1
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Liu H, Wu Y, Wu Z, Liu S, Zhang VL, Yu T. Coexisting Phases in Transition Metal Dichalcogenides: Overview, Synthesis, Applications, and Prospects. ACS NANO 2024; 18:2708-2729. [PMID: 38252696 DOI: 10.1021/acsnano.3c10665] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
Over the past decade, significant advancements have been made in phase engineering of two-dimensional transition metal dichalcogenides (TMDCs), thereby allowing controlled synthesis of various phases of TMDCs and facile conversion between them. Recently, there has been emerging interest in TMDC coexisting phases, which contain multiple phases within one nanostructured TMDC. By taking advantage of the merits from the component phases, the coexisting phases offer enhanced performance in many aspects compared with single-phase TMDCs. Herein, this review article thoroughly expounds the latest progress and ongoing efforts on the syntheses, properties, and applications of TMDC coexisting phases. The introduction section overviews the main phases of TMDCs (2H, 3R, 1T, 1T', 1Td), along with the advantages of phase coexistence. The subsequent section focuses on the synthesis methods for coexisting phases of TMDCs, with particular attention to local patterning and random formations. Furthermore, on the basis of the versatile properties of TMDC coexisting phases, their applications in magnetism, valleytronics, field-effect transistors, memristors, and catalysis are discussed. Lastly, a perspective is presented on the future development, challenges, and potential opportunities of TMDC coexisting phases. This review aims to provide insights into the phase engineering of 2D materials for both scientific and engineering communities and contribute to further advancements in this emerging field.
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Affiliation(s)
- Haiyang Liu
- School of Physics and Technology, Wuhan University, Wuhan 430072, China
| | - Yaping Wu
- School of Physics and Technology, Xiamen University, Xiamen 361005, China
| | - Zhiming Wu
- School of Physics and Technology, Xiamen University, Xiamen 361005, China
| | - Sheng Liu
- School of Physics and Technology, Wuhan University, Wuhan 430072, China
- Wuhan Institute of Quantum Technology, Wuhan 430206, China
| | - Vanessa Li Zhang
- School of Physics and Technology, Wuhan University, Wuhan 430072, China
| | - Ting Yu
- School of Physics and Technology, Wuhan University, Wuhan 430072, China
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2
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Serati de Brito C, Faria Junior PE, Ghiasi TS, Ingla-Aynés J, Rabahi CR, Cavalini C, Dirnberger F, Mañas-Valero S, Watanabe K, Taniguchi T, Zollner K, Fabian J, Schüller C, van der Zant HSJ, Gobato YG. Charge Transfer and Asymmetric Coupling of MoSe 2 Valleys to the Magnetic Order of CrSBr. NANO LETTERS 2023. [PMID: 38019289 DOI: 10.1021/acs.nanolett.3c03431] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2023]
Abstract
van der Waals heterostructures composed of two-dimensional (2D) transition metal dichalcogenides and vdW magnetic materials offer an intriguing platform to functionalize valley and excitonic properties in nonmagnetic TMDs. Here, we report magneto photoluminescence (PL) investigations of monolayer (ML) MoSe2 on the layered A-type antiferromagnetic (AFM) semiconductor CrSBr under different magnetic field orientations. Our results reveal a clear influence of the CrSBr magnetic order on the optical properties of MoSe2, such as an anomalous linear-polarization dependence, changes of the exciton/trion energies, a magnetic-field dependence of the PL intensities, and a valley g-factor with signatures of an asymmetric magnetic proximity interaction. Furthermore, first-principles calculations suggest that MoSe2/CrSBr forms a broken-gap (type-III) band alignment, facilitating charge transfer processes. The work establishes that antiferromagnetic-nonmagnetic interfaces can be used to control the valley and excitonic properties of TMDs, relevant for the development of opto-spintronics devices.
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Affiliation(s)
- Caique Serati de Brito
- Physics Department, Federal University of São Carlos, São Carlos, SP 13565-905, Brazil
- Institut für Experimentelle und Angewandte Physik, Universität Regensburg, D-93040 Regensburg, Germany
| | - Paulo E Faria Junior
- Institute for Theoretical Physics, University of Regensburg, D-93040 Regensburg, Germany
| | - Talieh S Ghiasi
- Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
| | - Josep Ingla-Aynés
- Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
| | - César Ricardo Rabahi
- Physics Department, Federal University of São Carlos, São Carlos, SP 13565-905, Brazil
| | - Camila Cavalini
- Physics Department, Federal University of São Carlos, São Carlos, SP 13565-905, Brazil
| | - Florian Dirnberger
- Institute of Applied Physics and Würzburg-Dresden Cluster of Excellence ct.qmat, Technische Universität, 01069 Dresden, Germany
| | - Samuel Mañas-Valero
- Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
- Instituto de Ciencia Molecular (ICMol), Universitat de València, Catedrático José Beltrán 2, Paterna 46980, Spain
| | - Kenji Watanabe
- Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Klaus Zollner
- Institute for Theoretical Physics, University of Regensburg, D-93040 Regensburg, Germany
| | - Jaroslav Fabian
- Institute for Theoretical Physics, University of Regensburg, D-93040 Regensburg, Germany
| | - Christian Schüller
- Institut für Experimentelle und Angewandte Physik, Universität Regensburg, D-93040 Regensburg, Germany
| | - Herre S J van der Zant
- Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
| | - Yara Galvão Gobato
- Physics Department, Federal University of São Carlos, São Carlos, SP 13565-905, Brazil
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3
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Rong R, Liu Y, Nie X, Zhang W, Zhang Z, Liu Y, Guo W. The Interaction of 2D Materials With Circularly Polarized Light. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2023; 10:e2206191. [PMID: 36698292 PMCID: PMC10074140 DOI: 10.1002/advs.202206191] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/24/2022] [Revised: 12/16/2022] [Indexed: 06/17/2023]
Abstract
2D materials (2DMs), due to spin-valley locking degree of freedom, exhibit strongly bound exciton and chiral optical selection rules and become promising material candidates for optoelectronic and spin/valleytronic devices. Over the last decade, the manifesting of 2D materials by circularly polarized lights expedites tremendous fascinating phenomena, such as valley/exciton Hall effect, Moiré exciton, optical Stark effect, circular dichroism, circularly polarized photoluminescence, and spintronic property. In this review, recent advance in the interaction of circularly polarized light with 2D materials covering from graphene, black phosphorous, transition metal dichalcogenides, van der Waals heterostructures as well as small proportion of quasi-2D perovskites and topological materials, is overviewed. The confronted challenges and theoretical and experimental opportunities are also discussed, attempting to accelerate the prosperity of chiral light-2DMs interactions.
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Affiliation(s)
- Rong Rong
- Key Laboratory for Intelligent Nano Materials and Devices of the Ministry of EducationState Key Laboratory of Mechanics and Control of Mechanical Structuresand Institute for Frontier ScienceNanjing University of Aeronautics and AstronauticsNanjing210016China
| | - Ying Liu
- Key Laboratory for Intelligent Nano Materials and Devices of the Ministry of EducationState Key Laboratory of Mechanics and Control of Mechanical Structuresand Institute for Frontier ScienceNanjing University of Aeronautics and AstronauticsNanjing210016China
| | - Xuchen Nie
- Key Laboratory for Intelligent Nano Materials and Devices of the Ministry of EducationState Key Laboratory of Mechanics and Control of Mechanical Structuresand Institute for Frontier ScienceNanjing University of Aeronautics and AstronauticsNanjing210016China
| | - Wei Zhang
- Key Laboratory for Intelligent Nano Materials and Devices of the Ministry of EducationState Key Laboratory of Mechanics and Control of Mechanical Structuresand Institute for Frontier ScienceNanjing University of Aeronautics and AstronauticsNanjing210016China
| | - Zhuhua Zhang
- Key Laboratory for Intelligent Nano Materials and Devices of the Ministry of EducationState Key Laboratory of Mechanics and Control of Mechanical Structuresand Institute for Frontier ScienceNanjing University of Aeronautics and AstronauticsNanjing210016China
| | - Yanpeng Liu
- Key Laboratory for Intelligent Nano Materials and Devices of the Ministry of EducationState Key Laboratory of Mechanics and Control of Mechanical Structuresand Institute for Frontier ScienceNanjing University of Aeronautics and AstronauticsNanjing210016China
| | - Wanlin Guo
- Key Laboratory for Intelligent Nano Materials and Devices of the Ministry of EducationState Key Laboratory of Mechanics and Control of Mechanical Structuresand Institute for Frontier ScienceNanjing University of Aeronautics and AstronauticsNanjing210016China
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4
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Intralayer charge-transfer moiré excitons in van der Waals superlattices. Nature 2022; 609:52-57. [PMID: 36045239 DOI: 10.1038/s41586-022-04991-9] [Citation(s) in RCA: 28] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2021] [Accepted: 06/17/2022] [Indexed: 11/08/2022]
Abstract
Moiré patterns of transition metal dichalcogenide heterobilayers have proved to be an ideal platform on which to host unusual correlated electronic phases, emerging magnetism and correlated exciton physics. Whereas the existence of new moiré excitonic states is established1-4 through optical measurements, the microscopic nature of these states is still poorly understood, often relying on empirically fit models. Here, combining large-scale first-principles GW (where G and W denote the one-particle Green's function and the screened Coulomb interaction, respectively) plus Bethe-Salpeter calculations and micro-reflection spectroscopy, we identify the nature of the exciton resonances in WSe2/WS2 moiré superlattices, discovering a rich set of moiré excitons that cannot be captured by prevailing continuum models. Our calculations show moiré excitons with distinct characters, including modulated Wannier excitons and previously unidentified intralayer charge-transfer excitons. Signatures of these distinct excitonic characters are confirmed experimentally by the unique carrier-density and magnetic-field dependences of different moiré exciton resonances. Our study highlights the highly non-trivial exciton states that can emerge in transition metal dichalcogenide moiré superlattices, and suggests new ways of tuning many-body physics in moiré systems by engineering excited-states with specific spatial characters.
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5
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Wang Z, Wang Z, Zhou X, Fu W, Li H, Liu C, Qiao J, Quek SY, Su C, Feng Y, Loh KP. Giant g-factor in Self-Intercalated 2D TaS 2. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2022; 18:e2201975. [PMID: 35989096 DOI: 10.1002/smll.202201975] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2022] [Revised: 07/21/2022] [Indexed: 06/15/2023]
Abstract
Central to the application of spintronic devices is the ability to manipulate spins by electric and magnetic fields, which relies on a large Landé g-factor. The self-intercalation of layered transitional metal dichalcogenides with native metal atoms can serve as a new strategy to enhance the g-factor by inducing ferromagnetic instability in the system via interlayer charge transfer. Here, scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) are performed to extract the g-factor and characterize the electronic structure of the self-intercalated phase of 2H-TaS2 . In Ta7 S12 , a sharp density of states (DOS) peak due to the Ta intercalant appears at the Fermi level, which satisfies the Stoner criteria for spontaneous ferromagnetism, leading to spin split states. The DOS peak shows sensitivity to magnetic field up to 1.85 mV T-1 , equivalent to an effective g-factor of ≈77. This work establishes self-intercalation as an approach for tuning the g-factor.
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Affiliation(s)
- Ziying Wang
- SZU-NUS Collaborative Innovation Centre for Optoelectronic Science & Technology, International Collaborative Laboratory of 2D Materials for Optoelectronics Science and Technology of Ministry of Education, Institute of Microscale Optoelectronics, Shenzhen University, Shenzhen, 518060, China
- Department of Chemistry, National University of Singapore, Singapore, 117543, Singapore
- Centre for Advanced 2D Materials, National University of Singapore, 6 Science Drive 2, Singapore, 117546, Singapore
| | - Zishen Wang
- Centre for Advanced 2D Materials, National University of Singapore, 6 Science Drive 2, Singapore, 117546, Singapore
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore, 117551, Singapore
| | - Xin Zhou
- Department of Chemistry, National University of Singapore, Singapore, 117543, Singapore
| | - Wei Fu
- Institute of Materials Research and Engineering, Agency for Science Technology and Research (A*STAR), 2 Fusionopolis Way, 08-03 Innovis, Singapore, 138634, Singapore
| | - Haohan Li
- Department of Chemistry, National University of Singapore, Singapore, 117543, Singapore
| | - Chaofei Liu
- Department of Chemistry, National University of Singapore, Singapore, 117543, Singapore
| | - Jingsi Qiao
- Centre for Advanced 2D Materials, National University of Singapore, 6 Science Drive 2, Singapore, 117546, Singapore
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore, 117551, Singapore
| | - Su Ying Quek
- Centre for Advanced 2D Materials, National University of Singapore, 6 Science Drive 2, Singapore, 117546, Singapore
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore, 117551, Singapore
| | - Chenliang Su
- SZU-NUS Collaborative Innovation Centre for Optoelectronic Science & Technology, International Collaborative Laboratory of 2D Materials for Optoelectronics Science and Technology of Ministry of Education, Institute of Microscale Optoelectronics, Shenzhen University, Shenzhen, 518060, China
| | - Yuanping Feng
- Centre for Advanced 2D Materials, National University of Singapore, 6 Science Drive 2, Singapore, 117546, Singapore
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore, 117551, Singapore
| | - Kian Ping Loh
- SZU-NUS Collaborative Innovation Centre for Optoelectronic Science & Technology, International Collaborative Laboratory of 2D Materials for Optoelectronics Science and Technology of Ministry of Education, Institute of Microscale Optoelectronics, Shenzhen University, Shenzhen, 518060, China
- Department of Chemistry, National University of Singapore, Singapore, 117543, Singapore
- Centre for Advanced 2D Materials, National University of Singapore, 6 Science Drive 2, Singapore, 117546, Singapore
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6
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Chen S, Wang F, Kuang F, Kang S, Liang H, Zheng L, Guan L, Wu Q. Femtosecond Pulsed Fiber Laser by an Optical Device Based on NaOH-LPE Prepared WSe 2 Saturable Absorber. NANOMATERIALS (BASEL, SWITZERLAND) 2022; 12:2747. [PMID: 36014612 PMCID: PMC9415237 DOI: 10.3390/nano12162747] [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: 07/07/2022] [Revised: 08/05/2022] [Accepted: 08/09/2022] [Indexed: 06/15/2023]
Abstract
We report on all-optical devices prepared from WSe2 combined with drawn tapered fibers as saturable absorbers to achieve ultrashort pulse output. The saturable absorber with a high damage threshold and high saturable absorption characteristics is prepared for application in erbium-doped fiber lasers by the liquid phase exfoliation method for WSe2, and the all-optical device exhibited strong saturable absorption characteristics with a modulation depth of 15% and a saturation intensity of 100.58 W. The net dispersion of the erbium-doped fiber laser cavity is ~-0.1 ps2, and a femtosecond pulse output with a bandwidth of 11.4 nm, a pulse width of 390 fs, and a single-pulse capability of 42 pJ is obtained. Results indicate that the proposed WSe2 saturable absorbers are efficient, photonic devices to realize stable fiber lasers. The results demonstrate that the WSe2 saturable absorber is an effective photonic device for realizing stable fiber lasers, which have a certain significance for the development of potential photonic devices.
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Affiliation(s)
- Si Chen
- School of Physics and Electronic Information, Gannan Normal University, Ganzhou 341000, China
| | - Fengpeng Wang
- School of Physics and Electronic Information, Gannan Normal University, Ganzhou 341000, China
| | - Fangguang Kuang
- School of Physics and Electronic Information, Gannan Normal University, Ganzhou 341000, China
| | - Shuying Kang
- School of Physics and Electronic Information, Gannan Normal University, Ganzhou 341000, China
| | - Hanwen Liang
- School of Physics and Electronic Information, Gannan Normal University, Ganzhou 341000, China
| | - Lijing Zheng
- School of Physics and Electronic Information, Gannan Normal University, Ganzhou 341000, China
| | - Lixin Guan
- School of Physics and Electronic Information, Gannan Normal University, Ganzhou 341000, China
| | - Qing Wu
- Heilongjiang Province Key Laboratory of Laser Spectroscopy Technology and Application, Harbin University of Science and Technology, Harbin 150080, China
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7
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Wang QH, Bedoya-Pinto A, Blei M, Dismukes AH, Hamo A, Jenkins S, Koperski M, Liu Y, Sun QC, Telford EJ, Kim HH, Augustin M, Vool U, Yin JX, Li LH, Falin A, Dean CR, Casanova F, Evans RFL, Chshiev M, Mishchenko A, Petrovic C, He R, Zhao L, Tsen AW, Gerardot BD, Brotons-Gisbert M, Guguchia Z, Roy X, Tongay S, Wang Z, Hasan MZ, Wrachtrup J, Yacoby A, Fert A, Parkin S, Novoselov KS, Dai P, Balicas L, Santos EJG. The Magnetic Genome of Two-Dimensional van der Waals Materials. ACS NANO 2022; 16:6960-7079. [PMID: 35442017 PMCID: PMC9134533 DOI: 10.1021/acsnano.1c09150] [Citation(s) in RCA: 70] [Impact Index Per Article: 35.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2021] [Accepted: 02/23/2022] [Indexed: 05/23/2023]
Abstract
Magnetism in two-dimensional (2D) van der Waals (vdW) materials has recently emerged as one of the most promising areas in condensed matter research, with many exciting emerging properties and significant potential for applications ranging from topological magnonics to low-power spintronics, quantum computing, and optical communications. In the brief time after their discovery, 2D magnets have blossomed into a rich area for investigation, where fundamental concepts in magnetism are challenged by the behavior of spins that can develop at the single layer limit. However, much effort is still needed in multiple fronts before 2D magnets can be routinely used for practical implementations. In this comprehensive review, prominent authors with expertise in complementary fields of 2D magnetism (i.e., synthesis, device engineering, magneto-optics, imaging, transport, mechanics, spin excitations, and theory and simulations) have joined together to provide a genome of current knowledge and a guideline for future developments in 2D magnetic materials research.
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Affiliation(s)
- Qing Hua Wang
- Materials
Science and Engineering, School for Engineering of Matter, Transport
and Energy, Arizona State University, Tempe, Arizona 85287, United States
| | - Amilcar Bedoya-Pinto
- NISE
Department, Max Planck Institute of Microstructure
Physics, 06120 Halle, Germany
- Instituto
de Ciencia Molecular (ICMol), Universitat
de València, 46980 Paterna, Spain
| | - Mark Blei
- Materials
Science and Engineering, School for Engineering of Matter, Transport
and Energy, Arizona State University, Tempe, Arizona 85287, United States
| | - Avalon H. Dismukes
- Department
of Chemistry, Columbia University, New York, New York 10027, United States
| | - Assaf Hamo
- Department
of Physics, Harvard University, Cambridge, Massachusetts 02138, United States
| | - Sarah Jenkins
- Twist
Group,
Faculty of Physics, University of Duisburg-Essen, Campus Duisburg, 47057 Duisburg, Germany
| | - Maciej Koperski
- Institute
for Functional Intelligent Materials, National
University of Singapore, 117544 Singapore
| | - Yu Liu
- Condensed
Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, United States
| | - Qi-Chao Sun
- Physikalisches
Institut, University of Stuttgart, 70569 Stuttgart, Germany
| | - Evan J. Telford
- Department
of Chemistry, Columbia University, New York, New York 10027, United States
- Department
of Physics, Columbia University, New York, New York 10027, United States
| | - Hyun Ho Kim
- School
of Materials Science and Engineering, Department of Energy Engineering
Convergence, Kumoh National Institute of
Technology, Gumi 39177, Korea
| | - Mathias Augustin
- Institute
for Condensed Matter Physics and Complex Systems, School of Physics
and Astronomy, The University of Edinburgh, Edinburgh, EH9 3FD, United Kingdom
- Donostia
International Physics Center (DIPC), 20018 Donostia-San Sebastián, Basque Country, Spain
| | - Uri Vool
- Department
of Physics, Harvard University, Cambridge, Massachusetts 02138, United States
- John Harvard
Distinguished Science Fellows Program, Harvard
University, Cambridge, Massachusetts 02138, United States
| | - Jia-Xin Yin
- Laboratory
for Topological Quantum Matter and Spectroscopy, Department of Physics, Princeton University, Princeton, New Jersey 08544, United States
| | - Lu Hua Li
- Institute
for Frontier Materials, Deakin University, Geelong Waurn Ponds Campus, Waurn Ponds, Victoria 3216, Australia
| | - Alexey Falin
- Institute
for Frontier Materials, Deakin University, Geelong Waurn Ponds Campus, Waurn Ponds, Victoria 3216, Australia
| | - Cory R. Dean
- Department
of Physics, Columbia University, New York, New York 10027, United States
| | - Fèlix Casanova
- CIC nanoGUNE
BRTA, 20018 Donostia - San Sebastián, Basque
Country, Spain
- IKERBASQUE,
Basque Foundation for Science, 48013 Bilbao, Basque Country, Spain
| | - Richard F. L. Evans
- Department
of Physics, University of York, Heslington, York YO10 5DD, United Kingdom
| | - Mairbek Chshiev
- Université
Grenoble Alpes, CEA, CNRS, Spintec, 38000 Grenoble, France
- Institut
Universitaire de France, 75231 Paris, France
| | - Artem Mishchenko
- Department
of Physics and Astronomy, University of
Manchester, Manchester, M13 9PL, United Kingdom
- National
Graphene Institute, University of Manchester, Manchester, M13 9PL, United Kingdom
| | - Cedomir Petrovic
- Condensed
Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, United States
| | - Rui He
- Department
of Electrical and Computer Engineering, Texas Tech University, 910 Boston Avenue, Lubbock, Texas 79409, United
States
| | - Liuyan Zhao
- Department
of Physics, University of Michigan, 450 Church Street, Ann Arbor, Michigan 48109, United States
| | - Adam W. Tsen
- Institute
for Quantum Computing and Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
| | - Brian D. Gerardot
- SUPA, Institute
of Photonics and Quantum Sciences, Heriot-Watt
University, Edinburgh EH14 4AS, United Kingdom
| | - Mauro Brotons-Gisbert
- SUPA, Institute
of Photonics and Quantum Sciences, Heriot-Watt
University, Edinburgh EH14 4AS, United Kingdom
| | - Zurab Guguchia
- Laboratory
for Muon Spin Spectroscopy, Paul Scherrer
Institute, CH-5232 Villigen PSI, Switzerland
| | - Xavier Roy
- Department
of Chemistry, Columbia University, New York, New York 10027, United States
| | - Sefaattin Tongay
- Materials
Science and Engineering, School for Engineering of Matter, Transport
and Energy, Arizona State University, Tempe, Arizona 85287, United States
| | - Ziwei Wang
- Department
of Physics and Astronomy, University of
Manchester, Manchester, M13 9PL, United Kingdom
- National
Graphene Institute, University of Manchester, Manchester, M13 9PL, United Kingdom
| | - M. Zahid Hasan
- Materials
Sciences Division, Lawrence Berkeley National
Laboratory, Berkeley, California 94720, United States
- Princeton
Institute for Science and Technology of Materials, Princeton University, Princeton, New Jersey 08544, United States
- National
High Magnetic Field Laboratory, Florida
State University, Tallahassee, Florida 32310, United States
| | - Joerg Wrachtrup
- Physikalisches
Institut, University of Stuttgart, 70569 Stuttgart, Germany
- Max Planck
Institute for Solid State Research, 70569 Stuttgart, Germany
| | - Amir Yacoby
- Department
of Physics, Harvard University, Cambridge, Massachusetts 02138, United States
- John A.
Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, United States
| | - Albert Fert
- Donostia
International Physics Center (DIPC), 20018 Donostia-San Sebastián, Basque Country, Spain
- Unité
Mixte de Physique, CNRS, Thales, Université Paris-Saclay, 91767 Palaiseau, France
- Department
of Materials Physics UPV/EHU, 20018 Donostia - San Sebastián, Basque Country, Spain
| | - Stuart Parkin
- NISE
Department, Max Planck Institute of Microstructure
Physics, 06120 Halle, Germany
| | - Kostya S. Novoselov
- Institute
for Functional Intelligent Materials, National
University of Singapore, 117544 Singapore
| | - Pengcheng Dai
- Department
of Physics and Astronomy, Rice University, Houston, Texas 77005, United States
| | - Luis Balicas
- National
High Magnetic Field Laboratory, Florida
State University, Tallahassee, Florida 32310, United States
- Department
of Physics, Florida State University, Tallahassee, Florida 32306, United States
| | - Elton J. G. Santos
- Institute
for Condensed Matter Physics and Complex Systems, School of Physics
and Astronomy, The University of Edinburgh, Edinburgh, EH9 3FD, United Kingdom
- Donostia
International Physics Center (DIPC), 20018 Donostia-San Sebastián, Basque Country, Spain
- Higgs Centre
for Theoretical Physics, The University
of Edinburgh, Edinburgh EH9 3FD, United Kingdom
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8
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Nguyen LAT, Dhakal KP, Lee Y, Choi W, Nguyen TD, Hong C, Luong DH, Kim YM, Kim J, Lee M, Choi T, Heinrich AJ, Kim JH, Lee D, Duong DL, Lee YH. Spin-Selective Hole-Exciton Coupling in a V-Doped WSe 2 Ferromagnetic Semiconductor at Room Temperature. ACS NANO 2021; 15:20267-20277. [PMID: 34807575 DOI: 10.1021/acsnano.1c08375] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
While valley polarization with strong Zeeman splitting is the most prominent characteristic of two-dimensional (2D) transition metal dichalcogenide (TMD) semiconductors under magnetic fields, enhancement of the Zeeman splitting has been demonstrated by incorporating magnetic dopants into the host materials. Unlike Fe, Mn, and Co, V is a distinctive dopant for ferromagnetic semiconducting properties at room temperature with large Zeeman shifting of band edges. Nevertheless, little known is the excitons interacting with spin-polarized carriers in V-doped TMDs. Here, we report anomalous circularly polarized photoluminescence (CPL) in a V-doped WSe2 monolayer at room temperature. Excitons couple to V-induced spin-polarized holes to generate spin-selective positive trions, leading to differences in the populations of neutral excitons and trions between left and right CPL. Using transient absorption spectroscopy, we elucidate the origin of excitons and trions that are inherently distinct for defect-mediated and impurity-mediated trions. Ferromagnetic characteristics are further confirmed by the significant Zeeman splitting of nanodiamonds deposited on the V-doped WSe2 monolayer.
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Affiliation(s)
- Lan-Anh T Nguyen
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Suwon 16419, Republic of Korea
- Department of Energy Science, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Krishna P Dhakal
- Department of Energy Science, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Yuhan Lee
- Department of Physics, Korea University, Seoul 02841, Republic of Korea
| | - Wooseon Choi
- Department of Energy Science, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Tuan Dung Nguyen
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Suwon 16419, Republic of Korea
- Department of Energy Science, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Chengyun Hong
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Suwon 16419, Republic of Korea
- Department of Energy Science, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Dinh Hoa Luong
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Suwon 16419, Republic of Korea
| | - Young-Min Kim
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Suwon 16419, Republic of Korea
- Department of Energy Science, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Jeongyong Kim
- Department of Energy Science, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Myeongwon Lee
- Department of Physics, Korea University, Seoul 02841, Republic of Korea
| | - Taeyoung Choi
- Center for Quantum Nanoscience, Institute for Basic Science (IBS), Seoul 03760, Korea
- Department of Physics, Ewha Womans University, Seoul 03760, Korea
| | - Andreas J Heinrich
- Center for Quantum Nanoscience, Institute for Basic Science (IBS), Seoul 03760, Korea
- Department of Physics, Ewha Womans University, Seoul 03760, Korea
| | - Ji-Hee Kim
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Suwon 16419, Republic of Korea
- Department of Energy Science, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Donghun Lee
- Department of Physics, Korea University, Seoul 02841, Republic of Korea
| | - Dinh Loc Duong
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Suwon 16419, Republic of Korea
- Department of Energy Science, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Young Hee Lee
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Suwon 16419, Republic of Korea
- Department of Energy Science, Sungkyunkwan University, Suwon 16419, Republic of Korea
- Department of Physics, Sungkyunkwan University, Suwon 16419, Republic of Korea
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9
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Liu H, Fu D, Li X, Han J, Chen X, Wu X, Sun B, Tang W, Ke C, Wu Y, Wu Z, Kang J. Enhanced Valley Splitting in Monolayer WSe 2 by Phase Engineering. ACS NANO 2021; 15:8244-8251. [PMID: 33982558 DOI: 10.1021/acsnano.0c08305] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Lifting the valley degeneracy in two-dimensional transition metal dichalcogenides could promote their applications in information processing. Various external regulations, including magnetic substrate, magnetic doping, electric field, and carrier doping, have been implemented to enhance the valley splitting under the magnetic field. Here, a phase engineering strategy, through modifying the intrinsic lattice structure, is proposed to enhance the valley splitting in monolayer WSe2. The valley splitting in hybrid H and T phase WSe2 is tunable by the concentration of the T phase. An obvious valley splitting of ∼4.1 meV is obtained with the T phase concentration of 31% under ±5 T magnetic fields, which corresponds to an effective Landé geff factor of -14, about 3.5-fold of that in pure H-WSe2. Comparing the temperature and magnetic field dependent polarized photoluminescence and also combining the theoretical simulations reveal the enhanced valley splitting is dominantly attributed to exchange interaction of H phase WSe2 with the local magnetic moments induced by the T phase. This finding provides a convenient solution for lifting the valley degeneracy of two-dimensional materials.
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Affiliation(s)
- Haiyang Liu
- Department of Physics, OSED, Fujian Provincial Key Laboratory of Semiconductor Materials and Applications, Xiamen University, Xiamen 361005, People's Republic of China
| | - Deyi Fu
- Department of Physics, OSED, Fujian Provincial Key Laboratory of Semiconductor Materials and Applications, Xiamen University, Xiamen 361005, People's Republic of China
| | - Xu Li
- Department of Physics, OSED, Fujian Provincial Key Laboratory of Semiconductor Materials and Applications, Xiamen University, Xiamen 361005, People's Republic of China
| | - Junbo Han
- Wuhan National High Magnetic Field Center and School of Physics, Huazhong University of Science and Technology, Wuhan 430074, People's Republic of China
| | - Xiaodie Chen
- Wuhan National High Magnetic Field Center and School of Physics, Huazhong University of Science and Technology, Wuhan 430074, People's Republic of China
| | - Xuefeng Wu
- Department of Physics, OSED, Fujian Provincial Key Laboratory of Semiconductor Materials and Applications, Xiamen University, Xiamen 361005, People's Republic of China
| | - Baofan Sun
- Department of Physics, OSED, Fujian Provincial Key Laboratory of Semiconductor Materials and Applications, Xiamen University, Xiamen 361005, People's Republic of China
| | - Weiqing Tang
- Department of Physics, OSED, Fujian Provincial Key Laboratory of Semiconductor Materials and Applications, Xiamen University, Xiamen 361005, People's Republic of China
| | - Congming Ke
- Department of Physics, OSED, Fujian Provincial Key Laboratory of Semiconductor Materials and Applications, Xiamen University, Xiamen 361005, People's Republic of China
| | - Yaping Wu
- Department of Physics, OSED, Fujian Provincial Key Laboratory of Semiconductor Materials and Applications, Xiamen University, Xiamen 361005, People's Republic of China
| | - Zhiming Wu
- Department of Physics, OSED, Fujian Provincial Key Laboratory of Semiconductor Materials and Applications, Xiamen University, Xiamen 361005, People's Republic of China
| | - Junyong Kang
- Department of Physics, OSED, Fujian Provincial Key Laboratory of Semiconductor Materials and Applications, Xiamen University, Xiamen 361005, People's Republic of China
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10
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Wu L, Cong C, Yang W, Chen Y, Shao Y, Do TTH, Wen W, Feng S, Zou C, Zhang H, Du B, Cao B, Shang J, Xiong Q, Loh KP, Yu T. Observation of Strong Valley Magnetic Response in Monolayer Transition Metal Dichalcogenide Alloys of Mo 0.5W 0.5Se 2 and Mo 0.5W 0.5Se 2/WS 2 Heterostructures. ACS NANO 2021; 15:8397-8406. [PMID: 33881826 DOI: 10.1021/acsnano.0c10478] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Monolayer transition metal dichalcogenide (TMD) alloys have emerged as a unique material system for promising applications in electronics, optoelectronics, and spintronics due to their tunable electronic structures, effective masses of carriers, and valley polarization with various alloy compositions. Although spin-orbit engineering has been extensively studied in monolayer TMD alloys, the valley Zeeman effect in these alloys still remains largely unexplored. Here we demonstrate the enhanced valley magnetic response in Mo0.5W0.5Se2 alloy monolayers and Mo0.5W0.5Se2/WS2 heterostructures probed by magneto-photoluminescence spectroscopy. The large g factors of negatively charged excitons (trions) of Mo0.5W0.5Se2 have been extracted for both pure Mo0.5W0.5Se2 monolayers and Mo0.5W0.5Se2/WS2 heterostructures, which are attributed to the significant impact of doping-induced strong many-body Coulomb interactions on trion emissions under an out-of-plane magnetic field. Moreover, compared with the monolayer Mo0.5W0.5Se2, the slightly reduced valley Zeeman splitting in Mo0.5W0.5Se2/WS2 is a consequence of the weakened exchange interaction arising from p-doping in Mo0.5W0.5Se2 via interlayer charge transfer between Mo0.5W0.5Se2 and WS2. Such interlayer charge transfer further evidences the formation of type-II band alignment, in agreement with the density functional theory calculations. Our findings give insights into the spin-valley and interlayer coupling effects in monolayer TMD alloys and their heterostructures, which are essential to develop valleytronic applications based on the emerging family of TMD alloys.
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Affiliation(s)
- Lishu Wu
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Chunxiao Cong
- State Key Laboratory of ASIC and System, School of Information Science and Technology, Fudan University, Shanghai 200433, P. R. China
| | - Weihuang Yang
- Key Laboratory of RF Circuits and System of Ministry of Education, Hangzhou Dianzi University, Hangzhou 310018, Zhejiang, P. R. China
| | - Yu Chen
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Yan Shao
- Department of Chemistry, National University of Singapore, Singapore 117543, Singapore
| | - T Thu Ha Do
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Wen Wen
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Shun Feng
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Chenji Zou
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Hongbo Zhang
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Bowen Du
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Bingchen Cao
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Jingzhi Shang
- Xi'an Institute of Flexible Electronics, Northwestern Polytechnical University, Xi'an 710072, Shaanxi, P. R. China
| | - Qihua Xiong
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Kian Ping Loh
- Department of Chemistry, National University of Singapore, Singapore 117543, Singapore
| | - Ting Yu
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
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11
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Li W, Lu X, Wu J, Srivastava A. Optical control of the valley Zeeman effect through many-exciton interactions. NATURE NANOTECHNOLOGY 2021; 16:148-152. [PMID: 33257895 DOI: 10.1038/s41565-020-00804-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2020] [Accepted: 10/26/2020] [Indexed: 06/12/2023]
Abstract
Charge carriers in two-dimensional transition metal dichalcogenides (TMDs), such as WSe2, have their spin and valley-pseudospin locked into an optically addressable index that is proposed as a basis for future information processing1,2. The manipulation of this spin-valley index, which carries a magnetic moment3, requires tuning its energy. This is typically achieved through an external magnetic field (B), which is practically cumbersome. However, the valley-contrasting optical Stark effect achieves valley control without B, but requires large incident powers4,5. Thus, other efficient routes to control the spin-valley index are desirable. Here we show that many-body interactions among interlayer excitons (IXs) in a WSe2/MoSe2 heterobilayer (HBL) induce a steady-state valley Zeeman splitting that corresponds to B ≈ 6 T. This anomalous splitting, present at incident powers as low as microwatts, increases with power and is able to enhance, suppress or even flip the sign of a B-induced splitting. Moreover, the g-factor of valley Zeeman splitting can be tuned by ~30% with incident power. In addition to valleytronics, our results could prove helpful to achieve optical non-reciprocity using two-dimensional materials.
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Affiliation(s)
- Weijie Li
- Department of Physics, Emory University, Atlanta, GA, USA
| | - Xin Lu
- Department of Physics, Emory University, Atlanta, GA, USA
| | - Jiatian Wu
- Department of Physics, Emory University, Atlanta, GA, USA
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12
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Li J, Goryca M, Wilson NP, Stier AV, Xu X, Crooker SA. Spontaneous Valley Polarization of Interacting Carriers in a Monolayer Semiconductor. PHYSICAL REVIEW LETTERS 2020; 125:147602. [PMID: 33064502 DOI: 10.1103/physrevlett.125.147602] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Accepted: 09/09/2020] [Indexed: 06/11/2023]
Abstract
We report magnetoabsorption spectroscopy of gated WSe_{2} monolayers in high magnetic fields up to 60 T. When doped with a 2D Fermi sea of mobile holes, well-resolved sequences of optical transitions are observed in both σ^{±} circular polarizations, which unambiguously and separately indicate the number of filled Landau levels (LLs) in both K and K^{'} valleys. This reveals the interaction-enhanced valley Zeeman energy, which is found to be highly tunable with hole density p. We exploit this tunability to align the LLs in K and K^{'}, and find that the 2D hole gas becomes unstable against small changes in LL filling and can spontaneously valley polarize. These results cannot be understood within a single-particle picture, highlighting the importance of exchange interactions in determining the ground state of 2D carriers in monolayer semiconductors.
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Affiliation(s)
- J Li
- National High Magnetic Field Laboratory, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - M Goryca
- National High Magnetic Field Laboratory, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - N P Wilson
- Department of Physics, University of Washington, Seattle, Washington 98195, USA
| | - A V Stier
- National High Magnetic Field Laboratory, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - X Xu
- Department of Physics, University of Washington, Seattle, Washington 98195, USA
| | - S A Crooker
- National High Magnetic Field Laboratory, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
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13
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Deilmann T, Krüger P, Rohlfing M. Ab Initio Studies of Exciton g Factors: Monolayer Transition Metal Dichalcogenides in Magnetic Fields. PHYSICAL REVIEW LETTERS 2020; 124:226402. [PMID: 32567922 DOI: 10.1103/physrevlett.124.226402] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2020] [Accepted: 05/15/2020] [Indexed: 06/11/2023]
Abstract
The effect of a magnetic field on the optical absorption in semiconductors has been measured experimentally and modeled theoretically for various systems in previous decades. We present a new first-principles approach to systematically determine the response of excitons to magnetic fields, i.e., exciton g factors. By utilizing the GW-Bethe-Salpeter equation methodology we show that g factors extracted from the Zeeman shift of electronic bands are strongly renormalized by many-body effects which we trace back to the extent of the excitons in reciprocal space. We apply our approach to monolayers of transition metal dichalcogenides (MoS_{2}, MoSe_{2}, MoTe_{2}, WS_{2}, and WSe_{2}) with strongly bound excitons for which g factors are weakened by about 30%.
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Affiliation(s)
- Thorsten Deilmann
- Institut für Festkörpertheorie, Westfälische Wilhelms-Universität Münster, 48149 Münster, Germany
| | - Peter Krüger
- Institut für Festkörpertheorie, Westfälische Wilhelms-Universität Münster, 48149 Münster, Germany
| | - Michael Rohlfing
- Institut für Festkörpertheorie, Westfälische Wilhelms-Universität Münster, 48149 Münster, Germany
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14
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Ersfeld M, Volmer F, Rathmann L, Kotewitz L, Heithoff M, Lohmann M, Yang B, Watanabe K, Taniguchi T, Bartels L, Shi J, Stampfer C, Beschoten B. Unveiling Valley Lifetimes of Free Charge Carriers in Monolayer WSe 2. NANO LETTERS 2020; 20:3147-3154. [PMID: 32202802 DOI: 10.1021/acs.nanolett.9b05138] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We report on nanosecond-long, gate-dependent valley lifetimes of free charge carriers in monolayer WSe2, unambiguously identified by the combination of time-resolved Kerr rotation and electrical transport measurements. While the valley polarization increases when tuning the Fermi level into the conduction or valence band, there is a strong decrease of the respective valley lifetime consistent with both electron-phonon and spin-orbit scattering. The longest lifetimes are seen for spin-polarized bound excitons in the band gap region. We explain our findings via two distinct, Fermi-level-dependent scattering channels of optically excited, valley-polarized bright trions either via dark or bound states. By electrostatic gating we demonstrate that the transition-metal dichalcogenide WSe2 can be tuned to be either an ideal host for long-lived localized spin states or allow for nanosecond valley lifetimes of free charge carriers (>10 ns).
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Affiliation(s)
- Manfred Ersfeld
- 2nd Institute of Physics and JARA-FIT, RWTH Aachen University, Aachen 52074, Germany
| | - Frank Volmer
- 2nd Institute of Physics and JARA-FIT, RWTH Aachen University, Aachen 52074, Germany
| | - Lars Rathmann
- 2nd Institute of Physics and JARA-FIT, RWTH Aachen University, Aachen 52074, Germany
| | - Luca Kotewitz
- 2nd Institute of Physics and JARA-FIT, RWTH Aachen University, Aachen 52074, Germany
| | - Maximilian Heithoff
- 2nd Institute of Physics and JARA-FIT, RWTH Aachen University, Aachen 52074, Germany
| | - Mark Lohmann
- Department of Physics and Astronomy, University of California, Riverside, Riverside 92521, California, United States
| | - Bowen Yang
- Department of Chemistry and Materials Science & Engineering Program, University of California, Riverside 92521, California, United States
| | - Kenji Watanabe
- National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Ludwig Bartels
- Department of Chemistry and Materials Science & Engineering Program, University of California, Riverside 92521, California, United States
| | - Jing Shi
- Department of Physics and Astronomy, University of California, Riverside, Riverside 92521, California, United States
| | - Christoph Stampfer
- 2nd Institute of Physics and JARA-FIT, RWTH Aachen University, Aachen 52074, Germany
- Peter Grünberg Institute, Forschungszentrum Jülich, Jülich 52425, Germany
| | - Bernd Beschoten
- 2nd Institute of Physics and JARA-FIT, RWTH Aachen University, Aachen 52074, Germany
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15
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Li Q, Zhao X, Deng L, Shi Z, Liu S, Wei Q, Zhang L, Cheng Y, Zhang L, Lu H, Gao W, Huang W, Qiu CW, Xiang G, Pennycook SJ, Xiong Q, Loh KP, Peng B. Enhanced Valley Zeeman Splitting in Fe-Doped Monolayer MoS 2. ACS NANO 2020; 14:4636-4645. [PMID: 32167276 DOI: 10.1021/acsnano.0c00291] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The "Zeeman effect" offers unique opportunities for magnetic manipulation of the spin degree of freedom (DOF). Recently, valley Zeeman splitting, referring to the lifting of valley degeneracy, has been demonstrated in two-dimensional transition metal dichalcogenides (TMDs) at liquid helium temperature. However, to realize the practical applications of valley pseudospins, the valley DOF must be controllable by a magnetic field at room temperature, which remains a significant challenge. Magnetic doping in TMDs can enhance the Zeeman splitting; however, to achieve this experimentally is not easy. Here, we report unambiguous magnetic manipulation of valley Zeeman splitting at 300 K (geff = -6.4) and 10 K (geff = -11) in a CVD-grown Fe-doped MoS2 monolayer; the effective Landé geff factor can be tuned to -20.7 by increasing the Fe dopant concentration, which represents an approximately 5-fold enhancement as compared to undoped MoS2. Our measurements and calculations reveal that the enhanced splitting and geff factors are due to the Heisenberg exchange interaction of the localized magnetic moments (Fe 3d electrons) with MoS2 through the d-orbital hybridization.
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Affiliation(s)
- Qi Li
- National Engineering Research Center of Electromagnetic Radiation Control Materials, School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu, 611731, China
| | - Xiaoxu Zhao
- Department of Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117575, Singapore
| | - Longjiang Deng
- National Engineering Research Center of Electromagnetic Radiation Control Materials, School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu, 611731, China
| | - Zhongtai Shi
- National Engineering Research Center of Electromagnetic Radiation Control Materials, School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu, 611731, China
| | - Sheng Liu
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Qilin Wei
- Key Laboratory of Flexible Electronics & Institute of Advanced Materials, Nanjing Tech University, Nanjing, 211816, China
| | - Linbo Zhang
- National Engineering Research Center of Electromagnetic Radiation Control Materials, School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu, 611731, China
| | - Yingchun Cheng
- Key Laboratory of Flexible Electronics & Institute of Advanced Materials, Nanjing Tech University, Nanjing, 211816, China
| | - Li Zhang
- National Engineering Research Center of Electromagnetic Radiation Control Materials, School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu, 611731, China
| | - Haipeng Lu
- National Engineering Research Center of Electromagnetic Radiation Control Materials, School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu, 611731, China
| | - Weibo Gao
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Wei Huang
- Key Laboratory of Flexible Electronics & Institute of Advanced Materials, Nanjing Tech University, Nanjing, 211816, China
| | - Cheng-Wei Qiu
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117583, Singapore
| | - Gang Xiang
- College of Physical Science and Technology, Sichuan University, Chengdu, 610064, China
| | - Stephen John Pennycook
- Department of Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117575, Singapore
| | - Qihua Xiong
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Kian Ping Loh
- Department of Chemistry and Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, Singapore 117549, Singapore
| | - Bo Peng
- National Engineering Research Center of Electromagnetic Radiation Control Materials, School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu, 611731, China
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16
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Wang Y, Deng L, Wei Q, Wan Y, Liu Z, Lu X, Li Y, Bi L, Zhang L, Lu H, Chen H, Zhou P, Zhang L, Cheng Y, Zhao X, Ye Y, Huang W, Pennycook SJ, Loh KP, Peng B. Spin-Valley Locking Effect in Defect States of Monolayer MoS 2. NANO LETTERS 2020; 20:2129-2136. [PMID: 32078769 DOI: 10.1021/acs.nanolett.0c00138] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Valley pseudospin in two-dimensional (2D) transition-metal dichalcogenides (TMDs) allows optical control of spin-valley polarization and intervalley quantum coherence. Defect states in TMDs give rise to new exciton features and theoretically exhibit spin-valley polarization; however, experimental achievement of this phenomenon remains challenges. Here, we report unambiguous valley pseudospin of defect-bound localized excitons in CVD-grown monolayer MoS2; enhanced valley Zeeman splitting with an effective g-factor of -6.2 is observed. Our results reveal that all five d-orbitals and the increased effective electron mass contribute to the band shift of defect states, demonstrating a new physics of the magnetic responses of defect-bound localized excitons, strikingly different from that of A excitons. Our work paves the way for the manipulation of the spin-valley degrees of freedom through defects toward valleytronic devices.
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Affiliation(s)
- Yaqian Wang
- National Engineering Research Center of Electromagnetic Radiation Control Materials, School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 611731, China
| | - Longjiang Deng
- National Engineering Research Center of Electromagnetic Radiation Control Materials, School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 611731, China
| | - Qilin Wei
- Key Laboratory of Flexible Electronics and Institute of Advanced Materials, Nanjing Tech University, Nanjing 211816, China
| | - Yi Wan
- State Key Laboratory for Artificial Microstructure and Mesoscopic Physics, Frontiers Center for Nano-optoelectronics, School of Physics, Peking University, Beijing 100871, China
| | - Zhen Liu
- National Engineering Research Center of Electromagnetic Radiation Control Materials, School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 611731, China
| | - Xiao Lu
- National Engineering Research Center of Electromagnetic Radiation Control Materials, School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 611731, China
| | - Yue Li
- National Engineering Research Center of Electromagnetic Radiation Control Materials, School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 611731, China
| | - Lei Bi
- National Engineering Research Center of Electromagnetic Radiation Control Materials, School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 611731, China
| | - Li Zhang
- National Engineering Research Center of Electromagnetic Radiation Control Materials, School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 611731, China
| | - Haipeng Lu
- National Engineering Research Center of Electromagnetic Radiation Control Materials, School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 611731, China
| | - Haiyan Chen
- National Engineering Research Center of Electromagnetic Radiation Control Materials, School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 611731, China
| | - Peiheng Zhou
- National Engineering Research Center of Electromagnetic Radiation Control Materials, School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 611731, China
| | - Linbo Zhang
- National Engineering Research Center of Electromagnetic Radiation Control Materials, School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 611731, China
| | - Yingchun Cheng
- Key Laboratory of Flexible Electronics and Institute of Advanced Materials, Nanjing Tech University, Nanjing 211816, China
| | - Xiaoxu Zhao
- Department of Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, 117575, Singapore
| | - Yu Ye
- State Key Laboratory for Artificial Microstructure and Mesoscopic Physics, Frontiers Center for Nano-optoelectronics, School of Physics, Peking University, Beijing 100871, China
| | - Wei Huang
- Key Laboratory of Flexible Electronics and Institute of Advanced Materials, Nanjing Tech University, Nanjing 211816, China
| | - Stephen John Pennycook
- Department of Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, 117575, Singapore
| | - Kian Ping Loh
- Department of Chemistry and Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, 117549, Singapore
| | - Bo Peng
- National Engineering Research Center of Electromagnetic Radiation Control Materials, School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 611731, China
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17
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Liu E, van Baren J, Taniguchi T, Watanabe K, Chang YC, Lui CH. Landau-Quantized Excitonic Absorption and Luminescence in a Monolayer Valley Semiconductor. PHYSICAL REVIEW LETTERS 2020; 124:097401. [PMID: 32202881 DOI: 10.1103/physrevlett.124.097401] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2019] [Revised: 10/09/2019] [Accepted: 01/17/2020] [Indexed: 06/10/2023]
Abstract
We investigate Landau-quantized excitonic absorption and luminescence of monolayer WSe_{2} under magnetic field. We observe gate-dependent quantum oscillations in the bright exciton and trions (or exciton polarons) as well as the dark trions and their phonon replicas. Our results reveal spin- and valley-polarized Landau levels (LLs) with filling factors n=+0, +1 in the bottom conduction band and n=-0 to -6 in the top valence band, including the Berry-curvature-induced n=±0 LLs of massive Dirac fermions. The LL filling produces periodic plateaus in the exciton energy shift accompanied by sharp oscillations in the exciton absorption width and magnitude. This peculiar exciton behavior can be simulated by semiempirical calculations. The experimentally deduced g factors of the conduction band (g∼2.5) and valence band (g∼15) exceed those predicted in a single-particle model (g=1.5, 5.5, respectively). Such g-factor enhancement implies strong many-body interactions in gated monolayer WSe_{2}. The complex interplay between Landau quantization, excitonic effects, and many-body interactions makes monolayer WSe_{2} a promising platform to explore novel correlated quantum phenomena.
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Affiliation(s)
- Erfu Liu
- Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
| | - Jeremiah van Baren
- Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
| | - Takashi Taniguchi
- National Institute for Materials Science, Tsukuba, Ibaraki 305-004, Japan
| | - Kenji Watanabe
- National Institute for Materials Science, Tsukuba, Ibaraki 305-004, Japan
| | - Yia-Chung Chang
- Research Center for Applied Sciences, Academia Sinica, Taipei 11529, Taiwan
| | - Chun Hung Lui
- Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
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18
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Zhang J, Du L, Feng S, Zhang RW, Cao B, Zou C, Chen Y, Liao M, Zhang B, Yang SA, Zhang G, Yu T. Enhancing and controlling valley magnetic response in MoS 2/WS 2 heterostructures by all-optical route. Nat Commun 2019; 10:4226. [PMID: 31530805 PMCID: PMC6748949 DOI: 10.1038/s41467-019-12128-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2019] [Accepted: 08/20/2019] [Indexed: 11/24/2022] Open
Abstract
Van der Waals heterostructures of transition metal dichalcogenides with interlayer coupling offer an exotic platform to realize fascinating phenomena. Due to the type II band alignment of these heterostructures, electrons and holes are separated into different layers. The localized electrons induced doping in one layer, in principle, would lift the Fermi level to cross the spin-polarized upper conduction band and lead to strong manipulation of valley magnetic response. Here, we report the significantly enhanced valley Zeeman splitting and magnetic tuning of polarization for the direct optical transition of MoS2 in MoS2/WS2 heterostructures. Such strong enhancement of valley magnetic response in MoS2 stems from the change of the spin-valley degeneracy from 2 to 4 and strong many-body Coulomb interactions induced by ultrafast charge transfer. Moreover, the magnetic splitting can be tuned monotonically by laser power, providing an effective all-optical route towards engineering and manipulating of valleytronic devices and quantum-computation. Van der Waals heterostructures may offer a suitable platform for all-optical manipulation of valleytronic devices. Here, the authors observe a strong enhancement of the valley magnetic response in MoS2, and magnetic tuning of the polarization of MoS2 direct optical transition
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Affiliation(s)
- Jing Zhang
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 63737, Singapore
| | - Luojun Du
- CAS Key Laboratory of Nanoscale Physics and Devices, Institute of Physics, Chinese Academy of Sciences, 100190, Beijing, China.,Department of Electronics and Nanoengineering, Aalto University, FI-02150, Tietotie 3, Finland
| | - Shun Feng
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 63737, Singapore
| | - Run-Wu Zhang
- Research Laboratory for Quantum Materials, Singapore University of Technology and Design, Singapore, 487372, Singapore.,Key Lab of advanced optoelectronic quantum architecture and measurement (MOE), Beijing Key Lab of Nanophotonics & ultrafine Optoelectronic Systems, and School of Physics, Beijing Institute of Technology, 100081, Beijing, China
| | - Bingchen Cao
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 63737, Singapore
| | - Chenji Zou
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 63737, Singapore
| | - Yu Chen
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 63737, Singapore
| | - Mengzhou Liao
- CAS Key Laboratory of Nanoscale Physics and Devices, Institute of Physics, Chinese Academy of Sciences, 100190, Beijing, China
| | - Baile Zhang
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 63737, Singapore
| | - Shengyuan A Yang
- Research Laboratory for Quantum Materials, Singapore University of Technology and Design, Singapore, 487372, Singapore
| | - Guangyu Zhang
- CAS Key Laboratory of Nanoscale Physics and Devices, Institute of Physics, Chinese Academy of Sciences, 100190, Beijing, China. .,Songshan Lake Materials Laboratory, Dongguan, 523808, Guangdong, China.
| | - Ting Yu
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 63737, Singapore.
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19
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Li Z, Wang T, Jin C, Lu Z, Lian Z, Meng Y, Blei M, Gao S, Taniguchi T, Watanabe K, Ren T, Tongay S, Yang L, Smirnov D, Cao T, Shi SF. Emerging photoluminescence from the dark-exciton phonon replica in monolayer WSe 2. Nat Commun 2019; 10:2469. [PMID: 31171789 PMCID: PMC6554274 DOI: 10.1038/s41467-019-10477-6] [Citation(s) in RCA: 60] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Accepted: 05/09/2019] [Indexed: 11/16/2022] Open
Abstract
Tungsten-based monolayer transition metal dichalcogenides host a long-lived "dark" exciton, an electron-hole pair in a spin-triplet configuration. The long lifetime and unique spin properties of the dark exciton provide exciting opportunities to explore light-matter interactions beyond electric dipole transitions. Here we demonstrate that the coupling of the dark exciton and an optically silent chiral phonon enables the intrinsic photoluminescence of the dark-exciton replica in monolayer WSe2. Gate and magnetic-field dependent PL measurements unveil a circularly-polarized replica peak located below the dark exciton by 21.6 meV, equal to E″ phonon energy from Se vibrations. First-principles calculations show that the exciton-phonon interaction selectively couples the spin-forbidden dark exciton to the intravalley spin-allowed bright exciton, permitting the simultaneous emission of a chiral phonon and a circularly-polarized photon. Our discovery and understanding of the phonon replica reveals a chirality dictated emission channel of the phonons and photons, unveiling a new route of manipulating valley-spin.
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Affiliation(s)
- Zhipeng Li
- Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy, NY, 12180, USA
- School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, 200240, Shanghai, China
| | - Tianmeng Wang
- Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy, NY, 12180, USA
| | - Chenhao Jin
- Kavli Institute at Cornell for Nanoscale Science, Ithaca, NY, 14853, USA
| | - Zhengguang Lu
- National High Magnetic Field Lab, Tallahassee, FL, 32310, USA
- Department of Physics, Florida State University, Tallahassee, FL, 32306, USA
| | - Zhen Lian
- Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy, NY, 12180, USA
| | - Yuze Meng
- Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy, NY, 12180, USA
- College of Physics, Nanjing University, 210093, Nanjing, China
| | - Mark Blei
- School for Engineering of Matter, Transport and Energy, Arizona State University, Tempe, AZ, 85287, USA
| | - Shiyuan Gao
- Department of Physics, Washington University in St. Louis, St. Louis, MO, 63136, USA
| | - Takashi Taniguchi
- National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Kenji Watanabe
- National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Tianhui Ren
- School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, 200240, Shanghai, China.
| | - Sefaattin Tongay
- School for Engineering of Matter, Transport and Energy, Arizona State University, Tempe, AZ, 85287, USA
| | - Li Yang
- Department of Physics, Washington University in St. Louis, St. Louis, MO, 63136, USA
| | - Dmitry Smirnov
- National High Magnetic Field Lab, Tallahassee, FL, 32310, USA
| | - Ting Cao
- Geballe Laboratory for Advanced Materials, Stanford University, Stanford, CA, 94305, USA.
- Department of Materials Science and Engineering, University of Washington, Seattle, WA, 98195, USA.
| | - Su-Fei Shi
- Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy, NY, 12180, USA.
- Department of Electrical, Computer & Systems Engineering, Rensselaer Polytechnic Institute, Troy, NY, 12180, USA.
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20
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Zhang F, Mi W, Wang X. Tunable valley and spin splitting in 2H-VSe 2/BiFeO 3(111) triferroic heterostructures. NANOSCALE 2019; 11:10329-10338. [PMID: 31107480 DOI: 10.1039/c9nr01171d] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The spin and valley degrees of freedom in monolayer transition metal dichalcogenides have potential applications in spintronics and valleytronics. However, nonvolatile control on the valley and spin degrees of freedom of two-dimensional ferromagnetic materials by multiferroic materials has been rarely reported. Here, the electronic structure of monolayer 2H-VSe2/BiFeO3(111) triferroic heterostructures has been investigated by first-principles calculations. It is found that the V magnetic moment, spin and valley splitting of monolayer VSe2 can be affected by the BiFeO3(111) substrate with ferroelectric polarization and G-type antiferromagnetic order. Particularly, the reversed orientation of ferroelectric polarization and magnetic order of the BiFeO3(111) substrate can modulate the magnitude of spin and valley splitting, and change the spin splitting direction and the spin-dependent valley state in the valence band of monolayer VSe2. The coupling among ferroelectrics, magnetism and ferrovalley is realized in 2H-VSe2/BiFeO3(111) triferroic heterostructures. These results provide a new platform for multiferroic regulation in spintronics and valleytronics, which can enrich the diversity for high-performance devices based on two dimensional multiferroic heterostructures.
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Affiliation(s)
- Fang Zhang
- Tianjin Key Laboratory of Low-Dimensional Materials Physics and Preparation Technology, School of Science, Tianjin University, Tianjin 300354, China.
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21
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Roch JG, Froehlicher G, Leisgang N, Makk P, Watanabe K, Taniguchi T, Warburton RJ. Spin-polarized electrons in monolayer MoS 2. NATURE NANOTECHNOLOGY 2019; 14:432-436. [PMID: 30858519 DOI: 10.1038/s41565-019-0397-y] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Accepted: 01/31/2019] [Indexed: 06/09/2023]
Abstract
Coulomb interactions are crucial in determining the ground state of an ideal two-dimensional electron gas (2DEG) in the limit of low electron densities1. In this regime, Coulomb interactions dominate over single-particle phase-space filling. In silicon and gallium arsenide, electrons are typically localized at these low densities. In contrast, in transition-metal dichalcogenides (TMDs), Coulomb correlations in a 2DEG can be anticipated at experimentally relevant electron densities. Here, we investigate a 2DEG in a gated monolayer of the TMD molybdenum disulfide2. We measure the optical susceptibility, a probe of the 2DEG which is local, minimally invasive and spin selective3. In a magnetic field of 9.0 T and at electron concentrations up to n ≃ 5 × 1012 cm-2, we present evidence that the ground state is spin-polarized. Out of the four available conduction bands4,5, only two are occupied. These two bands have the same spin but different valley quantum numbers. Our results suggest that only two bands are occupied even in the absence of a magnetic field. The spin polarization increases with decreasing 2DEG density, suggesting that Coulomb interactions are a key aspect of the symmetry breaking. We propose that exchange couplings align the spins6. The Bohr radius is so small7 that even electrons located far apart in phase-space interact with each other6.
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Affiliation(s)
- Jonas Gaël Roch
- Department of Physics, University of Basel, Basel, Switzerland.
| | | | - Nadine Leisgang
- Department of Physics, University of Basel, Basel, Switzerland
| | - Peter Makk
- Department of Physics, University of Basel, Basel, Switzerland
- Department of Physics, Budapest University of Technology and Economics and Nanoelectronics 'Momentum' Research Group of the Hungarian Academy of Sciences, Budapest, Hungary
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22
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Liu H, Sun JT, Liu M, Meng S. Screening Magnetic Two-Dimensional Atomic Crystals with Nontrivial Electronic Topology. J Phys Chem Lett 2018; 9:6709-6715. [PMID: 30403873 DOI: 10.1021/acs.jpclett.8b02783] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
To date, only a few two-dimensional (2D) magnetic crystals have been experimentally confirmed, such as CrI3 and CrGeTe3, all with very low Curie temperatures ( TC). High-throughput first-principles screening over a large set of materials yields 89 magnetic monolayers including 56 ferromagnetic (FM) and 33 antiferromagnetic compounds. Among them, 24 FM monolayers are promising candidates possessing TC higher than that of CrI3. High TC monolayers with fascinating electronic phases are identified: (i) quantum anomalous Hall and valley Hall effects coexist in a single material RuCl3 or VCl3, leading to a valley-polarized quantum anomalous Hall state; (ii) TiBr3, Co2NiO6, and V2H3O5 are revealed to be half-metals. More importantly, a new type of fermion dubbed type-II Weyl ring is discovered in ScCl. Our work provides a database of 2D magnetic materials, which could guide experimental realization of high-temperature magnetic monolayers with exotic electronic states for future spintronics and quantum computing applications.
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Affiliation(s)
- Hang Liu
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics , Chinese Academy of Sciences , Beijing 100190 , People's Republic of China
- University of Chinese Academy of Sciences , Beijing 100049 , People's Republic of China
| | - Jia-Tao Sun
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics , Chinese Academy of Sciences , Beijing 100190 , People's Republic of China
- University of Chinese Academy of Sciences , Beijing 100049 , People's Republic of China
| | - Miao Liu
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics , Chinese Academy of Sciences , Beijing 100190 , People's Republic of China
| | - Sheng Meng
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics , Chinese Academy of Sciences , Beijing 100190 , People's Republic of China
- Collaborative Innovation Center of Quantum Matter , Beijing 100190 , People's Republic of China
- University of Chinese Academy of Sciences , Beijing 100049 , People's Republic of China
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23
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Gustafsson MV, Yankowitz M, Forsythe C, Rhodes D, Watanabe K, Taniguchi T, Hone J, Zhu X, Dean CR. Ambipolar Landau levels and strong band-selective carrier interactions in monolayer WSe 2. NATURE MATERIALS 2018; 17:411-415. [PMID: 29581552 DOI: 10.1038/s41563-018-0036-2] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2017] [Accepted: 02/07/2018] [Indexed: 06/08/2023]
Abstract
Monolayers (MLs) of transition-metal dichalcogenides (TMDs) exhibit unusual electrical behaviour under magnetic fields due to their intrinsic spin-orbit coupling and lack of inversion symmetry1-15. Although recent experiments have also identified the critical role of carrier interactions within these materials11,15, a complete mapping of the ambipolar Landau level (LL) sequence has remained elusive. Here we use single-electron transistors (SETs)16,17 to perform LL spectroscopy in ML WSe2, and provide a comprehensive picture of the electronic structure of a ML TMD for both electrons and holes. We find that the LLs differ notably between the two bands, and follow a unique sequence in the valence band (VB) that is dominated by strong Zeeman effects. The Zeeman splitting in the VB is several times higher than the cyclotron energy, far exceeding the predictions of a single-particle model and, moreover, tunes significantly with doping 15 . This implies exceptionally strong many-body interactions, and suggests that ML WSe2 can serve as a host for new correlated-electron phenomena.
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Affiliation(s)
- Martin V Gustafsson
- Department of Chemistry, Columbia University, New York, NY, USA
- Department of Physics, Columbia University, New York, NY, USA
| | | | - Carlos Forsythe
- Department of Physics, Columbia University, New York, NY, USA
| | - Daniel Rhodes
- Center for Integrated Science and Engineering, Columbia University, New York, NY, USA
| | - Kenji Watanabe
- National Institute for Materials Science, Tsukuba, Japan
| | | | - James Hone
- Department of Mechanical Engineering, Columbia University, New York, NY, USA
| | - Xiaoyang Zhu
- Department of Chemistry, Columbia University, New York, NY, USA
| | - Cory R Dean
- Department of Physics, Columbia University, New York, NY, USA.
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