges with peak-to-peak value of 9.5 meV at charge neutrality. Mean-field theoretical calculations for model with short-ranged interactions indicate that two primary candidates for the appearance of this broken symmetry state are a charge-transfer excitonic insulator and a ferrimagnet. Finally, we show that ABCA graphene hosts surface topological helical edge states at natural interfaces with ABAB graphene which can be turned on and off with gate voltage, implying that small-angle twisted double-bilayer graphene is an ideal programmable topological quantum material.
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Affiliation(s)
| | | | - Lede Xian
- Theory Department, Max Planck Institute for the Structure and Dynamics of Matter, 22761 Hamburg, Germany
- Frontier Research Center, Songshan Lake Materials Laboratory, 523808 Dongguan, Guangdong, China
| | - Dante M Kennes
- Theory Department, Max Planck Institute for the Structure and Dynamics of Matter, 22761 Hamburg, Germany
- Institut für Theorie der Statistischen Physik, Rheinisch-Westfälische Technische Hochschule Aachen University, 52056 Aachen, Germany
- Jülich Aachen Research Alliance-Fundamentals of Future Information Technology, 52056 Aachen, Germany
| | - Dorri Halbertal
- Department of Physics, Columbia University, New York, NY 10027
| | - Nathan Finney
- Department of Mechanical Engineering, Columbia University, New York, NY 10027
| | - Larry Song
- Department of Physics, Columbia University, New York, NY 10027
| | - Simon Turkel
- Department of Physics, Columbia University, New York, NY 10027
| | - Lei Wang
- Department of Physics, Columbia University, New York, NY 10027
| | - Kenji Watanabe
- National Institute for Materials Science, 1-1 Namiki, 305-0044 Tsukuba, Japan
| | - Takashi Taniguchi
- National Institute for Materials Science, 1-1 Namiki, 305-0044 Tsukuba, Japan
| | - James Hone
- Department of Mechanical Engineering, Columbia University, New York, NY 10027
| | - Cory Dean
- Department of Physics, Columbia University, New York, NY 10027
| | - Dmitri N Basov
- Department of Physics, Columbia University, New York, NY 10027
| | - Angel Rubio
- Theory Department, Max Planck Institute for the Structure and Dynamics of Matter, 22761 Hamburg, Germany;
- Center for Computational Quantum Physics, The Flatiron Institute, New York, NY 10010
- Nano-Bio Spectroscopy Group, Departamento de Fisica de Materiales, Universidad del País Vasco, 20018 San Sebastian, Spain
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30
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Benyamini A, Kennes DM, Telford EJ, Watanabe K, Taniguchi T, Millis AJ, Hone J, Dean CR, Pasupathy AN. Nonmonotonic Temperature-Dependent Dissipation at Nonequilibrium in Atomically Thin Clean-Limit Superconductors. Nano Lett 2021; 21:583-589. [PMID: 33372802 DOI: 10.1021/acs.nanolett.0c04024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Resistance in superconductors arises from the motion of vortices driven by flowing supercurrents or external electromagnetic fields and may be strongly affected by thermal or quantum fluctuations. The common expectation is that as the temperature is lowered, vortex motion is suppressed, leading to a decreased resistance. We show experimentally that in clean-limit atomically thin 2H-NbSe2 the resistance below the superconducting transition temperature may be nonmonotonic, passing through a minimum before increasing again as the temperature is decreased further. The effect is most pronounced in monolayer devices and cannot be understood in terms of known mechanisms. We propose a qualitative two-fluid vortex model in which thermal fluctuations of pinned vortices control the mobility of the free vortices. The findings provide a new perspective on fundamental questions of vortex mobility and dissipation in superconductors.
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Affiliation(s)
- Avishai Benyamini
- Department of Mechanical Engineering, Columbia University, New York, New York 10027, United States
| | - Dante M Kennes
- Institut für Theorie der Statistischen Physik, RWTH Aachen University and JARA-Fundamentals of Future Information Technology, 52056 Aachen, Germany
| | - Evan J Telford
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Kenji Watanabe
- National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Andrew J Millis
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - James Hone
- Department of Mechanical Engineering, Columbia University, New York, New York 10027, United States
| | - Cory R Dean
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Abhay N Pasupathy
- Department of Physics, Columbia University, New York, New York 10027, United States
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31
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Halbertal D, Finney NR, Sunku SS, Kerelsky A, Rubio-Verdú C, Shabani S, Xian L, Carr S, Chen S, Zhang C, Wang L, Gonzalez-Acevedo D, McLeod AS, Rhodes D, Watanabe K, Taniguchi T, Kaxiras E, Dean CR, Hone JC, Pasupathy AN, Kennes DM, Rubio A, Basov DN. Moiré metrology of energy landscapes in van der Waals heterostructures. Nat Commun 2021; 12:242. [PMID: 33431846 PMCID: PMC7801382 DOI: 10.1038/s41467-020-20428-1] [Citation(s) in RCA: 38] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Accepted: 12/02/2020] [Indexed: 01/29/2023] Open
Abstract
The emerging field of twistronics, which harnesses the twist angle between two-dimensional materials, represents a promising route for the design of quantum materials, as the twist-angle-induced superlattices offer means to control topology and strong correlations. At the small twist limit, and particularly under strain, as atomic relaxation prevails, the emergent moiré superlattice encodes elusive insights into the local interlayer interaction. Here we introduce moiré metrology as a combined experiment-theory framework to probe the stacking energy landscape of bilayer structures at the 0.1 meV/atom scale, outperforming the gold-standard of quantum chemistry. Through studying the shapes of moiré domains with numerous nano-imaging techniques, and correlating with multi-scale modelling, we assess and refine first-principle models for the interlayer interaction. We document the prowess of moiré metrology for three representative twisted systems: bilayer graphene, double bilayer graphene and H-stacked MoSe2/WSe2. Moiré metrology establishes sought after experimental benchmarks for interlayer interaction, thus enabling accurate modelling of twisted multilayers.
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Affiliation(s)
- Dorri Halbertal
- Department of Physics, Columbia University, New York, NY, USA.
| | - Nathan R Finney
- Department of Mechanical Engineering, Columbia University, New York, NY, USA
| | - Sai S Sunku
- Department of Physics, Columbia University, New York, NY, USA
| | | | | | - Sara Shabani
- Department of Physics, Columbia University, New York, NY, USA
| | - Lede Xian
- Max Planck Institute for the Structure and Dynamics of Matter and Center Free-Electron Laser Science, Luruper. Chaussee 149, 22761, Hamburg, Germany
- Songshan Lake Materials Laboratory, Dongguan, Guangdong, 523808, China
| | - Stephen Carr
- Department of Physics, Harvard University, Cambridge, MA, 02138, USA
- Brown University, Providence, RI, 02912, USA
| | - Shaowen Chen
- Department of Physics, Columbia University, New York, NY, USA
- Department of Physics, Harvard University, Cambridge, MA, 02138, USA
| | - Charles Zhang
- Department of Physics, Columbia University, New York, NY, USA
- Department of Physics, University of California at Santa Barbara, Santa Barbara, CA, 93106, USA
| | - Lei Wang
- Department of Physics, Columbia University, New York, NY, USA
- National Laboratory of Solid-State Microstructures, School of Physics and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, China
| | - Derick Gonzalez-Acevedo
- Department of Physics, Columbia University, New York, NY, USA
- Department of Physics, Harvard University, Cambridge, MA, 02138, USA
| | | | - Daniel Rhodes
- Department of Physics, Columbia University, New York, NY, USA
- Department of Materials Science and Engineering, University of Winsconsin-Madison, Madison, WI, 53706, USA
| | | | | | - Efthimios Kaxiras
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, 02138, USA
| | - Cory R Dean
- Department of Physics, Columbia University, New York, NY, USA
| | - James C Hone
- Department of Mechanical Engineering, Columbia University, New York, NY, USA
| | | | - Dante M Kennes
- Max Planck Institute for the Structure and Dynamics of Matter and Center Free-Electron Laser Science, Luruper. Chaussee 149, 22761, Hamburg, Germany
- Institut fur Theorie der Statistischen Physik, RWTH Aachen University, 52056, Aachen, Germany
| | - Angel Rubio
- Max Planck Institute for the Structure and Dynamics of Matter and Center Free-Electron Laser Science, Luruper. Chaussee 149, 22761, Hamburg, Germany
- Center for Computational Quantum Physics, Flatiron Institute, New York, NY, 10010, USA
| | - D N Basov
- Department of Physics, Columbia University, New York, NY, USA
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32
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Bai Y, Zhou L, Wang J, Wu W, McGilly LJ, Halbertal D, Lo CFB, Liu F, Ardelean J, Rivera P, Finney NR, Yang XC, Basov DN, Yao W, Xu X, Hone J, Pasupathy AN, Zhu XY. Author Correction: Excitons in strain-induced one-dimensional moiré potentials at transition metal dichalcogenide heterojunctions. Nat Mater 2020; 19:1124. [PMID: 32690914 DOI: 10.1038/s41563-020-0773-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
An amendment to this paper has been published and can be accessed via a link at the top of the paper.
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Affiliation(s)
- Yusong Bai
- Department of Chemistry, Columbia University, New York, NY, USA
| | - Lin Zhou
- Department of Chemistry, Columbia University, New York, NY, USA
- College of Engineering and Applied Sciences, Nanjing University, Nanjing, China
| | - Jue Wang
- Department of Chemistry, Columbia University, New York, NY, USA
| | - Wenjing Wu
- Department of Chemistry, Columbia University, New York, NY, USA
| | - Leo J McGilly
- Department of Physics, Columbia University, New York, NY, USA
| | - Dorri Halbertal
- Department of Physics, Columbia University, New York, NY, USA
| | | | - Fang Liu
- Department of Chemistry, Columbia University, New York, NY, USA
| | - Jenny Ardelean
- Department of Mechanical Engineering, Columbia University, New York, NY, USA
| | - Pasqual Rivera
- Department of Physics and Department of Materials Science and Engineering, University of Washington, Seattle, WA, USA
| | - Nathan R Finney
- Department of Mechanical Engineering, Columbia University, New York, NY, USA
| | - Xu-Chen Yang
- Department of Physics, University of Hong Kong, Hong Kong, China
| | - D N Basov
- Department of Physics, Columbia University, New York, NY, USA
| | - Wang Yao
- Department of Physics, University of Hong Kong, Hong Kong, China
| | - Xiaodong Xu
- Department of Physics and Department of Materials Science and Engineering, University of Washington, Seattle, WA, USA
| | - James Hone
- Department of Mechanical Engineering, Columbia University, New York, NY, USA
| | | | - X-Y Zhu
- Department of Chemistry, Columbia University, New York, NY, USA.
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33
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Bai Y, Zhou L, Wang J, Wu W, McGilly LJ, Halbertal D, Lo CFB, Liu F, Ardelean J, Rivera P, Finney NR, Yang XC, Basov DN, Yao W, Xu X, Hone J, Pasupathy AN, Zhu XY. Excitons in strain-induced one-dimensional moiré potentials at transition metal dichalcogenide heterojunctions. Nat Mater 2020; 19:1068-1073. [PMID: 32661380 DOI: 10.1038/s41563-020-0730-8] [Citation(s) in RCA: 91] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2020] [Accepted: 06/10/2020] [Indexed: 06/11/2023]
Abstract
The possibility of confining interlayer excitons in interfacial moiré patterns has recently gained attention as a strategy to form ordered arrays of zero-dimensional quantum emitters and topological superlattices in transition metal dichalcogenide heterostructures. Strain is expected to play an important role in the modulation of the moiré potential landscape, tuning the array of quantum dot-like zero-dimensional traps into parallel stripes of one-dimensional quantum wires. Here, we present real-space imaging of unstrained zero-dimensional and strain-induced one-dimensional moiré patterns along with photoluminescence measurements of the corresponding excitonic emission from WSe2/MoSe2 heterobilayers. Whereas excitons in zero-dimensional moiré traps display quantum emitter-like sharp photoluminescence peaks with circular polarization, the photoluminescence emission from excitons in one-dimensional moiré potentials shows linear polarization and two orders of magnitude higher intensity. These results establish strain engineering as an effective method to tailor moiré potentials and their optoelectronic response on demand.
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Affiliation(s)
- Yusong Bai
- Department of Chemistry, Columbia University, New York, NY, USA
| | - Lin Zhou
- Department of Chemistry, Columbia University, New York, NY, USA
- College of Engineering and Applied Sciences, Nanjing University, Nanjing, China
| | - Jue Wang
- Department of Chemistry, Columbia University, New York, NY, USA
| | - Wenjing Wu
- Department of Chemistry, Columbia University, New York, NY, USA
| | - Leo J McGilly
- Department of Physics, Columbia University, New York, NY, USA
| | - Dorri Halbertal
- Department of Physics, Columbia University, New York, NY, USA
| | | | - Fang Liu
- Department of Chemistry, Columbia University, New York, NY, USA
| | - Jenny Ardelean
- Department of Mechanical Engineering, Columbia University, New York, NY, USA
| | - Pasqual Rivera
- Department of Physics and Department of Materials Science and Engineering, University of Washington, Seattle, WA, USA
| | - Nathan R Finney
- Department of Mechanical Engineering, Columbia University, New York, NY, USA
| | - Xu-Chen Yang
- Department of Physics, University of Hong Kong, Hong Kong, China
| | - D N Basov
- Department of Physics, Columbia University, New York, NY, USA
| | - Wang Yao
- Department of Physics, University of Hong Kong, Hong Kong, China
| | - Xiaodong Xu
- Department of Physics and Department of Materials Science and Engineering, University of Washington, Seattle, WA, USA
| | - James Hone
- Department of Mechanical Engineering, Columbia University, New York, NY, USA
| | | | - X-Y Zhu
- Department of Chemistry, Columbia University, New York, NY, USA.
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34
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Darlington TP, Carmesin C, Florian M, Yanev E, Ajayi O, Ardelean J, Rhodes DA, Ghiotto A, Krayev A, Watanabe K, Taniguchi T, Kysar JW, Pasupathy AN, Hone JC, Jahnke F, Borys NJ, Schuck PJ. Imaging strain-localized excitons in nanoscale bubbles of monolayer WSe 2 at room temperature. Nat Nanotechnol 2020; 15:854-860. [PMID: 32661371 DOI: 10.1038/s41565-020-0730-5] [Citation(s) in RCA: 68] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2020] [Accepted: 06/03/2020] [Indexed: 05/23/2023]
Abstract
In monolayer transition-metal dichalcogenides, localized strain can be used to design nanoarrays of single photon sources. Despite strong empirical correlation, the nanoscale interplay between excitons and local crystalline structure that gives rise to these quantum emitters is poorly understood. Here, we combine room-temperature nano-optical imaging and spectroscopic analysis of excitons in nanobubbles of monolayer WSe2 with atomistic models to study how strain induces nanoscale confinement potentials and localized exciton states. The imaging of nanobubbles in monolayers with low defect concentrations reveals localized excitons on length scales of around 10 nm at multiple sites around the periphery of individual nanobubbles, in stark contrast to predictions of continuum models of strain. These results agree with theoretical confinement potentials atomistically derived from the measured topographies of nanobubbles. Our results provide experimental and theoretical insights into strain-induced exciton localization on length scales commensurate with exciton size, realizing key nanoscale structure-property information on quantum emitters in monolayer WSe2.
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Affiliation(s)
| | - Christian Carmesin
- Institute for Theoretical Physics, University of Bremen, Bremen, Germany
| | - Matthias Florian
- Institute for Theoretical Physics, University of Bremen, Bremen, Germany
| | - Emanuil Yanev
- Department of Mechanical Engineering, Columbia University, New York, NY, USA
| | - Obafunso Ajayi
- Department of Mechanical Engineering, Columbia University, New York, NY, USA
| | - Jenny Ardelean
- Department of Mechanical Engineering, Columbia University, New York, NY, USA
| | - Daniel A Rhodes
- Department of Mechanical Engineering, Columbia University, New York, NY, USA
| | - Augusto Ghiotto
- Department of Physics, Columbia University, New York, NY, USA
| | | | - Kenji Watanabe
- National Institute for Materials Science, Tsukuba, Japan
| | | | - Jeffrey W Kysar
- Department of Mechanical Engineering, Columbia University, New York, NY, USA
| | | | - James C Hone
- Department of Mechanical Engineering, Columbia University, New York, NY, USA
| | - Frank Jahnke
- Institute for Theoretical Physics, University of Bremen, Bremen, Germany.
| | - Nicholas J Borys
- Department of Physics, Montana State University, Bozeman, MT, USA.
| | - P James Schuck
- Department of Mechanical Engineering, Columbia University, New York, NY, USA.
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35
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Telford EJ, Dismukes AH, Lee K, Cheng M, Wieteska A, Bartholomew AK, Chen YS, Xu X, Pasupathy AN, Zhu X, Dean CR, Roy X. Layered Antiferromagnetism Induces Large Negative Magnetoresistance in the van der Waals Semiconductor CrSBr. Adv Mater 2020; 32:e2003240. [PMID: 32776373 DOI: 10.1002/adma.202003240] [Citation(s) in RCA: 50] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2020] [Revised: 06/19/2020] [Indexed: 06/11/2023]
Abstract
The recent discovery of magnetism within the family of exfoliatable van der Waals (vdW) compounds has attracted considerable interest in these materials for both fundamental research and technological applications. However, current vdW magnets are limited by their extreme sensitivity to air, low ordering temperatures, and poor charge transport properties. Here the magnetic and electronic properties of CrSBr are reported, an air-stable vdW antiferromagnetic semiconductor that readily cleaves perpendicular to the stacking axis. Below its Néel temperature, TN = 132 ± 1 K, CrSBr adopts an A-type antiferromagnetic structure with each individual layer ferromagnetically ordered internally and the layers coupled antiferromagnetically along the stacking direction. Scanning tunneling spectroscopy and photoluminescence (PL) reveal that the electronic gap is ΔE = 1.5 ± 0.2 eV with a corresponding PL peak centered at 1.25 ± 0.07 eV. Using magnetotransport measurements, strong coupling between magnetic order and transport properties in CrSBr is demonstrated, leading to a large negative magnetoresistance response that is unique among vdW materials. These findings establish CrSBr as a promising material platform for increasing the applicability of vdW magnets to the field of spin-based electronics.
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Affiliation(s)
- Evan J Telford
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Avalon H Dismukes
- Department of Chemistry, Columbia University, New York, NY, 10027, USA
| | - Kihong Lee
- Department of Chemistry, Columbia University, New York, NY, 10027, USA
| | - Minghao Cheng
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Andrew Wieteska
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | | | - Yu-Sheng Chen
- NSF's ChemMatCARS, University of Chicago, Chicago, IL, 60439, USA
| | - Xiaodong Xu
- Department of Physics, University of Washington, Seattle, WA, 98195, USA
| | - Abhay N Pasupathy
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Xiaoyang Zhu
- Department of Chemistry, Columbia University, New York, NY, 10027, USA
| | - Cory R Dean
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Xavier Roy
- Department of Chemistry, Columbia University, New York, NY, 10027, USA
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36
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Wang L, Shih EM, Ghiotto A, Xian L, Rhodes DA, Tan C, Claassen M, Kennes DM, Bai Y, Kim B, Watanabe K, Taniguchi T, Zhu X, Hone J, Rubio A, Pasupathy AN, Dean CR. Correlated electronic phases in twisted bilayer transition metal dichalcogenides. Nat Mater 2020; 19:861-866. [PMID: 32572205 DOI: 10.1038/s41563-020-0708-6] [Citation(s) in RCA: 226] [Impact Index Per Article: 56.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2019] [Accepted: 05/11/2020] [Indexed: 05/06/2023]
Abstract
In narrow electron bands in which the Coulomb interaction energy becomes comparable to the bandwidth, interactions can drive new quantum phases. Such flat bands in twisted graphene-based systems result in correlated insulator, superconducting and topological states. Here we report evidence of low-energy flat bands in twisted bilayer WSe2, with signatures of collective phases observed over twist angles that range from 4 to 5.1°. At half-band filling, a correlated insulator appeared that is tunable with both twist angle and displacement field. At a 5.1° twist, zero-resistance pockets were observed on doping away from half filling at temperatures below 3 K, which indicates a possible transition to a superconducting state. The observation of tunable collective phases in a simple band, which hosts only two holes per unit cell at full filling, establishes twisted bilayer transition metal dichalcogenides as an ideal platform to study correlated physics in two dimensions on a triangular lattice.
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Affiliation(s)
- Lei Wang
- National Laboratory of Solid-State Microstructures, School of Physics and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, China
- Department of Physics, Columbia University, New York, NY, USA
| | - En-Min Shih
- Department of Physics, Columbia University, New York, NY, USA
| | - Augusto Ghiotto
- Department of Physics, Columbia University, New York, NY, USA
| | - Lede Xian
- Max Planck Institute for the Structure and Dynamics of Matter, Hamburg, Germany
| | - Daniel A Rhodes
- Department of Mechanical Engineering, Columbia University, New York, NY, USA
| | - Cheng Tan
- Department of Mechanical Engineering, Columbia University, New York, NY, USA
- Department of Electrical Engineering, Columbia University, New York, NY, USA
| | - Martin Claassen
- Center for Computational Quantum Physics, Flatiron Institute, New York, NY, USA
| | - Dante M Kennes
- Max Planck Institute for the Structure and Dynamics of Matter, Hamburg, Germany
- Institut für Theorie der Statistischen Physik RWTH Aachen University and JARA-Fundamentals of Future Information Technology, Aachen, Germany
| | - Yusong Bai
- Department of Chemistry, Columbia University, New York, NY, USA
| | - Bumho Kim
- Department of Mechanical Engineering, Columbia University, New York, NY, USA
| | - Kenji Watanabe
- National Institute for Materials Science, Tsukuba, Ibaraki, Japan
| | | | - Xiaoyang Zhu
- Department of Chemistry, Columbia University, New York, NY, USA
| | - James Hone
- Department of Mechanical Engineering, Columbia University, New York, NY, USA
| | - Angel Rubio
- Max Planck Institute for the Structure and Dynamics of Matter, Hamburg, Germany.
- Center for Computational Quantum Physics, Flatiron Institute, New York, NY, USA.
- Nano-Bio Spectroscopy Group, Departamento de Fisica de Materiales, Universidad del País Vasco, San Sebastian, Spain.
| | | | - Cory R Dean
- Department of Physics, Columbia University, New York, NY, USA.
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37
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McGilly LJ, Kerelsky A, Finney NR, Shapovalov K, Shih EM, Ghiotto A, Zeng Y, Moore SL, Wu W, Bai Y, Watanabe K, Taniguchi T, Stengel M, Zhou L, Hone J, Zhu X, Basov DN, Dean C, Dreyer CE, Pasupathy AN. Visualization of moiré superlattices. Nat Nanotechnol 2020; 15:580-584. [PMID: 32572229 DOI: 10.1038/s41565-020-0708-3] [Citation(s) in RCA: 92] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Accepted: 05/05/2020] [Indexed: 05/27/2023]
Abstract
Moiré superlattices in van der Waals heterostructures have given rise to a number of emergent electronic phenomena due to the interplay between atomic structure and electron correlations. Indeed, electrons in these structures have been recently found to exhibit a number of emergent properties that the individual layers themselves do not exhibit. This includes superconductivity1,2, magnetism3, topological edge states4,5, exciton trapping6 and correlated insulator phases7. However, the lack of a straightforward technique to characterize the local structure of moiré superlattices has thus far impeded progress in the field. In this work we describe a simple, room-temperature, ambient method to visualize real-space moiré superlattices with sub-5-nm spatial resolution in a variety of twisted van der Waals heterostructures including, but not limited to, conducting graphene, insulating boron nitride and semiconducting transition metal dichalcogenides. Our method uses piezoresponse force microscopy, an atomic force microscope modality that locally measures electromechanical surface deformation. We find that all moiré superlattices, regardless of whether the constituent layers have inversion symmetry, exhibit a mechanical response to out-of-plane electric fields. This response is closely tied to flexoelectricity wherein electric polarization and electromechanical response is induced through strain gradients present within moiré superlattices. Therefore, moiré superlattices of two-dimensional materials manifest themselves as an interlinked network of polarized domain walls in a non-polar background matrix.
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Affiliation(s)
- Leo J McGilly
- Department of Physics, Columbia University, New York, NY, USA
| | | | - Nathan R Finney
- Department of Mechanical Engineering, Columbia University, New York, NY, USA
| | | | - En-Min Shih
- Department of Physics, Columbia University, New York, NY, USA
| | - Augusto Ghiotto
- Department of Physics, Columbia University, New York, NY, USA
| | - Yihang Zeng
- Department of Physics, Columbia University, New York, NY, USA
| | - Samuel L Moore
- Department of Physics, Columbia University, New York, NY, USA
| | - Wenjing Wu
- Department of Chemistry, Columbia University, New York, NY, USA
| | - Yusong Bai
- Department of Chemistry, Columbia University, New York, NY, USA
| | - Kenji Watanabe
- National Institute for Materials Science, Tsukuba, Japan
| | | | - Massimiliano Stengel
- Institute of Materials Science of Barcelona, Bellaterra, Spain
- ICREA-Instució Catalana de Recerca i Estudis Avançats, Barcelona, Spain
| | - Lin Zhou
- Department of Chemistry, Columbia University, New York, NY, USA
- College of Engineering and Applied Sciences, Nanjing University, Nanjing, China
| | - James Hone
- Department of Mechanical Engineering, Columbia University, New York, NY, USA
| | - Xiaoyang Zhu
- Department of Chemistry, Columbia University, New York, NY, USA
| | - Dmitri N Basov
- Department of Physics, Columbia University, New York, NY, USA
| | - Cory Dean
- Department of Physics, Columbia University, New York, NY, USA
| | - Cyrus E Dreyer
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, USA
- Center for Computational Quantum Physics, Flatiron Institute, New York, NY, USA
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38
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Fu S, Kang K, Shayan K, Yoshimura A, Dadras S, Wang X, Zhang L, Chen S, Liu N, Jindal A, Li X, Pasupathy AN, Vamivakas AN, Meunier V, Strauf S, Yang EH. Enabling room temperature ferromagnetism in monolayer MoS 2 via in situ iron-doping. Nat Commun 2020; 11:2034. [PMID: 32341412 PMCID: PMC7184740 DOI: 10.1038/s41467-020-15877-7] [Citation(s) in RCA: 47] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Accepted: 03/24/2020] [Indexed: 12/15/2022] Open
Abstract
Two-dimensional semiconductors, including transition metal dichalcogenides, are of interest in electronics and photonics but remain nonmagnetic in their intrinsic form. Previous efforts to form two-dimensional dilute magnetic semiconductors utilized extrinsic doping techniques or bulk crystal growth, detrimentally affecting uniformity, scalability, or Curie temperature. Here, we demonstrate an in situ substitutional doping of Fe atoms into MoS2 monolayers in the chemical vapor deposition growth. The iron atoms substitute molybdenum sites in MoS2 crystals, as confirmed by transmission electron microscopy and Raman signatures. We uncover an Fe-related spectral transition of Fe:MoS2 monolayers that appears at 2.28 eV above the pristine bandgap and displays pronounced ferromagnetic hysteresis. The microscopic origin is further corroborated by density functional theory calculations of dipole-allowed transitions in Fe:MoS2. Using spatially integrating magnetization measurements and spatially resolving nitrogen-vacancy center magnetometry, we show that Fe:MoS2 monolayers remain magnetized even at ambient conditions, manifesting ferromagnetism at room temperature.
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Affiliation(s)
- Shichen Fu
- Department of Mechanical Engineering, Stevens Institute of Technology, Hoboken, NJ, 07030, USA
| | - Kyungnam Kang
- Department of Mechanical Engineering, Stevens Institute of Technology, Hoboken, NJ, 07030, USA
| | - Kamran Shayan
- Department of Physics, Stevens Institute of Technology, Hoboken, NJ, 07030, USA
- Center for Quantum Science and Engineering, Stevens Institute of Technology, Hoboken, NJ, 07030, USA
- Institute of Optics, University of Rochester, Rochester, NY, 14627, USA
| | - Anthony Yoshimura
- Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, NY, 12180, USA
| | - Siamak Dadras
- Institute of Optics, University of Rochester, Rochester, NY, 14627, USA
| | - Xiaotian Wang
- Department of Mechanical Engineering, Stevens Institute of Technology, Hoboken, NJ, 07030, USA
| | - Lihua Zhang
- Center of Functional Nanomaterials, Brookhaven National Laboratory, Upton, NY, 11973-5000, USA
| | - Siwei Chen
- Department of Mechanical Engineering, Stevens Institute of Technology, Hoboken, NJ, 07030, USA
| | - Na Liu
- Department of Physics, Stevens Institute of Technology, Hoboken, NJ, 07030, USA
- Center for Quantum Science and Engineering, Stevens Institute of Technology, Hoboken, NJ, 07030, USA
| | - Apoorv Jindal
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Xiangzhi Li
- Department of Physics, Stevens Institute of Technology, Hoboken, NJ, 07030, USA
- Center for Quantum Science and Engineering, Stevens Institute of Technology, Hoboken, NJ, 07030, USA
| | - Abhay N Pasupathy
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - A Nick Vamivakas
- Institute of Optics, University of Rochester, Rochester, NY, 14627, USA
| | - Vincent Meunier
- Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, NY, 12180, USA
| | - Stefan Strauf
- Department of Physics, Stevens Institute of Technology, Hoboken, NJ, 07030, USA.
- Center for Quantum Science and Engineering, Stevens Institute of Technology, Hoboken, NJ, 07030, USA.
| | - Eui-Hyeok Yang
- Department of Mechanical Engineering, Stevens Institute of Technology, Hoboken, NJ, 07030, USA.
- Center for Quantum Science and Engineering, Stevens Institute of Technology, Hoboken, NJ, 07030, USA.
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39
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Cheung SC, Shin JY, Lau Y, Chen Z, Sun J, Zhang Y, Müller MA, Eremin IM, Wright JN, Pasupathy AN. Dictionary learning in Fourier-transform scanning tunneling spectroscopy. Nat Commun 2020; 11:1081. [PMID: 32102995 PMCID: PMC7044214 DOI: 10.1038/s41467-020-14633-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2017] [Accepted: 01/17/2020] [Indexed: 11/15/2022] Open
Abstract
Modern high-resolution microscopes are commonly used to study specimens that have dense and aperiodic spatial structure. Extracting meaningful information from images obtained from such microscopes remains a formidable challenge. Fourier analysis is commonly used to analyze the structure of such images. However, the Fourier transform fundamentally suffers from severe phase noise when applied to aperiodic images. Here, we report the development of an algorithm based on nonconvex optimization that directly uncovers the fundamental motifs present in a real-space image. Apart from being quantitatively superior to traditional Fourier analysis, we show that this algorithm also uncovers phase sensitive information about the underlying motif structure. We demonstrate its usefulness by studying scanning tunneling microscopy images of a Co-doped iron arsenide superconductor and prove that the application of the algorithm allows for the complete recovery of quasiparticle interference in this material. Aperiodic structure imaging suffers limitations when utilizing Fourier analysis. The authors report an algorithm that quantitatively overcomes these limitations based on nonconvex optimization, demonstrated by studying aperiodic structures via the phase sensitive interference in STM images.
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Affiliation(s)
- Sky C Cheung
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - John Y Shin
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Yenson Lau
- Department of Electrical Engineering, Columbia University, New York, NY, 10027, USA
| | - Zhengyu Chen
- Department of Electrical Engineering, Columbia University, New York, NY, 10027, USA
| | - Ju Sun
- Department of Electrical Engineering, Columbia University, New York, NY, 10027, USA
| | - Yuqian Zhang
- Department of Electrical Engineering, Columbia University, New York, NY, 10027, USA
| | - Marvin A Müller
- Institut für Theoretische Physik III, Ruhr-Universität Bochum, 44801, Bochum, Germany
| | - Ilya M Eremin
- Institut für Theoretische Physik III, Ruhr-Universität Bochum, 44801, Bochum, Germany.,National University of Science and Technology MISiS, 119049, Moscow, Russian Federation
| | - John N Wright
- Department of Electrical Engineering, Columbia University, New York, NY, 10027, USA.
| | - Abhay N Pasupathy
- Department of Physics, Columbia University, New York, NY, 10027, USA.
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40
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Edelberg D, Rhodes D, Kerelsky A, Kim B, Wang J, Zangiabadi A, Kim C, Abhinandan A, Ardelean J, Scully M, Scullion D, Embon L, Zu R, Santos EJG, Balicas L, Marianetti C, Barmak K, Zhu X, Hone J, Pasupathy AN. Approaching the Intrinsic Limit in Transition Metal Diselenides via Point Defect Control. Nano Lett 2019; 19:4371-4379. [PMID: 31180688 DOI: 10.1021/acs.nanolett.9b00985] [Citation(s) in RCA: 77] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Two dimensional (2D) transition-metal dichalcogenide (TMD) based semiconductors have generated intense recent interest due to their novel optical and electronic properties and potential for applications. In this work, we characterize the atomic and electronic nature of intrinsic point defects found in single crystals of these materials synthesized by two different methods, chemical vapor transport and self-flux growth. Using a combination of scanning tunneling microscopy (STM) and scanning transmission electron microscopy (STEM), we show that the two major intrinsic defects in these materials are metal vacancies and chalcogen antisites. We show that by control of the synthetic conditions, we can reduce the defect concentration from above 1013/cm2 to below 1011/cm2. Because these point defects act as centers for nonradiative recombination of excitons, this improvement in material quality leads to a hundred-fold increase in the radiative recombination efficiency.
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Affiliation(s)
| | | | | | | | | | - Amirali Zangiabadi
- National High Magnetic Field Laboratory , Florida State University , Tallahassee , Florida 32310 , United States
| | - Chanul Kim
- National High Magnetic Field Laboratory , Florida State University , Tallahassee , Florida 32310 , United States
| | | | | | - Micheal Scully
- School of Mathematics and Physics , Queen's University , Belfast , BT7 1NN , United Kingdom
| | - Declan Scullion
- School of Mathematics and Physics , Queen's University , Belfast , BT7 1NN , United Kingdom
| | | | - Rui Zu
- National High Magnetic Field Laboratory , Florida State University , Tallahassee , Florida 32310 , United States
| | - Elton J G Santos
- School of Mathematics and Physics , Queen's University , Belfast , BT7 1NN , United Kingdom
| | - Luis Balicas
- National High Magnetic Field Laboratory , Florida State University , Tallahassee , Florida 32310 , United States
- Department of Physics , Florida State University , Tallahassee , Florida 32306 , United States
| | - Chris Marianetti
- Department of Applied Physics and Applied Math , Columbia University , New York , New York 10027 , United States
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41
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Zhou X, Kerelsky A, Elahi MM, Wang D, Habib KMM, Sajjad RN, Agnihotri P, Lee JU, Ghosh AW, Ross FM, Pasupathy AN. Atomic-Scale Characterization of Graphene p-n Junctions for Electron-Optical Applications. ACS Nano 2019; 13:2558-2566. [PMID: 30689949 DOI: 10.1021/acsnano.8b09575] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Graphene p-n junctions offer a potentially powerful approach toward controlling electron trajectories via collimation and focusing in ballistic solid-state devices. The ability of p-n junctions to control electron trajectories depends crucially on the doping profile and roughness of the junction. Here, we use four-probe scanning tunneling microscopy and spectroscopy (STM/STS) to characterize two state-of-the-art graphene p-n junction geometries at the atomic scale, one with CMOS polySi gates and another with naturally cleaved graphite gates. Using spectroscopic imaging, we characterize the local doping profile across and along the p-n junctions. We find that realistic junctions exhibit non-ideality both in their geometry as well as in the doping profile across the junction. We show that the geometry of the junction can be improved by using the cleaved edge of van der Waals metals such as graphite to define the junction. We quantify the geometric roughness and doping profiles of junctions experimentally and use these parameters in non-equilibrium Green's function-based simulations of focusing and collimation in these realistic junctions. We find that for realizing Veselago focusing, it is crucial to minimize lateral interface roughness which only natural graphite gates achieve and to reduce junction width, in which both devices under investigation underperform. We also find that carrier collimation is currently limited by the non-linearity of the doping profile across the junction. Our work provides benchmarks of the current graphene p-n junction quality and provides guidance for future improvements.
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Affiliation(s)
- Xiaodong Zhou
- Department of Physics , Columbia University , New York , New York 10027 , United States
- IBM T. J. Watson Research Center , Yorktown Heights , New York 10598 , United States
- Institute for Nanoelectronic Devices and Quantum Computing , Fudan University , Shanghai 200438 , P.R. China
| | - Alexander Kerelsky
- Department of Physics , Columbia University , New York , New York 10027 , United States
| | - Mirza M Elahi
- Department of Electrical and Computer Engineering , University of Virginia , Charlottesville , Virginia 22904 , United States
| | - Dennis Wang
- Department of Physics , Columbia University , New York , New York 10027 , United States
| | - K M Masum Habib
- Department of Electrical and Computer Engineering , University of Virginia , Charlottesville , Virginia 22904 , United States
- Intel Corporation , Santa Clara , California 95054 , United States
| | - Redwan N Sajjad
- Microsystems Technology Laboratories , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States
| | - Pratik Agnihotri
- College of Nanoscale Science and Engineering , The State University of New York at Albany , Albany , New York 12203 , United States
| | - Ji Ung Lee
- College of Nanoscale Science and Engineering , The State University of New York at Albany , Albany , New York 12203 , United States
| | - Avik W Ghosh
- Department of Electrical and Computer Engineering , University of Virginia , Charlottesville , Virginia 22904 , United States
- Department of Physics , University of Virginia , Charlottesville , Virginia 22904 , United States
| | - Frances M Ross
- IBM T. J. Watson Research Center , Yorktown Heights , New York 10598 , United States
- Department of Materials Science and Engineering , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States
| | - Abhay N Pasupathy
- Department of Physics , Columbia University , New York , New York 10027 , United States
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42
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Telford EJ, Benyamini A, Rhodes D, Wang D, Jung Y, Zangiabadi A, Watanabe K, Taniguchi T, Jia S, Barmak K, Pasupathy AN, Dean CR, Hone J. Via Method for Lithography Free Contact and Preservation of 2D Materials. Nano Lett 2018; 18:1416-1420. [PMID: 29385346 DOI: 10.1021/acs.nanolett.7b05161] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Atomically thin 2D materials span the common components of electronic circuits as metals, semiconductors, and insulators, and can manifest correlated phases such as superconductivity, charge density waves, and magnetism. An ongoing challenge in the field is to incorporate these 2D materials into multilayer heterostructures with robust electrical contacts while preventing disorder and degradation. In particular, preserving and studying air-sensitive 2D materials has presented a significant challenge since they readily oxidize under atmospheric conditions. We report a new technique for contacting 2D materials, in which metal via contacts are integrated into flakes of insulating hexagonal boron nitride, and then placed onto the desired conducting 2D layer, avoiding direct lithographic patterning onto the 2D conductor. The metal contacts are planar with the bottom surface of the boron nitride and form robust contacts to multiple 2D materials. These structures protect air-sensitive 2D materials for months with no degradation in performance. This via contact technique will provide the capability to produce "atomic printed circuit boards" that can form the basis of more complex multilayer heterostructures.
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Affiliation(s)
- Evan J Telford
- Department of Physics, Columbia University , New York, New York 10027, United States
| | - Avishai Benyamini
- Department of Mechanical Engineering, Columbia University , New York, New York 10027, United States
| | - Daniel Rhodes
- Department of Mechanical Engineering, Columbia University , New York, New York 10027, United States
| | - Da Wang
- Department of Physics, Columbia University , New York, New York 10027, United States
| | - Younghun Jung
- Department of Mechanical Engineering, Columbia University , New York, New York 10027, United States
| | - Amirali Zangiabadi
- Department of Applied Physics and Applied Mathematics, Columbia University , New York, New York 10027, United States
| | - Kenji Watanabe
- National Institute for Materials Science , 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- National Institute for Materials Science , 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Shuang Jia
- International Center for Quantum Materials, School of Physics, Peking University , Beijing 100871, China
- Collaborative Innovation Center of Quantum Matter , Beijing 100871, China
| | - Katayun Barmak
- Department of Applied Physics and Applied Mathematics, Columbia University , New York, New York 10027, United States
| | - Abhay N Pasupathy
- Department of Physics, Columbia University , New York, New York 10027, United States
| | - Cory R Dean
- Department of Physics, Columbia University , New York, New York 10027, United States
| | - James Hone
- Department of Mechanical Engineering, Columbia University , New York, New York 10027, United States
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43
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Rhodes D, Chenet DA, Janicek BE, Nyby C, Lin Y, Jin W, Edelberg D, Mannebach E, Finney N, Antony A, Schiros T, Klarr T, Mazzoni A, Chin M, Chiu YC, Zheng W, Zhang QR, Ernst F, Dadap JI, Tong X, Ma J, Lou R, Wang S, Qian T, Ding H, Osgood RM, Paley DW, Lindenberg AM, Huang PY, Pasupathy AN, Dubey M, Hone J, Balicas L. Engineering the Structural and Electronic Phases of MoTe 2 through W Substitution. Nano Lett 2017; 17:1616-1622. [PMID: 28145719 DOI: 10.1021/acs.nanolett.6b04814] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
MoTe2 is an exfoliable transition metal dichalcogenide (TMD) that crystallizes in three symmetries: the semiconducting trigonal-prismatic 2H- or α-phase, the semimetallic and monoclinic 1T'- or β-phase, and the semimetallic orthorhombic γ-structure. The 2H-phase displays a band gap of ∼1 eV making it appealing for flexible and transparent optoelectronics. The γ-phase is predicted to possess unique topological properties that might lead to topologically protected nondissipative transport channels. Recently, it was argued that it is possible to locally induce phase-transformations in TMDs, through chemical doping, local heating, or electric-field to achieve ohmic contacts or to induce useful functionalities such as electronic phase-change memory elements. The combination of semiconducting and topological elements based upon the same compound might produce a new generation of high performance, low dissipation optoelectronic elements. Here, we show that it is possible to engineer the phases of MoTe2 through W substitution by unveiling the phase-diagram of the Mo1-xWxTe2 solid solution, which displays a semiconducting to semimetallic transition as a function of x. We find that a small critical W concentration xc ∼ 8% stabilizes the γ-phase at room temperature. This suggests that crystals with x close to xc might be particularly susceptible to phase transformations induced by an external perturbation, for example, an electric field. Photoemission spectroscopy, indicates that the γ-phase possesses a Fermi surface akin to that of WTe2.
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Affiliation(s)
- D Rhodes
- National High Magnetic Field Laboratory, Florida State University , Tallahassee, Florida 32310, United States
- Department of Physics, Florida State University , Tallahassee, Florida 32306, United States
| | - D A Chenet
- Department of Mechanical Engineering, Columbia University , New York, New York 10027, United States
| | - B E Janicek
- Department of Materials Science and Engineering, University of Illinois Urbana-Champaign , Urbana, Illinois 61801, United States
| | - C Nyby
- Department of Chemistry, Stanford University , Stanford, California 94305-4401, United States
| | | | | | | | - E Mannebach
- Department of Materials Science and Engineering, Stanford University , Stanford, California 94305, United States
| | - N Finney
- Department of Mechanical Engineering, Columbia University , New York, New York 10027, United States
| | - A Antony
- Department of Mechanical Engineering, Columbia University , New York, New York 10027, United States
| | - T Schiros
- Materials Research Science and Engineering Center, Columbia University , New York, New York 10027 United States
- Department of Science and Mathematics, SUNY Fashion Institute of Technology , New York, New York 10001 United States
| | - T Klarr
- Sensors and Electronic Devices Directorate, United States Army Research Laboratory , Adelphi, Maryland 20723, United States
| | - A Mazzoni
- Sensors and Electronic Devices Directorate, United States Army Research Laboratory , Adelphi, Maryland 20723, United States
| | - M Chin
- Sensors and Electronic Devices Directorate, United States Army Research Laboratory , Adelphi, Maryland 20723, United States
| | - Y-C Chiu
- National High Magnetic Field Laboratory, Florida State University , Tallahassee, Florida 32310, United States
- Department of Physics, Florida State University , Tallahassee, Florida 32306, United States
| | - W Zheng
- National High Magnetic Field Laboratory, Florida State University , Tallahassee, Florida 32310, United States
- Department of Physics, Florida State University , Tallahassee, Florida 32306, United States
| | - Q R Zhang
- National High Magnetic Field Laboratory, Florida State University , Tallahassee, Florida 32310, United States
- Department of Physics, Florida State University , Tallahassee, Florida 32306, United States
| | - F Ernst
- Department of Applied Physics, Stanford University , Stanford, California 94305-4090, United States
- Stanford PULSE Institute, SLAC National Accelerator Laboratory , Menlo Park, California 94025, United States
| | - J I Dadap
- Department of Electrical Engineering, Columbia University , New York, New York 10027, United States
| | - X Tong
- Center for Functional Nanomaterials, Brookhaven National Laboratory , Upton, New York 11973-5000, United States
| | - J Ma
- Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences , Beijing 100190, China
| | - R Lou
- Department of Physics, Renmin University of China , Beijing 100872, China
| | - S Wang
- Department of Physics, Renmin University of China , Beijing 100872, China
| | - T Qian
- Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences , Beijing 100190, China
| | - H Ding
- Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences , Beijing 100190, China
| | - R M Osgood
- Department of Electrical Engineering, Columbia University , New York, New York 10027, United States
| | | | - A M Lindenberg
- Department of Materials Science and Engineering, Stanford University , Stanford, California 94305, United States
- Stanford PULSE Institute, SLAC National Accelerator Laboratory , Menlo Park, California 94025, United States
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory , Menlo Park, California 94025, United States
| | - P Y Huang
- Department of Mechanical Science and Engineering, University of Illinois Urbana-Champaign , Urbana, Illinois 61801, United States
| | | | - M Dubey
- Sensors and Electronic Devices Directorate, United States Army Research Laboratory , Adelphi, Maryland 20723, United States
| | - J Hone
- Department of Mechanical Engineering, Columbia University , New York, New York 10027, United States
| | - L Balicas
- National High Magnetic Field Laboratory, Florida State University , Tallahassee, Florida 32310, United States
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44
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Abstract
The electronic properties of semiconducting monolayer transition-metal dichalcogenides can be tuned by electrostatic gate potentials. Here we report gate-tunable imaging and spectroscopy of monolayer MoS2 by atomic-resolution scanning tunneling microscopy/spectroscopy (STM/STS). Our measurements are performed on large-area samples grown by metal-organic chemical vapor deposition (MOCVD) techniques on a silicon oxide substrate. Topographic measurements of defect density indicate a sample quality comparable to single-crystal MoS2. From gate voltage dependent spectroscopic measurements, we determine that in-gap states exist in or near the MoS2 film at a density of 1.3 × 10(12) eV(-1) cm(-2). By combining the single-particle band gap measured by STS with optical measurements, we estimate an exciton binding energy of 230 meV on this substrate, in qualitative agreement with numerical simulation. Grain boundaries are observed in these polycrystalline samples, which are seen to not have strong electronic signatures in STM imaging.
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Affiliation(s)
| | - Kibum Kang
- Department of Chemistry and Chemical Biology, Cornell University , Ithaca, New York 14853, United States
| | - Saien Xie
- Department of Chemistry and Chemical Biology, Cornell University , Ithaca, New York 14853, United States
| | | | | | | | - Jiwoong Park
- Department of Chemistry and Chemical Biology, Cornell University , Ithaca, New York 14853, United States
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45
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Adak O, Rosenthal E, Meisner J, Andrade EF, Pasupathy AN, Nuckolls C, Hybertsen MS, Venkataraman L. Flicker Noise as a Probe of Electronic Interaction at Metal-Single Molecule Interfaces. Nano Lett 2015; 15:4143-9. [PMID: 25942441 DOI: 10.1021/acs.nanolett.5b01270] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Charge transport properties of metal-molecule interfaces depend strongly on the character of molecule-electrode interactions. Although through-bond coupled systems have attracted the most attention, through-space coupling is important in molecular systems when, for example, through-bond coupling is suppressed due to quantum interference effects. To date, a probe that clearly distinguishes these two types of coupling has not yet been demonstrated. Here, we investigate the origin of flicker noise in single molecule junctions and demonstrate how the character of the molecule-electrode coupling influences the flicker noise behavior of single molecule junctions. Importantly, we find that flicker noise shows a power law dependence on conductance in all junctions studied with an exponent that can distinguish through-space and through-bond coupling. Our results provide a new and powerful tool for probing and understanding coupling at the metal-molecule interface.
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Affiliation(s)
| | | | | | | | | | | | - Mark S Hybertsen
- ∥Center for Functional Nanomaterials, Brookhaven National Laboratories, Upton, New York 11973, United States
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46
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Zhao L, He R, Zabet-Khosousi A, Kim KS, Schiros T, Roth M, Kim P, Flynn GW, Pinczuk A, Pasupathy AN. Dopant segregation in polycrystalline monolayer graphene. Nano Lett 2015; 15:1428-1436. [PMID: 25625227 DOI: 10.1021/nl504875x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Heterogeneity in dopant concentration has long been important to the electronic properties in chemically doped materials. In this work, we experimentally demonstrate that during the chemical vapor deposition process, in contrast to three-dimensional polycrystals, the substitutional nitrogen atoms avoid crystal grain boundaries and edges over micron length scales while distributing uniformly in the interior of each grain. This phenomenon is universally observed independent of the details of the growth procedure such as temperature, pressure, substrate, and growth precursor.
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Affiliation(s)
- Liuyan Zhao
- Department of Physics, Columbia University , New York, New York 10027, United States
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47
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Arguello CJ, Rosenthal EP, Andrade EF, Jin W, Yeh PC, Zaki N, Jia S, Cava RJ, Fernandes RM, Millis AJ, Valla T, Osgood RM, Pasupathy AN. Quasiparticle interference, quasiparticle interactions, and the origin of the charge density wave in 2H-NbSe2. Phys Rev Lett 2015; 114:037001. [PMID: 25659014 DOI: 10.1103/physrevlett.114.037001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Indexed: 06/04/2023]
Abstract
We show that a small number of intentionally introduced defects can be used as a spectroscopic tool to amplify quasiparticle interference in 2H-NbSe2 that we measure by scanning tunneling spectroscopic imaging. We show, from the momentum and energy dependence of the quasiparticle interference, that Fermi surface nesting is inconsequential to charge density wave formation in 2H-NbSe2. We demonstrate that, by combining quasiparticle interference data with additional knowledge of the quasiparticle band structure from angle resolved photoemission measurements, one can extract the wave vector and energy dependence of the important electronic scattering processes thereby obtaining direct information both about the fermiology and the interactions. In 2H-NbSe2, we use this combination to confirm that the important near-Fermi-surface electronic physics is dominated by the coupling of the quasiparticles to soft mode phonons at a wave vector different from the charge density wave ordering wave vector.
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Affiliation(s)
- C J Arguello
- Department of Physics, Columbia University, New York, New York 10027, USA
| | - E P Rosenthal
- Department of Physics, Columbia University, New York, New York 10027, USA
| | - E F Andrade
- Department of Physics, Columbia University, New York, New York 10027, USA
| | - W Jin
- Department of Applied Physics and Applied Math, Columbia University, New York, New York 10027, USA
| | - P C Yeh
- Department of Applied Physics and Applied Math, Columbia University, New York, New York 10027, USA
| | - N Zaki
- Department of Electrical Engineering, Columbia University, New York, New York 10027, USA
| | - S Jia
- Department of Chemistry, Princeton University, Princeton, New Jersey 08540, USA
| | - R J Cava
- Department of Chemistry, Princeton University, Princeton, New Jersey 08540, USA
| | - R M Fernandes
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - A J Millis
- Department of Physics, Columbia University, New York, New York 10027, USA
| | - T Valla
- Brookhaven National Laboratory, Upton, New York 11973, USA
| | - R M Osgood
- Department of Electrical Engineering, Columbia University, New York, New York 10027, USA and Department of Chemistry, Princeton University, Princeton, New Jersey 08540, USA
| | - A N Pasupathy
- Department of Physics, Columbia University, New York, New York 10027, USA
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48
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Okamoto JI, Arguello CJ, Rosenthal EP, Pasupathy AN, Millis AJ. Experimental evidence for a Bragg glass density wave phase in a transition-metal dichalcogenide. Phys Rev Lett 2015; 114:026802. [PMID: 25635556 DOI: 10.1103/physrevlett.114.026802] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2014] [Indexed: 06/04/2023]
Abstract
Analysis of the spatial dependence of current-voltage characteristics obtained from scanning tunneling microscopy experiments indicates that the charge density wave (CDW) occurring in NbSe_{2} is subject to locally strong pinning by a non-negligible density of defects, but that on the length scales accessible in this experiment the material is in a "Bragg glass" phase where dislocations and antidislocations occur in bound pairs and free dislocations are not observed. An analysis based on a Landau theory is presented showing how a strong local modulation may produce only a weak long range effect on the CDW phase.
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Affiliation(s)
- Jun-Ichi Okamoto
- Department of Physics, Columbia University, 538 West 120th Street, New York, New York 10027, USA
| | - Carlos J Arguello
- Department of Physics, Columbia University, 538 West 120th Street, New York, New York 10027, USA
| | - Ethan P Rosenthal
- Department of Physics, Columbia University, 538 West 120th Street, New York, New York 10027, USA
| | - Abhay N Pasupathy
- Department of Physics, Columbia University, 538 West 120th Street, New York, New York 10027, USA
| | - Andrew J Millis
- Department of Physics, Columbia University, 538 West 120th Street, New York, New York 10027, USA
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49
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Zabet-Khosousi A, Zhao L, Pálová L, Hybertsen MS, Reichman DR, Pasupathy AN, Flynn GW. Segregation of Sublattice Domains in Nitrogen-Doped Graphene. J Am Chem Soc 2014; 136:1391-7. [DOI: 10.1021/ja408463g] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- Amir Zabet-Khosousi
- Department
of Chemistry, Columbia University, New York, New York 10027, United States
| | - Liuyan Zhao
- Department
of Physics, Columbia University, New York, New York 10027, United States
| | - Lucia Pálová
- Department
of Chemistry, Columbia University, New York, New York 10027, United States
| | - Mark S. Hybertsen
- Center
for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973, United States
| | - David R. Reichman
- Department
of Chemistry, Columbia University, New York, New York 10027, United States
| | - Abhay N. Pasupathy
- Department
of Physics, Columbia University, New York, New York 10027, United States
| | - George W. Flynn
- Department
of Chemistry, Columbia University, New York, New York 10027, United States
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50
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Zhao L, Levendorf M, Goncher S, Schiros T, Pálová L, Zabet-Khosousi A, Rim KT, Gutiérrez C, Nordlund D, Jaye C, Hybertsen M, Reichman D, Flynn GW, Park J, Pasupathy AN. Local atomic and electronic structure of boron chemical doping in monolayer graphene. Nano Lett 2013; 13:4659-65. [PMID: 24032458 DOI: 10.1021/nl401781d] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
We use scanning tunneling microscopy and X-ray spectroscopy to characterize the atomic and electronic structure of boron-doped and nitrogen-doped graphene created by chemical vapor deposition on copper substrates. Microscopic measurements show that boron, like nitrogen, incorporates into the carbon lattice primarily in the graphitic form and contributes ~0.5 carriers into the graphene sheet per dopant. Density functional theory calculations indicate that boron dopants interact strongly with the underlying copper substrate while nitrogen dopants do not. The local bonding differences between graphitic boron and nitrogen dopants lead to large scale differences in dopant distribution. The distribution of dopants is observed to be completely random in the case of boron, while nitrogen displays strong sublattice clustering. Structurally, nitrogen-doped graphene is relatively defect-free while boron-doped graphene films show a large number of Stone-Wales defects. These defects create local electronic resonances and cause electronic scattering, but do not electronically dope the graphene film.
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Affiliation(s)
- Liuyan Zhao
- Department of Physics, Columbia University , New York, New York 10027, United States
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