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Molino L, Aggarwal L, Maity I, Plumadore R, Lischner J, Luican-Mayer A. Influence of Atomic Relaxations on the Moiré Flat Band Wave Functions in Antiparallel Twisted Bilayer WS 2. NANO LETTERS 2023; 23:11778-11784. [PMID: 38054731 DOI: 10.1021/acs.nanolett.3c03735] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/07/2023]
Abstract
Twisting bilayers of transition metal dichalcogenides gives rise to a moiré potential resulting in flat bands with localized wave functions and enhanced correlation effects. In this work, scanning tunneling microscopy is used to image a WS2 bilayer twisted approximately 3° off the antiparallel alignment. Scanning tunneling spectroscopy reveals localized states in the vicinity of the valence band onset, which is observed to occur first in regions with S-on-S Bernal stacking. In contrast, density functional theory calculations on twisted bilayers that have been relaxed in vacuum predict the highest-lying flat valence band to be localized in regions of AA' stacking. However, agreement with experiment is recovered when the calculations are performed on bilayers in which the atomic displacements from the unrelaxed positions have been reduced, reflecting the influence of the substrate and finite temperature. This demonstrates the delicate interplay of atomic relaxations and the electronic structure of twisted bilayer materials.
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Affiliation(s)
- Laurent Molino
- Department of Physics, University of Ottawa, Ottawa K1N 6X3, Canada
| | - Leena Aggarwal
- Department of Physics, University of Ottawa, Ottawa K1N 6X3, Canada
| | - Indrajit Maity
- Department of Materials, Imperial College London, and Thomas Young Centre for Theory and Simulation of Materials, London SW7 2BP, U.K
| | - Ryan Plumadore
- Department of Physics, University of Ottawa, Ottawa K1N 6X3, Canada
| | - Johannes Lischner
- Department of Materials, Imperial College London, and Thomas Young Centre for Theory and Simulation of Materials, London SW7 2BP, U.K
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2
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Liu Y, Chen R, Zhang Z, Bockrath M, Lau CN, Zhou YF, Yoon C, Li S, Liu X, Dhale N, Lv B, Zhang F, Watanabe K, Taniguchi T, Huang J, Yi M, Oh JS, Birgeneau RJ. Gate-Tunable Transport in Quasi-One-Dimensional α-Bi 4I 4 Field Effect Transistors. NANO LETTERS 2022; 22:1151-1158. [PMID: 35077182 DOI: 10.1021/acs.nanolett.1c04264] [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
Bi4I4 belongs to a novel family of quasi-one-dimensional (1D) topological insulators (TIs). While its β phase was demonstrated to be a prototypical weak TI, the α phase, long thought to be a trivial insulator, was recently predicted to be a rare higher order TI. Here, we report the first gate tunable transport together with evidence for unconventional band topology in exfoliated α-Bi4I4 field effect transistors. We observe a Dirac-like longitudinal resistance peak and a sign change in the Hall resistance; their temperature dependences suggest competing transport mechanisms: a hole-doped insulating bulk and one or more gate-tunable ambipolar boundary channels. Our combined transport, photoemission, and theoretical results indicate that the gate-tunable channels likely arise from novel gapped side surface states, two-dimensional (2D) TI in the bottommost layer, and/or helical hinge states of the upper layers. Markedly, a gate-tunable supercurrent is observed in an α-Bi4I4 Josephson junction, underscoring the potential of these boundary channels to mediate topological superconductivity.
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Affiliation(s)
- Yulu Liu
- Department of Physics, The Ohio State University, Columbus, Ohio 43210, United States
| | - Ruoyu Chen
- Department of Physics, The Ohio State University, Columbus, Ohio 43210, United States
| | - Zheneng Zhang
- Department of Physics, The Ohio State University, Columbus, Ohio 43210, United States
| | - Marc Bockrath
- Department of Physics, The Ohio State University, Columbus, Ohio 43210, United States
| | - Chun Ning Lau
- Department of Physics, The Ohio State University, Columbus, Ohio 43210, United States
| | - Yan-Feng Zhou
- Department of Physics, The University of Texas at Dallas, 800 West Campbell Road, Richardson, Texas 75080-3021, United States
| | - Chiho Yoon
- Department of Physics, The University of Texas at Dallas, 800 West Campbell Road, Richardson, Texas 75080-3021, United States
- Department of Physics and Astronomy, Seoul National University, Seoul 08826, Korea
| | - Sheng Li
- Department of Physics, The University of Texas at Dallas, 800 West Campbell Road, Richardson, Texas 75080-3021, United States
| | - Xiaoyuan Liu
- Department of Physics, The University of Texas at Dallas, 800 West Campbell Road, Richardson, Texas 75080-3021, United States
| | - Nikhil Dhale
- Department of Physics, The University of Texas at Dallas, 800 West Campbell Road, Richardson, Texas 75080-3021, United States
| | - Bing Lv
- Department of Physics, The University of Texas at Dallas, 800 West Campbell Road, Richardson, Texas 75080-3021, United States
| | - Fan Zhang
- Department of Physics, The University of Texas at Dallas, 800 West Campbell Road, Richardson, Texas 75080-3021, United States
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Jianwei Huang
- Department of Physics and Astronomy, Rice University, Houston, Texas 77005, United States
| | - Ming Yi
- Department of Physics and Astronomy, Rice University, Houston, Texas 77005, United States
| | - Ji Seop Oh
- Department of Physics, University of California, Berkeley, Berkeley, California 94720, United States
| | - Robert J Birgeneau
- Department of Physics, University of California, Berkeley, Berkeley, California 94720, United States
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3
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Li E, Hu JX, Feng X, Zhou Z, An L, Law KT, Wang N, Lin N. Lattice reconstruction induced multiple ultra-flat bands in twisted bilayer WSe 2. Nat Commun 2021; 12:5601. [PMID: 34556663 PMCID: PMC8460827 DOI: 10.1038/s41467-021-25924-6] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2021] [Accepted: 08/31/2021] [Indexed: 12/05/2022] Open
Abstract
Moiré superlattices in van der Waals heterostructures provide a tunable platform to study emergent properties that are absent in the natural crystal form. Twisted bilayer transition metal dichalcogenides (TB-TMDs) can host moiré flat bands over a wide range of twist angles. For twist angle close to 60°, it was predicted that TB-TMDs undergo a lattice reconstruction which causes the formation of ultra-flat bands. Here, by using scanning tunneling microscopy and spectroscopy, we show the emergence of multiple ultra-flat bands in twisted bilayer WSe2 when the twist angle is within 3° of 60°. The ultra-flat bands are manifested as narrow tunneling conductance peaks with estimated bandwidth less than 10 meV, which is only a fraction of the estimated on-site Coulomb repulsion energy. The number of these ultra-flat bands and spatial distribution of the wavefunctions match well with the theoretical predictions, strongly evidencing that the observed ultra-flat bands are induced by lattice reconstruction. Our work provides a foundation for further study of the exotic correlated phases in TB-TMDs. It was predicted that lattice reconstruction can lead to the emergence of multiple ultra-flat electronic bands in twisted bilayer transition metal dichalcogenides. Here, by using scanning tunneling microscopy and spectroscopy, the authors demonstrate such bands in twisted bilayer WSe2.
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Affiliation(s)
- En Li
- Department of Physics, The Hong Kong University of Science and Technology, Hong Kong SAR, China
| | - Jin-Xin Hu
- Department of Physics, The Hong Kong University of Science and Technology, Hong Kong SAR, China
| | - Xuemeng Feng
- Department of Physics, The Hong Kong University of Science and Technology, Hong Kong SAR, China
| | - Zishu Zhou
- Department of Physics, The Hong Kong University of Science and Technology, Hong Kong SAR, China
| | - Liheng An
- Department of Physics, The Hong Kong University of Science and Technology, Hong Kong SAR, China
| | - Kam Tuen Law
- Department of Physics, The Hong Kong University of Science and Technology, Hong Kong SAR, China.
| | - Ning Wang
- Department of Physics, The Hong Kong University of Science and Technology, Hong Kong SAR, China.
| | - Nian Lin
- Department of Physics, The Hong Kong University of Science and Technology, Hong Kong SAR, China.
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4
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Sattari F, Mirershadi S. Effect of the strain on spin-valley transport properties in MoS 2 superlattice. Sci Rep 2021; 11:17617. [PMID: 34475509 PMCID: PMC8413316 DOI: 10.1038/s41598-021-97189-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2021] [Accepted: 08/23/2021] [Indexed: 11/23/2022] Open
Abstract
The effect of the strain on the spin and valley dependent transport properties, including the conductance and polarization, through a monolayer MoS2 superlattice under Rashba spin-orbit coupling is theoretically investigated. It is found that the conductance strongly depends on the spin and valley degrees of freedom, and spin-inversion can be achieved by MoS2 superlattice. Also, the spin and valley dependent conductance in a monolayer MoS2 superlattice can be efficiently adjusted via strain and the number of the superlattice barriers. Moreover, it is demonstrated that both the magnitude and sign of the spin and valley polarization depend on the strain strength, the number of barriers, and electrostatic barrier height. Both full spin and valley polarized current (with 100% or - 100% efficiency) can be realized in a MoS2 superlattice under strain.
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Affiliation(s)
- Farhad Sattari
- Department of Physics, Faculty of Sciences, University of Mohaghegh Ardabili, P.O. Box 179, Ardabil, Iran.
- Nanoscience and Nanotechnology Research Group, University of Mohaghegh Ardabili, Ardabil, Iran.
| | - Soghra Mirershadi
- Department of Engineering Sciences, Faculty of Advanced Technologies, University of Mohaghegh Ardabili, Namin, Iran
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5
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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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6
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An L, Cai X, Pei D, Huang M, Wu Z, Zhou Z, Lin J, Ying Z, Ye Z, Feng X, Gao R, Cacho C, Watson M, Chen Y, Wang N. Interaction effects and superconductivity signatures in twisted double-bilayer WSe 2. NANOSCALE HORIZONS 2020; 5:1309-1316. [PMID: 32696773 DOI: 10.1039/d0nh00248h] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Twisted bilayer graphene provides a new two-dimensional platform for studying electron interaction phenomena and flat band properties such as correlated insulator transition, superconductivity and ferromagnetism at certain magic angles. Here, we present experimental characterization of interaction effects and superconductivity signatures in p-type twisted double-bilayer WSe2. Enhanced interlayer interactions are observed when the twist angle decreases to a few degrees as reflected by the high-order satellites in the electron diffraction patterns taken from the reconstructed domains from a conventional moiré superlattice. In contrast to twisted bilayer graphene, there is no specific magic angle for twisted WSe2. Flat band properties are observable at twist angles ranging from 1 to 4 degrees. Our work has facilitated future study in the area of flat band related properties in twisted transition metal dichalcogenide layered structures.
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Affiliation(s)
- Liheng An
- Department of Physics, Center for Quantum Materials and Willian Mong Institute of Nano Science and Technology, the Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China.
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7
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Shi R, He P, Cai X, Zhang Z, Wang W, Wang J, Feng X, Wu Z, Amini A, Wang N, Cheng C. Oxide Inhibitor-Assisted Growth of Single-Layer Molybdenum Dichalcogenides (MoX 2, X = S, Se, Te) with Controllable Molybdenum Release. ACS NANO 2020; 14:7593-7601. [PMID: 32491834 DOI: 10.1021/acsnano.0c03469] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Though chemical vapor deposition (CVD) methods have been widely used in the growth of two-dimensional transition-metal dichalcogenides (2D TMDCs), the controllable fabrication of 2D TMDCs is yet hard to achieve because of the great challenge of concisely controlling the release of precursors vapor, one of the most critical growth kinetic factors. To solve this important issue, here we report the utilization of oxide inhibitors covering Mo source during CVD reactions to manipulate the release of Mo vapor. In contrast to the lack of capability of conventional CVD methods, 2D molybdenum dichalcogenide (MoX2, X = S, Se, Te) monolayers were successfully fabricated through the proposed CVD protocol with the oxide-inhibitor-assisted growth (OIAG) strategy. In this way, despite the fact that only separated MoTe2 flakes were prepared, both MoS2 (continuous and clean) and MoSe2 (continuous but dotted) monolayer films at the scale of centimeter were obtained. The presented OIAG method enables a comprehensive understanding and precise control of the reaction kinetics for improved growth of 2D MoX2.
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Affiliation(s)
- Run Shi
- Department of Materials Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, P.R. China
- Department of Physics and Center for Quantum Materials, Hong Kong University of Science and Technology, Hong Kong, P.R. China
| | - Pingge He
- Department of Physics and Center for Quantum Materials, Hong Kong University of Science and Technology, Hong Kong, P.R. China
| | - Xiangbin Cai
- Department of Physics and Center for Quantum Materials, Hong Kong University of Science and Technology, Hong Kong, P.R. China
| | - Zhuoqiong Zhang
- Department of Materials Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, P.R. China
| | - Weijun Wang
- Department of Materials Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, P.R. China
| | - Jingwei Wang
- Department of Materials Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, P.R. China
- Department of Physics and Center for Quantum Materials, Hong Kong University of Science and Technology, Hong Kong, P.R. China
| | - Xuemeng Feng
- Department of Physics and Center for Quantum Materials, Hong Kong University of Science and Technology, Hong Kong, P.R. China
| | - Zefei Wu
- Department of Physics and Center for Quantum Materials, Hong Kong University of Science and Technology, Hong Kong, P.R. China
| | - Abbas Amini
- Center for Infrastructure Engineering, Western Sydney University, Kingswood, New South Wales 2751, Australia
| | - Ning Wang
- Department of Physics and Center for Quantum Materials, Hong Kong University of Science and Technology, Hong Kong, P.R. China
| | - Chun Cheng
- Department of Materials Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, P.R. China
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8
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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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9
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Introducing Electrode Contact by Controlled Micro-Alloying in Few-Layered GaTe Field Effect Transistors. CRYSTALS 2020. [DOI: 10.3390/cryst10030144] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Recently, gallium telluride (GaTe) has triggered much attention for its unique properties and offers excellent opportunities for nanoelectronics. Yet it is a challenge to bridge the semiconducting few-layered GaTe crystals with metallic electrodes for device applications. Here, we report a method on fabricating electrode contacts to few-layered GaTe field effect transistors (FETs) by controlled micro-alloying. The devices show linear I-V curves and on/off ratio of ∼10 4 on HfO 2 substrates. Kelvin probe force microscope (KPFM) and energy dispersion spectrum (EDS) are performed to characterize the electrode contacts, suggesting that the lowered Schottky barrier by the diffusion of Pd element into the GaTe conduction channel may play an important role. Our findings provide a strategy for the engineering of electrode contact for future device applications based on 2DLMs.
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10
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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: 26] [Impact Index Per Article: 5.2] [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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11
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Pisoni R, Davatz T, Watanabe K, Taniguchi T, Ihn T, Ensslin K. Absence of Interlayer Tunnel Coupling of K-Valley Electrons in Bilayer MoS_{2}. PHYSICAL REVIEW LETTERS 2019; 123:117702. [PMID: 31573263 DOI: 10.1103/physrevlett.123.117702] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2019] [Indexed: 06/10/2023]
Abstract
In Bernal stacked bilayer graphene interlayer coupling significantly affects the electronic band structure compared to monolayer graphene. Here we present magnetotransport experiments on high-quality n-doped bilayer MoS_{2}. By measuring the evolution of the Landau levels as a function of electron density and applied magnetic field we are able to investigate the occupation of conduction band states, the interlayer coupling in pristine bilayer MoS_{2}, and how these effects are governed by electron-electron interactions. We find that the two layers of the bilayer MoS_{2} behave as two independent electronic systems where a twofold Landau level's degeneracy is observed for each MoS_{2} layer. At the onset of the population of the bottom MoS_{2} layer we observe a large negative compressibility caused by the exchange interaction. These observations, enabled by the high electronic quality of our samples, demonstrate weak interlayer tunnel coupling but strong interlayer electrostatic coupling in pristine bilayer MoS_{2}. The conclusions from the experiments may be relevant also to other transition metal dichalcogenide materials.
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Affiliation(s)
- Riccardo Pisoni
- Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland
| | - Tim Davatz
- Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland
| | - Kenji Watanabe
- National Institute for Material Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- National Institute for Material Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Thomas Ihn
- Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland
| | - Klaus Ensslin
- Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland
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12
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Smoleński T, Cotlet O, Popert A, Back P, Shimazaki Y, Knüppel P, Dietler N, Taniguchi T, Watanabe K, Kroner M, Imamoglu A. Interaction-Induced Shubnikov-de Haas Oscillations in Optical Conductivity of Monolayer MoSe_{2}. PHYSICAL REVIEW LETTERS 2019; 123:097403. [PMID: 31524484 DOI: 10.1103/physrevlett.123.097403] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2018] [Indexed: 06/10/2023]
Abstract
We report polarization-resolved resonant reflection spectroscopy of a charge-tunable atomically thin valley semiconductor hosting tightly bound excitons coupled to a dilute system of fully spin- and valley-polarized holes in the presence of a strong magnetic field. We find that exciton-hole interactions manifest themselves in hole-density dependent, Shubnikov-de Haas-like oscillations in the energy and line broadening of the excitonic resonances. These oscillations are evidenced to be precisely correlated with the occupation of Landau levels, thus demonstrating that strong interactions between the excitons and Landau-quantized itinerant carriers enable optical investigation of quantum-Hall physics in transition metal dichalcogenides.
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Affiliation(s)
- T Smoleński
- Institute for Quantum Electronics, ETH Zürich, CH-8093 Zürich, Switzerland
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland
| | - O Cotlet
- Institute for Quantum Electronics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - A Popert
- Institute for Quantum Electronics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - P Back
- Institute for Quantum Electronics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Y Shimazaki
- Institute for Quantum Electronics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - P Knüppel
- Institute for Quantum Electronics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - N Dietler
- Institute for Quantum Electronics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - T Taniguchi
- National Institute for Materials Science, Tsukuba, Ibaraki 305-0044, Japan
| | - K Watanabe
- National Institute for Materials Science, Tsukuba, Ibaraki 305-0044, Japan
| | - M Kroner
- Institute for Quantum Electronics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - A Imamoglu
- Institute for Quantum Electronics, ETH Zürich, CH-8093 Zürich, Switzerland
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