1
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Parishani M, Nadafan M, Akbarpoor S. Enhancement of third-order optical nonlinearity of VSe 2 by hybridizing with CoSe 2 as flower-like nanoparticles. RSC Adv 2024; 14:27741-27748. [PMID: 39224626 PMCID: PMC11367623 DOI: 10.1039/d4ra04192e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2024] [Accepted: 08/10/2024] [Indexed: 09/04/2024] Open
Abstract
Through one-pot hydrothermal synthesis, we synthesized VSe2-CoSe2 nanostructures with a distinctive flower-like morphology. The structural characterizations were conducted using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and Fourier transform infrared spectroscopy (FTIR). By modulating the proportion of the CoSe2 phase, we transformed these hybrid nanostructures into nanoparticles, thereby influencing their nonlinear optical properties. The third-order nonlinear optical parameters (n 2 and β) were rigorously examined via the precise Z-scan technique under various laser power conditions. The nanostructures demonstrated a self-focusing refractive response and exhibited pronounced two-photon absorption during the nonlinear absorption process. The magnitudes of n 2 and β were determined to be in the order of 10-8 (cm2 W-1) and 10-4 (cm W-1), respectively. The exceptional figure of merit (FOM) of these composite flower-like structures underscores their superior nonlinear optical characteristics, establishing them as promising candidates for photonic applications, particularly in optical switching devices.
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Affiliation(s)
- Marziyeh Parishani
- Department of Physics, Tarbiat Modares University P. O. Box 14115-175 Tehran Iran
| | - Marzieh Nadafan
- Department of Physics, Shahid Rajaee Teacher Training University P. O. Box 16788-15811 Tehran Iran
| | - Sajad Akbarpoor
- Department of Physics, Shahid Rajaee Teacher Training University P. O. Box 16788-15811 Tehran Iran
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2
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Edwards B, Deaconu DA, Murgatroyd PAE, Buchberger S, Antonelli T, Halliday D, Siemann GR, Zivanovic A, Trzaska L, Rajan A, Abarca Morales E, Mayoh DA, Hall AE, Belosludov RV, Watson MD, Kim TK, Biswas D, Lee TL, Polley CM, Carbone D, Leandersson M, Balakrishnan G, Bahramy MS, King PDC. Chemical Trends of the Bulk and Surface Termination-Dependent Electronic Structure of Metal-Intercalated Transition Metal Dichalcogenides. CHEMISTRY OF MATERIALS : A PUBLICATION OF THE AMERICAN CHEMICAL SOCIETY 2024; 36:7117-7126. [PMID: 39156710 PMCID: PMC11325556 DOI: 10.1021/acs.chemmater.4c00824] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/20/2024] [Revised: 07/09/2024] [Accepted: 07/10/2024] [Indexed: 08/20/2024]
Abstract
The addition of metal intercalants into the van der Waals gaps of transition metal dichalcogenides has shown great promise as a method for controlling their functional properties. For example, chiral helimagnetic states, current-induced magnetization switching, and a giant valley-Zeeman effect have all been demonstrated, generating significant renewed interest in this materials family. Here, we present a combined photoemission and density-functional theory study of three such compounds: , , and , to investigate chemical trends of the intercalant species on their bulk and surface electronic structure. Our resonant photoemission measurements indicate increased hybridization with the itinerant NbS2-derived conduction states with increasing atomic number of the intercalant, leading to pronounced mixing of the nominally localized intercalant states at the Fermi level. Using spatially and angle-resolved photoemission spectroscopy, we show how this impacts surface-termination-dependent charge transfers and leads to the formation of new dispersive states of mixed intercalant-Nb character at the Fermi level for the intercalant-terminated surfaces. This provides an explanation for the origin of anomalous states previously reported in this family of compounds and paves the way for tuning the nature of the magnetic interactions in these systems via control of the hybridization of the magnetic ions with the itinerant states.
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Affiliation(s)
- Brendan Edwards
- SUPA,
School of Physics and Astronomy, University
of St Andrews, St Andrews KY16 9SS, U.K.
| | - Darius-A. Deaconu
- Department
of Physics and Astronomy, University of
Manchester, Oxford Road, Manchester M13 9PL, U.K.
| | | | - Sebastian Buchberger
- SUPA,
School of Physics and Astronomy, University
of St Andrews, St Andrews KY16 9SS, U.K.
- Max
Planck Institute for Chemical Physics of Solids, Nöthnitzer Strasse 40, Dresden 01187, Germany
| | - Tommaso Antonelli
- SUPA,
School of Physics and Astronomy, University
of St Andrews, St Andrews KY16 9SS, U.K.
| | - Daniel Halliday
- SUPA,
School of Physics and Astronomy, University
of St Andrews, St Andrews KY16 9SS, U.K.
- Diamond
Light Source Ltd, Harwell
Science and Innovation Campus, Didcot OX11 0DE, U.K.
| | - Gesa-R. Siemann
- SUPA,
School of Physics and Astronomy, University
of St Andrews, St Andrews KY16 9SS, U.K.
| | - Andela Zivanovic
- SUPA,
School of Physics and Astronomy, University
of St Andrews, St Andrews KY16 9SS, U.K.
- Max
Planck Institute for Chemical Physics of Solids, Nöthnitzer Strasse 40, Dresden 01187, Germany
| | - Liam Trzaska
- SUPA,
School of Physics and Astronomy, University
of St Andrews, St Andrews KY16 9SS, U.K.
| | - Akhil Rajan
- SUPA,
School of Physics and Astronomy, University
of St Andrews, St Andrews KY16 9SS, U.K.
| | - Edgar Abarca Morales
- SUPA,
School of Physics and Astronomy, University
of St Andrews, St Andrews KY16 9SS, U.K.
- Max
Planck Institute for Chemical Physics of Solids, Nöthnitzer Strasse 40, Dresden 01187, Germany
| | - Daniel A. Mayoh
- Department
of Physics, University of Warwick, Coventry CV4 7AL, U.K.
| | - Amelia E. Hall
- Department
of Physics, University of Warwick, Coventry CV4 7AL, U.K.
| | | | - Matthew D. Watson
- Diamond
Light Source Ltd, Harwell
Science and Innovation Campus, Didcot OX11 0DE, U.K.
| | - Timur K. Kim
- Diamond
Light Source Ltd, Harwell
Science and Innovation Campus, Didcot OX11 0DE, U.K.
| | - Deepnarayan Biswas
- Diamond
Light Source Ltd, Harwell
Science and Innovation Campus, Didcot OX11 0DE, U.K.
| | - Tien-Lin Lee
- Diamond
Light Source Ltd, Harwell
Science and Innovation Campus, Didcot OX11 0DE, U.K.
| | - Craig M. Polley
- MAX
IV Laboratory, Lund University, P.O. Box 118, Lund 221 00, Sweden
| | - Dina Carbone
- MAX
IV Laboratory, Lund University, P.O. Box 118, Lund 221 00, Sweden
| | - Mats Leandersson
- MAX
IV Laboratory, Lund University, P.O. Box 118, Lund 221 00, Sweden
| | | | - Mohammad Saeed Bahramy
- Department
of Physics and Astronomy, University of
Manchester, Oxford Road, Manchester M13 9PL, U.K.
| | - Phil D. C. King
- SUPA,
School of Physics and Astronomy, University
of St Andrews, St Andrews KY16 9SS, U.K.
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3
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Rajan A, Buchberger S, Edwards B, Zivanovic A, Kushwaha N, Bigi C, Nanao Y, Saika BK, Armitage OR, Wahl P, Couture P, King PDC. Epitaxial Growth of Large-Area Monolayers and van der Waals Heterostructures of Transition-Metal Chalcogenides via Assisted Nucleation. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024; 36:e2402254. [PMID: 38884948 DOI: 10.1002/adma.202402254] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2024] [Revised: 06/08/2024] [Indexed: 06/18/2024]
Abstract
The transition-metal chalcogenides include some of the most important and ubiquitous families of 2D materials. They host an exceptional variety of electronic and collective states, which can in principle be readily tuned by combining different compounds in van der Waals heterostructures. Achieving this, however, presents a significant materials challenge. The highest quality heterostructures are usually fabricated by stacking layers exfoliated from bulk crystals, which - while producing excellent prototype devices - is time consuming, cannot be easily scaled, and can lead to significant complications for materials stability and contamination. Growth via the ultra-high vacuum deposition technique of molecular-beam epitaxy (MBE) should be a premier route for 2D heterostructure fabrication, but efforts to achieve this are complicated by non-uniform layer coverage, unfavorable growth morphologies, and the presence of significant rotational disorder of the grown epilayer. This work demonstrates a dramatic enhancement in the quality of MBE grown 2D materials by exploiting simultaneous deposition of a sacrificial species from an electron-beam evaporator during the growth. This approach dramatically enhances the nucleation of the desired epi-layer, in turn enabling the synthesis of large-area, uniform monolayers with enhanced quasiparticle lifetimes, and facilitating the growth of epitaxial van der Waals heterostructures.
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Affiliation(s)
- Akhil Rajan
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, KY16 9SS, UK
| | - Sebastian Buchberger
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, KY16 9SS, UK
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Strasse 40, 01187, Dresden, Germany
| | - Brendan Edwards
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, KY16 9SS, UK
| | - Andela Zivanovic
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, KY16 9SS, UK
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Strasse 40, 01187, Dresden, Germany
| | - Naina Kushwaha
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, KY16 9SS, UK
- STFC Central Laser Facility, Research Complex at Harwell, Harwell Campus, Didcot, OX11 0QX, UK
| | - Chiara Bigi
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, KY16 9SS, UK
| | - Yoshiko Nanao
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, KY16 9SS, UK
| | - Bruno K Saika
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, KY16 9SS, UK
| | - Olivia R Armitage
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, KY16 9SS, UK
| | - Peter Wahl
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, KY16 9SS, UK
- Physikalisches Institut, Universität Bonn, Nussallee 12, 53115, Bonn, Germany
| | - Pierre Couture
- Ion Beam Centre, University of Surrey, Guildford, Surrey, GU2 7XH, UK
| | - Phil D C King
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, KY16 9SS, UK
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4
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He Z, Poudel SP, Stolz S, Wang T, Rossi A, Wang F, Mo SK, Weber-Bargioni A, Qiu ZQ, Barraza-Lopez S, Zhu T, Crommie MF. Synthesis and Polymorph Manipulation of FeSe 2 Monolayers. NANO LETTERS 2024; 24:8535-8541. [PMID: 38968422 DOI: 10.1021/acs.nanolett.4c01286] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/07/2024]
Abstract
Polymorph engineering involves the manipulation of material properties through controlled structural modification and is a candidate technique for creating unique two-dimensional transition metal dichalcogenide (TMDC) nanodevices. Despite its promise, polymorph engineering of magnetic TMDC monolayers has not yet been demonstrated. Here we grow FeSe2 monolayers via molecular beam epitaxy and find that they have great promise for magnetic polymorph engineering. Using scanning tunneling microscopy (STM) and spectroscopy (STS), we find that FeSe2 monolayers predominantly display a 1T' structural polymorph at 5 K. Application of voltage pulses from an STM tip causes a local, reversible transition from the 1T' phase to the 1T phase. Density functional theory calculations suggest that this single-layer structural phase transition is accompanied by a magnetic transition from an antiferromagnetic to a ferromagnetic configuration. These results open new possibilities for creating functional magnetic devices with TMDC monolayers via polymorph engineering.
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Affiliation(s)
- Zehao He
- Department of Physics, University of California, Berkeley, California 94720, United States
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
- Department of Material Science and Engineering, University of California, Berkeley, California 94720, United States
| | - Shiva Prasad Poudel
- Department of Physics and MonArk NSF Quantum Foundry, University of Arkansas, Fayetteville, Arkansas 72701, United States
| | - Samuel Stolz
- Department of Physics, University of California, Berkeley, California 94720, United States
| | - Tianye Wang
- Department of Physics, University of California, Berkeley, California 94720, United States
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Antonio Rossi
- The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Feng Wang
- Department of Physics, University of California, Berkeley, California 94720, United States
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
- Kavli Energy NanoScience Institute at the University of California, Berkeley, and Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Sung-Kwan Mo
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Alexander Weber-Bargioni
- The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Zi Qiang Qiu
- Department of Physics, University of California, Berkeley, California 94720, United States
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Salvador Barraza-Lopez
- Department of Physics and MonArk NSF Quantum Foundry, University of Arkansas, Fayetteville, Arkansas 72701, United States
| | - Tiancong Zhu
- Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana, 47907, United States
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana, 47907, United States
| | - Michael F Crommie
- Department of Physics, University of California, Berkeley, California 94720, United States
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
- Kavli Energy NanoScience Institute at the University of California, Berkeley, and Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
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5
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Rhee TG, Lam NH, Kim YG, Gu M, Hwang J, Bostwick A, Mo SK, Chun SH, Kim J, Chang YJ, Choi BK. Emergence of two distinct phase transitions in monolayer CoSe 2 on graphene. NANO CONVERGENCE 2024; 11:21. [PMID: 38789878 PMCID: PMC11126552 DOI: 10.1186/s40580-024-00427-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2024] [Accepted: 05/09/2024] [Indexed: 05/26/2024]
Abstract
Dimensional modifications play a crucial role in various applications, especially in the context of device miniaturization, giving rise to novel quantum phenomena. The many-body dynamics induced by dimensional modifications, including electron-electron, electron-phonon, electron-magnon and electron-plasmon coupling, are known to significantly affect the atomic and electronic properties of the materials. By reducing the dimensionality of orthorhombic CoSe2 and forming heterostructure with bilayer graphene using molecular beam epitaxy, we unveil the emergence of two types of phase transitions through angle-resolved photoemission spectroscopy and scanning tunneling microscopy measurements. We disclose that the 2 × 1 superstructure is associated with charge density wave induced by Fermi surface nesting, characterized by a transition temperature of 340 K. Additionally, another phase transition at temperature of 160 K based on temperature dependent gap evolution are observed with renormalized electronic structure induced by electron-boson coupling. These discoveries of the electronic and atomic modifications, influenced by electron-electron and electron-boson interactions, underscore that many-body physics play significant roles in understanding low-dimensional properties of non-van der Waals Co-chalcogenides and related heterostructures.
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Affiliation(s)
- Tae Gyu Rhee
- Department of Physics, University of Seoul, Seoul, 02504, Korea
- Department of Smart Cities, University of Seoul, Seoul, 02504, Korea
| | - Nguyen Huu Lam
- Department of Physics, University of Ulsan, Ulsan, 44610, Korea
| | - Yeong Gwang Kim
- Department of Physics, University of Seoul, Seoul, 02504, Korea
- Department of Smart Cities, University of Seoul, Seoul, 02504, Korea
| | - Minseon Gu
- Department of Physics, University of Seoul, Seoul, 02504, Korea
| | - Jinwoong Hwang
- Department of Physics, Institute of Quantum Convergence Technology, Kangwon National University, Chuncheon, 24341, Korea
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Aaron Bostwick
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Sung-Kwan Mo
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Seung-Hyun Chun
- Department of Physics, Sejong University, Seoul, 05006, Korea
| | - Jungdae Kim
- Department of Physics, University of Ulsan, Ulsan, 44610, Korea.
| | - Young Jun Chang
- Department of Physics, University of Seoul, Seoul, 02504, Korea.
- Department of Smart Cities, University of Seoul, Seoul, 02504, Korea.
- Department of Intelligent Semiconductor Engineering, University of Seoul, Seoul, 02504, Korea.
| | - Byoung Ki Choi
- Department of Physics, University of Seoul, Seoul, 02504, Korea.
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
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6
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Hwang J, Ruan W, Chen Y, Tang S, Crommie MF, Shen ZX, Mo SK. Charge density waves in two-dimensional transition metal dichalcogenides. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2024; 87:044502. [PMID: 38518359 DOI: 10.1088/1361-6633/ad36d3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2023] [Accepted: 03/22/2024] [Indexed: 03/24/2024]
Abstract
Charge density wave (CDW is one of the most ubiquitous electronic orders in quantum materials. While the essential ingredients of CDW order have been extensively studied, a comprehensive microscopic understanding is yet to be reached. Recent research efforts on the CDW phenomena in two-dimensional (2D) materials provide a new pathway toward a deeper understanding of its complexity. This review provides an overview of the CDW orders in 2D with atomically thin transition metal dichalcogenides (TMDCs) as the materials platform. We mainly focus on the electronic structure investigations on the epitaxially grown TMDC samples with angle-resolved photoemission spectroscopy and scanning tunneling microscopy/spectroscopy as complementary experimental tools. We discuss the possible origins of the 2D CDW, novel quantum states coexisting with them, and exotic types of charge orders that can only be realized in the 2D limit.
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Affiliation(s)
- Jinwoong Hwang
- Department of Physics and Institute of Quantum Convergence Technology, Kangwon National University, Chuncheon 24341, Republic of Korea
| | - Wei Ruan
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200438, People's Republic of China
| | - Yi Chen
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, People's Republic of China
- Collaborative Innovation Center of Quantum Matter, Beijing 100871, People's Republic of China
- Interdisciplinary Institute of Light-Element Quantum Materials and Research Center for Light-Element Advanced Materials, Peking University, Beijing 100871, People's Republic of China
| | - Shujie Tang
- State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, People's Republic of China
| | - Michael F Crommie
- Department of Physics, University of California, Berkeley, CA, United States of America
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States of America
- Kavli Energy NanoSciences Institute at the University of California at Berkeley, Berkeley, CA 94720, United States of America
| | - Zhi-Xun Shen
- Geballe Laboratory for Advanced Materials, Departments of Physics and Applied Physics, Stanford University, Stanford, CA, United States of America
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, United States of America
| | - Sung-Kwan Mo
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 United States of America
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7
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Pathirage V, Khatun S, Lisenkov S, Lasek K, Li J, Kolekar S, Valvidares M, Gargiani P, Xin Y, Ponomareva I, Batzill M. 2D Materials by Design: Intercalation of Cr or Mn between two VSe 2 van der Waals Layers. NANO LETTERS 2023; 23:9579-9586. [PMID: 37818868 DOI: 10.1021/acs.nanolett.3c03169] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/13/2023]
Abstract
Insertion of metal layers between layered transition-metal dichalcogenides (TMDs) enables the design of new pseudo-2D nanomaterials. The general premise is that various metal atoms may adopt energetically favorable intercalation sites between two TMD sheets. These covalently bound metals arrange in metastable configurations and thus enable the controlled synthesis of nanomaterials in a bottom-up approach. Here, this method is demonstrated by the insertion of Cr or Mn between VSe2 layers. Vacuum-deposited transition metals diffuse between VSe2 layers with increasing concentration, arranging in ordered phases. The Cr3+ or Mn2+ ions are in octahedral coordination and thus in a high-spin state. Measured and computed magnetic moments are high for dilute Cr atoms, but with increasing Cr concentration the average magnetic moment decreases, suggesting antiferromagnetic ordering between Cr ions. The many possible combinations of transition metals with TMDs form a library for exploring quantum phenomena in these nanomaterials.
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Affiliation(s)
- Vimukthi Pathirage
- Department of Physics, University of South Florida, Tampa, Florida 33647, United States
| | - Salma Khatun
- Department of Physics, University of South Florida, Tampa, Florida 33647, United States
| | - Sergey Lisenkov
- Department of Physics, University of South Florida, Tampa, Florida 33647, United States
| | - Kinga Lasek
- Department of Physics, University of South Florida, Tampa, Florida 33647, United States
| | - Jingfeng Li
- Department of Physics, University of South Florida, Tampa, Florida 33647, United States
| | - Sadhu Kolekar
- Department of Physics, University of South Florida, Tampa, Florida 33647, United States
| | - Manuel Valvidares
- ALBA Synchrotron Light Source E-08290 Cerdanyola del Vallès, Barcelona, Spain
| | - Pierluigi Gargiani
- ALBA Synchrotron Light Source E-08290 Cerdanyola del Vallès, Barcelona, Spain
| | - Yan Xin
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310 United States
| | - Inna Ponomareva
- Department of Physics, University of South Florida, Tampa, Florida 33647, United States
| | - Matthias Batzill
- Department of Physics, University of South Florida, Tampa, Florida 33647, United States
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8
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Korshunov A, Hu H, Subires D, Jiang Y, Călugăru D, Feng X, Rajapitamahuni A, Yi C, Roychowdhury S, Vergniory MG, Strempfer J, Shekhar C, Vescovo E, Chernyshov D, Said AH, Bosak A, Felser C, Bernevig BA, Blanco-Canosa S. Softening of a flat phonon mode in the kagome ScV 6Sn 6. Nat Commun 2023; 14:6646. [PMID: 37863907 PMCID: PMC10589229 DOI: 10.1038/s41467-023-42186-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2023] [Accepted: 09/29/2023] [Indexed: 10/22/2023] Open
Abstract
Geometrically frustrated kagome lattices are raising as novel platforms to engineer correlated topological electron flat bands that are prominent to electronic instabilities. Here, we demonstrate a phonon softening at the kz = π plane in ScV6Sn6. The low energy longitudinal phonon collapses at ~98 K and q = [Formula: see text] due to the electron-phonon interaction, without the emergence of long-range charge order which sets in at a different propagation vector qCDW = [Formula: see text]. Theoretical calculations corroborate the experimental finding to indicate that the leading instability is located at [Formula: see text] of a rather flat mode. We relate the phonon renormalization to the orbital-resolved susceptibility of the trigonal Sn atoms and explain the approximately flat phonon dispersion. Our data report the first example of the collapse of a kagome bosonic mode and promote the 166 compounds of kagomes as primary candidates to explore correlated flat phonon-topological flat electron physics.
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Affiliation(s)
- A Korshunov
- European Synchrotron Radiation Facility (ESRF), BP 220, F-38043, Grenoble, France
| | - H Hu
- Donostia International Physics Center (DIPC), Paseo Manuel de Lardizábal, 20018, San Sebastián, Spain
| | - D Subires
- Donostia International Physics Center (DIPC), Paseo Manuel de Lardizábal, 20018, San Sebastián, Spain
| | - Y Jiang
- Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - D Călugăru
- Department of Physics, Princeton University, Princeton, NJ, 08544, USA
| | - X Feng
- Donostia International Physics Center (DIPC), Paseo Manuel de Lardizábal, 20018, San Sebastián, Spain
- Max Planck Institute for Chemical Physics of Solids, 01187, Dresden, Germany
| | - A Rajapitamahuni
- National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - C Yi
- Max Planck Institute for Chemical Physics of Solids, 01187, Dresden, Germany
| | - S Roychowdhury
- Max Planck Institute for Chemical Physics of Solids, 01187, Dresden, Germany
| | - M G Vergniory
- Donostia International Physics Center (DIPC), Paseo Manuel de Lardizábal, 20018, San Sebastián, Spain
- Max Planck Institute for Chemical Physics of Solids, 01187, Dresden, Germany
| | - J Strempfer
- Advanced Photon Source, Argonne National Laboratory, Lemont, IL, 60439, USA
| | - C Shekhar
- Max Planck Institute for Chemical Physics of Solids, 01187, Dresden, Germany
| | - E Vescovo
- National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - D Chernyshov
- Swiss-Norwegian BeamLines at European Synchrotron Radiation Facility, Grenoble, France
| | - A H Said
- Advanced Photon Source, Argonne National Laboratory, Lemont, IL, 60439, USA
| | - A Bosak
- European Synchrotron Radiation Facility (ESRF), BP 220, F-38043, Grenoble, France
| | - C Felser
- Max Planck Institute for Chemical Physics of Solids, 01187, Dresden, Germany
| | - B Andrei Bernevig
- Donostia International Physics Center (DIPC), Paseo Manuel de Lardizábal, 20018, San Sebastián, Spain.
- Department of Physics, Princeton University, Princeton, NJ, 08544, USA.
- IKERBASQUE, Basque Foundation for Science, 48013, Bilbao, Spain.
| | - S Blanco-Canosa
- Donostia International Physics Center (DIPC), Paseo Manuel de Lardizábal, 20018, San Sebastián, Spain.
- IKERBASQUE, Basque Foundation for Science, 48013, Bilbao, Spain.
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9
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Sun R, Deng J, Ma Y, Hao M, Chen X, Meng D, Zhao C, Du S, Jin S, Chen X. Ferromagnetism induced by in-plane strain in a bulk VS 2-based superlattice: (LiOH) 0.1VS 2. Chem Commun (Camb) 2023; 59:10556-10559. [PMID: 37578117 DOI: 10.1039/d3cc01662e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/15/2023]
Abstract
Transition metal dichalcogenides (TMDs) have attracted intensive research interest due to their diverse properties. However, ferromagnetism is not observed in layered TMDs, except for monolayer VSe2. In this study, we report the synthesis of a bulk ferromagnetic material (LiOH)0.1VS2 based on topochemical reactions. The results demonstrate that the (LiOH)0.1VS2 crystal exhibits strong anisotropic ferromagnetism below a critical temperature of 40 K. Calculations uncover that the in-plane strains in a VS2 superlattice can induce large magnetic anisotropic energy, which stabilizes the long-range ferromagnetic order. The findings provide a new approach to induce ferromagnetism in bulk TMD materials.
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Affiliation(s)
- Ruijin Sun
- School of Science, China University of Geosciences, Beijing (CUGB), Beijing, 100083, China.
| | - Jun Deng
- Institute of Physics, Chinese Academy of Science, Beijing, 100190, China
| | - Yuxin Ma
- Institute of Physics, Chinese Academy of Science, Beijing, 100190, China
| | - Munan Hao
- Institute of Physics, Chinese Academy of Science, Beijing, 100190, China
| | - Xu Chen
- Institute of Physics, Chinese Academy of Science, Beijing, 100190, China
| | - Dezhong Meng
- School of Science, China University of Geosciences, Beijing (CUGB), Beijing, 100083, China.
| | - Changchun Zhao
- School of Science, China University of Geosciences, Beijing (CUGB), Beijing, 100083, China.
| | - Shixuan Du
- Institute of Physics, Chinese Academy of Science, Beijing, 100190, China
| | - Shifeng Jin
- Institute of Physics, Chinese Academy of Science, Beijing, 100190, China
| | - Xiaolong Chen
- Institute of Physics, Chinese Academy of Science, Beijing, 100190, China
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10
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Zong J, Dong ZY, Huang J, Wang K, Wang QW, Meng Q, Tian Q, Qiu X, Mu Y, Wang L, Ren W, Xie X, Chen W, Zhang Y, Wang C, Li FS, Li SC, Li JX, Yuan H, Zhang Y. Inducing itinerant ferromagnetism by manipulating van Hove singularity in epitaxial monolayer 1T-VSe 2. Sci Bull (Beijing) 2023; 68:990-997. [PMID: 37100643 DOI: 10.1016/j.scib.2023.04.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Revised: 03/16/2023] [Accepted: 04/06/2023] [Indexed: 04/28/2023]
Abstract
The itinerant ferromagnetism can be induced by a van Hove singularity (VHS) with a divergent density of states at Fermi level. Utilizing the giant magnified dielectric constant εr of SrTiO3(111) substrate with cooling, here we successfully manipulated the VHS in the epitaxial monolayer (ML) 1T-VSe2 film approaching to Fermi level via the large interfacial charge transfer, and thus induced a two-dimensional (2D) itinerant ferromagnetic state below 3.3 K. Combining the direct characterization of the VHS structure via angle-resolved photoemission spectroscopy (ARPES), together with the theoretical analysis, we ascribe the manipulation of VHS to the physical origin of the itinerant ferromagnetic state in ML 1T-VSe2. Therefore, we further demonstrated that the ferromagnetic state in the 2D system can be controlled through manipulating the VHS by engineering the film thickness or replacing the substrate. Our findings clearly evidence that the VHS can serve as an effective manipulating degree of freedom for the itinerant ferromagnetic state, expanding the application potentials of 2D magnets for the next-generation information technology.
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Affiliation(s)
- Junyu Zong
- National Laboratory of Solid-State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China
| | - Zhao-Yang Dong
- Department of Applied Physics, Nanjing University of Science and Technology, Nanjing 210094, China
| | - Junwei Huang
- College of Engineering and Applied Sciences and National Laboratory of Solid-State Microstructures, Nanjing University, Nanjing 210093, China
| | - Kaili Wang
- National Laboratory of Solid-State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China
| | - Qi-Wei Wang
- National Laboratory of Solid-State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China
| | - Qinghao Meng
- National Laboratory of Solid-State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China
| | - Qichao Tian
- National Laboratory of Solid-State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China
| | - Xiaodong Qiu
- National Laboratory of Solid-State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China
| | - Yuyang Mu
- National Laboratory of Solid-State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China
| | - Li Wang
- Vacuum Interconnected NanoTech Workstation (Nano-X), Suzhou Institute of Nano-Tech and Nano-Bionics (SINANO), Chinese Academy of Sciences, Suzhou 215123, China
| | - Wei Ren
- Vacuum Interconnected NanoTech Workstation (Nano-X), Suzhou Institute of Nano-Tech and Nano-Bionics (SINANO), Chinese Academy of Sciences, Suzhou 215123, China
| | - Xuedong Xie
- National Laboratory of Solid-State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China
| | - Wang Chen
- National Laboratory of Solid-State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China
| | - Yongheng Zhang
- National Laboratory of Solid-State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China
| | - Can Wang
- National Laboratory of Solid-State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China; Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Fang-Sen Li
- Vacuum Interconnected NanoTech Workstation (Nano-X), Suzhou Institute of Nano-Tech and Nano-Bionics (SINANO), Chinese Academy of Sciences, Suzhou 215123, China
| | - Shao-Chun Li
- National Laboratory of Solid-State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China; Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Jian-Xin Li
- National Laboratory of Solid-State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China; Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China.
| | - Hongtao Yuan
- College of Engineering and Applied Sciences and National Laboratory of Solid-State Microstructures, Nanjing University, Nanjing 210093, China; Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China.
| | - Yi Zhang
- National Laboratory of Solid-State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China; Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China.
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11
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Wines D, Tiihonen J, Saritas K, Krogel JT, Ataca C. A Quantum Monte Carlo Study of the Structural, Energetic, and Magnetic Properties of Two-Dimensional H and T Phase VSe 2. J Phys Chem Lett 2023; 14:3553-3560. [PMID: 37017431 DOI: 10.1021/acs.jpclett.3c00497] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
Previous works have controversially claimed near-room-temperature ferromagnetism in two-dimensional (2D) VSe2, with conflicting results throughout the literature. These discrepancies in magnetic properties between both phases (T and H) of 2D VSe2 are most likely due to the structural parameters being coupled to the magnetic properties. Specifically, both phases have a close lattice match and similar total energies, which makes it difficult to determine which phase is being observed experimentally. In this study, we used a combination of density functional theory, highly accurate diffusion Monte Carlo (DMC), and a surrogate Hessian line-search optimization technique to resolve the previously reported discrepancy in structural parameters and relative phase stability. With DMC accuracy, we determined the free-standing geometry of both phases and constructed a phase diagram. Our findings demonstrate the successes of the DMC method coupled with the surrogate Hessian structural optimization technique when applied to a 2D magnetic system.
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Affiliation(s)
- Daniel Wines
- Materials Science and Engineering Division, National Institute of Standards and Technology (NIST), Gaithersburg, Maryland 20899, United States
| | - Juha Tiihonen
- Department of Physics, Nanoscience Center, University of Jyväskylä, P.O. Box 35, 40014 Jyväskylä, Finland
| | - Kayahan Saritas
- Material Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Jaron T Krogel
- Material Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Can Ataca
- Department of Physics, University of Maryland Baltimore County, Baltimore, Maryland 21250, United States
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12
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Mi K, Guo Y. Magnetism in curved VSe 2 monolayers. RSC Adv 2023; 13:8307-8316. [PMID: 36926003 PMCID: PMC10012335 DOI: 10.1039/d3ra01319g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Accepted: 03/06/2023] [Indexed: 03/18/2023] Open
Abstract
Our extensive first-principles calculations on magnetic VSe2 monolayers reveal the curvature-induced periodic fluctuation in the magnetic moments of V atoms and the occurrence of charge density waves for curved VSe2 monolayers. The bending energies of curved 2H-VSe2 monolayers increase with increasing curvature but that of curved 1T-VSe2 monolayers with curvature is not monotonic. The significant periodic magnetic orders in curved VSe2 monolayers can be attributed to the curvature-induced modification of V-Se bond structure and periodic length variations in V-Se bonds. A phenomenological model is established to describe the relation of the total magnetic moment in one period of a curved VSe2 monolayer with its curvature radius and the number of hexagonal rings that forms one period. These results unveil the effect of bending deformation on magnetic van der Waals monolayers and provide a possible way to develop functional magnetic devices by mechanical design.
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Affiliation(s)
- Kexin Mi
- State Key Laboratory of Mechanics and Control of Mechanical Structures, MOE Key Laboratory for Intelligent Nano Materials and Devices, College of Aerospace Engineering, Nanjing University of Aeronautics and Astronautics Nanjing 210016 China
| | - Yufeng Guo
- State Key Laboratory of Mechanics and Control of Mechanical Structures, MOE Key Laboratory for Intelligent Nano Materials and Devices, College of Aerospace Engineering, Nanjing University of Aeronautics and Astronautics Nanjing 210016 China
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13
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Fumega AO, Diego J, Pardo V, Blanco-Canosa S, Errea I. Anharmonicity Reveals the Tunability of the Charge Density Wave Orders in Monolayer VSe 2. NANO LETTERS 2023; 23:1794-1800. [PMID: 36825982 PMCID: PMC9999451 DOI: 10.1021/acs.nanolett.2c04584] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/21/2022] [Revised: 02/22/2023] [Indexed: 06/18/2023]
Abstract
VSe2 is a layered compound that has attracted great attention due to its proximity to a ferromagnetic state that is quenched by its charge density wave (CDW) phase. In the monolayer limit, unrelated experiments have reported different CDW orders with different transition temperatures, making this monolayer very controversial. Here we perform first-principles nonperturbative anharmonic phonon calculations in monolayer VSe2 in order to estimate the CDW order and the corresponding transition temperature. They reveal that monolayer VSe2 develops two independent charge density wave orders that compete as a function of strain. Variations of only 1.5% in the lattice parameter are enough to stabilize one order or the other. Moreover, we analyze the impact of external Lennard-Jones interactions, showing that these can act together with anharmonicity to suppress the CDW orders. Our results solve previous experimental contradictions, highlighting the high tunability and substrate dependency of the CDW orders of monolayer VSe2.
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Affiliation(s)
| | - Josu Diego
- Fisika
Aplikatua Saila, Gipuzkoako Ingeniaritza Eskola, University of the Basque Country (UPV/EHU), 20018 San Sebastián, Spain
- Centro
de Física de Materiales (CSIC-UPV/EHU), 20018 San Sebastián, Spain
| | - Victor Pardo
- Departamento
de Física Aplicada, Universidade
de Santiago de Compostela, 15782 Santiago de Compostela, Spain
- Instituto
de Materiais iMATUS, Universidade de Santiago
de Compostela, 15782 Santiago de Compostela, Spain
| | - Santiago Blanco-Canosa
- Donostia
International Physics Center (DIPC), 20018 San Sebastián, Spain
- IKERBASQUE, Basque Foundation
for Science, 48013 Bilbao, Spain
| | - Ion Errea
- Fisika
Aplikatua Saila, Gipuzkoako Ingeniaritza Eskola, University of the Basque Country (UPV/EHU), 20018 San Sebastián, Spain
- Centro
de Física de Materiales (CSIC-UPV/EHU), 20018 San Sebastián, Spain
- Donostia
International Physics Center (DIPC), 20018 San Sebastián, Spain
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14
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You J, Pan J, Shang SL, Xu X, Liu Z, Li J, Liu H, Kang T, Xu M, Li S, Kong D, Wang W, Gao Z, Zhou X, Zhai T, Liu ZK, Kim JK, Luo Z. Salt-Assisted Selective Growth of H-phase Monolayer VSe 2 with Apparent Hole Transport Behavior. NANO LETTERS 2022; 22:10167-10175. [PMID: 36475688 DOI: 10.1021/acs.nanolett.2c04133] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Vanadium diselenide (VSe2) exhibits versatile electronic and magnetic properties in the trigonal prismatic (H-) and octahedral (T-) phases. Compared to the metallic T-phase, the H-phase with a tunable semiconductor property is predicted to be a ferrovalley material with spontaneous valley polarization. Herein we report an epitaxial growth of the monolayer 2D VSe2 on a mica substrate via the chemical vapor deposition (CVD) method by introducing salt in the precursor. Our first-principles calculations suggest that the monolayer H-phase VSe2 with a large lateral size is thermodynamically favorable. The honeycomb-like structure and the broken symmetry are directly observed by spherical aberration-corrected scanning transmission electron microscopy (STEM) and confirmed by giant second harmonic generation (SHG) intensity. The p-type transport behavior is further evidenced by the temperature-dependent resistance and field-effect device study. The present work introduces a new phase-stable 2D transition metal dichalcogenide, opening the prospect of novel electronic and spintronics device design.
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Affiliation(s)
- Jiawen You
- Department of Chemical and Biological Engineering, Guangdong-Hong Kong-Macao Joint Laboratory for Intelligent Micro-Nano Optoelectronic Technology, William Mong Institute of Nano Science and Technology and Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong999777, P. R. China
| | - Jie Pan
- Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong999777, P. R. China
| | - Shun-Li Shang
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania16802, United States
| | - Xiang Xu
- School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan430074, P. R. China
| | - Zhenjing Liu
- Department of Chemical and Biological Engineering, Guangdong-Hong Kong-Macao Joint Laboratory for Intelligent Micro-Nano Optoelectronic Technology, William Mong Institute of Nano Science and Technology and Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong999777, P. R. China
| | - Jingwei Li
- Department of Chemical and Biological Engineering, Guangdong-Hong Kong-Macao Joint Laboratory for Intelligent Micro-Nano Optoelectronic Technology, William Mong Institute of Nano Science and Technology and Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong999777, P. R. China
| | - Hongwei Liu
- Department of Chemical and Biological Engineering, Guangdong-Hong Kong-Macao Joint Laboratory for Intelligent Micro-Nano Optoelectronic Technology, William Mong Institute of Nano Science and Technology and Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong999777, P. R. China
| | - Ting Kang
- Department of Chemical and Biological Engineering, Guangdong-Hong Kong-Macao Joint Laboratory for Intelligent Micro-Nano Optoelectronic Technology, William Mong Institute of Nano Science and Technology and Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong999777, P. R. China
| | - Mengyang Xu
- Department of Chemical and Biological Engineering, Guangdong-Hong Kong-Macao Joint Laboratory for Intelligent Micro-Nano Optoelectronic Technology, William Mong Institute of Nano Science and Technology and Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong999777, P. R. China
| | - Shaobo Li
- Department of Chemical and Biological Engineering, Guangdong-Hong Kong-Macao Joint Laboratory for Intelligent Micro-Nano Optoelectronic Technology, William Mong Institute of Nano Science and Technology and Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong999777, P. R. China
- State Key Laboratory of Luminescent Materials and Devices, Department of Electronic Materials, School of Materials Science and Engineering, South China University of Technology, Guangzhou, 510640, P. R. China
| | - Deqi Kong
- State Key Laboratory of Luminescent Materials and Devices, Department of Electronic Materials, School of Materials Science and Engineering, South China University of Technology, Guangzhou, 510640, P. R. China
| | - Wenliang Wang
- Department of Chemical and Biological Engineering, Guangdong-Hong Kong-Macao Joint Laboratory for Intelligent Micro-Nano Optoelectronic Technology, William Mong Institute of Nano Science and Technology and Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong999777, P. R. China
- State Key Laboratory of Luminescent Materials and Devices, Department of Electronic Materials, School of Materials Science and Engineering, South China University of Technology, Guangzhou, 510640, P. R. China
| | - Zhaoli Gao
- Department of Biomedical Engineering, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong999777, P. R. China
- CUHK Shenzhen Research Institute, No.10, second, Yuexing Road, Nanshan, Shenzhen518057, P. R. China
| | - Xing Zhou
- School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan430074, P. R. China
| | - Tianyou Zhai
- School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan430074, P. R. China
| | - Zi-Kui Liu
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania16802, United States
| | - Jang-Kyo Kim
- Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong999777, P. R. China
| | - Zhengtang Luo
- Department of Chemical and Biological Engineering, Guangdong-Hong Kong-Macao Joint Laboratory for Intelligent Micro-Nano Optoelectronic Technology, William Mong Institute of Nano Science and Technology and Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong999777, P. R. China
- The Hong Kong University of Science and Technology Shenzhen Research Institute, No. 9 Yuexing first RD, South Area Hi-tech Park, Nanshan, Shenzhen518057, China
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15
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Lin D, Ranjbar A, Li X, Huang X, Huang Y, Berger H, Forró L, Watanabe K, Taniguchi T, Belosludov RV, Kühne TD, Ding H, Bahramy MS, Xi X. Axial-Bonding-Driven Dimensionality Effect on the Charge-Density Wave in NbSe 2. NANO LETTERS 2022; 22:9389-9395. [PMID: 36416790 DOI: 10.1021/acs.nanolett.2c03280] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
2H-NbSe2 is a prototypical charge-density-wave (CDW) system, exhibiting such a symmetry-breaking quantum ground state in its bulk and down to a single-atomic-layer limit. However, how this state depends on dimensionality and what governs the dimensionality effect remain controversial. Here, we experimentally demonstrate a robust 3 × 3 CDW phase in both freestanding and substrate-supported bilayer NbSe2, far above the bulk transition temperature. We exclude environmental effects and reveal a strong temperature and thickness dependence of Raman intensity from an axially vibrating A1g phonon mode, involving Se ions. Using first-principles calculations, we show that these result from a delicate but profound competition between the intra- and interlayer bonding formed between Se-pz orbitals. Our results suggest the crucial role of Se out-of-plane displacement in driving the CDW distortion, revealing the Se-dominated dimensionality effect and establishing a new perspective on the chemical bonding and mechanical stability in layered CDW materials.
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Affiliation(s)
- Dongjing Lin
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing210093, People's Republic of China
| | - Ahmad Ranjbar
- Dynamics of Condensed Matter and Center for Sustainable Systems Design, Theoretical Chemistry, University of Paderborn, Paderborn33098, Germany
| | - Xiaoxia Li
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing210093, People's Republic of China
| | - Xinyu Huang
- Advanced Research Institute of Multidisciplinary Science, Beijing Institute of Technology, Beijing100081, People's Republic of China
| | - Yuan Huang
- Advanced Research Institute of Multidisciplinary Science, Beijing Institute of Technology, Beijing100081, People's Republic of China
| | - Helmuth Berger
- Institute of Condensed Matter Physics, École Polytechnique Fédérale de Lausanne, 1015Lausanne, Switzerland
| | - László Forró
- Institute of Condensed Matter Physics, École Polytechnique Fédérale de Lausanne, 1015Lausanne, Switzerland
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba305-0044, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba305-0044, Japan
| | | | - Thomas D Kühne
- Dynamics of Condensed Matter and Center for Sustainable Systems Design, Theoretical Chemistry, University of Paderborn, Paderborn33098, Germany
| | - Haifeng Ding
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing210093, People's Republic of China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing210093, People's Republic of China
| | - Mohammad Saeed Bahramy
- Department of Physics and Astronomy, The University of Manchester, Oxford Road, ManchesterM13 9PL, United Kingdom
| | - Xiaoxiang Xi
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing210093, People's Republic of China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing210093, People's Republic of China
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16
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Friedensen S, Yasini P, Keneipp R, Castan A, Drndić M. Solvent-Induced Degradation of Electrochemically Exfoliated Vanadium Selenide Visualized by Electron Microscopy. ACS OMEGA 2022; 7:42146-42154. [PMID: 36440127 PMCID: PMC9685602 DOI: 10.1021/acsomega.2c04749] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/27/2022] [Accepted: 10/26/2022] [Indexed: 06/16/2023]
Abstract
Recently discovered two-dimensional ferromagnetic materials (2DFMs) have rapidly gained much interest in the fields of spintronics and computing, where they may prove powerful tools for miniaturizing devices such as magnetic tunnel junctions and spin-transfer torque memory bits. In addition, heterojunctions and twisted bilayer stacks of such materials may yield exotic spin textures. However, preparation of such devices is complicated by the air sensitivity of many 2DFMs. Here, we report details on the preparation of few-to-monolayer flakes of vanadium selenide (VSe2) using electrochemical exfoliation in propylene carbonate. We also present a detailed study of the effects of air on the structure and magnetic properties of bare and passivated VSe2 after different concentrations of surface passivation treatment. We characterized the microstructure of holes in the VSe2 flakes and the formation of new compounds arising from air exposure, solvent exposure during the exfoliating process, and deliberate electron beam irradiation (sculpting). We sculpt VSe2 flakes while retaining the 1T-VSe2 lattice structure, opening the door for top-down patterned high-resolution 2DFM nanostructures. Additionally, investigation of the magnetic response of nanosheets using magnetic force microscopy (MFM) showed that the oxidation-induced damage only affects the surface fields locally and does not quench large-scale magnetic signal. The findings of this study pave the way toward practical incorporation of 2D ferromagnetic materials in nanoelectronics.
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17
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Jiang J, Li R, Mi W. Exchange interactions in the 1T-VSe 2 monolayer and their modulation via electron doping using alkali metal adsorption and the electride substrate. MATERIALS HORIZONS 2022; 9:2785-2796. [PMID: 36040428 DOI: 10.1039/d2mh00888b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
The modulation of exchange interactions in layered magnets has fundamental research value and potential applications in spintronics. Based on first-principles calculations, the exchange interactions in the experimentally controversial room-temperature ferromagnetic 1T-VSe2 monolayer are systematically studied. It is found that three shells of nearest-neighbor Heisenberg exchange interactions and higher-order interactions are crucial for an accurate description of the magnetism and its thermal stability in the 1T-VSe2 monolayer. Based on our understanding of tuning the magnetic interactions and the magnetic ground state in the 1T-VSe2 monolayer via external factors, two modulation methods, involving adsorption of the alkali metal lithium and the electride Ca2N substrate, are proposed. In both Li-VSe2 and VSe2/Ca2N systems, the strongly frustrated Heisenberg exchange interaction competes with the Dzyaloshinskii-Moriya interaction and magnetocrystalline anisotropy, leading to complex magnetic ground states, such as antiferromagnetic spin spiral and periodic antiferromagnetic cycloidal states. Moreover, the higher-order exchange interactions play a crucial role in the stabilization of long-range double-row-wise antiferromagnetic states in Li-VSe2 and VSe2/Ca2N. These results highlight the effective manipulation of exchange interactions in two-dimensional magnets.
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Affiliation(s)
- Jiawei Jiang
- Tianjin Key Laboratory of Low Dimensional Materials Physics and Preparation Technology, School of Science, Tianjin University, Tianjin, 300354, China.
| | - Rui Li
- Tianjin Key Laboratory of Low Dimensional Materials Physics and Preparation Technology, School of Science, Tianjin University, Tianjin, 300354, China.
| | - Wenbo Mi
- Tianjin Key Laboratory of Low Dimensional Materials Physics and Preparation Technology, School of Science, Tianjin University, Tianjin, 300354, China.
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18
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Firouzeh S, Rahman MW, Pramanik S. Thermally-driven large current-perpendicular-to-plane magnetoresistance in ultrathin flakes of vanadium diselenide. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:495802. [PMID: 36240752 DOI: 10.1088/1361-648x/ac9a94] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2022] [Accepted: 10/14/2022] [Indexed: 06/16/2023]
Abstract
Current-perpendicular-to-plane magnetoresistance (CPP MR) in layered heterojunctions is at the heart of modern magnetic field sensing and data storage technologies. van der waals heterostructures and two-dimensional (2D) magnets opened a new playground for exploring this effect, although most 2D magnets exhibit large CPP MR only at very low temperatures due to their very low Curie temperatures. vanadium diselenide (VSe2) is a promising material since its monolayers can potentially act as room temperature ferromagnets. VSe2multilayers have been predicted to exhibit CPP MR effects, although experimental work in this area remains scarce. In this work we investigate CPP MR in 1T-VSe2ultrathin flakes, revealing alarge (∼60%-70%), positive, linear, and non saturating CPP MR, which persists close to room temperature (∼250 K), in a relatively small magnetic field range of ±12 kG. The CPP MR has been found to increase with decreasing flake thickness. The CPP MR originates due to the intrinsic inhomogeneity in the CPP transport path, andexhibits unprecedented immunity against thermal fluctuations, leading to increasingly enhanced MR as temperature is increased, even significantly beyond the charge density wave transition temperature. The observed 'thermally-driven' MR features are remarkably robust and reproducible, and can offer a viable route for developing practical room temperature 2D based magnetic sensor technologies. Our results also suggest that harnessing similar effects in other 2D systems could result in large MR as well, thereby motivating further research on CPP transport in these systems, which has been relatively unexplored so far.
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Affiliation(s)
- Seyedamin Firouzeh
- Electrical and Computer Engineering, University of Alberta, Room- W3-075, ECERF Building, Edmonton, Alberta T6G 2R3, Canada
| | - Md Wazedur Rahman
- Department of Electrical and Computer Engineering, University of Alberta, Edmonton, Alberta T6G 1H9, Canada
| | - Sandipan Pramanik
- Department of Electrical and Computer Engineering, University of Alberta, Edmonton, Alberta T6G 1H9, Canada
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19
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Zhu W, Song C, Wang Q, Bai H, Yin S, Pan F. Anomalous displacement reaction for synthesizing above-room-temperature and air-stable vdW ferromagnet PtTe 2Ge 1/3. Natl Sci Rev 2022; 10:nwac173. [PMID: 36684515 PMCID: PMC9843128 DOI: 10.1093/nsr/nwac173] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2022] [Accepted: 08/10/2022] [Indexed: 01/25/2023] Open
Abstract
Emerging van der Waals (vdW) magnets provide a paradise for the exploration of magnetism in the ultimate two-dimensional (2D) limit, and the construction of integrated spintronic devices, and have become a research frontier in the field of low-dimensional materials. To date, prototypical vdW magnets based on metals of the first transition series (e.g. V, Cr, Mn and Fe) and chalcogen elements suffer from rapid oxidation restricted by the Hard-Soft-Acid-Base principle, as well as low Curie temperatures (T C), which has become a generally admitted challenge in 2D spintronics. Here, starting from air-unstable Cr2Ge2Te6 vdW thin flakes, we synthesize Ge-embedded PtTe2 (namely PtTe2Ge1/3) with superior air stability, through the displacement reaction in the Cr2Ge2Te6/Pt bilayer. In this process, the anomalous substitution of Cr with Pt in the thermal diffusion is inverse to the metal activity order, which can be attributed to the compatibility between soft-acid (Pt) and soft-base (Te) elements. Meanwhile, the layered uniform insertion of Ge unbalances Pt-Te bonds and introduces long-range ordered ferromagnetism with perpendicular magnetic anisotropy and a Curie temperature above room temperature. Our work demonstrates the anti-metal-activity-order reaction tendency unique in 2D transition-metal magnets and boosts progress towards practical 2D spintronics.
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Affiliation(s)
- Wenxuan Zhu
- Key Laboratory of Advanced Materials, School of Materials Science and Engineering, Beijing Innovation Center for Future Chips, Tsinghua University, Beijing 100084, China
| | | | - Qian Wang
- Key Laboratory of Advanced Materials, School of Materials Science and Engineering, Beijing Innovation Center for Future Chips, Tsinghua University, Beijing 100084, China
| | - Hua Bai
- Key Laboratory of Advanced Materials, School of Materials Science and Engineering, Beijing Innovation Center for Future Chips, Tsinghua University, Beijing 100084, China
| | - Siqi Yin
- Key Laboratory of Advanced Materials, School of Materials Science and Engineering, Beijing Innovation Center for Future Chips, Tsinghua University, Beijing 100084, China
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20
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Zhu Y, Gao Y, Jiang X, Zhao J. Effects of vacancy defects on the magnetic properties of vanadium diselenide monolayers: a first principle investigation. Phys Chem Chem Phys 2022; 24:17615-17622. [PMID: 35833467 DOI: 10.1039/d2cp01537d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Long-range ferromagnetic (FM) order in vanadium diselenide (VSe2) monolayers (MLs) remains a controversial subject. In this theoretical study, we examined the effect of vacancy defects on the magnetic properties of octahedrally coordinated 1T-VSe2 MLs using spin-polarized density functional theory (DFT). In total, 45 different kinds of defects with various concentrations were introduced, including two single vacancies (S), 27 double vacancies (D), nine triple vacancies (T), and seven quadruple vacancies (Q). To understand the magnetic properties, SSe, DSe-(10), TSe-(10)(10), and QSe-(21)(10)(10) were selected to be analyzed because they had low formation energies and large variations in magnetic moments (M). Compared with the perfect VSe2 ML, the values of the M of vanadium (V) decreased from 0.675 to 0.466, 0.183, 0.213, and 0.208 μB with increasing vacancy concentration. The same trend was also found for the energy differences between FM and antiferromagnetic (AFM) ordering. These results generally indicated weaker FM coupling and a lower Curie temperature in defective VSe2. Vacancy-induced lattice distortion, d orbital shifting, electronic occupation, and spin density redistribution were discussed in order to explain the above observations. Our investigation demonstrated a strong dependence of M and the magnetic interaction of VSe2 on the concentration and types of Se vacancies, which would explain the uncertainties encountered in magnetic experiments.
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Affiliation(s)
- Yan Zhu
- Key Laboratory of Material Modification by Laser, Ion and Electron Beams, Dalian University of Technology, Ministry of Education, Dalian 116024, China.
| | - Yinlu Gao
- Key Laboratory of Material Modification by Laser, Ion and Electron Beams, Dalian University of Technology, Ministry of Education, Dalian 116024, China.
| | - Xue Jiang
- Key Laboratory of Material Modification by Laser, Ion and Electron Beams, Dalian University of Technology, Ministry of Education, Dalian 116024, China.
| | - Jijun Zhao
- Key Laboratory of Material Modification by Laser, Ion and Electron Beams, Dalian University of Technology, Ministry of Education, Dalian 116024, China.
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21
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Göhler F, Ramasubramanian S, Rajak SK, Rösch N, Schütze A, Wolff S, Cordova DLM, Johnson DC, Seyller T. Modulation doping and charge density wave transition in layered PbSe-VSe 2 ferecrystal heterostructures. NANOSCALE 2022; 14:10143-10154. [PMID: 35796182 DOI: 10.1039/d2nr01071b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Controlling charge carrier concentrations remains a major challenge in the application of quasi-two-dimensional materials. A promising approach is the modulation doping of transport channels via charge transfer from neighboring layers in stacked heterostructures. Ferecrystals, which are metastable layered structures created from artificial elemental precursors, are a perfect model system to investigate modulation doping, as they offer unparalleled freedom in the combination of different constituents and variable layering sequences. In this work, differently stacked combinations of rock-salt structured PbSe and VSe2 were investigated using X-ray photoelectron spectroscopy. The PbSe layers act as electron donors in all heterostructures, with about 0.1 to 0.3 donated electrons per VSe2 unit cell. While they initially retain their inherent semiconducting behavior, they themselves become metallic when combined with a larger number of VSe2 layers, as evidenced by a change of the XPS core level lineshape. Additional analysis of the valence band structure was performed for selected stacking orders at different sample temperatures to investigate a predicted charge density wave (CDW) transition. While there appear to be hints of a gap opening, the data so far is inconclusive and the application of spatially resolved techniques such as scanning tunneling microscopy is encouraged for further studies.
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Affiliation(s)
- Fabian Göhler
- Institute of Physics, Chemnitz University of Technology, 09126 Chemnitz, Germany.
- Center for Materials, Architectures and Integration of Nanomembranes (MAIN), 09126 Chemnitz, Germany
| | | | - Sanam Kumari Rajak
- Institute of Physics, Chemnitz University of Technology, 09126 Chemnitz, Germany.
| | - Niels Rösch
- Institute of Physics, Chemnitz University of Technology, 09126 Chemnitz, Germany.
| | - Adrian Schütze
- Institute of Physics, Chemnitz University of Technology, 09126 Chemnitz, Germany.
- Center for Materials, Architectures and Integration of Nanomembranes (MAIN), 09126 Chemnitz, Germany
| | - Susanne Wolff
- Institute of Physics, Chemnitz University of Technology, 09126 Chemnitz, Germany.
- Center for Materials, Architectures and Integration of Nanomembranes (MAIN), 09126 Chemnitz, Germany
| | | | - David C Johnson
- Department of Chemistry, University of Oregon, Eugene, Oregon 97401, USA
| | - Thomas Seyller
- Institute of Physics, Chemnitz University of Technology, 09126 Chemnitz, Germany.
- Center for Materials, Architectures and Integration of Nanomembranes (MAIN), 09126 Chemnitz, Germany
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22
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Wan W, Wickramaratne D, Dreher P, Harsh R, Mazin II, Ugeda MM. Nontrivial Doping Evolution of Electronic Properties in Ising-Superconducting Alloys. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022; 34:e2200492. [PMID: 35243698 DOI: 10.1002/adma.202200492] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2022] [Revised: 02/16/2022] [Indexed: 06/14/2023]
Abstract
Transition metal dichalcogenides offer unprecedented versatility to engineer 2D materials with tailored properties to explore novel structural and electronic phase transitions. In this work, the atomic-scale evolution of the electronic ground state of a monolayer of Nb1- δ Moδ Se2 across the entire alloy composition range (0 < δ < 1) is investigated using low-temperature (300 mK) scanning tunneling microscopy and spectroscopy (STM/STS). In particular, the atomic and electronic structure of this 2D alloy throughout the metal to semiconductor transition (monolayer NbSe2 to MoSe2 ) is studied. The measurements enable extraction of the effective doping of Mo atoms, the bandgap evolution and the band shifts, which are monotonic with δ. Furthermore, it is demonstrated that collective electronic phases (charge density wave and superconductivity) are remarkably robust against disorder and further shown that the superconducting TC changes non-monotonically with doping. This contrasting behavior in the normal and superconducting state is explained using first-principles calculations. Mo doping is shown to decrease the density of states at the Fermi level and the magnitude of pair-breaking spin fluctuations as a function of Mo content. These results paint a detailed picture of the electronic structure evolution in 2D TMD alloys, which is of utmost relevance for future 2D materials design.
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Affiliation(s)
- Wen Wan
- Donostia International Physics Center (DIPC), Paseo Manuel de Lardizábal 4, San Sebastián, 20018, Spain
| | - Darshana Wickramaratne
- Center for Computational Materials Science, U.S. Naval Research Laboratory, Washington, DC 20375, USA
| | - Paul Dreher
- Donostia International Physics Center (DIPC), Paseo Manuel de Lardizábal 4, San Sebastián, 20018, Spain
| | - Rishav Harsh
- Donostia International Physics Center (DIPC), Paseo Manuel de Lardizábal 4, San Sebastián, 20018, Spain
| | - Igor I Mazin
- Department of Physics and Astronomy, George Mason University, Fairfax, VA, 22030, USA
- Quantum Science and Engineering Center, George Mason University, Fairfax, VA, 22030, USA
| | - Miguel M Ugeda
- Donostia International Physics Center (DIPC), Paseo Manuel de Lardizábal 4, San Sebastián, 20018, Spain
- Centro de Física de Materiales (CSIC-UPV-EHU), Paseo Manuel de Lardizábal 5, San Sebastián, 20018, Spain
- Ikerbasque, Basque Foundation for Science, Bilbao, 48013, Spain
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23
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Chowdhury S, Rigosi AF, Hill HM, Briggs A, Newell DB, Berger H, Hight Walker AR, Tavazza F. Influence of Dimensionality on the Charge Density Wave Phase of 2H‐TaSe
2. ADVANCED THEORY AND SIMULATIONS 2022. [DOI: 10.1002/adts.202100329] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Sugata Chowdhury
- Department of Physics and Astronomy Howard University Washington DC 20059 USA
| | - Albert F. Rigosi
- National Institute of Standards and Technology Gaithersburg MD 20899 USA
| | - Heather M. Hill
- National Institute of Standards and Technology Gaithersburg MD 20899 USA
| | - Andrew Briggs
- National Institute of Standards and Technology Gaithersburg MD 20899 USA
| | - David B. Newell
- National Institute of Standards and Technology Gaithersburg MD 20899 USA
| | - Helmuth Berger
- École Polytechnique Fédérale de Lausanne (EPFL) Institut de Physique des Nanostructures Lausanne CH‐1015 Switzerland
| | | | - Francesca Tavazza
- National Institute of Standards and Technology Gaithersburg MD 20899 USA
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24
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Chowdhury S, Rigosi AF, Hill HM, Vora P, Hight Walker AR, Tavazza F. Computational Methods for Charge Density Waves in 2D Materials. NANOMATERIALS (BASEL, SWITZERLAND) 2022; 12:504. [PMID: 35159849 PMCID: PMC8839743 DOI: 10.3390/nano12030504] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Revised: 01/20/2022] [Accepted: 01/26/2022] [Indexed: 11/29/2022]
Abstract
Two-dimensional (2D) materials that exhibit charge density waves (CDWs)-spontaneous reorganization of their electrons into a periodic modulation-have generated many research endeavors in the hopes of employing their exotic properties for various quantum-based technologies. Early investigations surrounding CDWs were mostly focused on bulk materials. However, applications for quantum devices require few-layer materials to fully utilize the emergent phenomena. The CDW field has greatly expanded over the decades, warranting a focus on the computational efforts surrounding them specifically in 2D materials. In this review, we cover ground in the following relevant theory-driven subtopics for TaS2 and TaSe2: summary of general computational techniques and methods, resulting atomic structures, the effect of electron-phonon interaction of the Raman scattering modes, the effects of confinement and dimensionality on the CDW, and we end with a future outlook. Through understanding how the computational methods have enabled incredible advancements in quantum materials, one may anticipate the ever-expanding directions available for continued pursuit as the field brings us through the 21st century.
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Affiliation(s)
- Sugata Chowdhury
- Department of Physics and Astronomy, Howard University, Washington, DC 20059, USA;
- Material Measurement Laboratory, National Institute of Standards and Technology (NIST), Gaithersburg, MD 20899, USA
| | - Albert F. Rigosi
- Physical Measurement Laboratory, National Institute of Standards and Technology (NIST), Gaithersburg, MD 20899, USA; (A.F.R.); (H.M.H.); (A.R.H.W.)
| | - Heather M. Hill
- Physical Measurement Laboratory, National Institute of Standards and Technology (NIST), Gaithersburg, MD 20899, USA; (A.F.R.); (H.M.H.); (A.R.H.W.)
- Physics Today, American Institute of Physics, College Park, MD 20740, USA
| | - Patrick Vora
- Quantum Science and Engineering Center, George Mason University, Fairfax, VA 22030, USA;
- Department of Physics and Astronomy, George Mason University, Fairfax, VA 22030, USA
| | - Angela R. Hight Walker
- Physical Measurement Laboratory, National Institute of Standards and Technology (NIST), Gaithersburg, MD 20899, USA; (A.F.R.); (H.M.H.); (A.R.H.W.)
| | - Francesca Tavazza
- Material Measurement Laboratory, National Institute of Standards and Technology (NIST), Gaithersburg, MD 20899, USA
- Physical Measurement Laboratory, National Institute of Standards and Technology (NIST), Gaithersburg, MD 20899, USA; (A.F.R.); (H.M.H.); (A.R.H.W.)
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25
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Chua R, Henke J, Saha S, Huang Y, Gou J, He X, Das T, van Wezel J, Soumyanarayanan A, Wee ATS. Coexisting Charge-Ordered States with Distinct Driving Mechanisms in Monolayer VSe 2. ACS NANO 2022; 16:783-791. [PMID: 34931805 DOI: 10.1021/acsnano.1c08304] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Thinning crystalline materials to two dimensions (2D) creates a rich playground for electronic phases, including charge, spin, superconducting, and topological order. Bulk materials hosting charge density waves (CDWs), when reduced to ultrathin films, have shown CDW enhancement and tunability. However, charge order confined to only 2D remains elusive. Here we report a distinct charge ordered state emerging in the monolayer limit of 1T-VSe2. Systematic scanning tunneling microscopy experiments reveal that bilayer VSe2 largely retains the bulk electronic structure, hosting a tridirectional CDW. However, monolayer VSe2 ─consistently across distinct substrates─exhibits a dimensional crossover, hosting two CDWs with distinct wavelengths and transition temperatures. Electronic structure calculations reveal that while one CDW is bulk-like and arises from the well-known Peierls mechanism, the other is decidedly unconventional. The observed CDW-lattice decoupling and the emergence of a flat band suggest that the second CDW could arise from enhanced electron-electron interactions in the 2D limit. These findings establish monolayer-VSe2 as a host of coexisting charge orders with distinct origins, and enable the tailoring of electronic phenomena via emergent interactions in 2D materials.
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Affiliation(s)
- Rebekah Chua
- Department of Physics, National University of Singapore, Singapore 117542, Singapore
| | - Jans Henke
- Institute for Theoretical Physics Amsterdam and Delta Institute for Theoretical Physics, University of Amsterdam, Amsterdam 1098XH, The Netherlands
| | - Surabhi Saha
- Department of Physics, Indian Institute of Science, Bangalore 560012, India
| | - Yuli Huang
- Department of Physics, National University of Singapore, Singapore 117542, Singapore
- Joint School of National University of Singapore and Tianjin University, Binhai New City, Fuzhou 350207, China
| | - Jian Gou
- Department of Physics, National University of Singapore, Singapore 117542, Singapore
| | - Xiaoyue He
- Department of Physics, National University of Singapore, Singapore 117542, Singapore
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China
| | - Tanmoy Das
- Department of Physics, Indian Institute of Science, Bangalore 560012, India
| | - Jasper van Wezel
- Institute for Theoretical Physics Amsterdam and Delta Institute for Theoretical Physics, University of Amsterdam, Amsterdam 1098XH, The Netherlands
| | - Anjan Soumyanarayanan
- Department of Physics, National University of Singapore, Singapore 117542, Singapore
- Institute of Materials Research & Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), Singapore 138634, Singapore
| | - Andrew T S Wee
- Department of Physics, National University of Singapore, Singapore 117542, Singapore
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26
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Ren MQ, Han S, Fan JQ, Wang L, Wang P, Ren W, Peng K, Li S, Wang SZ, Zheng FW, Zhang P, Li F, Ma X, Xue QK, Song CL. Semiconductor-Metal Phase Transition and Emergent Charge Density Waves in 1 T-ZrX 2 (X = Se, Te) at the Two-Dimensional Limit. NANO LETTERS 2022; 22:476-484. [PMID: 34978815 DOI: 10.1021/acs.nanolett.1c04372] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
A charge density wave (CDW) is a collective quantum phenomenon in metals and features a wavelike modulation of the conduction electron density. A microscopic understanding and experimental control of this many-body electronic state in atomically thin materials remain hot topics in materials physics. By means of material engineering, we realized a dimensionality and Zr intercalation induced semiconductor-metal phase transition in 1T-ZrX2 (X = Se, Te) ultrathin films, accompanied by a commensurate 2 × 2 CDW order. Furthermore, we observed a CDW energy gap of up to 22 meV around the Fermi level. Fourier-transformed scanning tunneling microscopy and angle-resolved photoemission spectroscopy reveal that 1T-ZrX2 films exhibit the simplest Fermi surface among the known CDW materials in TMDCs, consisting only of a Zr 4d derived elliptical electron conduction band at the corners of the Brillouin zone.
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Affiliation(s)
- Ming-Qiang Ren
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, People's Republic of China
| | - Sha Han
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, People's Republic of China
| | - Jia-Qi Fan
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, People's Republic of China
| | - Li Wang
- Vacuum Interconnected Nanotech Workstation, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, People's Republic of China
| | - Pengdong Wang
- Vacuum Interconnected Nanotech Workstation, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, People's Republic of China
| | - Wei Ren
- Vacuum Interconnected Nanotech Workstation, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, People's Republic of China
| | - Kun Peng
- Vacuum Interconnected Nanotech Workstation, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, People's Republic of China
| | - Shujing Li
- College of Mathematics and Physics, Beijing University of Chemical Technology, Beijing 100029, People's Republic of China
| | - Shu-Ze Wang
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, People's Republic of China
| | - Fa-Wei Zheng
- Institute of Applied Physics and Computational Mathematics, Beijing 100088, People's Republic of China
| | - Ping Zhang
- College of Mathematics and Physics, Beijing University of Chemical Technology, Beijing 100029, People's Republic of China
| | - Fangsen Li
- Vacuum Interconnected Nanotech Workstation, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, People's Republic of China
| | - Xucun Ma
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, People's Republic of China
- Frontier Science Center for Quantum Information, Beijing 100084, People's Republic of China
| | - Qi-Kun Xue
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, People's Republic of China
- Frontier Science Center for Quantum Information, Beijing 100084, People's Republic of China
- Beijing Academy of Quantum Information Sciences, Beijing 100193, People's Republic of China
| | - Can-Li Song
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, People's Republic of China
- Frontier Science Center for Quantum Information, Beijing 100084, People's Republic of China
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27
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Dreher P, Wan W, Chikina A, Bianchi M, Guo H, Harsh R, Mañas-Valero S, Coronado E, Martínez-Galera AJ, Hofmann P, Miwa JA, Ugeda MM. Proximity Effects on the Charge Density Wave Order and Superconductivity in Single-Layer NbSe 2. ACS NANO 2021; 15:19430-19438. [PMID: 34846856 PMCID: PMC8717633 DOI: 10.1021/acsnano.1c06012] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Accepted: 11/05/2021] [Indexed: 06/10/2023]
Abstract
Collective electronic states such as the charge density wave (CDW) order and superconductivity (SC) respond sensitively to external perturbations. Such sensitivity is dramatically enhanced in two dimensions (2D), where 2D materials hosting such electronic states are largely exposed to the environment. In this regard, the ineludible presence of supporting substrates triggers various proximity effects on 2D materials that may ultimately compromise the stability and properties of the electronic ground state. In this work, we investigate the impact of proximity effects on the CDW and superconducting states in single-layer (SL) NbSe2 on four substrates of diverse nature, namely, bilayer graphene (BLG), SL-boron nitride (h-BN), Au(111), and bulk WSe2. By combining low-temperature (340 mK) scanning tunneling microscopy/spectroscopy and angle-resolved photoemission spectroscopy, we compare the electronic structure of this prototypical 2D superconductor on each substrate. We find that, even when the electronic band structure of SL-NbSe2 remains largely unaffected by the substrate except when placed on Au(111), where a charge transfer occurs, both the CDW and SC show disparate behaviors. On the insulating h-BN/Ir(111) substrate and the metallic BLG/SiC(0001) substrate, both the 3 × 3 CDW and superconducting phases persist in SL-NbSe2 with very similar properties, which reveals the negligible impact of graphene on these electronic phases. In contrast, these collective electronic phases are severely weakened and even absent on the bulk insulating WSe2 substrate and the metallic single-crystal Au(111) substrate. Our results provide valuable insights into the fragile stability of such electronic ground states in 2D materials.
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Affiliation(s)
- Paul Dreher
- Donostia
International Physics Center (DIPC), Paseo Manuel de Lardizábal 4, 20018 San Sebastián, Spain
| | - Wen Wan
- Donostia
International Physics Center (DIPC), Paseo Manuel de Lardizábal 4, 20018 San Sebastián, Spain
| | - Alla Chikina
- Department
of Physics and Astronomy, Interdisciplinary Nanoscience Center, Aarhus University, 8000 Aarhus C, Denmark
| | - Marco Bianchi
- Department
of Physics and Astronomy, Interdisciplinary Nanoscience Center, Aarhus University, 8000 Aarhus C, Denmark
| | - Haojie Guo
- Departamento
de Física de la Materia Condensada, Universidad Autonoma de Madrid, Madrid E-28049, Spain
| | - Rishav Harsh
- Donostia
International Physics Center (DIPC), Paseo Manuel de Lardizábal 4, 20018 San Sebastián, Spain
| | - Samuel Mañas-Valero
- Instituto
de Ciencia Molecular (ICMol), Universitat
de València, c/
Catedrático José Beltrán 2, 46980 Paterna, Spain
| | - Eugenio Coronado
- Instituto
de Ciencia Molecular (ICMol), Universitat
de València, c/
Catedrático José Beltrán 2, 46980 Paterna, Spain
| | - Antonio J. Martínez-Galera
- Departamento
de Física de la Materia Condensada, Universidad Autonoma de Madrid, Madrid E-28049, Spain
- Insitituto
Nicolás Cabrera, Universidad Autnoma
de Madrid, Madrid E-28049, Spain
| | - Philip Hofmann
- Department
of Physics and Astronomy, Interdisciplinary Nanoscience Center, Aarhus University, 8000 Aarhus C, Denmark
| | - Jill A. Miwa
- Department
of Physics and Astronomy, Interdisciplinary Nanoscience Center, Aarhus University, 8000 Aarhus C, Denmark
| | - Miguel M. Ugeda
- Donostia
International Physics Center (DIPC), Paseo Manuel de Lardizábal 4, 20018 San Sebastián, Spain
- Centro
de Física de Materiales (CSIC-UPV-EHU), Paseo Manuel de Lardizábal 5, 20018 San Sebastián, Spain
- Ikerbasque,
Basque Foundation for Science, 48013 Bilbao, Spain
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28
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van Efferen C, Berges J, Hall J, van Loon E, Kraus S, Schobert A, Wekking T, Huttmann F, Plaar E, Rothenbach N, Ollefs K, Arruda LM, Brookes N, Schönhoff G, Kummer K, Wende H, Wehling T, Michely T. A full gap above the Fermi level: the charge density wave of monolayer VS 2. Nat Commun 2021; 12:6837. [PMID: 34824213 PMCID: PMC8617271 DOI: 10.1038/s41467-021-27094-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Accepted: 11/04/2021] [Indexed: 11/09/2022] Open
Abstract
In the standard model of charge density wave (CDW) transitions, the displacement along a single phonon mode lowers the total electronic energy by creating a gap at the Fermi level, making the CDW a metal-insulator transition. Here, using scanning tunneling microscopy and spectroscopy and ab initio calculations, we show that VS2 realizes a CDW which stands out of this standard model. There is a full CDW gap residing in the unoccupied states of monolayer VS2. At the Fermi level, the CDW induces a topological metal-metal (Lifshitz) transition. Non-linear coupling of transverse and longitudinal phonons is essential for the formation of the CDW and the full gap above the Fermi level. Additionally, x-ray magnetic circular dichroism reveals the absence of net magnetization in this phase, pointing to coexisting charge and spin density waves in the ground state.
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Affiliation(s)
- Camiel van Efferen
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937, Köln, Germany.
| | - Jan Berges
- Institut für Theoretische Physik, Bremen Center for Computational Materials Science, and MAPEX Center for Materials and Processes, Universität Bremen, Otto-Hahn-Allee 1, 28359, Bremen, Germany
| | - Joshua Hall
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937, Köln, Germany
| | - Erik van Loon
- Institut für Theoretische Physik, Bremen Center for Computational Materials Science, and MAPEX Center for Materials and Processes, Universität Bremen, Otto-Hahn-Allee 1, 28359, Bremen, Germany
| | - Stefan Kraus
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937, Köln, Germany
| | - Arne Schobert
- Institut für Theoretische Physik, Bremen Center for Computational Materials Science, and MAPEX Center for Materials and Processes, Universität Bremen, Otto-Hahn-Allee 1, 28359, Bremen, Germany
| | - Tobias Wekking
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937, Köln, Germany
| | - Felix Huttmann
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937, Köln, Germany
| | - Eline Plaar
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937, Köln, Germany
| | - Nico Rothenbach
- Fakultät für Physik und Center für Nanointegration Duisburg-Essen (CENIDE), Universität Duisburg-Essen, Carl-Benz-Straße, 47057, Duisburg, Germany
| | - Katharina Ollefs
- Fakultät für Physik und Center für Nanointegration Duisburg-Essen (CENIDE), Universität Duisburg-Essen, Carl-Benz-Straße, 47057, Duisburg, Germany
| | - Lucas Machado Arruda
- Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195, Berlin, Germany
| | - Nick Brookes
- European Synchrotron Research Facility (ESRF), Avenue des Martyrs 71, CS 40220, 38043, Grenoble Cedex 9, France
| | - Gunnar Schönhoff
- Institut für Theoretische Physik, Bremen Center for Computational Materials Science, and MAPEX Center for Materials and Processes, Universität Bremen, Otto-Hahn-Allee 1, 28359, Bremen, Germany
| | - Kurt Kummer
- European Synchrotron Research Facility (ESRF), Avenue des Martyrs 71, CS 40220, 38043, Grenoble Cedex 9, France
| | - Heiko Wende
- Fakultät für Physik und Center für Nanointegration Duisburg-Essen (CENIDE), Universität Duisburg-Essen, Carl-Benz-Straße, 47057, Duisburg, Germany
| | - Tim Wehling
- Institut für Theoretische Physik, Bremen Center for Computational Materials Science, and MAPEX Center for Materials and Processes, Universität Bremen, Otto-Hahn-Allee 1, 28359, Bremen, Germany
- Institute of Theoretical Physics, Universität Hamburg, Notkestraße 9-11, 22607, Hamburg, Germany
| | - Thomas Michely
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937, Köln, Germany
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29
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Zhao Y, Gobbi M, Hueso LE, Samorì P. Molecular Approach to Engineer Two-Dimensional Devices for CMOS and beyond-CMOS Applications. Chem Rev 2021; 122:50-131. [PMID: 34816723 DOI: 10.1021/acs.chemrev.1c00497] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Two-dimensional materials (2DMs) have attracted tremendous research interest over the last two decades. Their unique optical, electronic, thermal, and mechanical properties make 2DMs key building blocks for the fabrication of novel complementary metal-oxide-semiconductor (CMOS) and beyond-CMOS devices. Major advances in device functionality and performance have been made by the covalent or noncovalent functionalization of 2DMs with molecules: while the molecular coating of metal electrodes and dielectrics allows for more efficient charge injection and transport through the 2DMs, the combination of dynamic molecular systems, capable to respond to external stimuli, with 2DMs makes it possible to generate hybrid systems possessing new properties by realizing stimuli-responsive functional devices and thereby enabling functional diversification in More-than-Moore technologies. In this review, we first introduce emerging 2DMs, various classes of (macro)molecules, and molecular switches and discuss their relevant properties. We then turn to 2DM/molecule hybrid systems and the various physical and chemical strategies used to synthesize them. Next, we discuss the use of molecules and assemblies thereof to boost the performance of 2D transistors for CMOS applications and to impart diverse functionalities in beyond-CMOS devices. Finally, we present the challenges, opportunities, and long-term perspectives in this technologically promising field.
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Affiliation(s)
- Yuda Zhao
- University of Strasbourg, CNRS, ISIS UMR 7006, 8 allée Gaspard Monge, F-67000 Strasbourg, France.,School of Micro-Nano Electronics, ZJU-Hangzhou Global Scientific and Technological Innovation Centre, Zhejiang University, 38 Zheda Road, 310027 Hangzhou, People's Republic of China
| | - Marco Gobbi
- Centro de Fisica de Materiales (CSIC-UPV/EHU), Paseo Manuel de Lardizabal 5, E-20018 Donostia-San Sebastián, Spain.,CIC nanoGUNE, E-20018 Donostia-San Sebastian, Basque Country, Spain.,IKERBASQUE, Basque Foundation for Science, 48009 Bilbao, Spain
| | - Luis E Hueso
- CIC nanoGUNE, E-20018 Donostia-San Sebastian, Basque Country, Spain.,IKERBASQUE, Basque Foundation for Science, 48009 Bilbao, Spain
| | - Paolo Samorì
- University of Strasbourg, CNRS, ISIS UMR 7006, 8 allée Gaspard Monge, F-67000 Strasbourg, France
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30
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Wang X, Li D, Li Z, Wu C, Che CM, Chen G, Cui X. Ferromagnetism in 2D Vanadium Diselenide. ACS NANO 2021; 15:16236-16241. [PMID: 34581581 DOI: 10.1021/acsnano.1c05232] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Two-dimensional (2D) van der Waals ferromagnets carry the promise of ultimately miniature spintronics and information storage devices. Among the 2D ferromagnets, all inherit the magnetic ordering from their bulk ancestors. Here we report a 2D ferromagnetic semiconductor at room temperature, 2H-phase vanadium diselenide (VSe2), which shows ferromagnetic at the 2D form only. This 2D ferromagnetic semiconductor manifests an enhanced magnetic ordering owing to structural anisotropy at the 2D limit.
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Affiliation(s)
- Xiong Wang
- Physics Department, University of Hong Kong, Hong Kong 999077, People's Republic of China
| | - Dian Li
- Physics Department, University of Hong Kong, Hong Kong 999077, People's Republic of China
| | - Zejun Li
- Hefei National Laboratory for Physical Sciences at the Microscale, CAS Center for Excellence in Nanoscience, and CAS Key Laboratory of Mechanical Behavior and Design of Materials, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China
| | - Changzheng Wu
- Hefei National Laboratory for Physical Sciences at the Microscale, CAS Center for Excellence in Nanoscience, and CAS Key Laboratory of Mechanical Behavior and Design of Materials, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China
| | - Chi-Ming Che
- Department of Chemistry, State Key Laboratory of Synthetic Chemistry, HKU-CAS Joint Laboratory on New Materials, The University of Hong Kong, Pokfulam Road, Hong Kong 999077, People's Republic of China
| | - Gang Chen
- Physics Department, University of Hong Kong, Hong Kong 999077, People's Republic of China
| | - Xiaodong Cui
- Physics Department, University of Hong Kong, Hong Kong 999077, People's Republic of China
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31
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Kwon IS, Kwak IH, Debela TT, Kim JY, Yoo SJ, Kim JG, Park J, Kang HS. Phase-Transition Mo 1-xV xSe 2 Alloy Nanosheets with Rich V-Se Vacancies and Their Enhanced Catalytic Performance of Hydrogen Evolution Reaction. ACS NANO 2021; 15:14672-14682. [PMID: 34496215 DOI: 10.1021/acsnano.1c04453] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Alloys of transition-metal dichalcogenide can display distinctive phase evolution because of their two-dimensional structures. Herein, we report the colloidal synthesis of Mo1-xVxSe2 alloy nanosheets with full composition tuning. Alloying led to a phase transition at x = 0.7 from the semiconducting 2H phase MoSe2 to the metallic 1T phase VSe2. It also produced significant V and Se vacancies, which became the richest in the 2H phase at x = 0.3-0.5. Extensive spin-polarized density functional theory calculations consistently predicted the 2H-1T phase transition at x = 0.7, in agreement with the experimental results. The vacancy formation energy also supports the formation of V and Se vacancies. Alloying in the 2H phase enhanced the electrocatalytic performance toward hydrogen evolution reaction (HER) at x = 0.3 (in 0.5 M H2SO4) or 0.4 (in 1 M KOH). The Gibbs free energy along the HER pathway indicates that this maximum performance is due to the highest concentration of active V and Se vacancy sites.
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Affiliation(s)
- Ik Seon Kwon
- Department of Advanced Materials Chemistry, Korea University, Sejong 339-700, Republic of Korea
| | - In Hye Kwak
- Department of Advanced Materials Chemistry, Korea University, Sejong 339-700, Republic of Korea
| | - Tekalign Terfa Debela
- Institute for Application of Advanced Materials, Jeonju University, Chonju, Chonbuk 55069, Republic of Korea
| | - Ju Yeon Kim
- Department of Advanced Materials Chemistry, Korea University, Sejong 339-700, Republic of Korea
- Institute for Application of Advanced Materials, Jeonju University, Chonju, Chonbuk 55069, Republic of Korea
| | - Seung Jo Yoo
- Division of Electron Microscopic Research, Korea Basic Science Institute, Daejeon 305-806, Republic of Korea
| | - Jin-Gyu Kim
- Division of Electron Microscopic Research, Korea Basic Science Institute, Daejeon 305-806, Republic of Korea
| | - Jeunghee Park
- Department of Advanced Materials Chemistry, Korea University, Sejong 339-700, Republic of Korea
| | - Hong Seok Kang
- Department of Nano and Advanced Materials, Jeonju University, Chonju, Chonbuk 55069, Republic of Korea
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32
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Observation of pressure induced charge density wave order and eightfold structure in bulk VSe 2. Sci Rep 2021; 11:18157. [PMID: 34518573 PMCID: PMC8437963 DOI: 10.1038/s41598-021-97630-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Accepted: 08/19/2021] [Indexed: 11/30/2022] Open
Abstract
Pressure-induced charge density wave (CDW) state can overcome the low-temperature limitation for practical application, thus seeking its traces in experiments is of great importance. Herein, we provide spectroscopic evidence for the emergence of room temperature CDW order in the narrow pressure range of 10–15 GPa in bulk VSe2. Moreover, we discovered an 8-coordination structure of VSe2 with C2/m symmetry in the pressure range of 35–65 GPa by combining the X-ray absorption spectroscopy, X-ray diffraction experiments, and the first-principles calculations. These findings are beneficial for furthering our understanding of the charge modulated structure and its behavior under high pressure.
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33
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Divilov S, Mayo SG, Soler JM, Yndurain F. Critical analysis of the response function in low-dimensional materials. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 33:295701. [PMID: 33636715 DOI: 10.1088/1361-648x/abea41] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Accepted: 02/26/2021] [Indexed: 06/12/2023]
Abstract
The presence of sharp peaks in the real part of the static dielectric response function are usually accepted as indication of charge or spin instabilities in a material. However, there are misconceptions that Fermi surface (FS) nesting guarantees a peak in the response function like in one-dimensional systems, and, in addition, response function matrix elements between empty and occupied states are usually considered of secondary importance and typically set to unity like in the free electron gas case. In this work, we explicitly show, through model systems and real materials, within the framework of density functional theory, that predictions about the peaks in the response function, using FS nesting and constant matrix elements yields erroneous conclusions. We find that the inclusion of the matrix elements completely alters the structure of the response function. In all the cases studied other than the one-dimensional case we find that the inclusion of matrix elements washes out the structure found with constant matrix elements. Our conclusion is that it is imperative to calculate the full response function, with matrix elements, when making predictions about instabilities in novel materials.
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Affiliation(s)
- Simon Divilov
- Departamento de Física de la Materia Condensada and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain
| | - Sara G Mayo
- Departamento de Física de la Materia Condensada and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain
| | - Jose M Soler
- Departamento de Física de la Materia Condensada and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain
| | - Felix Yndurain
- Departamento de Física de la Materia Condensada and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain
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34
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Room-temperature intrinsic ferromagnetism in epitaxial CrTe 2 ultrathin films. Nat Commun 2021; 12:2492. [PMID: 33941773 PMCID: PMC8093203 DOI: 10.1038/s41467-021-22777-x] [Citation(s) in RCA: 80] [Impact Index Per Article: 26.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2020] [Accepted: 03/22/2021] [Indexed: 11/08/2022] Open
Abstract
While the discovery of two-dimensional (2D) magnets opens the door for fundamental physics and next-generation spintronics, it is technically challenging to achieve the room-temperature ferromagnetic (FM) order in a way compatible with potential device applications. Here, we report the growth and properties of single- and few-layer CrTe2, a van der Waals (vdW) material, on bilayer graphene by molecular beam epitaxy (MBE). Intrinsic ferromagnetism with a Curie temperature (TC) up to 300 K, an atomic magnetic moment of ~0.21 [Formula: see text]/Cr and perpendicular magnetic anisotropy (PMA) constant (Ku) of 4.89 × 105 erg/cm3 at room temperature in these few-monolayer films have been unambiguously evidenced by superconducting quantum interference device and X-ray magnetic circular dichroism. This intrinsic ferromagnetism has also been identified by the splitting of majority and minority band dispersions with ~0.2 eV at Г point using angle-resolved photoemission spectroscopy. The FM order is preserved with the film thickness down to a monolayer (TC ~ 200 K), benefiting from the strong PMA and weak interlayer coupling. The successful MBE growth of 2D FM CrTe2 films with room-temperature ferromagnetism opens a new avenue for developing large-scale 2D magnet-based spintronics devices.
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35
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Park TG, Choi BK, Park J, Kim J, Chang YJ, Rotermund F. Interlayer Coupling and Ultrafast Hot Electron Transfer Dynamics in Metallic VSe 2/Graphene van der Waals Heterostructures. ACS NANO 2021; 15:7756-7764. [PMID: 33761743 DOI: 10.1021/acsnano.1c01723] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Atomically thin vanadium diselenide (VSe2) is a two-dimensional transition metal dichalcogenide exhibiting attractive properties due to its metallic 1T phase. With the recent development of methods to manufacture high-quality monolayer VSe2 on van der Waals materials, the outstanding properties of VSe2-based heterostructures have been widely studied for diverse applications. Dimensional reduction and interlayer coupling with a van der Waals substrate lead to its distinguishable characteristics from its bulk counterparts. However, only a few fundamental studies have investigated the interlayer coupling effects and hot electron transfer dynamics in VSe2 heterostructures. In this work, we reveal ultrafast and efficient interlayer hot electron transfer and interlayer coupling effects in VSe2/graphene heterostructures. Femtosecond time-resolved reflectivity measurements showed that hot electrons in VSe2 were transferred to graphene within a 100 fs time scale with high efficiency. Besides, coherent acoustic phonon dynamics indicated interlayer coupling in VSe2/graphene heterostructures and efficient thermal energy transfer to three-dimensional substrates. Our results provide valuable insights into the intriguing properties of metallic transition metal dichalcogenide heterostructures and motivate designing optoelectronic and photonic devices with tailored properties.
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Affiliation(s)
- Tae Gwan Park
- Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Republic of Korea
| | - Byoung Ki Choi
- Department of Physics, University of Seoul, Seoul 02504, Republic of Korea
| | - Junho Park
- Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Republic of Korea
| | - Jungdae Kim
- Department of Physics, University of Ulsan, Ulsan 44610, Republic of Korea
| | - Young Jun Chang
- Department of Physics, University of Seoul, Seoul 02504, Republic of Korea
- Department of Smart Cities, University of Seoul, Seoul 02504, Republic of Korea
| | - Fabian Rotermund
- Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Republic of Korea
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36
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King PDC, Picozzi S, Egdell RG, Panaccione G. Angle, Spin, and Depth Resolved Photoelectron Spectroscopy on Quantum Materials. Chem Rev 2021; 121:2816-2856. [PMID: 33346644 DOI: 10.1021/acs.chemrev.0c00616] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The role of X-ray based electron spectroscopies in determining chemical, electronic, and magnetic properties of solids has been well-known for several decades. A powerful approach is angle-resolved photoelectron spectroscopy, whereby the kinetic energy and angle of photoelectrons emitted from a sample surface are measured. This provides a direct measurement of the electronic band structure of crystalline solids. Moreover, it yields powerful insights into the electronic interactions at play within a material and into the control of spin, charge, and orbital degrees of freedom, central pillars of future solid state science. With strong recent focus on research of lower-dimensional materials and modified electronic behavior at surfaces and interfaces, angle-resolved photoelectron spectroscopy has become a core technique in the study of quantum materials. In this review, we provide an introduction to the technique. Through examples from several topical materials systems, including topological insulators, transition metal dichalcogenides, and transition metal oxides, we highlight the types of information which can be obtained. We show how the combination of angle, spin, time, and depth-resolved experiments are able to reveal "hidden" spectral features, connected to semiconducting, metallic and magnetic properties of solids, as well as underlining the importance of dimensional effects in quantum materials.
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Affiliation(s)
- Phil D C King
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews KY16 9SS, United Kingdom
| | - Silvia Picozzi
- Consiglio Nazionale delle Ricerche, CNR-SPIN, Via dei Vestini 31, Chieti 66100, Italy
| | - Russell G Egdell
- Department of Chemistry, Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QR, United Kingdom
| | - Giancarlo Panaccione
- Istituto Officina dei Materiali (IOM)-CNR, Laboratorio TASC, in Area Science Park, S.S.14, Km 163.5, I-34149 Trieste, Italy
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37
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Biswas D, Jones AJH, Majchrzak P, Choi BK, Lee TH, Volckaert K, Feng J, Marković I, Andreatta F, Kang CJ, Kim HJ, Lee IH, Jozwiak C, Rotenberg E, Bostwick A, Sanders CE, Zhang Y, Karras G, Chapman RT, Wyatt AS, Springate E, Miwa JA, Hofmann P, King PDC, Chang YJ, Lanatà N, Ulstrup S. Ultrafast Triggering of Insulator-Metal Transition in Two-Dimensional VSe 2. NANO LETTERS 2021; 21:1968-1975. [PMID: 33600187 DOI: 10.1021/acs.nanolett.0c04409] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The transition-metal dichalcogenide VSe2 exhibits an increased charge density wave transition temperature and an emerging insulating phase when thinned to a single layer. Here, we investigate the interplay of electronic and lattice degrees of freedom that underpin these phases in single-layer VSe2 using ultrafast pump-probe photoemission spectroscopy. In the insulating state, we observe a light-induced closure of the energy gap, which we disentangle from the ensuing hot carrier dynamics by fitting a model spectral function to the time-dependent photoemission intensity. This procedure leads to an estimated time scale of 480 fs for the closure of the gap, which suggests that the phase transition in single-layer VSe2 is driven by electron-lattice interactions rather than by Mott-like electronic effects. The ultrafast optical switching of these interactions in SL VSe2 demonstrates the potential for controlling phase transitions in 2D materials with light.
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Affiliation(s)
- Deepnarayan Biswas
- Department of Physics and Astronomy, Interdisciplinary Nanoscience Center, Aarhus University, 8000 Aarhus C, Denmark
| | - Alfred J H Jones
- Department of Physics and Astronomy, Interdisciplinary Nanoscience Center, Aarhus University, 8000 Aarhus C, Denmark
| | - Paulina Majchrzak
- Department of Physics and Astronomy, Interdisciplinary Nanoscience Center, Aarhus University, 8000 Aarhus C, Denmark
- Central Laser Facility, STFC Rutherford Appleton Laboratory, Harwell 0 × 11 0QX, U.K
| | - Byoung Ki Choi
- Department of Physics, University of Seoul, Seoul 02504, Republic of Korea
| | - Tsung-Han Lee
- Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08856, United States
| | - Klara Volckaert
- Department of Physics and Astronomy, Interdisciplinary Nanoscience Center, Aarhus University, 8000 Aarhus C, Denmark
| | - Jiagui Feng
- SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS, U.K
- Suzhou Institute of Nano-Tech. and Nanobionics (SINANO), CAS, 398 Ruoshui Road, SEID, SIP, Suzhou 215123, China
| | - Igor Marković
- SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS, U.K
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - Federico Andreatta
- Department of Physics and Astronomy, Interdisciplinary Nanoscience Center, Aarhus University, 8000 Aarhus C, Denmark
| | - Chang-Jong Kang
- Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08856, United States
| | - Hyuk Jin Kim
- Department of Physics, University of Seoul, Seoul 02504, Republic of Korea
| | - In Hak Lee
- Department of Physics, University of Seoul, Seoul 02504, Republic of Korea
| | - Chris Jozwiak
- Advanced Light Source, E. O. Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Eli Rotenberg
- Advanced Light Source, E. O. Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Aaron Bostwick
- Advanced Light Source, E. O. Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Charlotte E Sanders
- Central Laser Facility, STFC Rutherford Appleton Laboratory, Harwell 0 × 11 0QX, U.K
| | - Yu Zhang
- Central Laser Facility, STFC Rutherford Appleton Laboratory, Harwell 0 × 11 0QX, U.K
| | - Gabriel Karras
- Central Laser Facility, STFC Rutherford Appleton Laboratory, Harwell 0 × 11 0QX, U.K
| | - Richard T Chapman
- Central Laser Facility, STFC Rutherford Appleton Laboratory, Harwell 0 × 11 0QX, U.K
| | - Adam S Wyatt
- Central Laser Facility, STFC Rutherford Appleton Laboratory, Harwell 0 × 11 0QX, U.K
| | - Emma Springate
- Central Laser Facility, STFC Rutherford Appleton Laboratory, Harwell 0 × 11 0QX, U.K
| | - Jill A Miwa
- Department of Physics and Astronomy, Interdisciplinary Nanoscience Center, Aarhus University, 8000 Aarhus C, Denmark
| | - Philip Hofmann
- Department of Physics and Astronomy, Interdisciplinary Nanoscience Center, Aarhus University, 8000 Aarhus C, Denmark
| | - Phil D C King
- SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS, U.K
| | - Young Jun Chang
- Department of Physics, University of Seoul, Seoul 02504, Republic of Korea
- Department of Smart Cities, University of Seoul, Seoul, 02504, Republic of Korea
| | - Nicola Lanatà
- Department of Physics and Astronomy, Interdisciplinary Nanoscience Center, Aarhus University, 8000 Aarhus C, Denmark
- Nordita, KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, 10691 Stockholm, Sweden
| | - Søren Ulstrup
- Department of Physics and Astronomy, Interdisciplinary Nanoscience Center, Aarhus University, 8000 Aarhus C, Denmark
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38
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Yang J, Luo J, Kuang Y, He Y, Wen P, Xiong L, Wang X, Yang Z. Exploring the Efficient Na/K Storage Mechanism and Vacancy Defect-Boosted Li + Diffusion Based on VSe 2/MoSe 2 Heterostructure Engineering. ACS APPLIED MATERIALS & INTERFACES 2021; 13:2072-2080. [PMID: 33347756 DOI: 10.1021/acsami.0c19934] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
As typical 2D materials, VSe2 and MoSe2 both play a complementary role in Li/Na/K storage. Therefore, we designed and optimized the VSe2/MoSe2 heterostructure to gain highly efficient Li/Na/K-ion batteries. Most importantly, achieving fast Li/Na/K-ion diffusion kinetics in the interlayer of VSe2/MoSe2 is a key point. First of all, first-principles calculations were carried out to systematically investigate the packing structure, mechanical properties, band structure, and Li/Na/K storage mechanism. Our calculated results suggest that a large interlayer spacing (3.80 Å), robust structure, and metallic character pave the way for achieving excellent charge-discharge performance for the VSe2/MoSe2 heterostructure. Moreover, V and Mo ions both suffer a very mild redox reaction even if Li/Na/K ions fill the interlayer space. These structures were all further verified to show thermal stability (300 K) by means of the AIMD method. By analyzing the Li/Na/K diffusion behavior and the effect of vacancy defect on the structural stability and energy barrier for Li interlayer diffusion, it is found that the VSe2/MoSe2 heterostructure exhibits very low-energy barriers for Na/K interlayer diffusion (0.21 eV for Na and 0.11 eV for K). Compared with the VSe2/MoSe2 heterostructure, the V0.92Se1.84/MoSe2 heterostructure not only can still maintain a stable structure and metallic character but also has much lower energy barrier for Li interlayer diffusion (0.07 vs 0.48 eV). These discoveries also break new ground to eliminate the obstacles preventing Li+ diffusion in the interlayer of other heterostructure materials. Besides, both VSe2/MoSe2 and V0.92Se1.84/MoSe2 heterostructures have low average open-circuit voltage (OCV) values during Li/Na/K interlayer diffusion (1.07 V for V0.92Se1.84/MoSe2 vs Li+, 0.86 V for VSe2/MoSe2 vs Na+, and 0.54 V for VSe2/MoSe2 vs K+), such low OCV values are beneficial for anode materials with excellent electrochemical properties. The above findings offer a new route to design anode materials for Li/Na/K-ion batteries.
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Affiliation(s)
- Jing Yang
- Key Laboratory of Low Dimensional Materials & Application Technology of Ministry of Education, School of Materials Science and Engineering, Xiangtan University, Xiangtan 411105, Hunan, China
| | - Jinda Luo
- Key Laboratory of Low Dimensional Materials & Application Technology of Ministry of Education, School of Materials Science and Engineering, Xiangtan University, Xiangtan 411105, Hunan, China
| | - Yi Kuang
- Key Laboratory of Low Dimensional Materials & Application Technology of Ministry of Education, School of Materials Science and Engineering, Xiangtan University, Xiangtan 411105, Hunan, China
| | - Yichu He
- Key Laboratory of Low Dimensional Materials & Application Technology of Ministry of Education, School of Materials Science and Engineering, Xiangtan University, Xiangtan 411105, Hunan, China
| | - Piaopiao Wen
- Key Laboratory of Low Dimensional Materials & Application Technology of Ministry of Education, School of Materials Science and Engineering, Xiangtan University, Xiangtan 411105, Hunan, China
| | - Lingling Xiong
- Key Laboratory of Low Dimensional Materials & Application Technology of Ministry of Education, School of Materials Science and Engineering, Xiangtan University, Xiangtan 411105, Hunan, China
| | - Xianyou Wang
- National Base for International Science & Technology Cooperation, National-Local Joint Engineering Laboratory for Key Materials of New Energy Storage Battery, Hunan Province Key Laboratory of Electrochemical Energy Storage and Conversion, School of Chemistry, Xiangtan University, Xiangtan 411105, China
| | - Zhenhua Yang
- Key Laboratory of Low Dimensional Materials & Application Technology of Ministry of Education, School of Materials Science and Engineering, Xiangtan University, Xiangtan 411105, Hunan, China
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Chowdhury S, Hill HM, Rigosi AF, Briggs A, Berger H, Newell DB, Walker ARH, Tavazza F. Examining Experimental Raman Mode Behavior in Mono- and Bilayer 2H-TaSe 2 via Density Functional Theory: Implications for Quantum Information Science. ACS APPLIED NANO MATERIALS 2021; 4:10.1021/acsanm.0c03222. [PMID: 34250452 PMCID: PMC8268966 DOI: 10.1021/acsanm.0c03222] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Tantalum diselenide (TaSe2) is a metallic transition metal dichalcogenide whose structure and vibrational behavior strongly depend on temperature and thickness, and this behavior includes the emergence of charge density wave (CDW) states at very low temperatures. In this work, observed Raman modes for mono- and bilayer are described across several spectral regions and compared to those seen in the bulk case. These modes, which include an experimentally observed forbidden Raman mode and low-frequency CDWs, are then matched to corresponding vibrations predicted by density functional theory (DFT). The reported match between experimental and computational results supports the presented vibrational visualizations of these modes. Support is also provided by experimental phonons observed in additional Raman spectra as a function of temperature and thickness. These results highlight the importance of understanding CDWs since they are likely to play a fundamental role in the future realization of solid-state quantum information platforms based on nonequilibrium phenomena.
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Affiliation(s)
- Sugata Chowdhury
- National Institute of Standards and Technology (NIST), Gaithersburg, Maryland 20899, United States; Department of Physics and Astronomy, Howard University, Washington, D.C. 20059, United States
| | - Heather M Hill
- National Institute of Standards and Technology (NIST), Gaithersburg, Maryland 20899, United States
| | - Albert F Rigosi
- National Institute of Standards and Technology (NIST), Gaithersburg, Maryland 20899, United States
| | - Andrew Briggs
- National Institute of Standards and, Technology (NIST), Gaithersburg, Maryland 20899, United States
| | - Helmuth Berger
- École Polytechnique Fédérale de Lausanne (EPFL), Institut de Physique des Nanostructures, CH-1015 Lausanne, Switzerland
| | - David B Newell
- National Institute of Standards and Technology (NIST), Gaithersburg, Maryland 20899, United States
| | - Angela R Hight Walker
- National Institute of Standards and Technology (NIST), Gaithersburg, Maryland 20899, United States
| | - Francesca Tavazza
- National Institute of Standards and Technology (NIST), Gaithersburg, Maryland 20899, United States
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40
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Yang S, Zhang T, Jiang C. van der Waals Magnets: Material Family, Detection and Modulation of Magnetism, and Perspective in Spintronics. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2021; 8:2002488. [PMID: 33511010 PMCID: PMC7816723 DOI: 10.1002/advs.202002488] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 09/09/2020] [Indexed: 06/02/2023]
Abstract
van der Waals (vdW) materials exhibit great potential in spintronics, arising from their excellent spin transportation, large spin-orbit coupling, and high-quality interfaces. The recent discovery of intrinsic vdW antiferromagnets and ferromagnets has laid the foundation for the construction of all-vdW spintronic devices, and enables the study of low-dimensional magnetism, which is of both technical and scientific significance. In this review, several representative families of vdW magnets are introduced, followed by a comprehensive summary of the methods utilized in reading out the magnetic states of vdW magnets. Thereafter, it is shown that various electrical, mechanical, and chemical approaches are employed to modulate the magnetism of vdW magnets. Finally, the perspective of vdW magnets in spintronics is discussed and an outlook of future development direction in this field is also proposed.
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Affiliation(s)
- Shengxue Yang
- School of Materials Science and EngineeringBeihang UniversityBeijing100191P. R. China
| | - Tianle Zhang
- School of Materials Science and EngineeringBeihang UniversityBeijing100191P. R. China
| | - Chengbao Jiang
- School of Materials Science and EngineeringBeihang UniversityBeijing100191P. R. China
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41
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Huang B, McGuire MA, May AF, Xiao D, Jarillo-Herrero P, Xu X. Emergent phenomena and proximity effects in two-dimensional magnets and heterostructures. NATURE MATERIALS 2020; 19:1276-1289. [PMID: 32948831 DOI: 10.1038/s41563-020-0791-8] [Citation(s) in RCA: 106] [Impact Index Per Article: 26.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Accepted: 07/30/2020] [Indexed: 05/24/2023]
Abstract
Ultrathin van der Waals materials and their heterostructures offer a simple, yet powerful platform for discovering emergent phenomena and implementing device structures in the two-dimensional limit. The past few years has pushed this frontier to include magnetism. These advances have brought forth a new assortment of layered materials that intrinsically possess a wide variety of magnetic properties and are instrumental in integrating exchange and spin-orbit interactions into van der Waals heterostructures. This Review Article summarizes recent progress in exploring the intrinsic magnetism of atomically thin van der Waals materials, manipulation of their magnetism by tuning the interlayer coupling, and device structures for spin- and valleytronic applications.
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Affiliation(s)
- Bevin Huang
- Department of Physics, University of Washington, Seattle, WA, USA.
| | - Michael A McGuire
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - Andrew F May
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - Di Xiao
- Department of Physics, Carnegie Mellon University, Pittsburgh, PA, USA
| | | | - Xiaodong Xu
- Department of Physics, University of Washington, Seattle, WA, USA.
- Department of Materials Science and Engineering, University of Washington, Seattle, WA, USA.
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42
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Precise nanoscale temperature mapping in operational microelectronic devices by use of a phase change material. Sci Rep 2020; 10:20087. [PMID: 33208765 PMCID: PMC7674486 DOI: 10.1038/s41598-020-77021-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Accepted: 10/21/2020] [Indexed: 01/16/2023] Open
Abstract
The microelectronics industry is pushing the fundamental limit on the physical size of individual elements to produce faster and more powerful integrated chips. These chips have nanoscale features that dissipate power resulting in nanoscale hotspots leading to device failures. To understand the reliability impact of the hotspots, the device needs to be tested under the actual operating conditions. Therefore, the development of high-resolution thermometry techniques is required to understand the heat dissipation processes during the device operation. Recently, several thermometry techniques have been proposed, such as radiation thermometry, thermocouple based contact thermometry, scanning thermal microscopy, scanning transmission electron microscopy and transition based threshold thermometers. However, most of these techniques have limitations including the need for extensive calibration, perturbation of the actual device temperature, low throughput, and the use of ultra-high vacuum. Here, we present a facile technique, which uses a thin film contact thermometer based on the phase change material \documentclass[12pt]{minimal}
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\begin{document}$$Ge_2 Sb_2 Te_5$$\end{document}Ge2Sb2Te5, to precisely map thermal contours from the nanoscale to the microscale. \documentclass[12pt]{minimal}
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\begin{document}$$Ge_2 Sb_2 Te_5$$\end{document}Ge2Sb2Te5 undergoes a crystalline transition at \documentclass[12pt]{minimal}
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\begin{document}$$\hbox {T}_{{g}}$$\end{document}Tg with large changes in its electric conductivity, optical reflectivity and density. Using this approach, we map the surface temperature of a nanowire and an embedded micro-heater on the same chip where the scales of the temperature contours differ by three orders of magnitude. The spatial resolution can be as high as 20 nanometers thanks to the continuous nature of the thin film.
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43
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Wang Y, Hamann DM, Cordova DLM, Chen J, Wang B, Shen L, Cai Z, Shi H, Karapetrova E, Aravind I, Shi L, Johnson DC, Cronin SB. Enhanced Low-Temperature Thermoelectric Performance in (PbSe) 1+δ(VSe 2) 1 Heterostructures due to Highly Correlated Electrons in Charge Density Waves. NANO LETTERS 2020; 20:8008-8014. [PMID: 33095023 DOI: 10.1021/acs.nanolett.0c02882] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
We explore the effect of charge density wave (CDW) on the in-plane thermoelectric transport properties of (PbSe)1+δ(VSe2)1 and (PbSe)1+δ(VSe2)2 heterostructures. In (PbSe)1+δ(VSe2)1 we observe an abrupt 86% increase in the Seebeck coefficient, 245% increase in the power factor, and a slight decrease in resistivity over the CDW transition. This behavior is not observed in (PbSe)1+δ(VSe2)2 and is rather unusual compared to the general trend observed in other materials. The abrupt transition causes a deviation from the Mott relationship through correlated electron states. Raman spectra of the (PbSe)1+δ(VSe2)1 material show the emergence of additional peaks below the CDW transition temperature associated with VSe2 material. Temperature-dependent in-plane X-ray diffraction (XRD) spectra show a change in the in-plane thermal expansion of VSe2 in (PbSe)1+δ(VSe2)1 due to lattice distortion. The increase in the power factor and decrease in the resistivity due to CDW suggest a potential mechanism for enhancing the thermoelectric performance at the low temperature region.
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Affiliation(s)
| | - Danielle M Hamann
- Department of Chemistry, University of Oregon, Eugene, Oregon 97403-1253, United States
| | - Dmitri Leo M Cordova
- Department of Chemistry, University of Oregon, Eugene, Oregon 97403-1253, United States
| | | | | | | | | | | | - Evguenia Karapetrova
- Advanced Photon Source, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | | | - Li Shi
- Department of Mechanical Engineering and Texas Materials Institute, University of Texas at Austin, Austin, Texas 78712, United States
| | - David C Johnson
- Department of Chemistry, University of Oregon, Eugene, Oregon 97403-1253, United States
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Lin MK, Hlevyack JA, Chen P, Liu RY, Mo SK, Chiang TC. Charge Instability in Single-Layer TiTe_{2} Mediated by van der Waals Bonding to Substrates. PHYSICAL REVIEW LETTERS 2020; 125:176405. [PMID: 33156647 DOI: 10.1103/physrevlett.125.176405] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Accepted: 09/10/2020] [Indexed: 06/11/2023]
Abstract
Single layers of transition metal dichalcogenides are of interest for emergent properties; an often-neglected issue is substrate effects. Our experiments show that the charge density wave in a single-layer TiTe_{2} grown on PtTe_{2} films is strongly suppressed by increasing the PtTe_{2} substrate thickness. Given that the interfacial bonding remains of the weak incommensurate van der Waals type, the observed changes are correlated with a thickness-dependent metallicity transformation in the PtTe_{2} substrate. The results illustrate the crucial role of the substrate in single-layer physics.
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Affiliation(s)
- Meng-Kai Lin
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
- Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - Joseph A Hlevyack
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
- Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - Peng Chen
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science and Shanghai Center for Complex Physics, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Ro-Ya Liu
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
- Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
- Institute of Physics, Academia Sinica, Taipei 10617, Taiwan
| | - Sung-Kwan Mo
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - T-C Chiang
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
- Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
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45
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Boukhvalov DW, Politano A. Unveiling the origin of room-temperature ferromagnetism in monolayer VSe 2: the role of extrinsic effects. NANOSCALE 2020; 12:20875-20882. [PMID: 33047776 DOI: 10.1039/d0nr04663a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Room-temperature ferromagnetism in monolayer vanadium diselenide (VSe2) on graphite is the object of a controversial debate. Herein, we unveil the contribution from extrinsic factors to the magnetic properties of monolayer VSe2 by means of density functional theory. Specifically, we demonstrate that either intrinsic defects or the adsorption of molecules enhances ferromagnetic interactions. The expansion of the VSe2 lattice increases the magnetic moment on vanadium ions, whereas both compression and out-of-plane distortion withdraw magnetic moments. The exchange interactions between vanadium ions and magnetic defects (vacancies and impurities) in the surface and subsurface layers of the substrate are able to turn the unstable two-dimensional (2D) ferromagnetism into stable three-dimensional (3D) ferromagnetism. Definitely, the combination of effects related to chemisorption, substrate-induced distortion and magnetic defects of the substrate could enhance or suppress ferromagnetism in monolayer VSe2.
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Affiliation(s)
- Danil W Boukhvalov
- College of Science, Institute of Materials Physics and Chemistry, Nanjing Forestry University, Nanjing 210037, P. R. China. and Institute of Physics and Technology, Ural Federal University, Mira Street 19, 620002 Yekaterinburg, Russia
| | - Antonio Politano
- Department of Physical and Chemical Sciences, University of L'Aquila, via Vetoio, 67100 L'Aquila, AQ, Italy and CNR-IMM Istituto per la Microelettronica e Microsistemi, VIII strada 5, I-95121 Catania, Italy
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46
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Kundu AK, Liu Y, Petrovic C, Valla T. Valence band electronic structure of the van der Waals ferromagnetic insulators: VI[Formula: see text] and CrI[Formula: see text]. Sci Rep 2020; 10:15602. [PMID: 32973193 PMCID: PMC7515918 DOI: 10.1038/s41598-020-72487-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2020] [Accepted: 08/28/2020] [Indexed: 12/03/2022] Open
Abstract
Ferromagnetic van der Waals (vdW) insulators are of great scientific interest for their promising applications in spintronics. It has been indicated that in the two materials within this class, CrI[Formula: see text] and VI[Formula: see text], the magnetic ground state, the band gap, and the Fermi level could be manipulated by varying the layer thickness, strain or doping. To understand how these factors impact the properties, a detailed understanding of the electronic structure would be required. However, the experimental studies of the electronic structure of these materials are still very sparse. Here, we present the detailed electronic structure of CrI[Formula: see text] and VI[Formula: see text] measured by angle-resolved photoemission spectroscopy (ARPES). Our results show a band-gap of the order of 1 eV, sharply contrasting some theoretical predictions such as Dirac half-metallicity and metallic phases, indicating that the intra-atomic interaction parameter (U) and spin-orbit coupling (SOC) were not properly accounted for in the calculations. We also find significant differences in the electronic properties of these two materials, in spite of similarities in their crystal structure. In CrI[Formula: see text], the valence band maximum is dominated by the I 5p, whereas in VI[Formula: see text] it is dominated by the V 3d derived states. Our results represent valuable input for further improvements in the theoretical modeling of these systems.
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Affiliation(s)
- Asish K. Kundu
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973 USA
| | - Yu Liu
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973 USA
- Present Address: Los Alamos National Laboratory, MS K764, Los Alamos, NM 87545 USA
| | - C. Petrovic
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973 USA
| | - T. Valla
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973 USA
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Zhang L, Yang T, He X, Zhang W, Vinai G, Tang CS, Yin X, Torelli P, Feng YP, Wong PKJ, Wee ATS. Molecular Beam Epitaxy of Two-Dimensional Vanadium-Molybdenum Diselenide Alloys. ACS NANO 2020; 14:11140-11149. [PMID: 32794699 DOI: 10.1021/acsnano.0c02124] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Two-dimensional (2D) alloys represent a versatile platform that extends the properties of atomically thin transition-metal dichalcogenides. Here, using molecular beam epitaxy, we investigate the growth of 2D vanadium-molybdenum diselenide alloys, VxMo1-xSe2, on highly oriented pyrolytic graphite and unveil their structural, chemical, and electronic integrities via measurements by scanning tunneling microscopy/spectroscopy, synchrotron X-ray photoemission, and X-ray absorption spectroscopy (XAS). Essentially, we found a critical value of x = ∼0.44, below which phase separation occurs and above which a homogeneous metallic phase is favored. Another observation is an effective increase in the density of mirror twin boundaries of constituting MoSe2 in the low V concentration regime (x ≤ 0.05). Density functional theory calculations support our experimental results on the thermal stability of 2D VxMo1-xSe2 alloys and suggest an H phase of the homogeneous alloys with alternating parallel V and Mo strips randomly in-plane stacked. Element-specific XAS of the 2D alloys, which clearly indicates quenched atomic multiplets similar to the case of 2H-VSe2, provides strong evidence for the H phase of the 2D alloys. This work provides a comprehensive understanding of the thermal stability, chemical state, and electronic structure of 2D VxMo1-xSe2 alloys, useful for the future design of 2D electronic devices.
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Affiliation(s)
- Lei Zhang
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542, Singapore
- Centre for Advanced 2D Materials (CA2DM) and Graphene Research Centre (GRC), National University of Singapore, 6 Science Drive 2, Singapore 117546, Singapore
| | - Tong Yang
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542, Singapore
| | - Xiaoyue He
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542, Singapore
- Songshan Lake Materials Laboratory, Dongguan 523808, China
| | - Wen Zhang
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542, Singapore
- School of Electronics and Information, Northwestern Polytechnical University, Xi'an 710072, P.R. China
| | - Giovanni Vinai
- Instituto Officina dei Materiali (IOM)-CNR, Laboratorio TASC, Area Science Park, S.S. km 163.5, Trieste I-34149, Italy
| | - Chi Sin Tang
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542, Singapore
- NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore 117456, Singapore
| | - Xinmao Yin
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542, Singapore
- Singapore Synchrotron Light Source (SSLS), National University of Singapore, 5 Research Link, Singapore 117603, Singapore
| | - Piero Torelli
- Instituto Officina dei Materiali (IOM)-CNR, Laboratorio TASC, Area Science Park, S.S. km 163.5, Trieste I-34149, Italy
| | - Yuan Ping Feng
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542, Singapore
| | - Ping Kwan Johnny Wong
- Centre for Advanced 2D Materials (CA2DM) and Graphene Research Centre (GRC), National University of Singapore, 6 Science Drive 2, Singapore 117546, Singapore
- School of Electronics and Information, Northwestern Polytechnical University, Xi'an 710072, P.R. China
| | - Andrew T S Wee
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542, Singapore
- Centre for Advanced 2D Materials (CA2DM) and Graphene Research Centre (GRC), National University of Singapore, 6 Science Drive 2, Singapore 117546, Singapore
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48
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Lasek K, Coelho PM, Zberecki K, Xin Y, Kolekar SK, Li J, Batzill M. Molecular Beam Epitaxy of Transition Metal (Ti-, V-, and Cr-) Tellurides: From Monolayer Ditellurides to Multilayer Self-Intercalation Compounds. ACS NANO 2020; 14:8473-8484. [PMID: 32584543 DOI: 10.1021/acsnano.0c02712] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Material growth by van der Waals epitaxy has the potential to isolate monolayer (ML) materials and synthesize ultrathin films not easily prepared by exfoliation or other growth methods. Here, the synthesis of the early transition metal (Ti, V, and Cr) tellurides by molecular beam epitaxy (MBE) in the mono- to few-layer regime is investigated. The layered ditellurides of these materials are known for their intriguing quantum- and layer dependent- properties. Here we show by a combination of in situ sample characterization and comparison with computational predictions that ML ditellurides with octahedral 1T structure are readily grown, but for multilayers, the transition metal dichalcogenide (TMDC) formation competes with self-intercalated compounds. CrTe2, a TMDC that is known to be metastable in bulk and easily decomposes into intercalation compounds, has been synthesized successfully in the ML regime at low growth temperatures. At elevated growth temperatures or for multilayers, only the intercalation compound, equivalent to a bulk Cr3Te4, could be obtained. ML VTe2 is more stable and can be synthesized at higher growth temperatures in the ML regime, but multilayers also convert to a bulk-equivalent V3Te4 compound. TiTe2 is the most stable of the TMDCs studied; nevertheless, a detailed analysis of multilayers also indicates the presence of intercalated metals. Computation suggests that the intercalation-induced distortion of the TMDC-layers is much reduced in Ti-telluride compared to V-, and Cr-telluride. This makes the identification of intercalated materials by scanning tunneling microscopy more challenging for Ti-telluride. The identification of self-intercalation compounds in MBE grown multilayer chalcogenides may explain observed lattice distortions in previously reported MBE grown early transition metal chalcogenides. On the other hand, these intercalation compounds in their ultrathin limit can be considered van der Waals materials in their own right. This class of materials is only accessible by direct growth methods but may be used as "building blocks" in MBE-grown van der Waals heterostructures. Controlling their growth is an important step for understanding and studying the properties of these materials.
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Affiliation(s)
- Kinga Lasek
- Department of Physics, University of South Florida, Tampa, Florida 33620, United States
| | - Paula Mariel Coelho
- Department of Physics, University of South Florida, Tampa, Florida 33620, United States
| | - Krzysztof Zberecki
- Faculty of Physics, Warsaw University of Technology, ul. Koszykowa 75, 00-662 Warsaw, Poland
| | - Yan Xin
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, United States
| | - Sadhu K Kolekar
- Department of Physics, University of South Florida, Tampa, Florida 33620, United States
| | - Jingfeng Li
- Department of Physics, University of South Florida, Tampa, Florida 33620, United States
| | - Matthias Batzill
- Department of Physics, University of South Florida, Tampa, Florida 33620, United States
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Mallet P, Chiapello F, Okuno H, Boukari H, Jamet M, Veuillen JY. Bound Hole States Associated to Individual Vanadium Atoms Incorporated into Monolayer WSe_{2}. PHYSICAL REVIEW LETTERS 2020; 125:036802. [PMID: 32745415 DOI: 10.1103/physrevlett.125.036802] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Accepted: 06/09/2020] [Indexed: 06/11/2023]
Abstract
Doping a two-dimensional semiconductor with magnetic atoms is a possible route to induce magnetism in the material. We report on the atomic structure and electronic properties of monolayer WSe_{2} intentionally doped with vanadium atoms by means of scanning transmission electron microscopy and scanning tunneling microscopy and spectroscopy. Most of the V atoms incorporate at W sites. These V_{W} dopants are negatively charged, which induces a localized bound state located 140 meV above the valence band maximum. The overlap of the electronic potential of two charged V_{W} dopants generates additional in-gap states. Eventually, the negative charge may suppress the magnetic moment on the V_{W} dopants.
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Affiliation(s)
- Pierre Mallet
- Université Grenoble Alpes, Institut Neel, F-38042 Grenoble, France
- CNRS, Institut Neel, F-38042 Grenoble, France
| | - Florian Chiapello
- Université Grenoble Alpes, Institut Neel, F-38042 Grenoble, France
- CNRS, Institut Neel, F-38042 Grenoble, France
| | - Hanako Okuno
- Université Grenoble Alpes, CEA, IRIG-MEM, 38000 Grenoble, France
| | - Hervé Boukari
- Université Grenoble Alpes, Institut Neel, F-38042 Grenoble, France
- CNRS, Institut Neel, F-38042 Grenoble, France
| | - Matthieu Jamet
- Université Grenoble Alpes, CEA, CNRS, Grenoble INP, IRIG-SPINTEC, 38000 Grenoble, France
| | - Jean-Yves Veuillen
- Université Grenoble Alpes, Institut Neel, F-38042 Grenoble, France
- CNRS, Institut Neel, F-38042 Grenoble, France
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Purbawati A, Coraux J, Vogel J, Hadj-Azzem A, Wu N, Bendiab N, Jegouso D, Renard J, Marty L, Bouchiat V, Sulpice A, Aballe L, Foerster M, Genuzio F, Locatelli A, Menteş TO, Han ZV, Sun X, Núñez-Regueiro M, Rougemaille N. In-Plane Magnetic Domains and Néel-like Domain Walls in Thin Flakes of the Room Temperature CrTe 2 Van der Waals Ferromagnet. ACS APPLIED MATERIALS & INTERFACES 2020; 12:30702-30710. [PMID: 32515190 DOI: 10.1021/acsami.0c07017] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The recent discovery of magnetic van der Waals (vdW) materials triggered a wealth of investigations in materials science and now offers genuinely new prospects for both fundamental and applied research. Although the catalog of vdW ferromagnets is rapidly expanding, most of them have a Curie temperature below 300 K, a notable disadvantage for potential applications. Combining element-selective X-ray magnetic imaging and magnetic force microscopy, we resolve at room temperature the magnetic domains and domain walls in micron-sized flakes of the CrTe2 vdW ferromagnet. Flux-closure magnetic patterns suggesting an in-plane six-fold symmetry are observed. Upon annealing the material above its Curie point (315 K), the magnetic domains disappear. By cooling back the sample, a different magnetic domain distribution is obtained, indicating material stability and lack of magnetic memory upon thermal cycling. The domain walls presumably have Néel texture, are preferentially oriented along directions separated by 120°, and have a width of several tens of nanometers. Besides microscopic mapping of magnetic domains and domain walls, the coercivity of the material is found to be of a few millitesla only, showing that the CrTe2 compound is magnetically soft. The coercivity is found to increase as the volume of the material decreases.
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Affiliation(s)
- Anike Purbawati
- Univ. Grenoble Alpes, CNRS, Grenoble INP, Institut NEEL, 38000 Grenoble, France
| | - Johann Coraux
- Univ. Grenoble Alpes, CNRS, Grenoble INP, Institut NEEL, 38000 Grenoble, France
| | - Jan Vogel
- Univ. Grenoble Alpes, CNRS, Grenoble INP, Institut NEEL, 38000 Grenoble, France
| | | | - NianJheng Wu
- Univ. Grenoble Alpes, CNRS, Grenoble INP, Institut NEEL, 38000 Grenoble, France
| | - Nedjma Bendiab
- Univ. Grenoble Alpes, CNRS, Grenoble INP, Institut NEEL, 38000 Grenoble, France
| | - David Jegouso
- Univ. Grenoble Alpes, CNRS, Grenoble INP, Institut NEEL, 38000 Grenoble, France
| | - Julien Renard
- Univ. Grenoble Alpes, CNRS, Grenoble INP, Institut NEEL, 38000 Grenoble, France
| | - Laetitia Marty
- Univ. Grenoble Alpes, CNRS, Grenoble INP, Institut NEEL, 38000 Grenoble, France
| | - Vincent Bouchiat
- Univ. Grenoble Alpes, CNRS, Grenoble INP, Institut NEEL, 38000 Grenoble, France
| | - André Sulpice
- Univ. Grenoble Alpes, CNRS, Grenoble INP, Institut NEEL, 38000 Grenoble, France
| | - Lucia Aballe
- ALBA Synchrotron Light Facility, 08290 Cerdanyola Del Valles, Spain
| | - Michael Foerster
- ALBA Synchrotron Light Facility, 08290 Cerdanyola Del Valles, Spain
| | - Francesca Genuzio
- Elettra-Sincrotrone Trieste S.C.p.A., S:S. 14, km 163.5 in AREA Science Park, Basovizza, 34149 Trieste, Italy
| | - Andrea Locatelli
- Elettra-Sincrotrone Trieste S.C.p.A., S:S. 14, km 163.5 in AREA Science Park, Basovizza, 34149 Trieste, Italy
| | - Tevfik Onur Menteş
- Elettra-Sincrotrone Trieste S.C.p.A., S:S. 14, km 163.5 in AREA Science Park, Basovizza, 34149 Trieste, Italy
| | - Zheng Vitto Han
- Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China
- School of Material Science and Engineering, University of Science and Technology of China, Anhui 230026, China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, P. R.China
| | - Xingdan Sun
- Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China
- School of Material Science and Engineering, University of Science and Technology of China, Anhui 230026, China
| | | | - Nicolas Rougemaille
- Univ. Grenoble Alpes, CNRS, Grenoble INP, Institut NEEL, 38000 Grenoble, France
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