1
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Kumar AM, Yagodkin D, Rosati R, Bock DJ, Schattauer C, Tobisch S, Hagel J, Höfer B, Kirchhof JN, Hernández López P, Burfeindt K, Heeg S, Gahl C, Libisch F, Malic E, Bolotin KI. Strain fingerprinting of exciton valley character in 2D semiconductors. Nat Commun 2024; 15:7546. [PMID: 39214968 PMCID: PMC11364664 DOI: 10.1038/s41467-024-51195-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2024] [Accepted: 07/30/2024] [Indexed: 09/04/2024] Open
Abstract
Intervalley excitons with electron and hole wavefunctions residing in different valleys determine the long-range transport and dynamics observed in many semiconductors. However, these excitons with vanishing oscillator strength do not directly couple to light and, hence, remain largely unstudied. Here, we develop a simple nanomechanical technique to control the energy hierarchy of valleys via their contrasting response to mechanical strain. We use our technique to discover previously inaccessible intervalley excitons associated with K, Γ, or Q valleys in prototypical 2D semiconductors WSe2 and WS2. We also demonstrate a new brightening mechanism, rendering an otherwise "dark" intervalley exciton visible via strain-controlled hybridization with an intravalley exciton. Moreover, we classify various localized excitons from their distinct strain response and achieve large tuning of their energy. Overall, our valley engineering approach establishes a new way to identify intervalley excitons and control their interactions in a diverse class of 2D systems.
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Affiliation(s)
- Abhijeet M Kumar
- Department of Physics, Freie Universität Berlin, Arnimallee 14, Berlin, Germany
| | - Denis Yagodkin
- Department of Physics, Freie Universität Berlin, Arnimallee 14, Berlin, Germany
| | - Roberto Rosati
- Philipps-Universität Marburg, Mainzer Gasse 33, Marburg, Germany
| | - Douglas J Bock
- Department of Physics, Freie Universität Berlin, Arnimallee 14, Berlin, Germany
| | - Christoph Schattauer
- Institute for Theoretical Physics, TU Wien, Wiedner Hauptstraße 8-10, Vienna, Austria
| | - Sarah Tobisch
- Institute for Theoretical Physics, TU Wien, Wiedner Hauptstraße 8-10, Vienna, Austria
| | - Joakim Hagel
- Department of Physics, Chalmers University of Technology, 412 96 Gothenburg, Gothenburg, Sweden
| | - Bianca Höfer
- Department of Physics, Freie Universität Berlin, Arnimallee 14, Berlin, Germany
| | - Jan N Kirchhof
- Department of Physics, Freie Universität Berlin, Arnimallee 14, Berlin, Germany
- Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, Delft, The Netherlands
| | - Pablo Hernández López
- Institute for Physics and IRIS Adlershof, Humboldt-Universität Berlin, Newtonstraße 15, Berlin, Germany
| | - Kenneth Burfeindt
- Department of Physics, Freie Universität Berlin, Arnimallee 14, Berlin, Germany
| | - Sebastian Heeg
- Institute for Physics and IRIS Adlershof, Humboldt-Universität Berlin, Newtonstraße 15, Berlin, Germany
| | - Cornelius Gahl
- Department of Physics, Freie Universität Berlin, Arnimallee 14, Berlin, Germany
| | - Florian Libisch
- Institute for Theoretical Physics, TU Wien, Wiedner Hauptstraße 8-10, Vienna, Austria
| | - Ermin Malic
- Philipps-Universität Marburg, Mainzer Gasse 33, Marburg, Germany
| | - Kirill I Bolotin
- Department of Physics, Freie Universität Berlin, Arnimallee 14, Berlin, Germany.
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2
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Seiler AM, Statz M, Weimer I, Jacobsen N, Watanabe K, Taniguchi T, Dong Z, Levitov LS, Weitz RT. Interaction-Driven Quasi-Insulating Ground States of Gapped Electron-Doped Bilayer Graphene. PHYSICAL REVIEW LETTERS 2024; 133:066301. [PMID: 39178453 DOI: 10.1103/physrevlett.133.066301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2023] [Revised: 03/11/2024] [Accepted: 06/26/2024] [Indexed: 08/25/2024]
Abstract
Bernal bilayer graphene has recently been discovered to exhibit a wide range of unique ordered phases resulting from interaction-driven effects and encompassing spin and valley magnetism, correlated insulators, correlated metals, and superconductivity. This Letter reports on a novel family of correlated phases characterized by spin and valley ordering, distinct from those reported previously. These phases emerge in electron-doped bilayer graphene where the energy bands are exceptionally flat, manifested through an intriguing nonlinear current-bias behavior that occurs at the onset of the phases and is accompanied by an insulating temperature dependence. These characteristics align with the presence of charge- or spin-density-wave states that open a gap on a portion of the Fermi surface or fully gapped Wigner crystals, resulting in an exceptionally intricate phase diagram.
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3
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Karmakar A, Al-Mahboob A, Zawadzka N, Raczyński M, Yang W, Arfaoui M, Gayatri, Kucharek J, Sadowski JT, Shin HS, Babiński A, Pacuski W, Kazimierczuk T, Molas MR. Twisted MoSe 2 Homobilayer Behaving as a Heterobilayer. NANO LETTERS 2024; 24:9459-9467. [PMID: 39042710 PMCID: PMC11311526 DOI: 10.1021/acs.nanolett.4c01764] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2024] [Revised: 07/11/2024] [Accepted: 07/11/2024] [Indexed: 07/25/2024]
Abstract
Heterostructures (HSs) formed by the transition-metal dichalcogenide materials have shown great promise in next-generation (opto)electronic applications. An artificially twisted HS allows us to manipulate the optical and electronic properties. In this work, we introduce the understanding of the energy transfer (ET) process governed by the dipolar interaction in a twisted molybdenum diselenide (MoSe2) homobilayer without any charge-blocking interlayer. We fabricated an unconventional homobilayer (i.e., HS) with a large twist angle (∼57°) by combining the chemical vapor deposition (CVD) and mechanical exfoliation (Exf.) techniques to fully exploit the lattice parameter mismatch and indirect/direct (CVD/Exf.) bandgap nature. These effectively weaken the interlayer charge transfer and allow the ET to control the carrier recombination channels. Our experimental and theoretical results explain a massive HS photoluminescence enhancement due to an efficient ET process. This work shows that the electronically decoupled MoSe2 homobilayer is coupled by the ET process, mimicking a "true" heterobilayer nature.
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Affiliation(s)
- Arka Karmakar
- Institute
of Experimental Physics, Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland
| | - Abdullah Al-Mahboob
- Center
for Functional Nanomaterials, Brookhaven
National Laboratory, Upton, New York 11973, United States
| | - Natalia Zawadzka
- Institute
of Experimental Physics, Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland
| | - Mateusz Raczyński
- Institute
of Experimental Physics, Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland
| | - Weiguang Yang
- Department
of Chemistry, Ulsan National Institute of
Science and Technology, Ulsan 44919, Republic
of Korea
| | - Mehdi Arfaoui
- Département
de Physique, Faculté des Sciences de Tunis, Université Tunis El Manar, Campus Universitaire, 1060 Tunis, Tunisia
| | - Gayatri
- Institute
of Experimental Physics, Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland
| | - Julia Kucharek
- Institute
of Experimental Physics, Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland
| | - Jerzy T. Sadowski
- Center
for Functional Nanomaterials, Brookhaven
National Laboratory, Upton, New York 11973, United States
| | - Hyeon Suk Shin
- Department
of Chemistry, Ulsan National Institute of
Science and Technology, Ulsan 44919, Republic
of Korea
- Center
for 2D Quantum Heterostructures, Institute
for Basic Science (IBS), Suwon 16419, Republic
of Korea
- Department
of Energy Science, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Adam Babiński
- Institute
of Experimental Physics, Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland
| | - Wojciech Pacuski
- Institute
of Experimental Physics, Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland
| | - Tomasz Kazimierczuk
- Institute
of Experimental Physics, Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland
| | - Maciej R. Molas
- Institute
of Experimental Physics, Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland
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4
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Ju Q, Cai Q, Jian C, Hong W, Sun F, Wang B, Liu W. Infrared Interlayer Excitons in Twist-Free MoTe 2/MoS 2 Heterobilayers. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024; 36:e2404371. [PMID: 39007276 DOI: 10.1002/adma.202404371] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2024] [Revised: 06/13/2024] [Indexed: 07/16/2024]
Abstract
Excitonic devices based on interlayer excitons in van der Waals heterobilayers are a promising platform for advancing photoelectric interconnection telecommunications. However, the absence of exciton emission in the crucial telecom C-band has constrained their practical applications. Here, this limitation is addressed by reporting exciton emission at 0.8 eV (1550 nm) in a chemically vapor-deposited, strictly aligned MoTe2/MoS2 heterobilayer, resulting from the direct bandgap transitions of interlayer excitons as identified by momentum-space imaging of their electrons and holes. The decay mechanisms dominated by direct radiative recombination ensure constant emission quantum yields, a basic demand for efficient excitonic devices. The atomically sharp interface enables the resolution of two narrowly-splitter transitions induced by spin-orbit coupling, further distinguished through the distinct Landé g-factors as the fingerprint of spin configurations. By electrical control, the double transitions coupling into opposite circularly-polarized photon modes, preserve or reverse the helicities of the incident light with a degree of polarization up to 90%. The Stark effect tuning extends the emission energy range by over 150 meV (270 nm), covering the telecom C-band. The findings provide a material platform for studying the excitonic complexes and significantly boost the application prospects of excitonic devices in silicon photonics and all-optical telecommunications.
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Affiliation(s)
- Qiankun Ju
- CAS Key Laboratory of Design and Assembly of Functional Nanostructures, Fujian Provincial Key Laboratory of Materials and Techniques toward Hydrogen Energy, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian, 350002, P. R. China
- University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
| | - Qian Cai
- CAS Key Laboratory of Design and Assembly of Functional Nanostructures, Fujian Provincial Key Laboratory of Materials and Techniques toward Hydrogen Energy, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian, 350002, P. R. China
| | - Chuanyong Jian
- CAS Key Laboratory of Design and Assembly of Functional Nanostructures, Fujian Provincial Key Laboratory of Materials and Techniques toward Hydrogen Energy, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian, 350002, P. R. China
| | - Wenting Hong
- CAS Key Laboratory of Design and Assembly of Functional Nanostructures, Fujian Provincial Key Laboratory of Materials and Techniques toward Hydrogen Energy, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian, 350002, P. R. China
| | - Fapeng Sun
- CAS Key Laboratory of Design and Assembly of Functional Nanostructures, Fujian Provincial Key Laboratory of Materials and Techniques toward Hydrogen Energy, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian, 350002, P. R. China
- University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
| | - Bicheng Wang
- CAS Key Laboratory of Design and Assembly of Functional Nanostructures, Fujian Provincial Key Laboratory of Materials and Techniques toward Hydrogen Energy, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian, 350002, P. R. China
| | - Wei Liu
- CAS Key Laboratory of Design and Assembly of Functional Nanostructures, Fujian Provincial Key Laboratory of Materials and Techniques toward Hydrogen Energy, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian, 350002, P. R. China
- Fujian Science & Technology Innovation Laboratory for Optoelectronic Information of China, Fuzhou, Fujian, 350108, P. R. China
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5
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Beaulieu S, Dong S, Christiansson V, Werner P, Pincelli T, Ziegler JD, Taniguchi T, Watanabe K, Chernikov A, Wolf M, Rettig L, Ernstorfer R, Schüler M. Berry curvature signatures in chiroptical excitonic transitions. SCIENCE ADVANCES 2024; 10:eadk3897. [PMID: 38941460 PMCID: PMC11212730 DOI: 10.1126/sciadv.adk3897] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Accepted: 05/24/2024] [Indexed: 06/30/2024]
Abstract
The topology of the electronic band structure of solids can be described by its Berry curvature distribution across the Brillouin zone. We theoretically introduce and experimentally demonstrate a general methodology based on the measurement of energy- and momentum-resolved optical transition rates, allowing to reveal signatures of Berry curvature texture in reciprocal space. By performing time- and angle-resolved photoemission spectroscopy of atomically thin WSe2 using polarization-modulated excitations, we demonstrate that excitons become an asset in extracting the quantum geometrical properties of solids. We also investigate the resilience of our measurement protocol against ultrafast scattering processes following direct chiroptical transitions.
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Affiliation(s)
- Samuel Beaulieu
- Université de Bordeaux - CNRS - CEA, CELIA, UMR5107, F33405 Talence, France
| | - Shuo Dong
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
| | | | - Philipp Werner
- Department of Physics, University of Fribourg, 1700 Fribourg, Switzerland
| | - Tommaso Pincelli
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
- Institut für Optik und Atomare Physik, Technische Universität Berlin, Strasse des 17 Juni 135, 10623 Berlin, Germany
| | - Jonas D. Ziegler
- Institute of Applied Physics and Würzburg-Dresden Cluster of Excellence ct.qmat, Technische Universität Dresden, 01062 Dresden, Germany
| | - 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
| | - Alexey Chernikov
- Institute of Applied Physics and Würzburg-Dresden Cluster of Excellence ct.qmat, Technische Universität Dresden, 01062 Dresden, Germany
| | - Martin Wolf
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
| | - Laurenz Rettig
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
| | - Ralph Ernstorfer
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
- Institut für Optik und Atomare Physik, Technische Universität Berlin, Strasse des 17 Juni 135, 10623 Berlin, Germany
| | - Michael Schüler
- Laboratory for Materials Simulations, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
- Department of Physics, University of Fribourg, CH-1700 Fribourg, Switzerland
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6
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Luo W, Song R, Whetten BG, Huang D, Cheng X, Belyanin A, Jiang T, Raschke MB. Nonlinear Nano-Imaging of Interlayer Coupling in 2D Graphene-Semiconductor Heterostructures. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2024; 20:e2307345. [PMID: 38279570 DOI: 10.1002/smll.202307345] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2023] [Revised: 12/13/2023] [Indexed: 01/28/2024]
Abstract
The emergent electronic, spin, and other quantum properties of 2D heterostructures of graphene and transition metal dichalcogenides are controlled by the underlying interlayer coupling and associated charge and energy transfer dynamics. However, these processes are sensitive to interlayer distance and crystallographic orientation, which are in turn affected by defects, grain boundaries, or other nanoscale heterogeneities. This obfuscates the distinction between interlayer charge and energy transfer. Here, nanoscale imaging in coherent four-wave mixing (FWM) and incoherent two-photon photoluminescence (2PPL) is combined with a tip distance-dependent coupled rate equation model to resolve the underlying intra- and inter-layer dynamics while avoiding the influence of structural heterogeneities in mono- to multi-layer graphene/WSe2 heterostructures. With selective insertion of hBN spacer layers, it is shown that energy, as opposed to charge transfer, dominates the interlayer-coupled optical response. From the distinct nano-FWM and -2PPL tip-sample distance-dependent modification of interlayer and intralayer relaxation by tip-induced enhancement and quenching, an interlayer energy transfer time ofτ ET ≈ ( 0 . 35 - 0.15 + 0.65 ) $\tau _{\rm ET} \approx (0.35^{+0.65}_{-0.15})$ ps consistent with recent reports is derived. As a local probe technique, this approach highlights the ability to determine intrinsic sample properties even in the presence of large sample heterogeneity.
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Affiliation(s)
- Wenjin Luo
- MOE Key Laboratory of Advanced Micro-Structured Materials, Shanghai Frontiers Science Center of Digital Optics, Institute of Precision Optical Engineering and School of Physics Science and Engineering Tongji University, Shanghai, 200092, China
- Department of Physics and JILA, University of Colorado, Boulder, CO, 80309, USA
| | - Renkang Song
- MOE Key Laboratory of Advanced Micro-Structured Materials, Shanghai Frontiers Science Center of Digital Optics, Institute of Precision Optical Engineering and School of Physics Science and Engineering Tongji University, Shanghai, 200092, China
| | - Benjamin G Whetten
- Department of Physics and JILA, University of Colorado, Boulder, CO, 80309, USA
| | - Di Huang
- MOE Key Laboratory of Advanced Micro-Structured Materials, Shanghai Frontiers Science Center of Digital Optics, Institute of Precision Optical Engineering and School of Physics Science and Engineering Tongji University, Shanghai, 200092, China
| | - Xinbin Cheng
- MOE Key Laboratory of Advanced Micro-Structured Materials, Shanghai Frontiers Science Center of Digital Optics, Institute of Precision Optical Engineering and School of Physics Science and Engineering Tongji University, Shanghai, 200092, China
| | - Alexey Belyanin
- Department of Physics and Astronomy, Texas A&M University, College Station, TX, 77843, USA
| | - Tao Jiang
- MOE Key Laboratory of Advanced Micro-Structured Materials, Shanghai Frontiers Science Center of Digital Optics, Institute of Precision Optical Engineering and School of Physics Science and Engineering Tongji University, Shanghai, 200092, China
| | - Markus B Raschke
- Department of Physics and JILA, University of Colorado, Boulder, CO, 80309, USA
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7
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Catanzaro A, Genco A, Louca C, Ruiz-Tijerina DA, Gillard DJ, Sortino L, Kozikov A, Alexeev EM, Pisoni R, Hague L, Watanabe K, Taniguchi T, Ensslin K, Novoselov KS, Fal'ko V, Tartakovskii AI. Resonant Band Hybridization in Alloyed Transition Metal Dichalcogenide Heterobilayers. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024; 36:e2309644. [PMID: 38279553 DOI: 10.1002/adma.202309644] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Revised: 12/20/2023] [Indexed: 01/28/2024]
Abstract
Bandstructure engineering using alloying is widely utilized for achieving optimized performance in modern semiconductor devices. While alloying has been studied in monolayer transition metal dichalcogenides, its application in van der Waals heterostructures built from atomically thin layers is largely unexplored. Here, heterobilayers made from monolayers of WSe2 (or MoSe2) and MoxW1 - xSe2 alloy are fabricated and nontrivial tuning of the resultant bandstructure is observed as a function of concentration x. This evolution is monitored by measuring the energy of photoluminescence (PL) of the interlayer exciton (IX) composed of an electron and hole residing in different monolayers. In MoxW1 - xSe2/WSe2, a strong IX energy shift of ≈100 meV is observed for x varied from 1 to 0.6. However, for x < 0.6 this shift saturates and the IX PL energy asymptotically approaches that of the indirect bandgap in bilayer WSe2. This observation is theoretically interpreted as the strong variation of the conduction band K valley for x > 0.6, with IX PL arising from the K - K transition, while for x < 0.6, the bandstructure hybridization becomes prevalent leading to the dominating momentum-indirect K - Q transition. This bandstructure hybridization is accompanied with strong modification of IX PL dynamics and nonlinear exciton properties. This work provides foundation for bandstructure engineering in van der Waals heterostructures highlighting the importance of hybridization effects and opening a way to devices with accurately tailored electronic properties.
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Affiliation(s)
- Alessandro Catanzaro
- Department of Physics and Astronomy, The University of Sheffield, Sheffield, S3 7RH, UK
| | - Armando Genco
- Department of Physics and Astronomy, The University of Sheffield, Sheffield, S3 7RH, UK
- Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci, 32, Milano, 20133, Italy
| | - Charalambos Louca
- Department of Physics and Astronomy, The University of Sheffield, Sheffield, S3 7RH, UK
- Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci, 32, Milano, 20133, Italy
| | - David A Ruiz-Tijerina
- Departamento de Física Química, Instituto de Física, Universidad Nacional Autónoma de México, Ciudad de México, C.P., 04510, Mexico, México
| | - Daniel J Gillard
- Department of Physics and Astronomy, The University of Sheffield, Sheffield, S3 7RH, UK
| | - Luca Sortino
- Department of Physics and Astronomy, The University of Sheffield, Sheffield, S3 7RH, UK
- Chair in Hybrid Nanosystems, Nanoinstitute Munich, Faculty of Physics, Ludwig-Maximilians-Universität München, 80539, Munich, Germany
| | - Aleksey Kozikov
- Department of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK
- School of Mathematics, Statistics and Physics, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK
| | - Evgeny M Alexeev
- Department of Physics and Astronomy, The University of Sheffield, Sheffield, S3 7RH, UK
- Cambridge Graphene Centre, University of Cambridge, 9 J. J. Thomson Avenue, Cambridge, CB3 0FA, UK
| | - Riccardo Pisoni
- Solid State Physics Laboratory, ETH Zurich, Zurich, CH-8093, Switzerland
| | - Lee Hague
- National Graphene Institute, University of Manchester, Manchester, M13 9PL, UK
| | - 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
| | - Klaus Ensslin
- Solid State Physics Laboratory, ETH Zurich, Zurich, CH-8093, Switzerland
| | - Kostya S Novoselov
- Institute for Functional Intelligent Materials, National University of Singapore, Singapore, 117546, Singapore
| | - Vladimir Fal'ko
- Department of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK
- Henry Royce Institute for Advanced Materials, University of Manchester, Manchester, M13 9PL, United Kingdom
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8
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Graham AJ, Park H, Nguyen PV, Nunn J, Kandyba V, Cattelan M, Giampietri A, Barinov A, Watanabe K, Taniguchi T, Andreev A, Rudner M, Xu X, Wilson NR, Cobden DH. Conduction Band Replicas in a 2D Moiré Semiconductor Heterobilayer. NANO LETTERS 2024; 24:5117-5124. [PMID: 38629940 DOI: 10.1021/acs.nanolett.3c04866] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2024]
Abstract
Stacking monolayer semiconductors creates moiré patterns, leading to correlated and topological electronic phenomena, but measurements of the electronic structure underpinning these phenomena are scarce. Here, we investigate the properties of the conduction band in moiré heterobilayers of WS2/WSe2 using submicrometer angle-resolved photoemission spectroscopy with electrostatic gating. We find that at all twist angles the conduction band edge is the K-point valley of the WS2, with a band gap of 1.58 ± 0.03 eV. From the resolved conduction band dispersion, we deduce an effective mass of 0.15 ± 0.02 me. Additionally, we observe replicas of the conduction band displaced by reciprocal lattice vectors of the moiré superlattice. We argue that the replicas result from the moiré potential modifying the conduction band states rather than final-state diffraction. Interestingly, the replicas display an intensity pattern with reduced 3-fold symmetry, which we show implicates the pseudo vector potential associated with in-plane strain in moiré band formation.
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Affiliation(s)
- Abigail J Graham
- Department of Physics, University of Warwick, Coventry CV4 7AL, U.K
| | - Heonjoon Park
- Department of Physics, University of Washington, Seattle, Washington 98195, United States
| | - Paul V Nguyen
- Department of Physics, University of Washington, Seattle, Washington 98195, United States
| | - James Nunn
- Department of Physics, University of Warwick, Coventry CV4 7AL, U.K
| | - Viktor Kandyba
- Elettra - Sincrotrone Trieste, S.C.p.A, Basovizza (TS), Friuli-Venezia Giulia 34149, Italy
| | - Mattia Cattelan
- Elettra - Sincrotrone Trieste, S.C.p.A, Basovizza (TS), Friuli-Venezia Giulia 34149, Italy
| | - Alessio Giampietri
- Elettra - Sincrotrone Trieste, S.C.p.A, Basovizza (TS), Friuli-Venezia Giulia 34149, Italy
| | - Alexei Barinov
- Elettra - Sincrotrone Trieste, S.C.p.A, Basovizza (TS), Friuli-Venezia Giulia 34149, Italy
| | - 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
| | - Anton Andreev
- Department of Physics, University of Washington, Seattle, Washington 98195, United States
| | - Mark Rudner
- Department of Physics, University of Washington, Seattle, Washington 98195, United States
| | - Xiaodong Xu
- Department of Physics, University of Washington, Seattle, Washington 98195, United States
- Department of Materials Science and Engineering, University of Washington, Seattle, Washington 98195, United States
| | - Neil R Wilson
- Department of Physics, University of Warwick, Coventry CV4 7AL, U.K
| | - David H Cobden
- Department of Physics, University of Washington, Seattle, Washington 98195, United States
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9
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Meneghini G, Brem S, Malic E. Excitonic Thermalization Bottleneck in Twisted TMD Heterostructures. NANO LETTERS 2024; 24:4505-4511. [PMID: 38578047 DOI: 10.1021/acs.nanolett.4c00450] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/06/2024]
Abstract
Twisted van der Waals heterostructures show intriguing interface exciton physics, including hybridization effects and emergence of moiré potentials. Recent experiments have revealed that moiré-trapped excitons exhibit remarkable dynamics, where excited states show lifetimes that are several orders of magnitude longer than in monolayers. The origin of this behavior is still under debate. Based on a microscopic many-particle approach, we investigate the phonon-driven relaxation cascade of nonequilibrium moiré excitons in the exemplary MoSe2-WSe2 heterostructure. We track exciton relaxation pathways across different moiré mini-bands and identify the phonon-scattering channels assisting the spatial redistribution of excitons into low-energy pockets of the moiré potential. We unravel a phonon bottleneck in the flat band structure at low twist angles preventing excitons from fully thermalizing into the lowest state, explaining the measured enhanced emission intensity and lifetime of excited moiré excitons. Overall, our work provides important insights into exciton relaxation dynamics in flat-band exciton materials.
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Affiliation(s)
- Giuseppe Meneghini
- Department of Physics, Philipps University of Marburg, 35037 Marburg, Germany
| | - Samuel Brem
- Department of Physics, Philipps University of Marburg, 35037 Marburg, Germany
| | - Ermin Malic
- Department of Physics, Philipps University of Marburg, 35037 Marburg, Germany
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10
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Knorr W, Brem S, Meneghini G, Malic E. Polaron-induced changes in moiré exciton propagation in twisted van der Waals heterostructures. NANOSCALE 2024. [PMID: 38623653 DOI: 10.1039/d4nr00136b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/17/2024]
Abstract
Twisted transition metal dichalcogenides (TMDs) present an intriguing platform for exploring excitons and their transport properties. By introducing a twist angle, a moiré superlattice forms, providing a spatially dependent exciton energy landscape. Based on a microscopic many-particle theory, we investigate in this work polaron-induced changes in exciton transport properties in the exemplary MoSe2/WSe2 heterostructure. We demonstrate that polaron formation and the associated enhancement of the moiré exciton mass lead to a significant band flattening. As a result, the moiré inter-cell tunneling and the propagation velocity undergo noticeable temperature and twist-angle dependent changes. We predict a reduction of the hopping strength ranging from 80% at a twist angle of 1° to 30% at 3° at room temperature. The provided microscopic insights into the spatio-temporal exciton dynamics in presence of a moiré potential further expand the possibilities to tune charge and energy transport in 2D materials.
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Affiliation(s)
- Willy Knorr
- Department of Physics, Philipps University, 35037 Marburg, Germany.
| | - Samuel Brem
- Department of Physics, Philipps University, 35037 Marburg, Germany.
| | | | - Ermin Malic
- Department of Physics, Philipps University, 35037 Marburg, Germany.
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11
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Graml M, Zollner K, Hernangómez-Pérez D, Faria Junior PE, Wilhelm J. Low-Scaling GW Algorithm Applied to Twisted Transition-Metal Dichalcogenide Heterobilayers. J Chem Theory Comput 2024; 20:2202-2208. [PMID: 38353944 PMCID: PMC10938508 DOI: 10.1021/acs.jctc.3c01230] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2023] [Revised: 12/30/2023] [Accepted: 01/08/2024] [Indexed: 03/13/2024]
Abstract
The GW method is widely used for calculating the electronic band structure of materials. The high computational cost of GW algorithms prohibits their application to many systems of interest. We present a periodic, low-scaling, and highly efficient GW algorithm that benefits from the locality of the Gaussian basis and the polarizability. The algorithm enables G0W0 calculations on a MoSe2/WS2 bilayer with 984 atoms per unit cell, in 42 h using 1536 cores. This is 4 orders of magnitude faster than a plane-wave G0W0 algorithm, allowing for unprecedented computational studies of electronic excitations at the nanoscale.
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Affiliation(s)
- Maximilian Graml
- Institute
of Theoretical Physics, University of Regensburg, 93053 Regensburg, Germany
- Regensburg
Center for Ultrafast Nanoscopy (RUN), University
of Regensburg, 93053 Regensburg, Germany
| | - Klaus Zollner
- Institute
of Theoretical Physics, University of Regensburg, 93053 Regensburg, Germany
| | - Daniel Hernangómez-Pérez
- Department
of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Paulo E. Faria Junior
- Institute
of Theoretical Physics, University of Regensburg, 93053 Regensburg, Germany
| | - Jan Wilhelm
- Institute
of Theoretical Physics, University of Regensburg, 93053 Regensburg, Germany
- Regensburg
Center for Ultrafast Nanoscopy (RUN), University
of Regensburg, 93053 Regensburg, Germany
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12
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Dufresne SKY, Zhdanovich S, Michiardi M, Guislain BG, Zonno M, Mazzotti V, O'Brien L, Kung S, Levy G, Mills AK, Boschini F, Jones DJ, Damascelli A. A versatile laser-based apparatus for time-resolved ARPES with micro-scale spatial resolution. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2024; 95:033907. [PMID: 38517258 DOI: 10.1063/5.0176170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2023] [Accepted: 02/28/2024] [Indexed: 03/23/2024]
Abstract
We present the development of a versatile apparatus for 6.2 eV laser-based time and angle-resolved photoemission spectroscopy with micrometer spatial resolution (time-resolved μ-ARPES). With a combination of tunable spatial resolution down to ∼11 μm, high energy resolution (∼11 meV), near-transform-limited temporal resolution (∼280 fs), and tunable 1.55 eV pump fluence up to 3 mJ/cm2, this time-resolved μ-ARPES system enables the measurement of ultrafast electron dynamics in exfoliated and inhomogeneous materials. We demonstrate the performance of our system by correlating the spectral broadening of the topological surface state of Bi2Se3 with the spatial dimension of the probe pulse, as well as resolving the spatial inhomogeneity contribution to the observed spectral broadening. Finally, after in situ exfoliation, we performed time-resolved μ-ARPES on a ∼30 μm flake of transition metal dichalcogenide WTe2, thus demonstrating the ability to access ultrafast electron dynamics with momentum resolution on micro-exfoliated materials.
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Affiliation(s)
- S K Y Dufresne
- Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
- Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
| | - S Zhdanovich
- Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
- Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
| | - M Michiardi
- Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
- Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
| | - B G Guislain
- Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
- Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
| | - M Zonno
- Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
- Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
| | - V Mazzotti
- Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
| | - L O'Brien
- Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
| | - S Kung
- Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
- Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
| | - G Levy
- Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
- Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
| | - A K Mills
- Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
- Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
| | - F Boschini
- Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
- Centre Énergie Matériaux Télécommunications, Institut National de la Recherche Scientifique, Varennes, Québec J3X 1S2, Canada
| | - D J Jones
- Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
- Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
| | - A Damascelli
- Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
- Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
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13
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Bennecke W, Windischbacher A, Schmitt D, Bange JP, Hemm R, Kern CS, D'Avino G, Blase X, Steil D, Steil S, Aeschlimann M, Stadtmüller B, Reutzel M, Puschnig P, Jansen GSM, Mathias S. Disentangling the multiorbital contributions of excitons by photoemission exciton tomography. Nat Commun 2024; 15:1804. [PMID: 38413573 PMCID: PMC10899218 DOI: 10.1038/s41467-024-45973-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2023] [Accepted: 02/08/2024] [Indexed: 02/29/2024] Open
Abstract
Excitons are realizations of a correlated many-particle wave function, specifically consisting of electrons and holes in an entangled state. Excitons occur widely in semiconductors and are dominant excitations in semiconducting organic and low-dimensional quantum materials. To efficiently harness the strong optical response and high tuneability of excitons in optoelectronics and in energy-transformation processes, access to the full wavefunction of the entangled state is critical, but has so far not been feasible. Here, we show how time-resolved photoemission momentum microscopy can be used to gain access to the entangled wavefunction and to unravel the exciton's multiorbital electron and hole contributions. For the prototypical organic semiconductor buckminsterfullerene (C60), we exemplify the capabilities of exciton tomography and achieve unprecedented access to key properties of the entangled exciton state including localization, charge-transfer character, and ultrafast exciton formation and relaxation dynamics.
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Affiliation(s)
- Wiebke Bennecke
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077, Göttingen, Germany
| | - Andreas Windischbacher
- Institute of Physics, University of Graz, NAWI Graz, Universitätsplatz 5, 8010, Graz, Austria
| | - David Schmitt
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077, Göttingen, Germany
| | - Jan Philipp Bange
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077, Göttingen, Germany
| | - Ralf Hemm
- Department of Physics and Research Center OPTIMAS, University of Kaiserslautern-Landau, Erwin-Schrödinger-Straße 46, 67663, Kaiserslautern, Germany
| | - Christian S Kern
- Institute of Physics, University of Graz, NAWI Graz, Universitätsplatz 5, 8010, Graz, Austria
| | - Gabriele D'Avino
- Univ. Grenoble Alpes, CNRS, Inst NEEL, F-38042, Grenoble, France
| | - Xavier Blase
- Univ. Grenoble Alpes, CNRS, Inst NEEL, F-38042, Grenoble, France
| | - Daniel Steil
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077, Göttingen, Germany
| | - Sabine Steil
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077, Göttingen, Germany
| | - Martin Aeschlimann
- Department of Physics and Research Center OPTIMAS, University of Kaiserslautern-Landau, Erwin-Schrödinger-Straße 46, 67663, Kaiserslautern, Germany
| | - Benjamin Stadtmüller
- Department of Physics and Research Center OPTIMAS, University of Kaiserslautern-Landau, Erwin-Schrödinger-Straße 46, 67663, Kaiserslautern, Germany
| | - Marcel Reutzel
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077, Göttingen, Germany
| | - Peter Puschnig
- Institute of Physics, University of Graz, NAWI Graz, Universitätsplatz 5, 8010, Graz, Austria
| | - G S Matthijs Jansen
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077, Göttingen, Germany.
| | - Stefan Mathias
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077, Göttingen, Germany.
- International Center for Advanced Studies of Energy Conversion (ICASEC), University of Göttingen, Göttingen, Germany.
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14
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Ge A, Ge X, Sun L, Lu X, Ma L, Zhao X, Yao B, Zhang X, Zhang T, Jing W, Zhou X, Shen X, Lu W. Unraveling the strain tuning mechanism of interlayer excitons in WSe 2/MoSe 2heterostructure. NANOTECHNOLOGY 2024; 35:175207. [PMID: 38266306 DOI: 10.1088/1361-6528/ad2232] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2023] [Accepted: 01/23/2024] [Indexed: 01/26/2024]
Abstract
Atomically thin transition metal dichalcogenides (TMDs) exhibit rich excitonic physics, due to reduced dielectric screening and strong Coulomb interactions. Especially, some attractive topics in modern condensed matter physics, such as correlated insulator, superconductivity, topological excitons bands, are recently reported in stacking two monolayer (ML) TMDs. Here, we clearly reveal the tuning mechanism of tensile strain on interlayer excitons (IEXs) and intralayer excitons (IAXs) in WSe2/MoSe2heterostructure (HS) at low temperature. We utilize the cryogenic tensile strain platform to stretch the HS, and measure by micro-photoluminescence (μ-PL). The PL peaks redshifts of IEXs and IAXs in WSe2/MoSe2HS under tensile strain are well observed. The first-principles calculations by using density functional theory reveals the PL peaks redshifts of IEXs and IAXs origin from bandgap shrinkage. The calculation results also show the Mo-4d states dominating conduction band minimum shifts of the ML MoSe2plays a dominant role in the redshifts of IEXs. This work provides new insights into understanding the tuning mechanism of tensile strain on IEXs and IAXs in two-dimensional (2D) HS, and paves a way to the development of flexible optoelectronic devices based on 2D materials.
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Affiliation(s)
- Anping Ge
- State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai, 200083, People's Republic of China
- University of Chinese Academy of Sciences, Beijing, 100049, People's Republic of China
| | - Xun Ge
- State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai, 200083, People's Republic of China
| | - Liaoxin Sun
- State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai, 200083, People's Republic of China
- University of Chinese Academy of Sciences, Beijing, 100049, People's Republic of China
| | - Xinle Lu
- Key Laboratory of Polar Materials and Devices, Department of Electronics, East China Normal University, Shanghai, 200241, People's Republic of China
| | - Lei Ma
- State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai, 200083, People's Republic of China
- School of Physical Science and Technology, ShanghaiTech University, Shanghai, 201210, People's Republic of China
| | - Xinchao Zhao
- State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai, 200083, People's Republic of China
- University of Chinese Academy of Sciences, Beijing, 100049, People's Republic of China
| | - Bimu Yao
- State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai, 200083, People's Republic of China
- University of Chinese Academy of Sciences, Beijing, 100049, People's Republic of China
| | - Xin Zhang
- State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai, 200083, People's Republic of China
- Department of Physics, Shanghai Normal University, Shanghai, 200234, People's Republic of China
| | - Tao Zhang
- State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai, 200083, People's Republic of China
- University of Chinese Academy of Sciences, Beijing, 100049, People's Republic of China
| | - Wenji Jing
- State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai, 200083, People's Republic of China
- University of Chinese Academy of Sciences, Beijing, 100049, People's Republic of China
| | - Xiaohao Zhou
- State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai, 200083, People's Republic of China
| | - Xuechu Shen
- State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai, 200083, People's Republic of China
| | - Wei Lu
- State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai, 200083, People's Republic of China
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15
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Bange JP, Schmitt D, Bennecke W, Meneghini G, AlMutairi A, Watanabe K, Taniguchi T, Steil D, Steil S, Weitz RT, Jansen GSM, Hofmann S, Brem S, Malic E, Reutzel M, Mathias S. Probing electron-hole Coulomb correlations in the exciton landscape of a twisted semiconductor heterostructure. SCIENCE ADVANCES 2024; 10:eadi1323. [PMID: 38324690 PMCID: PMC10849592 DOI: 10.1126/sciadv.adi1323] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2023] [Accepted: 01/10/2024] [Indexed: 02/09/2024]
Abstract
In two-dimensional semiconductors, cooperative and correlated interactions determine the material's excitonic properties and can even lead to the creation of correlated states of matter. Here, we study the fundamental two-particle correlated exciton state formed by the Coulomb interaction between single-particle holes and electrons. We find that the ultrafast transfer of an exciton's hole across a type II band-aligned semiconductor heterostructure leads to an unexpected sub-200-femtosecond upshift of the single-particle energy of the electron being photoemitted from the two-particle exciton state. While energy relaxation usually leads to an energetic downshift of the spectroscopic signature, we show that this upshift is a clear fingerprint of the correlated interaction of the electron and hole parts of the exciton. In this way, time-resolved photoelectron spectroscopy is straightforwardly established as a powerful method to access electron-hole correlations and cooperative behavior in quantum materials. Our work highlights this capability and motivates the future study of optically inaccessible correlated excitonic and electronic states of matter.
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Affiliation(s)
- Jan Philipp Bange
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - David Schmitt
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Wiebke Bennecke
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Giuseppe Meneghini
- Fachbereich Physik, Philipps-Universität Marburg, 35032 Marburg, Germany
| | | | - 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
| | - Daniel Steil
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Sabine Steil
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - R. Thomas Weitz
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
- International Center for Advanced Studies of Energy Conversion (ICASEC), University of Göttingen, Göttingen, Germany
| | - G. S. Matthijs Jansen
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Stephan Hofmann
- Department of Engineering, University of Cambridge, Cambridge CB3 0FA, UK
| | - Samuel Brem
- Fachbereich Physik, Philipps-Universität Marburg, 35032 Marburg, Germany
| | - Ermin Malic
- Fachbereich Physik, Philipps-Universität Marburg, 35032 Marburg, Germany
- Department of Physics, Chalmers University of Technology, Gothenburg, Sweden
| | - Marcel Reutzel
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Stefan Mathias
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
- International Center for Advanced Studies of Energy Conversion (ICASEC), University of Göttingen, Göttingen, Germany
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16
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Günder D, Axt M, Witte G. Heteroepitaxy in Organic/TMD Hybrids and Challenge to Achieve it for TMD Monolayers: The Case of Pentacene on WS 2 and WSe 2. ACS APPLIED MATERIALS & INTERFACES 2024; 16:1911-1920. [PMID: 38154080 DOI: 10.1021/acsami.3c15829] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2023]
Abstract
The intriguing photophysical properties of monolayer stacks of different transition-metal dichalcogenides (TMDs), revealing rich exciton physics including interfacial and moiré excitons, have recently prompted an extension of similar investigations to hybrid systems of TMDs and organic films, as the latter combine large photoabsorption cross sections with the ability to tailor energy levels by targeted synthesis. To go beyond single-molecule photoexcitations and exploit the excitonic signatures of organic solids, crystalline molecular films are required. Moreover, a defined registry on the substrate, ideally an epitaxy, is desirable to also achieve an excitonic coupling in momentum space. This poses a certain challenge as excitonic dipole moments of organic films are closely related to the molecular orientation and film structure, which critically depend on the support roughness. Using X-ray diffraction, optical polarization, and atomic force microscopy, we analyzed the structure of pentacene (PEN) multilayer films grown on WSe2(001) and WS2(001) and identified an epitaxial alignment. While (022)-oriented PEN films are formed on both substrates, their azimuthal orientations are quite different, showing an alignment of the molecular L-axis along the ⟨ 110 ⟩ WSe 2 and ⟨ 100 ⟩ WS 2 directions. This intrinsic epitaxial PEN growth depends, however, sensitively on the substrates surface quality. While it occurs on exfoliated TMD single crystals and multilayer flakes, it is hardly found on exfoliated monolayers, which often exhibit bubbles and wrinkles. This enhances the surface roughness and results in (001)-oriented PEN films with upright molecular orientation but without any azimuthal alignment. However, monolayer flakes can be smoothed by AFM operated in contact mode or by transferring to ultrasmooth substrates such as hBN, which again yields epitaxial PEN films. As different PEN orientations result in different characteristic film morphologies (elongated mesa islands vs pyramidal dendrites), which can be easily distinguished by AFM or optical microscopy, this provides a simple means to judge the roughness of the used TMD surface.
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Affiliation(s)
- Darius Günder
- Molekulare Festkörperphysik, Philipps-Universität Marburg, Marburg 35032, Germany
| | - Marleen Axt
- Oberflächenphysik, Philipps-Universität Marburg, Marburg 35032, Germany
| | - Gregor Witte
- Molekulare Festkörperphysik, Philipps-Universität Marburg, Marburg 35032, Germany
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17
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Lei Y, Xie X, Ma H, Ma J. Vitality of Intralayer Vibration in hBN for Effective Long-Range Interlayer Hole Transfer across High Barriers in MoSe 2/hBN/WSe 2 Heterostructures. J Phys Chem Lett 2023:11190-11199. [PMID: 38055859 DOI: 10.1021/acs.jpclett.3c03040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/08/2023]
Abstract
Introducing the two-dimensional (2D) hexagonal boron nitride (hBN) between 2D transition metal dichalcogenide (TMD) layers promises convenient manipulation of the interlayer exciton (IX) and interlayer charge transfer in TMD/hBN/TMD heterostructures, while the role of inserted hBN layers during IX formation is controversial. Employing ab initio nonadiabatic molecular dynamics (NAMD) simulations and the electron-phonon coupling model, we systematically investigate interlayer hole transfer in MoSe2/WSe2 bilayers intercalated by hBN layers with various thicknesses. The conventional direct hole transfer from MoSe2 to WSe2 is decelerated by 2-3 orders of magnitude after the hBN insertion. Meanwhile, a novel channel intermediated by a deeper hole of WSe2 becomes dominant, where the intralayer shear mode of hBN plays a crucial role by reducing the energy barriers for this new channel. The unique role of hBN layers is revealed for the first time, enriching the knowledge of the underlying microscopic mechanisms and providing instructive guidance to practical van der Waals optoelectronic devices.
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Affiliation(s)
- Yuli Lei
- Key Laboratory of Mesoscopic Chemistry of Ministry of Education, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Xiaoyu Xie
- Qingdao Institute for Theoretical and Computational Sciences, Qingdao Institute of Frontier and Interdisciplinary Science, Shandong University, Qingdao 266237, China
| | - Haibo Ma
- Qingdao Institute for Theoretical and Computational Sciences, Qingdao Institute of Frontier and Interdisciplinary Science, Shandong University, Qingdao 266237, China
| | - Jing Ma
- Key Laboratory of Mesoscopic Chemistry of Ministry of Education, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
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18
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Policht VR, Mittenzwey H, Dogadov O, Katzer M, Villa A, Li Q, Kaiser B, Ross AM, Scotognella F, Zhu X, Knorr A, Selig M, Cerullo G, Dal Conte S. Time-domain observation of interlayer exciton formation and thermalization in a MoSe 2/WSe 2 heterostructure. Nat Commun 2023; 14:7273. [PMID: 37949848 PMCID: PMC10638375 DOI: 10.1038/s41467-023-42915-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2023] [Accepted: 10/26/2023] [Indexed: 11/12/2023] Open
Abstract
Vertical heterostructures of transition metal dichalcogenides (TMDs) host interlayer excitons with electrons and holes residing in different layers. With respect to their intralayer counterparts, interlayer excitons feature longer lifetimes and diffusion lengths, paving the way for room temperature excitonic optoelectronic devices. The interlayer exciton formation process and its underlying physical mechanisms are largely unexplored. Here we use ultrafast transient absorption spectroscopy with a broadband white-light probe to simultaneously resolve interlayer charge transfer and interlayer exciton formation dynamics in a MoSe2/WSe2 heterostructure. We observe an interlayer exciton formation timescale nearly an order of magnitude (~1 ps) longer than the interlayer charge transfer time (~100 fs). Microscopic calculations attribute this relative delay to an interplay of a phonon-assisted interlayer exciton cascade and thermalization, and excitonic wave-function overlap. Our results may explain the efficient photocurrent generation observed in optoelectronic devices based on TMD heterostructures, as the interlayer excitons are able to dissociate during thermalization.
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Affiliation(s)
- Veronica R Policht
- Department of Physics, Politecnico di Milano, Piazza Leonardo da Vinci 32, Milano, 20133, Italy.
- NRC Postdoc residing at U.S. Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, DC, 20375, USA.
| | - Henry Mittenzwey
- Institut für Theoretische Physik, Nichtlineare Optik und Quantenelektronik, Technische Universität Berlin, Hardenbergstraße 36, 10623, Berlin, Germany.
| | - Oleg Dogadov
- Department of Physics, Politecnico di Milano, Piazza Leonardo da Vinci 32, Milano, 20133, Italy
| | - Manuel Katzer
- Institut für Theoretische Physik, Nichtlineare Optik und Quantenelektronik, Technische Universität Berlin, Hardenbergstraße 36, 10623, Berlin, Germany
| | - Andrea Villa
- Department of Physics, Politecnico di Milano, Piazza Leonardo da Vinci 32, Milano, 20133, Italy
| | - Qiuyang Li
- Department of Chemistry, Columbia University, 3000 Broadway, New York, NY, 10027, USA
| | | | - Aaron M Ross
- Department of Physics, Politecnico di Milano, Piazza Leonardo da Vinci 32, Milano, 20133, Italy
| | - Francesco Scotognella
- Department of Physics, Politecnico di Milano, Piazza Leonardo da Vinci 32, Milano, 20133, Italy
- Department of Applied Science and Technology, Politecnico di Torino, Corso Duca degli Abruzzi 24, Torino, 10129, Italy
| | - Xiaoyang Zhu
- Department of Chemistry, Columbia University, 3000 Broadway, New York, NY, 10027, USA
| | - Andreas Knorr
- Institut für Theoretische Physik, Nichtlineare Optik und Quantenelektronik, Technische Universität Berlin, Hardenbergstraße 36, 10623, Berlin, Germany
| | - Malte Selig
- Institut für Theoretische Physik, Nichtlineare Optik und Quantenelektronik, Technische Universität Berlin, Hardenbergstraße 36, 10623, Berlin, Germany
| | - Giulio Cerullo
- Department of Physics, Politecnico di Milano, Piazza Leonardo da Vinci 32, Milano, 20133, Italy
- CNR-IFN, Piazza Leonardo da Vinci 32, Milano, 20133, Italy
| | - Stefano Dal Conte
- Department of Physics, Politecnico di Milano, Piazza Leonardo da Vinci 32, Milano, 20133, Italy.
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19
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Domröse T, Danz T, Schaible SF, Rossnagel K, Yalunin SV, Ropers C. Light-induced hexatic state in a layered quantum material. NATURE MATERIALS 2023; 22:1345-1351. [PMID: 37414945 PMCID: PMC10627829 DOI: 10.1038/s41563-023-01600-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2022] [Accepted: 06/05/2023] [Indexed: 07/08/2023]
Abstract
The tunability of materials properties by light promises a wealth of future applications in energy conversion and information technology. Strongly correlated materials such as transition metal dichalcogenides offer optical control of electronic phases, charge ordering and interlayer correlations by photodoping. Here, we find the emergence of a transient hexatic state during the laser-induced transformation between two charge-density wave phases in a thin-film transition metal dichalcogenide, 1T-type tantalum disulfide (1T-TaS2). Introducing tilt-series ultrafast nanobeam electron diffraction, we reconstruct charge-density wave rocking curves at high momentum resolution. An intermittent suppression of three-dimensional structural correlations promotes a loss of in-plane translational order caused by a high density of unbound topological defects, characteristic of a hexatic intermediate. Our results demonstrate the merit of tomographic ultrafast structural probing in tracing coupled order parameters, heralding universal nanoscale access to laser-induced dimensionality control in functional heterostructures and devices.
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Affiliation(s)
- Till Domröse
- Department of Ultrafast Dynamics, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
- 4th Physical Institute - Solids and Nanostructures, University of Göttingen, Göttingen, Germany
| | - Thomas Danz
- Department of Ultrafast Dynamics, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Sophie F Schaible
- 4th Physical Institute - Solids and Nanostructures, University of Göttingen, Göttingen, Germany
| | - Kai Rossnagel
- Institute of Experimental and Applied Physics, Kiel University, Kiel, Germany
- Ruprecht Haensel Laboratory, Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany
| | - Sergey V Yalunin
- Department of Ultrafast Dynamics, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Claus Ropers
- Department of Ultrafast Dynamics, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany.
- 4th Physical Institute - Solids and Nanostructures, University of Göttingen, Göttingen, Germany.
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20
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Fang H, Lin Q, Zhang Y, Thompson J, Xiao S, Sun Z, Malic E, Dash SP, Wieczorek W. Localization and interaction of interlayer excitons in MoSe 2/WSe 2 heterobilayers. Nat Commun 2023; 14:6910. [PMID: 37903787 PMCID: PMC10616232 DOI: 10.1038/s41467-023-42710-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Accepted: 10/19/2023] [Indexed: 11/01/2023] Open
Abstract
Transition metal dichalcogenide (TMD) heterobilayers provide a versatile platform to explore unique excitonic physics via the properties of the constituent TMDs and external stimuli. Interlayer excitons (IXs) can form in TMD heterobilayers as delocalized or localized states. However, the localization of IX in different types of potential traps, the emergence of biexcitons in the high-excitation regime, and the impact of potential traps on biexciton formation have remained elusive. In our work, we observe two types of potential traps in a MoSe2/WSe2 heterobilayer, which result in significantly different emission behavior of IXs at different temperatures. We identify the origin of these traps as localized defect states and the moiré potential of the TMD heterobilayer. Furthermore, with strong excitation intensity, a superlinear emission behavior indicates the emergence of interlayer biexcitons, whose formation peaks at a specific temperature. Our work elucidates the different excitation and temperature regimes required for the formation of both localized and delocalized IX and biexcitons and, thus, contributes to a better understanding and application of the rich exciton physics in TMD heterostructures.
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Affiliation(s)
- Hanlin Fang
- Department of Microtechnology and Nanoscience (MC2), Chalmers University of Technology, 41296, Gothenburg, Sweden.
| | - Qiaoling Lin
- Department of Electrical and Photonics Engineering, Technical University of Denmark, DK-2800, Kongens Lyngby, Denmark
| | - Yi Zhang
- Department of Electronics and Nanoengineering and QTF Centre of Excellence, Aalto University, Espoo, 02150, Finland
| | - Joshua Thompson
- Department of Physics, Philipps-Universität Marburg, 35037, Marburg, Germany
| | - Sanshui Xiao
- Department of Electrical and Photonics Engineering, Technical University of Denmark, DK-2800, Kongens Lyngby, Denmark
| | - Zhipei Sun
- Department of Electronics and Nanoengineering and QTF Centre of Excellence, Aalto University, Espoo, 02150, Finland
| | - Ermin Malic
- Department of Physics, Philipps-Universität Marburg, 35037, Marburg, Germany
| | - Saroj P Dash
- Department of Microtechnology and Nanoscience (MC2), Chalmers University of Technology, 41296, Gothenburg, Sweden
| | - Witlef Wieczorek
- Department of Microtechnology and Nanoscience (MC2), Chalmers University of Technology, 41296, Gothenburg, Sweden.
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21
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Yagodkin D, Kumar A, Ankerhold E, Richter J, Watanabe K, Taniguchi T, Gahl C, Bolotin KI. Probing the Formation of Dark Interlayer Excitons via Ultrafast Photocurrent. NANO LETTERS 2023; 23:9212-9218. [PMID: 37788809 PMCID: PMC10603811 DOI: 10.1021/acs.nanolett.3c01708] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2023] [Revised: 08/15/2023] [Indexed: 10/05/2023]
Abstract
Optically dark excitons determine a wide range of properties of photoexcited semiconductors yet are hard to access via conventional time-resolved spectroscopies. Here, we develop a time-resolved ultrafast photocurrent technique (trPC) to probe the formation dynamics of optically dark excitons. The nonlinear nature of the trPC makes it particularly sensitive to the formation of excitons occurring at the femtosecond time scale after the excitation. As a proof of principle, we extract the interlayer exciton formation time of 0.4 ps at 160 μJ/cm2 fluence in a MoS2/MoSe2 heterostructure and show that this time decreases with fluence. In addition, our approach provides access to the dynamics of carriers and their interlayer transport. Overall, our work establishes trPC as a technique to study dark excitons in various systems that are hard to probe by other approaches.
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Affiliation(s)
- Denis Yagodkin
- Department
of Physics, Freie Universität Berlin, Arnimallee 14, Berlin 14195, Germany
| | - Abhijeet Kumar
- Department
of Physics, Freie Universität Berlin, Arnimallee 14, Berlin 14195, Germany
| | - Elias Ankerhold
- Department
of Physics, Freie Universität Berlin, Arnimallee 14, Berlin 14195, Germany
| | - Johanna Richter
- Department
of Physics, Freie Universität Berlin, Arnimallee 14, Berlin 14195, Germany
| | - 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
| | - Cornelius Gahl
- Department
of Physics, Freie Universität Berlin, Arnimallee 14, Berlin 14195, Germany
| | - Kirill I. Bolotin
- Department
of Physics, Freie Universität Berlin, Arnimallee 14, Berlin 14195, Germany
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22
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Qin Y, Wang R, Wu X, Wang Y, Li X, Gao Y, Peng L, Gong Q, Liu Y. Ultrafast Electronic Dynamics in Anisotropic Indirect Interlayer Excitonic States of Monolayer WSe 2/ReS 2 Heterojunctions. NANO LETTERS 2023; 23:8643-8649. [PMID: 37672749 DOI: 10.1021/acs.nanolett.3c02488] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/08/2023]
Abstract
Understanding ultrafast electronic dynamics of the interlayer excitonic states in atomically thin transition metal dichalcogenides is of importance in engineering valleytronics and developing excitonic integrated circuits. In this work, we experimentally explored the ultrafast dynamics of indirect interlayer excitonic states in monolayer type II WSe2/ReS2 heterojunctions using time-resolved photoemission electron microscopy, which reveals its anisotropic behavior. The ultrafast cooling and decay of excited-state electrons exhibit significant linear dichroism. The ab initio theoretical calculations provide unambiguous evidence that this linear dichroism result is primarily associated with the anisotropic nonradiative recombination of indirect interlayer excitonic states. Measuring time-resolved photoemission energy spectra, we have further revealed the ultrafast evolution of excited-state electrons in anisotropic indirect interlayer excitonic states. The findings have important implications for controlling the interlayer moiré excitonic effects and designing anisotropic optoelectronic devices.
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Affiliation(s)
- Yulu Qin
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-Optoelectronics, School of Physics, Peking University, Beijing 100871, China
| | - Rui Wang
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-Optoelectronics, School of Physics, Peking University, Beijing 100871, China
| | - Xiaoyuan Wu
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-Optoelectronics, School of Physics, Peking University, Beijing 100871, China
| | - Yunkun Wang
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-Optoelectronics, School of Physics, Peking University, Beijing 100871, China
| | - Xiaofang Li
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-Optoelectronics, School of Physics, Peking University, Beijing 100871, China
| | - Yunan Gao
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-Optoelectronics, School of Physics, Peking University, Beijing 100871, China
| | - Liangyou Peng
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-Optoelectronics, School of Physics, Peking University, Beijing 100871, China
| | - Qihuang Gong
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-Optoelectronics, School of Physics, Peking University, Beijing 100871, China
- Peking University Yangtze Delta Institute of Optoelectronics, Nantong, Jiangsu 226010, China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi 030006, China
| | - Yunquan Liu
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-Optoelectronics, School of Physics, Peking University, Beijing 100871, China
- Peking University Yangtze Delta Institute of Optoelectronics, Nantong, Jiangsu 226010, China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi 030006, China
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23
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Zhang Z, Zhang B, Wang Y, Wang M, Zhang Y, Li H, Zhang J, Song A. Toward High-Peak-to-Valley-Ratio Graphene Resonant Tunneling Diodes. NANO LETTERS 2023; 23:8132-8139. [PMID: 37668256 PMCID: PMC10510586 DOI: 10.1021/acs.nanolett.3c02281] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2023] [Revised: 08/27/2023] [Indexed: 09/06/2023]
Abstract
The resonant tunneling diode (RTD) is one of the very few room-temperature-operating quantum devices to date that is able to exhibit negative differential resistance. However, the reported key figure of merit, the current peak-to-valley ratio (PVR), of graphene RTDs has been up to only 3.9 at room temperature thus far. This remains very puzzling, given the atomically flat interfaces of the 2D materials. By varying the active area and perimeter of RTDs based on a graphene/hexagonal boron nitride/graphene heterostructure, we discovered that the edge doping can play a dominant role in determining the resonant tunneling, and a large area-to-perimeter ratio is necessary to obtain a high PVR. The understanding enables establishing a novel design rule and results in a PVR of 14.9, which is at least a factor of 3.8 higher than previously reported graphene RTDs. Furthermore, a theory is developed allowing extraction of the edge doping depth for the first time.
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Affiliation(s)
- Zihao Zhang
- Shandong
Technology Center of Nanodevices and Integration, School of Microelectronics, Shandong University, Jinan 250100, China
| | - Baoqing Zhang
- Shandong
Technology Center of Nanodevices and Integration, School of Microelectronics, Shandong University, Jinan 250100, China
| | - Yiming Wang
- Shandong
Technology Center of Nanodevices and Integration, School of Microelectronics, Shandong University, Jinan 250100, China
| | - Mingyang Wang
- Shandong
Technology Center of Nanodevices and Integration, School of Microelectronics, Shandong University, Jinan 250100, China
| | - Yifei Zhang
- Shandong
Technology Center of Nanodevices and Integration, School of Microelectronics, Shandong University, Jinan 250100, China
| | - Hu Li
- Shandong
Technology Center of Nanodevices and Integration, School of Microelectronics, Shandong University, Jinan 250100, China
| | - Jiawei Zhang
- Shandong
Technology Center of Nanodevices and Integration, School of Microelectronics, Shandong University, Jinan 250100, China
- Suzhou
Research Institute, Shandong University, Suzhou 215123, China
| | - Aimin Song
- Shandong
Technology Center of Nanodevices and Integration, School of Microelectronics, Shandong University, Jinan 250100, China
- Department
of Electrical and Electronic Engineering, University of Manchester, Manchester M13 9PL, United
Kingdom
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24
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Li Y, Wan Q, Xu N. Recent Advances in Moiré Superlattice Systems by Angle-Resolved Photoemission Spectroscopy. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023:e2305175. [PMID: 37689836 DOI: 10.1002/adma.202305175] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Revised: 08/16/2023] [Indexed: 09/11/2023]
Abstract
The last decade has witnessed a flourish in 2D materials including graphene and transition metal dichalcogenides (TMDs) as atomic-scale Legos. Artificial moiré superlattices via stacking 2D materials with a twist angle and/or a lattice mismatch have recently become a fertile playground exhibiting a plethora of emergent properties beyond their building blocks. These rich quantum phenomena stem from their nontrivial electronic structures that are effectively tuned by the moiré periodicity. Modern angle-resolved photoemission spectroscopy (ARPES) can directly visualize electronic structures with decent momentum, energy, and spatial resolution, thus can provide enlightening insights into fundamental physics in moiré superlattice systems and guides for designing novel devices. In this review, first, a brief introduction is given on advanced ARPES techniques and basic ideas of band structures in a moiré superlattice system. Then ARPES research results of various moiré superlattice systems are highlighted, including graphene on substrates with small lattice mismatches, twisted graphene/TMD moiré systems, and high-order moiré superlattice systems. Finally, it discusses important questions that remain open, challenges in current experimental investigations, and presents an outlook on this field of research.
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Affiliation(s)
- Yiwei Li
- Institute for Advanced Studies (IAS), Wuhan University, Wuhan, 430072, China
| | - Qiang Wan
- Institute for Advanced Studies (IAS), Wuhan University, Wuhan, 430072, China
| | - Nan Xu
- Institute for Advanced Studies (IAS), Wuhan University, Wuhan, 430072, China
- Wuhan Institute of Quantum Technology, Wuhan, 430206, China
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25
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Sebait R, Rosati R, Yun SJ, Dhakal KP, Brem S, Biswas C, Puretzky A, Malic E, Lee YH. Sequential order dependent dark-exciton modulation in bi-layered TMD heterostructure. Nat Commun 2023; 14:5548. [PMID: 37684279 PMCID: PMC10491585 DOI: 10.1038/s41467-023-41047-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Accepted: 08/22/2023] [Indexed: 09/10/2023] Open
Abstract
We report the emergence of dark-excitons in transition-metal-dichalcogenide (TMD) heterostructures that strongly rely on the stacking sequence, i.e., momentum-dark K-Q exciton located exclusively at the top layer of the heterostructure. The feature stems from band renormalization and is distinct from those of typical neutral excitons or trions, regardless of materials, substrates, and even homogeneous bilayers, which is further confirmed by scanning tunneling spectroscopy. To understand the unusual stacking sequence, we introduce the excitonic Elliot formula by imposing strain exclusively on the top layer that could be a consequence of the stacking process. We further find that the intensity ratio of Q- to K-excitons in the same layer is inversely proportional to laser power, unlike for conventional K-K excitons. This can be a metric for engineering the intensity of dark K-Q excitons in TMD heterostructures, which could be useful for optical power switches in solar panels.
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Affiliation(s)
- Riya Sebait
- Deparment of Energy Science (DOES), Sungkyunkwan University, Suwon, 16419, Republic of Korea
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Sungkyunkwan University, Suwon, 16419, Republic of Korea
| | - Roberto Rosati
- Department of Physics, Philipps-Universität Marburg, Marburg, 35032, Germany
| | - Seok Joon Yun
- Center for Nanophase Materials Sciences (CNMS), Oak Ridge National Laboratory, Oak Ridge, TN, 37830, USA
| | - Krishna P Dhakal
- Deparment of Energy Science (DOES), Sungkyunkwan University, Suwon, 16419, Republic of Korea
| | - Samuel Brem
- Department of Physics, Philipps-Universität Marburg, Marburg, 35032, Germany
| | - Chandan Biswas
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Sungkyunkwan University, Suwon, 16419, Republic of Korea
| | - Alexander Puretzky
- Center for Nanophase Materials Sciences (CNMS), Oak Ridge National Laboratory, Oak Ridge, TN, 37830, USA
| | - Ermin Malic
- Department of Physics, Philipps-Universität Marburg, Marburg, 35032, Germany.
| | - Young Hee Lee
- Deparment of Energy Science (DOES), Sungkyunkwan University, Suwon, 16419, Republic of Korea.
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Sungkyunkwan University, Suwon, 16419, Republic of Korea.
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26
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Erkensten D, Brem S, Perea-Causín R, Hagel J, Tagarelli F, Lopriore E, Kis A, Malic E. Electrically tunable dipolar interactions between layer-hybridized excitons. NANOSCALE 2023; 15:11064-11071. [PMID: 37309577 PMCID: PMC10324325 DOI: 10.1039/d3nr01049j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Accepted: 06/02/2023] [Indexed: 06/14/2023]
Abstract
Transition-metal dichalcogenide bilayers exhibit a rich exciton landscape including layer-hybridized excitons, i.e. excitons which are of partly intra- and interlayer nature. In this work, we study hybrid exciton-exciton interactions in naturally stacked WSe2 homobilayers. In these materials, the exciton landscape is electrically tunable such that the low-energy states can be rendered more or less interlayer-like depending on the strength of the external electric field. Based on a microscopic and material-specific many-particle theory, we reveal two intriguing interaction regimes: a low-dipole regime at small electric fields and a high-dipole regime at larger fields, involving interactions between hybrid excitons with a substantially different intra- and interlayer composition in the two regimes. While the low-dipole regime is characterized by weak inter-excitonic interactions between intralayer-like excitons, the high-dipole regime involves mostly interlayer-like excitons which display a strong dipole-dipole repulsion and give rise to large spectral blue-shifts and a highly anomalous diffusion. Overall, our microscopic study sheds light on the remarkable electrical tunability of hybrid exciton-exciton interactions in atomically thin semiconductors and can guide future experimental studies in this growing field of research.
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Affiliation(s)
- Daniel Erkensten
- Department of Physics, Chalmers University of Technology, 41296 Gothenburg, Sweden.
| | - Samuel Brem
- Department of Physics, Philipps-Universität Marburg, 35037 Marburg, Germany
| | - Raül Perea-Causín
- Department of Physics, Chalmers University of Technology, 41296 Gothenburg, Sweden.
| | - Joakim Hagel
- Department of Physics, Chalmers University of Technology, 41296 Gothenburg, Sweden.
| | - Fedele Tagarelli
- Institute of Electrical and Microengineering, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
- Institute of Materials Science and Engineering, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Edoardo Lopriore
- Institute of Electrical and Microengineering, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
- Institute of Materials Science and Engineering, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Andras Kis
- Institute of Electrical and Microengineering, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
- Institute of Materials Science and Engineering, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Ermin Malic
- Department of Physics, Philipps-Universität Marburg, 35037 Marburg, Germany
- Department of Physics, Chalmers University of Technology, 41296 Gothenburg, Sweden.
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27
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Potočnik T, Burton O, Reutzel M, Schmitt D, Bange JP, Mathias S, Geisenhof FR, Weitz RT, Xin L, Joyce HJ, Hofmann S, Alexander-Webber JA. Fast Twist Angle Mapping of Bilayer Graphene Using Spectroscopic Ellipsometric Contrast Microscopy. NANO LETTERS 2023. [PMID: 37289669 DOI: 10.1021/acs.nanolett.3c00619] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Twisted bilayer graphene provides an ideal solid-state model to explore correlated material properties and opportunities for a variety of optoelectronic applications, but reliable, fast characterization of the twist angle remains a challenge. Here we introduce spectroscopic ellipsometric contrast microscopy (SECM) as a tool for mapping twist angle disorder in optically resonant twisted bilayer graphene. We optimize the ellipsometric angles to enhance the image contrast based on measured and calculated reflection coefficients of incident light. The optical resonances associated with van Hove singularities correlate well to Raman and angle-resolved photoelectron emission spectroscopy, confirming the accuracy of SECM. The results highlight the advantages of SECM, which proves to be a fast, nondestructive method for characterization of twisted bilayer graphene over large areas, unlocking process, material, and device screening and cross-correlative measurement potential for bilayer and multilayer materials.
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Affiliation(s)
- Teja Potočnik
- Department of Engineering, University of Cambridge, 9 JJ Thompson Avenue, Cambridge CB3 0FA, United Kingdom
| | - Oliver Burton
- Department of Engineering, University of Cambridge, 9 JJ Thompson Avenue, Cambridge CB3 0FA, United Kingdom
| | - Marcel Reutzel
- I. Physikalisches Institut, Georg-August-Universität Göttingen, 37077 Göttingen, Germany
| | - David Schmitt
- I. Physikalisches Institut, Georg-August-Universität Göttingen, 37077 Göttingen, Germany
| | - Jan Philipp Bange
- I. Physikalisches Institut, Georg-August-Universität Göttingen, 37077 Göttingen, Germany
| | - Stefan Mathias
- I. Physikalisches Institut, Georg-August-Universität Göttingen, 37077 Göttingen, Germany
| | - Fabian R Geisenhof
- Physics of Nanosystems, Department of Physics, Ludwig-Maximilians-Universität München, Geschwister-Scholl-Platz 1, Munich 80539, Germany
| | - R Thomas Weitz
- I. Physikalisches Institut, Georg-August-Universität Göttingen, 37077 Göttingen, Germany
- Physics of Nanosystems, Department of Physics, Ludwig-Maximilians-Universität München, Geschwister-Scholl-Platz 1, Munich 80539, Germany
| | - Linyuan Xin
- Department of Engineering, University of Cambridge, 9 JJ Thompson Avenue, Cambridge CB3 0FA, United Kingdom
| | - Hannah J Joyce
- Department of Engineering, University of Cambridge, 9 JJ Thompson Avenue, Cambridge CB3 0FA, United Kingdom
| | - Stephan Hofmann
- Department of Engineering, University of Cambridge, 9 JJ Thompson Avenue, Cambridge CB3 0FA, United Kingdom
| | - Jack A Alexander-Webber
- Department of Engineering, University of Cambridge, 9 JJ Thompson Avenue, Cambridge CB3 0FA, United Kingdom
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28
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Abstract
In superlattices of twisted semiconductor monolayers, tunable moiré potentials emerge, trapping excitons into periodic arrays. In particular, spatially separated interlayer excitons are subject to a deep potential landscape and they exhibit a permanent dipole providing a unique opportunity to study interacting bosonic lattices. Recent experiments have demonstrated density-dependent transport properties of moiré excitons, which could play a key role for technological applications. However, the intriguing interplay between exciton-exciton interactions and moiré trapping has not been well understood yet. In this work, we develop a microscopic theory of interacting excitons in external potentials allowing us to tackle this highly challenging problem. We find that interactions between moiré excitons lead to a delocalization at intermediate densities, and we show how this transition can be tuned via twist angle and temperature. The delocalization is accompanied by a modification of optical moiré resonances, which gradually merge into a single free exciton peak.
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Affiliation(s)
- Samuel Brem
- Department of Physics, Philipps University, 35037 Marburg, Germany
| | - Ermin Malic
- Department of Physics, Philipps University, 35037 Marburg, Germany
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29
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Rosati R, Paradisanos I, Huang L, Gan Z, George A, Watanabe K, Taniguchi T, Lombez L, Renucci P, Turchanin A, Urbaszek B, Malic E. Interface engineering of charge-transfer excitons in 2D lateral heterostructures. Nat Commun 2023; 14:2438. [PMID: 37117167 PMCID: PMC10147613 DOI: 10.1038/s41467-023-37889-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2022] [Accepted: 04/04/2023] [Indexed: 04/30/2023] Open
Abstract
The existence of bound charge transfer (CT) excitons at the interface of monolayer lateral heterojunctions has been debated in literature, but contrary to the case of interlayer excitons in vertical heterostructure their observation still has to be confirmed. Here, we present a microscopic study investigating signatures of bound CT excitons in photoluminescence spectra at the interface of hBN-encapsulated lateral MoSe2-WSe2 heterostructures. Based on a fully microscopic and material-specific theory, we reveal the many-particle processes behind the formation of CT excitons and how they can be tuned via interface- and dielectric engineering. For junction widths smaller than the Coulomb-induced Bohr radius we predict the appearance of a low-energy CT exciton. The theoretical prediction is compared with experimental low-temperature photoluminescence measurements showing emission in the bound CT excitons energy range. We show that for hBN-encapsulated heterostructures, CT excitons exhibit small binding energies of just a few tens meV and at the same time large dipole moments, making them promising materials for optoelectronic applications (benefiting from an efficient exciton dissociation and fast dipole-driven exciton propagation). Our joint theory-experiment study presents a significant step towards a microscopic understanding of optical properties of technologically promising 2D lateral heterostructures.
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Affiliation(s)
- Roberto Rosati
- Department of Physics, Philipps-Universität Marburg, Renthof 7, D-35032, Marburg, Germany.
| | - Ioannis Paradisanos
- Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Avenue Rangueil, 31077, Toulouse, France
| | - Libai Huang
- Department of Chemistry, Purdue University, West Lafayette, IN, USA
| | - Ziyang Gan
- Friedrich Schiller University Jena, Institute of Physical Chemistry, 07743, Jena, Germany
- Abbe Centre of Photonics, 07745, Jena, Germany
| | - Antony George
- Friedrich Schiller University Jena, Institute of Physical Chemistry, 07743, Jena, Germany
- Abbe Centre of Photonics, 07745, Jena, Germany
| | - 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
| | - Laurent Lombez
- Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Avenue Rangueil, 31077, Toulouse, France
| | - Pierre Renucci
- Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Avenue Rangueil, 31077, Toulouse, France
| | - Andrey Turchanin
- Friedrich Schiller University Jena, Institute of Physical Chemistry, 07743, Jena, Germany
- Abbe Centre of Photonics, 07745, Jena, Germany
| | - Bernhard Urbaszek
- Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Avenue Rangueil, 31077, Toulouse, France
- Institute of Condensed Matter Physics, Technische Universität Darmstadt, 64289, Darmstadt, Germany
| | - Ermin Malic
- Department of Physics, Philipps-Universität Marburg, Renthof 7, D-35032, Marburg, Germany
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30
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Yang B, Li Y, Xiang H, Lin H, Huang B. Moiré magnetic exchange interactions in twisted magnets. NATURE COMPUTATIONAL SCIENCE 2023; 3:314-320. [PMID: 38177935 DOI: 10.1038/s43588-023-00430-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2022] [Accepted: 03/10/2023] [Indexed: 01/06/2024]
Abstract
In addition to moiré superlattices, twisting can also generate moiré magnetic exchange interactions (MMEIs) in van der Waals magnets. However, owing to the extreme complexity and twist-angle-dependent sensitivity, all existing models fail to fully capture MMEIs and thus cannot provide an understanding of MMEI-induced physics. Here, we develop a microscopic moiré spin Hamiltonian that enables the effective description of MMEIs via a sliding-mapping approach in twisted magnets, as demonstrated in twisted bilayer CrI3. We show that the emergence of MMEIs can create a magnetic skyrmion bubble with non-conserved helicity, a 'moiré-type skyrmion bubble'. This represents a unique spin texture solely generated by MMEIs and ready to be detected under the current experimental conditions. Importantly, the size and population of skyrmion bubbles can be finely controlled by twist angle, a key step for skyrmion-based information storage. Furthermore, we reveal that MMEIs can be effectively manipulated by substrate-induced interfacial Dzyaloshinskii-Moriya interactions, modulating the twist-angle-dependent magnetic phase diagram, which solves outstanding disagreements between theories and experiments.
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Affiliation(s)
- Baishun Yang
- Beijing Computational Science Research Center, Beijing, China
- Shenzhen JL Computational Science and Applied Research Institute, Shenzhen, China
| | - Yang Li
- Beijing Computational Science Research Center, Beijing, China
| | - Hongjun Xiang
- Key Laboratory of Computational Physical Sciences (Ministry of Education), Institute of Computational Physical Sciences, State Key Laboratory of Surface Physics, and Department of Physics, Fudan University, Shanghai, China
| | - Haiqing Lin
- Beijing Computational Science Research Center, Beijing, China
- School of Physics, Zhejiang University, Hangzhou, China
- Department of Physics, Beijing Normal University, Beijing, China
| | - Bing Huang
- Beijing Computational Science Research Center, Beijing, China.
- Department of Physics, Beijing Normal University, Beijing, China.
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31
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Koo Y, Lee H, Ivanova T, Savelev RS, Petrov MI, Kravtsov V, Park KD. Nanocavity-Integrated van der Waals Heterobilayers for Nano-excitonic Transistor. ACS NANO 2023; 17:4854-4861. [PMID: 36857198 DOI: 10.1021/acsnano.2c11509] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Optical computing with optical transistors has emerged as a possible solution to the exponentially growing computational workloads, yet an on-chip nano-optical modulation remains a challenge due to the intrinsically noninteracting nature of photons in addition to the diffraction limit. Here, we present an all-optical approach toward nano-excitonic transistors using an atomically thin WSe2/Mo0.5W0.5Se2 heterobilayer inside a plasmonic tip-based nanocavity. Through optical wavefront shaping, we selectively modulate tip-enhanced photoluminescence (TEPL) responses of intra- and interlayer excitons in a ∼25 nm2 area, demonstrating the enabling concept of an ultrathin 2-bit nano-excitonic transistor. We suggest a simple theoretical model describing the underlying adaptive TEPL modulation mechanism, which relies on the additional spatial degree of freedom provided by the presence of the plasmonic tip. Furthermore, we experimentally demonstrate a concept of a 2-trit nano-excitonic transistor, which can provide a technical basis for processing the massive amounts of data generated by emerging artificial intelligence technologies.
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Affiliation(s)
- Yeonjeong Koo
- Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea
| | - Hyeongwoo Lee
- Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea
| | - Tatiana Ivanova
- School of Physics and Engineering, ITMO University, Saint Petersburg 197101, Russia
| | - Roman S Savelev
- School of Physics and Engineering, ITMO University, Saint Petersburg 197101, Russia
| | - Mihail I Petrov
- School of Physics and Engineering, ITMO University, Saint Petersburg 197101, Russia
| | - Vasily Kravtsov
- School of Physics and Engineering, ITMO University, Saint Petersburg 197101, Russia
| | - Kyoung-Duck Park
- Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea
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32
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Kunin A, Chernov S, Bakalis J, Li Z, Cheng S, Withers ZH, White MG, Schönhense G, Du X, Kawakami RK, Allison TK. Momentum-Resolved Exciton Coupling and Valley Polarization Dynamics in Monolayer WS_{2}. PHYSICAL REVIEW LETTERS 2023; 130:046202. [PMID: 36763432 DOI: 10.1103/physrevlett.130.046202] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2022] [Accepted: 12/22/2022] [Indexed: 06/18/2023]
Abstract
Using time- and angle-resolved photoemission, we present momentum- and energy-resolved measurements of exciton coupling in monolayer WS_{2}. We observe strong intravalley coupling between the B_{1s} exciton and A_{n>1} states. Our measurements indicate that the dominant valley depolarization mechanism conserves the exciton binding energy and momentum. While this conservation is consistent with Coulomb exchange-driven valley depolarization, we do not observe a momentum or energy dependence to the depolarization rate as would be expected for the exchange-based mechanism.
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Affiliation(s)
- Alice Kunin
- Department of Chemistry, Stony Brook University, Stony Brook, New York 11794, USA
| | - Sergey Chernov
- Department of Chemistry, Stony Brook University, Stony Brook, New York 11794, USA
| | - Jin Bakalis
- Department of Chemistry, Stony Brook University, Stony Brook, New York 11794, USA
| | - Ziling Li
- Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA
| | - Shuyu Cheng
- Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA
| | - Zachary H Withers
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794, USA
| | - Michael G White
- Department of Chemistry, Stony Brook University, Stony Brook, New York 11794, USA
- Chemistry Division, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - Gerd Schönhense
- Johannes Gutenberg-Universität, Institut für Physik, D-55099 Mainz, Germany
| | - Xu Du
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794, USA
| | - Roland K Kawakami
- Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA
| | - Thomas K Allison
- Department of Chemistry, Stony Brook University, Stony Brook, New York 11794, USA
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794, USA
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33
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Liu F. Time- and angle-resolved photoemission spectroscopy (TR-ARPES) of TMDC monolayers and bilayers. Chem Sci 2023; 14:736-750. [PMID: 36755720 PMCID: PMC9890651 DOI: 10.1039/d2sc04124c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2022] [Accepted: 12/04/2022] [Indexed: 12/12/2022] Open
Abstract
Many unique properties in two-dimensional (2D) materials and their heterostructures rely on charge excitation, scattering, transfer, and relaxation dynamics across different points in the momentum space. Understanding these dynamics is crucial in both the fundamental study of 2D physics and their incorporation in optoelectronic and quantum devices. A direct method to probe charge carrier dynamics with momentum resolution is time- and angle-resolved photoemission spectroscopy (TR-ARPES). Such measurements have been challenging, since photoexcited carriers in many 2D monolayers reside at high crystal momenta, requiring probe photon energies in the extreme UV (EUV) regime. These challenges have been recently addressed by development of table-top pulsed EUV sources based on high harmonic generation, and the successful integration into a TR-ARPES and/or time-resolved momentum microscope. Such experiments will allow direct imaging of photoelectrons with superior time, energy, and crystal momentum resolution, with unique advantage over traditional optical measurements. Recently, TR-ARPES experiments of 2D transition metal dichalcogenide (TMDC) monolayers and bilayers have created unprecedented opportunities to reveal many intrinsic dynamics of 2D materials, such as bandgap renormalization, charge carrier scattering, relaxation, and wavefunction localization in moiré patterns. This perspective aims to give a short review of recent discoveries and discuss the challenges and opportunities of such techniques in the future.
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Affiliation(s)
- Fang Liu
- Department of Chemistry and the PULSE Institute, Stanford University Stanford California 94305 USA
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34
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Karni O, Esin I, Dani KM. Through the Lens of a Momentum Microscope: Viewing Light-Induced Quantum Phenomena in 2D Materials. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022:e2204120. [PMID: 35817468 DOI: 10.1002/adma.202204120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Revised: 06/23/2022] [Indexed: 06/15/2023]
Abstract
Van der Waals (vdW) materials at their 2D limit are diverse, flexible, and unique laboratories to study fundamental quantum phenomena and their future applications. Their novel properties rely on their pronounced Coulomb interactions, variety of crystal symmetries and spin-physics, and the ease of incorporation of different vdW materials to form sophisticated heterostructures. In particular, the excited state properties of many 2D semiconductors and semi-metals are relevant for their technological applications, particularly those that can be induced by light. In this paper, the recent advances made in studying out-of-equilibrium, light-induced, phenomena in these materials are reviewed using powerful, surface-sensitive, time-resolved photoemission-based techniques, with a particular emphasis on the emerging multi-dimensional photoemission spectroscopy technique of time-resolved momentum microscopy. The advances this technique has enabled in studying the nature and dynamics of occupied excited states in these materials are discussed. Then, the future research directions opened by these scientific and instrumental advancements are projected for studying the physics of 2D materials and the opportunities to engineer their band-structure and band-topology by laser fields.
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Affiliation(s)
- Ouri Karni
- Department of Applied Physics, Stanford University, Stanford, CA, 94305, USA
- SLAC National Accelerator Laboratory, Menlo Park, CA, 94025, USA
| | - Iliya Esin
- Department of Physics, California Institute of Technology, Pasadena, CA, 91125, USA
| | - Keshav M Dani
- Femtosecond Spectroscopy Unit, Okinawa Institute of Science and Technology Graduate University, Onna-son, Okinawa, 904-0495, Japan
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