1
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Davydov K, Zhang X, Ren W, Coles M, Kline L, Zucker B, Watanabe K, Taniguchi T, Wang K. Easy-to-configure zero-dimensional valley-chiral modes in a graphene point junction. SCIENCE ADVANCES 2024; 10:eadp6296. [PMID: 39259786 PMCID: PMC11389794 DOI: 10.1126/sciadv.adp6296] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2024] [Accepted: 08/05/2024] [Indexed: 09/13/2024]
Abstract
The valley degree of freedom in two-dimensional (2D) materials can be manipulated for low-dissipation quantum electronics called valleytronics. At the boundary between two regions of bilayer graphene with different atomic or electrostatic configuration, valley-polarized current has been realized. However, the demanding fabrication and operation requirements limit device reproducibility and scalability toward more advanced valleytronics circuits. We demonstrate a device architecture of a point junction where a valley-chiral 0D PN junction is easily configured, switchable, and capable of carrying valley current with an estimated polarization of ~80%. This work provides a building block in manipulating valley quantum numbers and scalable valleytronics.
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Affiliation(s)
- Konstantin Davydov
- School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA
| | - Xi Zhang
- School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA
| | - Wei Ren
- School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA
| | - Matthew Coles
- School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA
| | - Logan Kline
- School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA
| | - Bryan Zucker
- Department of Physics, The Ohio State University, Columbus, OH 43221, USA
| | - Kenji Watanabe
- Research Center for Electronic and Optical Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Ke Wang
- School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA
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2
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Wu R, Zhang H, Ma H, Zhao B, Li W, Chen Y, Liu J, Liang J, Qin Q, Qi W, Chen L, Li J, Li B, Duan X. Synthesis, Modulation, and Application of Two-Dimensional TMD Heterostructures. Chem Rev 2024; 124:10112-10191. [PMID: 39189449 DOI: 10.1021/acs.chemrev.4c00174] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/28/2024]
Abstract
Two-dimensional (2D) transition metal dichalcogenide (TMD) heterostructures have attracted a lot of attention due to their rich material diversity and stack geometry, precise controllability of structure and properties, and potential practical applications. These heterostructures not only overcome the inherent limitations of individual materials but also enable the realization of new properties through appropriate combinations, establishing a platform to explore new physical and chemical properties at micro-nano-pico scales. In this review, we systematically summarize the latest research progress in the synthesis, modulation, and application of 2D TMD heterostructures. We first introduce the latest techniques for fabricating 2D TMD heterostructures, examining the rationale, mechanisms, advantages, and disadvantages of each strategy. Furthermore, we emphasize the importance of characteristic modulation in 2D TMD heterostructures and discuss some approaches to achieve novel functionalities. Then, we summarize the representative applications of 2D TMD heterostructures. Finally, we highlight the challenges and future perspectives in the synthesis and device fabrication of 2D TMD heterostructures and provide some feasible solutions.
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Affiliation(s)
- Ruixia Wu
- Key Laboratory for Micro-Nano Optoelectronic Devices of Ministry of Education, School of Physics and Electronics, Hunan University, Changsha 410082, China
- Hunan Provincial Key Laboratory of Two-Dimensional Materials, State Key Laboratory for Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, China
| | - Hongmei Zhang
- Hunan Provincial Key Laboratory of Two-Dimensional Materials, State Key Laboratory for Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, China
| | - Huifang Ma
- Innovation Center for Gallium Oxide Semiconductor (IC-GAO), National and Local Joint Engineering Laboratory for RF Integration and Micro-Assembly Technologies, College of Integrated Circuit Science and Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210023, China
- School of Flexible Electronics (Future Technologies) Institute of Advanced Materials, Jiangsu National Synergetic Innovation Center for Advanced Materials, Nanjing Tech University, Nanjing 211816, China
| | - Bei Zhao
- School of Physics and Key Laboratory of Quantum Materials and Devices of Ministry of Education, Southeast University, Nanjing 211189, China
| | - Wei Li
- Hunan Provincial Key Laboratory of Two-Dimensional Materials, State Key Laboratory for Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, China
| | - Yang Chen
- Hunan Provincial Key Laboratory of Two-Dimensional Materials, State Key Laboratory for Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, China
| | - Jianteng Liu
- Key Laboratory for Micro-Nano Optoelectronic Devices of Ministry of Education, School of Physics and Electronics, Hunan University, Changsha 410082, China
| | - Jingyi Liang
- Hunan Provincial Key Laboratory of Two-Dimensional Materials, State Key Laboratory for Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, China
| | - Qiuyin Qin
- Hunan Provincial Key Laboratory of Two-Dimensional Materials, State Key Laboratory for Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, China
| | - Weixu Qi
- Key Laboratory for Micro-Nano Optoelectronic Devices of Ministry of Education, School of Physics and Electronics, Hunan University, Changsha 410082, China
| | - Liang Chen
- Hunan Provincial Key Laboratory of Two-Dimensional Materials, State Key Laboratory for Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, China
| | - Jia Li
- Hunan Provincial Key Laboratory of Two-Dimensional Materials, State Key Laboratory for Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, China
| | - Bo Li
- Changsha Semiconductor Technology and Application Innovation Research Institute, School of Physics and Electronics, College of Semiconductors (College of Integrated Circuits), Hunan University, Changsha 410082, China
| | - Xidong Duan
- Hunan Provincial Key Laboratory of Two-Dimensional Materials, State Key Laboratory for Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, China
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3
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Huang K, Fu H, Watanabe K, Taniguchi T, Zhu J. High-temperature quantum valley Hall effect with quantized resistance and a topological switch. Science 2024; 385:657-661. [PMID: 39024378 DOI: 10.1126/science.adj3742] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Accepted: 07/08/2024] [Indexed: 07/20/2024]
Abstract
Edge states of a topological insulator can be used to explore fundamental science emerging at the interface of low dimensionality and topology. Achieving a robust conductance quantization, however, has proven challenging for helical edge states. In this work, we show wide resistance plateaus in kink states-a manifestation of the quantum valley Hall effect in Bernal bilayer graphene-quantized to the predicted value at zero magnetic field. The plateau resistance has a very weak temperature dependence up to 50 kelvin and is flat within a dc bias window of tens of millivolts. We demonstrate the electrical operation of a topology-controlled switch with an on/off ratio of 200. These results demonstrate the robustness and tunability of the kink states and its promise in constructing electron quantum optics devices.
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Affiliation(s)
- Ke Huang
- Department of Physics, The Pennsylvania State University, University Park, PA 16802, USA
| | - Hailong Fu
- Department of Physics, The Pennsylvania State University, University Park, PA 16802, USA
| | - Kenji Watanabe
- Research Center for Electronic and Optical Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Jun Zhu
- Department of Physics, The Pennsylvania State University, University Park, PA 16802, USA
- Center for 2-Dimensional and Layered Materials, The Pennsylvania State University, University Park, PA 16802, USA
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4
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Leem YC, Fang Z, Lee YK, Kim NY, Kakekhani A, Liu W, Cho SP, Kim C, Wang Y, Ji Z, Patra A, Kronik L, Rappe AM, Yim SY, Agarwal R. Optically Triggered Emergent Mesostructures in Monolayer WS 2. NANO LETTERS 2024; 24:5436-5443. [PMID: 38656103 DOI: 10.1021/acs.nanolett.4c00358] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/26/2024]
Abstract
The ultrahigh surface area of two-dimensional materials can drive multimodal coupling between optical, electrical, and mechanical properties that leads to emergent dynamical responses not possible in three-dimensional systems. We observed that optical excitation of the WS2 monolayer above the exciton energy creates symmetrically patterned mechanical protrusions which can be controlled by laser intensity and wavelength. This observed photostrictive behavior is attributed to lattice expansion due to the formation of polarons, which are charge carriers dressed by lattice vibrations. Scanning Kelvin probe force microscopy measurements and density functional theory calculations reveal unconventional charge transport properties such as the spatially and optical intensity-dependent conversion in the WS2 monolayer from apparent n- to p-type and the subsequent formation of effective p-n junctions at the boundaries between regions with different defect densities. The strong opto-electrical-mechanical coupling in the WS2 monolayer reveals previously unexplored properties, which can lead to new applications in optically driven ultrathin microactuators.
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Affiliation(s)
- Young-Chul Leem
- Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia 19104, Pennsylvania, United States
| | - Zhenyao Fang
- Department of Chemistry, University of Pennsylvania, Philadelphia 19104-6323, Pennsylvania, United States
| | - Yun-Kyung Lee
- Application Technology Center, Park Systems Corp., Suwon 16229, Republic of Korea
| | - Na-Yeong Kim
- Advanced Photonics Research Institute, Gwangju Institute of Science and Technology, Gwangju 61005, Republic of Korea
| | - Arvin Kakekhani
- Department of Chemistry, University of Pennsylvania, Philadelphia 19104-6323, Pennsylvania, United States
| | - Wenjing Liu
- Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia 19104, Pennsylvania, United States
| | - Sung-Pyo Cho
- National Center for Inter-University Research Facilities, Seoul National University, Seoul 08826, Republic of Korea
| | - Cheolsu Kim
- Application Technology Center, Park Systems Corp., Suwon 16229, Republic of Korea
| | - Yuhui Wang
- Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia 19104, Pennsylvania, United States
| | - Zhurun Ji
- Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia 19104, Pennsylvania, United States
| | - Abhirup Patra
- Department of Chemistry, University of Pennsylvania, Philadelphia 19104-6323, Pennsylvania, United States
| | - Leeor Kronik
- Department of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovoth 7610001, Israel
| | - Andrew M Rappe
- Department of Chemistry, University of Pennsylvania, Philadelphia 19104-6323, Pennsylvania, United States
| | - Sang-Youp Yim
- Advanced Photonics Research Institute, Gwangju Institute of Science and Technology, Gwangju 61005, Republic of Korea
| | - Ritesh Agarwal
- Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia 19104, Pennsylvania, United States
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5
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Cao Z, Zhu L, Yao K. Low-Power Transistors with Ideal p-type Ohmic Contacts Based on VS 2/WSe 2 van der Waals Heterostructures. ACS APPLIED MATERIALS & INTERFACES 2024; 16:19158-19166. [PMID: 38572998 DOI: 10.1021/acsami.4c00640] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/05/2024]
Abstract
Achieving low-resistance Ohmic contacts with a vanishing Schottky barrier is crucial for enhancing the performance of two-dimensional (2D) field-effect transistors (FETs). In this paper, we present a theoretical investigation of VS2/WSe2-vdWHs-FETs with a gate length (Lg) in the range of 1-5 nm, using ab initio quantum transport simulations. The results show that a very low hole Schottky barrier height (-0.01 eV) can be achieved with perfect band offsets and reduced metal-induced gap states (MIGS), indicating the formation of p-type Ohmic contacts. Additionally, these FETs also exhibit an impressive low subthreshold swing (SS) (69 mV/dec) and high Ion/Ioff (>107) with an appropriate underlap (UL) structure consisting of pristine WSe2. Furthermore, even when the Lg is scaled down to 3 nm, the device can still meet the low-power (LP) requirements of the International Technology Roadmap for Semiconductors (ITRS) by controlling the UL. Consequently, this study provides valuable insights for the future development of LP 2D FETs.
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Affiliation(s)
- Zenglin Cao
- School of Physics and Wuhan National High Magnetic field center, Huazhong University of Science and Technology, Wuhan 430074, People's Republic of China
| | - Lin Zhu
- School of Physics and Wuhan National High Magnetic field center, Huazhong University of Science and Technology, Wuhan 430074, People's Republic of China
| | - Kailun Yao
- School of Physics and Wuhan National High Magnetic field center, Huazhong University of Science and Technology, Wuhan 430074, People's Republic of China
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6
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Shao K, Geng H, Liu E, Lado JL, Chen W, Xing DY. Non-Hermitian Moiré Valley Filter. PHYSICAL REVIEW LETTERS 2024; 132:156301. [PMID: 38683008 DOI: 10.1103/physrevlett.132.156301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2023] [Revised: 03/01/2024] [Accepted: 03/22/2024] [Indexed: 05/01/2024]
Abstract
A valley filter capable of generating a valley-polarized current is a crucial element in valleytronics, yet its implementation remains challenging. Here, we propose a valley filter made of a graphene bilayer which exhibits a 1D moiré pattern in the overlapping region of the two layers controlled by heterostrain. In the presence of a lattice modulation between layers, electrons propagating in one layer can have valley-dependent dissipation due to valley asymmetric interlayer coupling, thus giving rise to a valley-polarized current. Such a process can be described by an effective non-Hermitian theory, in which the valley filter is driven by a valley-resolved non-Hermitian skin effect. Nearly 100% valley polarization can be achieved within a wide parameter range and the functionality of the valley filter is electrically tunable. The non-Hermitian topological scenario of the valley filter ensures high tolerance against imperfections such as disorder and edge defects. Our work opens a new route for efficient and robust valley filters while significantly relaxing the stringent implementation requirements.
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Affiliation(s)
- Kai Shao
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Hao Geng
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Erfu Liu
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Jose L Lado
- Department of Applied Physics, Aalto University, 02150 Espoo, Finland
| | - Wei Chen
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - D Y Xing
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
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7
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Srivastav SK, Udupa A, Watanabe K, Taniguchi T, Sen D, Das A. Electric-Field-Tunable Edge Transport in Bernal-Stacked Trilayer Graphene. PHYSICAL REVIEW LETTERS 2024; 132:096301. [PMID: 38489611 DOI: 10.1103/physrevlett.132.096301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2023] [Revised: 08/29/2023] [Accepted: 01/29/2024] [Indexed: 03/17/2024]
Abstract
This Letter presents a nonlocal study on the electric-field-tunable edge transport in h-BN-encapsulated dual-gated Bernal-stacked (ABA) trilayer graphene across various displacement fields (D) and temperatures (T). Our measurements revealed that the nonlocal resistance (R_{NL}) surpassed the expected classical Ohmic contribution by a factor of at least 2 orders of magnitude. Through scaling analysis, we found that the nonlocal resistance scales linearly with the local resistance (R_{L}) only when the D exceeds a critical value of ∼0.2 V/nm. Additionally, we observed that the scaling exponent remains constant at unity for temperatures below the bulk-band gap energy threshold (T<25 K). Further, the value of R_{NL} decreases in a linear fashion as the channel length (L) increases. These experimental findings provide evidence for edge-mediated charge transport in ABA trilayer graphene under the influence of a finite displacement field. Furthermore, our theoretical calculations support these results by demonstrating the emergence of dispersive edge modes within the bulk-band gap energy range when a sufficient displacement field is applied.
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Affiliation(s)
| | - Adithi Udupa
- Centre for High Energy Physics, Indian Institute of Science, Bangalore 560012, India
| | - K Watanabe
- National Institute of Material Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - T Taniguchi
- National Institute of Material Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Diptiman Sen
- Centre for High Energy Physics, Indian Institute of Science, Bangalore 560012, India
| | - Anindya Das
- Department of Physics, Indian Institute of Science, Bangalore 560012, India
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8
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Fu H, Huang K, Watanabe K, Taniguchi T, Zhu J. Charge Oscillations in Bilayer Graphene Quantum Confinement Devices. NANO LETTERS 2023; 23:9726-9732. [PMID: 37862439 DOI: 10.1021/acs.nanolett.3c02253] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2023]
Abstract
Quantum confinement structures are building blocks of quantum devices in fundamental physics exploration and technological applications. In this work, we fabricate dual-gated bilayer graphene Fabry-Pérot quantum Hall interferometers employing two different gating strategies and conduct finite element simulations to understand the electrostatics of the confinement structures and to guide device design and fabrication. We observe two types of resistance oscillations arising from the charging of quantum dots formed inside the interferometers. We obtain the size, location, and charging energy of the dots by measuring the dependence of the oscillations on the magnetic field, gate voltages, and dc bias. We analyze and discuss the origin of the quantum dots and their impact on quantum Hall edge state backscattering and interference. Insights gained in these studies shed light on the construction of van der Waals quantum confinement devices.
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Affiliation(s)
- Hailong Fu
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- School of Physics, Zhejiang University, Hangzhou 310058, China
| | - Ke Huang
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Kenji Watanabe
- Research Center for Electronic and Optical Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Jun Zhu
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Center for Two-Dimensional and Layered Materials, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
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9
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Ingla-Aynés J, Manesco ALR, Ghiasi TS, Volosheniuk S, Watanabe K, Taniguchi T, van der Zant HSJ. Specular Electron Focusing between Gate-Defined Quantum Point Contacts in Bilayer Graphene. NANO LETTERS 2023; 23:5453-5459. [PMID: 37289250 PMCID: PMC10311585 DOI: 10.1021/acs.nanolett.3c00499] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2023] [Revised: 06/02/2023] [Indexed: 06/09/2023]
Abstract
We report multiterminal measurements in a ballistic bilayer graphene (BLG) channel, where multiple spin- and valley-degenerate quantum point contacts (QPCs) are defined by electrostatic gating. By patterning QPCs of different shapes along different crystallographic directions, we study the effect of size quantization and trigonal warping on transverse electron focusing (TEF). Our TEF spectra show eight clear peaks with comparable amplitudes and weak signatures of quantum interference at the lowest temperature, indicating that reflections at the gate-defined edges are specular, and transport is phase coherent. The temperature dependence of the focusing signal shows that, despite the small gate-induced bandgaps in our sample (≲45 meV), several peaks are visible up to 100 K. The achievement of specular reflection, which is expected to preserve the pseudospin information of the electron jets, is promising for the realization of ballistic interconnects for new valleytronic devices.
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Affiliation(s)
- Josep Ingla-Aynés
- Kavli
Institute of Nanoscience, Delft University
of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
| | - Antonio L. R. Manesco
- Kavli
Institute of Nanoscience, Delft University
of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
| | - Talieh S. Ghiasi
- Kavli
Institute of Nanoscience, Delft University
of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
| | - Serhii Volosheniuk
- Kavli
Institute of Nanoscience, Delft University
of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
| | - 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
| | - Herre S. J. van der Zant
- Kavli
Institute of Nanoscience, Delft University
of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
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10
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Observation of electronic modes in open cavity resonator. Nat Commun 2023; 14:415. [PMID: 36697407 PMCID: PMC9876930 DOI: 10.1038/s41467-023-36012-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2022] [Accepted: 01/12/2023] [Indexed: 01/27/2023] Open
Abstract
The resemblance between electrons and optical waves has strongly driven the advancement of mesoscopic physics, evidenced by the widespread use of terms such as fermion or electron optics. However, electron waves have yet to be understood in open cavity structures which have provided contemporary optics with rich insight towards non-Hermitian systems and complex interactions between resonance modes. Here, we report the realization of an open cavity resonator in a two-dimensional electronic system. We studied the resonant electron modes within the cavity and resolved the signatures of longitudinal and transverse quantization, showing that the modes are robust despite the cavity being highly coupled to the open background continuum. The transverse modes were investigated by applying a controlled deformation to the cavity, and their spatial distributions were further analyzed using magnetoconductance measurements and numerical simulation. These results lay the groundwork to exploring matter waves in the context of modern optical frameworks.
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11
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Fu H, Huang K, Watanabe K, Taniguchi T, Kayyalha M, Zhu J. Aharonov-Bohm Oscillations in Bilayer Graphene Quantum Hall Edge State Fabry-Pérot Interferometers. NANO LETTERS 2023; 23:718-725. [PMID: 36622939 DOI: 10.1021/acs.nanolett.2c05004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Bernal-stacked bilayer graphene exhibits a wealth of interaction-driven phenomena, including robust even-denominator fractional quantum Hall states. We construct Fabry-Pérot interferometers using a split-gate design and present measurements of the Aharonov-Bohm oscillations. The edge state velocity is found to be approximately 6 × 104 m/s at filling factor ν = 2 and decreases with increasing filling factor. The dc bias and temperature dependence of the interference point to electron-electron interaction induced decoherence mechanisms. These results pave the way for the quest of fractional and non-Abelian braiding statistics in this promising device platform.
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Affiliation(s)
- Hailong Fu
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania16802, United States
- School of Physics, Zhejiang University, Hangzhou310058, People's Republic of China
| | - Ke Huang
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania16802, United States
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba305-0044, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba305-0044, Japan
| | - Morteza Kayyalha
- Department of Electrical Engineering, The Pennsylvania State University, University Park, Pennsylvania16802, United States
| | - Jun Zhu
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania16802, United States
- Center for 2-Dimensional and Layered Materials, The Pennsylvania State University, University Park, Pennsylvania16802, United States
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12
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Wang M, Ma Q, Liu S, Zhang RY, Zhang L, Ke M, Liu Z, Chan CT. Observation of boundary induced chiral anomaly bulk states and their transport properties. Nat Commun 2022; 13:5916. [PMID: 36207327 PMCID: PMC9546894 DOI: 10.1038/s41467-022-33447-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Accepted: 09/19/2022] [Indexed: 11/09/2022] Open
Abstract
The most useful property of topological materials is perhaps the robust transport of topological edge modes, whose existence depends on bulk topological invariants. This means that we need to make volumetric changes to many atoms in the bulk to control the transport properties of the edges in a sample. We suggest here that we can do the reverse in some cases: the properties of the edge can be used to induce chiral transport phenomena in some bulk modes. Specifically, we show that a topologically trivial 2D hexagonal phononic crystal slab (waveguide) bounded by hard-wall boundaries guarantees the existence of bulk modes with chiral anomaly inside a pseudogap due to finite size effect. We experimentally observed robust valley-selected transport, complete valley state conversion, and valley focusing of the chiral anomaly bulk states (CABSs) in such phononic crystal waveguides. The same concept also applies to electromagnetics.
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Affiliation(s)
- Mudi Wang
- Department of Physics, The Hong Kong University of Science and Technology, Hong Kong, China
| | - Qiyun Ma
- Key Laboratory of Artificial Micro- and Nanostructures of Ministry of Education and School of Physics and Technology, Wuhan University, Wuhan, China
| | - Shan Liu
- Key Laboratory of Artificial Micro- and Nanostructures of Ministry of Education and School of Physics and Technology, Wuhan University, Wuhan, China
| | - Ruo-Yang Zhang
- Department of Physics, The Hong Kong University of Science and Technology, Hong Kong, China
| | - Lei Zhang
- State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Laser Spectroscopy, Shanxi University, Taiyuan, 030006, China.,Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, 030006, China
| | - Manzhu Ke
- Key Laboratory of Artificial Micro- and Nanostructures of Ministry of Education and School of Physics and Technology, Wuhan University, Wuhan, China
| | - Zhengyou Liu
- Key Laboratory of Artificial Micro- and Nanostructures of Ministry of Education and School of Physics and Technology, Wuhan University, Wuhan, China. .,Institute for Advanced Studies, Wuhan University, Wuhan, China.
| | - C T Chan
- Department of Physics, The Hong Kong University of Science and Technology, Hong Kong, China.
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13
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Yang J, Liu Y, Sun D, Hu N, Ning H. Inverse Design of Valley-Like Edge States of Sound Degenerated Away from the High-Symmetry Points in a Square Lattice. MATERIALS (BASEL, SWITZERLAND) 2022; 15:6697. [PMID: 36234042 PMCID: PMC9571283 DOI: 10.3390/ma15196697] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Revised: 09/16/2022] [Accepted: 09/22/2022] [Indexed: 06/16/2023]
Abstract
Robust edge states of periodic crystals with Dirac points fixed at the corners or centers of the Brillouin zones have drawn extensive attention. Recently, researchers have observed a special edge state associated with Dirac cones degenerated at the high symmetric boundaries of the first irreducible Brillouin zone. These nodal points, characterized by vortex structures in the momentum space, are attributed to the unavailable band crossing protected by mirror symmetry. By breaking the time reversal symmetry with intuitive rotations, valley-like states can be observed in a pair of inequivalent insulators. In this paper, an improved direct inverse design method is first applied to realize the valley-like states. Compared with the conventional strategy, the preparation of transition structures with degeneracy points is skipped. By introducing the quantitative gauge of mode inversion error, insulator pairs are directly obtained without manually tuning the structure with Dirac cone features.
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Affiliation(s)
- Jishi Yang
- College of Aerospace Engineering, Chongqing University, Chongqing 400044, China
| | - Yaolu Liu
- College of Aerospace Engineering, Chongqing University, Chongqing 400044, China
| | - Dongyang Sun
- Nanjing Research Institute, Chongqing University, Nanjing 211800, China
| | - Ning Hu
- College of Aerospace Engineering, Chongqing University, Chongqing 400044, China
- School of Mechanical Engineering, and National Engineering Research Center for Technological Innovation Method and Tool, Hebei University of Technology, Tianjin 300401, China
| | - Huiming Ning
- College of Aerospace Engineering, Chongqing University, Chongqing 400044, China
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14
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Interplay between topological valley and quantum Hall edge transport. Nat Commun 2022; 13:4187. [PMID: 35858959 PMCID: PMC9300606 DOI: 10.1038/s41467-022-31680-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Accepted: 06/21/2022] [Indexed: 11/08/2022] Open
Abstract
An established way of realising topologically protected states in a two-dimensional electron gas is by applying a perpendicular magnetic field thus creating quantum Hall edge channels. In electrostatically gapped bilayer graphene intriguingly, even in the absence of a magnetic field, topologically protected electronic states can emerge at naturally occurring stacking domain walls. While individually both types of topologically protected states have been investigated, their intriguing interplay remains poorly understood. Here, we focus on the interplay between topological domain wall states and quantum Hall edge transport within the eight-fold degenerate zeroth Landau level of high-quality suspended bilayer graphene. We find that the two-terminal conductance remains approximately constant for low magnetic fields throughout the distinct quantum Hall states since the conduction channels are traded between domain wall and device edges. For high magnetic fields, however, we observe evidence of transport suppression at the domain wall, which can be attributed to the emergence of spectral minigaps. This indicates that stacking domain walls potentially do not correspond to a topological domain wall in the order parameter.
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15
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Ren YN, Cheng Q, Sun QF, He L. Realizing Valley-Polarized Energy Spectra in Bilayer Graphene Quantum Dots via Continuously Tunable Berry Phases. PHYSICAL REVIEW LETTERS 2022; 128:206805. [PMID: 35657882 DOI: 10.1103/physrevlett.128.206805] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Revised: 11/08/2021] [Accepted: 04/25/2022] [Indexed: 06/15/2023]
Abstract
The Berry phase plays an important role in determining many physical properties of quantum systems. However, tuning the energy spectrum of a quantum system via Berry phase is comparatively rare because the Berry phase is usually a fixed constant. Here, we report the realization of an unusual valley-polarized energy spectra via continuously tunable Berry phases in Bernal-stacked bilayer graphene quantum dots. In our experiment, the Berry phase of electron orbital states is continuously tuned from about π to 2π by perpendicular magnetic fields. When the Berry phase equals π or 2π, the electron states in the two inequivalent valleys are energetically degenerate. By altering the Berry phase to noninteger multiples of π, large and continuously tunable valley-polarized energy spectra are realized. Our result reveals the Berry phase's essential role in valleytronics and the observed valley splitting, on the order of 10 meV at a magnetic field of 1 T, is about 100 times larger than Zeeman splitting for spin, shedding light on graphene-based valleytronics.
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Affiliation(s)
- Ya-Ning Ren
- Center for Advanced Quantum Studies, Department of Physics, Beijing Normal University, Beijing 100875, China
| | - Qiang Cheng
- School of Science, Qingdao University of Technology, Qingdao, Shandong 266520, China
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Qing-Feng Sun
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100871, China
- Beijing Academy of Quantum Information Sciences, West Building #3, No. 10 Xibeiwang East Road, Haidian District, Beijing 100193, China
| | - Lin He
- Center for Advanced Quantum Studies, Department of Physics, Beijing Normal University, Beijing 100875, China
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16
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Huang L, Zhu X, Hu G, Deng C, Sun Y, Wang D, Lu M, Yun B, Zhang R, Zhang Y, Cui Y. Electrical Switching of the Off-Resonance Room-Temperature Valley Polarization in Monolayer MoS 2 by a Double-Resonance Chiral Microstructure. ACS APPLIED MATERIALS & INTERFACES 2022; 14:22381-22388. [PMID: 35511437 DOI: 10.1021/acsami.2c03688] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Enhancing and expanding the manipulated range of room-temperature valley polarization at off-resonance wavelength is extremely crucial to developing various functional valleytronic devices. Although these have been realized through the double-resonance strategy or twist-angle engineering, the demand for electrical control over the concepts remains elusive. Here, we fabricate a gate-tunable double-resonance chiral microstructure using a molybdenum disulfides (MoS2) monolayer. On the basis of the varied interface charge density, we demonstrate the huge photoluminescence (PL) tuning ability of this configuration. Furthermore, benefiting predominately from the screening of long-range e-h exchange interactions and the chiral Purcell effect, the electrical switching of the room-temperature valley polarization at off-resonance wavelength is also realized. Our work enriches the functions of TMDs-based optoelectronic devices and may create important applications in future valley-polarized encode and information processing devices.
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Affiliation(s)
- Lei Huang
- Advanced Photonics Center, School of Electronic Science and Engineering, Southeast University, Nanjing, Jiangsu 210096, China
| | - Xiaofan Zhu
- Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments, School of Mechanical Engineering, Southeast University, Nanjing 211189, China
| | - Guohua Hu
- Advanced Photonics Center, School of Electronic Science and Engineering, Southeast University, Nanjing, Jiangsu 210096, China
| | - Chunyu Deng
- Advanced Photonics Center, School of Electronic Science and Engineering, Southeast University, Nanjing, Jiangsu 210096, China
| | - Yu Sun
- Advanced Photonics Center, School of Electronic Science and Engineering, Southeast University, Nanjing, Jiangsu 210096, China
| | - Dongyu Wang
- Advanced Photonics Center, School of Electronic Science and Engineering, Southeast University, Nanjing, Jiangsu 210096, China
| | - Mengjia Lu
- Advanced Photonics Center, School of Electronic Science and Engineering, Southeast University, Nanjing, Jiangsu 210096, China
| | - Binfeng Yun
- Advanced Photonics Center, School of Electronic Science and Engineering, Southeast University, Nanjing, Jiangsu 210096, China
| | - Ruohu Zhang
- Advanced Photonics Center, School of Electronic Science and Engineering, Southeast University, Nanjing, Jiangsu 210096, China
| | - Yan Zhang
- Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments, School of Mechanical Engineering, Southeast University, Nanjing 211189, China
| | - Yiping Cui
- Advanced Photonics Center, School of Electronic Science and Engineering, Southeast University, Nanjing, Jiangsu 210096, China
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17
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Li H, Luo C, Zhang T, Xu J, Zhou X, Shen Y, Deng X. Topological Refraction in Kagome Split-Ring Photonic Insulators. NANOMATERIALS 2022; 12:nano12091493. [PMID: 35564202 PMCID: PMC9105598 DOI: 10.3390/nano12091493] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Revised: 03/31/2022] [Accepted: 03/31/2022] [Indexed: 02/05/2023]
Abstract
A valley-Hall-like photonic insulator based on C3v Kagome split-ring is proposed. Theoretical analysis and numerical calculations illustrate that C3v symmetry can be broken not only by global rotation α but also individual rotation θ of the split rings, providing topological phase transitions. Furthermore, refraction of the edge state from the interface into the background space at Zigzag termination is explored. It is shown that positive/negative refraction of the outgoing beam depends on the type of valley (K or K′), from which the edge state is projected. These results provide a new way to manipulate terahertz wave propagation and facilitate the potential applications in directional collimation, beam splitting, negative refraction image, etc.
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Affiliation(s)
- Huichang Li
- School of Physics and Materials Science, Nanchang University, Nanchang 330031, China; (H.L.); (C.L.); (T.Z.); (J.X.); (X.Z.)
| | - Chen Luo
- School of Physics and Materials Science, Nanchang University, Nanchang 330031, China; (H.L.); (C.L.); (T.Z.); (J.X.); (X.Z.)
| | - Tailin Zhang
- School of Physics and Materials Science, Nanchang University, Nanchang 330031, China; (H.L.); (C.L.); (T.Z.); (J.X.); (X.Z.)
| | - Jianwei Xu
- School of Physics and Materials Science, Nanchang University, Nanchang 330031, China; (H.L.); (C.L.); (T.Z.); (J.X.); (X.Z.)
| | - Xiang Zhou
- School of Physics and Materials Science, Nanchang University, Nanchang 330031, China; (H.L.); (C.L.); (T.Z.); (J.X.); (X.Z.)
| | - Yun Shen
- School of Physics and Materials Science, Nanchang University, Nanchang 330031, China; (H.L.); (C.L.); (T.Z.); (J.X.); (X.Z.)
- Correspondence: (Y.S.); (X.D.)
| | - Xiaohua Deng
- School of Physics and Materials Science, Nanchang University, Nanchang 330031, China; (H.L.); (C.L.); (T.Z.); (J.X.); (X.Z.)
- Institute of Space Science and Technology, Nanchang University, Nanchang 330031, China
- Correspondence: (Y.S.); (X.D.)
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18
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Zhou T, Cheng S, Schleenvoigt M, Schüffelgen P, Jiang H, Yang Z, Žutić I. Quantum Spin-Valley Hall Kink States: From Concept to Materials Design. PHYSICAL REVIEW LETTERS 2021; 127:116402. [PMID: 34558920 DOI: 10.1103/physrevlett.127.116402] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2020] [Revised: 05/13/2021] [Accepted: 08/12/2021] [Indexed: 06/13/2023]
Abstract
We propose a general and tunable platform to realize high-density arrays of quantum spin-valley Hall kink (QSVHK) states with spin-valley-momentum locking based on a two-dimensional hexagonal topological insulator. Through the analysis of Berry curvature and topological charge, the QSVHK states are found to be topologically protected by the valley-inversion and time-reversal symmetries. Remarkably, the conductance of QSVHK states remains quantized against both nonmagnetic short- and long-range and magnetic long-range disorder, verified by the Green-function calculations. Based on first-principles results and our fabricated samples, we show that QSVHK states, protected with a gap up to 287 meV, can be realized in bismuthene by alloy engineering, surface functionalization, or electric field, supporting nonvolatile applications of spin-valley filters, valves, and waveguides even at room temperature.
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Affiliation(s)
- Tong Zhou
- Department of Physics, University at Buffalo, State University of New York, Buffalo, New York 14260, USA
| | - Shuguang Cheng
- Department of Physics, Northwest University, Xi'an 710069, China
| | - Michael Schleenvoigt
- Peter Grünberg Institute 9, Forschungszentrum Jülich & JARA Jülich-Aachen Research Alliance, 52425 Jülich, Germany
| | - Peter Schüffelgen
- Peter Grünberg Institute 9, Forschungszentrum Jülich & JARA Jülich-Aachen Research Alliance, 52425 Jülich, Germany
| | - Hua Jiang
- School of Physical Science and Technology, Soochow University, Suzhou 215006, China
| | - Zhongqin Yang
- State Key Laboratory of Surface Physics and Key Laboratory of Computational Physical Sciences (MOE) and Department of Physics and Collaborative Innovation Center of Advanced Microstructures, Fudan University, Shanghai 200433, China
| | - Igor Žutić
- Department of Physics, University at Buffalo, State University of New York, Buffalo, New York 14260, USA
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19
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Wang Z, Cheng S, Liu X, Jiang H. Topological kink states in graphene. NANOTECHNOLOGY 2021; 32:402001. [PMID: 34161935 DOI: 10.1088/1361-6528/ac0dd8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Accepted: 06/23/2021] [Indexed: 06/13/2023]
Abstract
Due to the unique band structure, graphene exhibits a number of exotic electronic properties that have not been observed in other materials. Among them, it has been demonstrated that there exist the one-dimensional valley-polarized topological kink states localized in the vicinity of the domain wall of graphene systems, where a bulk energy gap opens due to the inversion symmetry breaking. Notably, the valley-momentum locking nature makes the topological kink states attractive to the property manipulation in valleytronics. This paper systematically reviews both the theoretical research and experimental progress on topological kink states in monolayer graphene, bilayer graphene and graphene-like classical wave systems. Besides, various applications of topological kink states, including the valley filter, current partition, current manipulation, Majorana zero modes and etc, are also introduced.
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Affiliation(s)
- Zibo Wang
- College of Physics and Electronic Engineering, Sichuan Normal University, Chengdu 610068, People's Republic of China
- Center for Computational Sciences, Sichuan Normal University, Chengdu 610068, People's Republic of China
| | - Shuguang Cheng
- Department of Physics, Northwest University, Xi'an 710069, People's Republic of China
| | - Xiao Liu
- School of Physical Science and Technology, Soochow University, Suzhou 215006, People's Republic of China
| | - Hua Jiang
- School of Physical Science and Technology, Soochow University, Suzhou 215006, People's Republic of China
- Institute for Advanced Study of Soochow University, Suzhou 215006, People's Republic of China
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20
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Lotfizadeh N, Senger MJ, McCulley DR, Minot ED, Deshpande VV. Quantum Interferences in Ultraclean Carbon Nanotubes. PHYSICAL REVIEW LETTERS 2021; 126:216802. [PMID: 34114831 DOI: 10.1103/physrevlett.126.216802] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2020] [Accepted: 04/15/2021] [Indexed: 06/12/2023]
Abstract
Electronic analogs of optical interferences are powerful tools to investigate quantum phenomena in condensed matter. In carbon nanotubes (CNTs), it is well established that an electronic Fabry-Perot interferometer can be realized. Other types of quantum interferences should also arise in CNTs, but have proven challenging to realize. In particular, CNTs have been identified as a system to realize the electronic analog of a Sagnac interferometer-the most sensitive optical interferometer. To realize this Sagnac effect, interference between nonidentical transmission channels in a single CNT must be observed. Here, we use suspended, ultraclean CNTs of known chiral index to study both Fabry-Perot and Sagnac electron interferences. We verify theoretical predictions for the behavior of Sagnac oscillations and the persistence of the Sagnac oscillations at high temperatures. As suggested by existing theoretical studies, our results show that these quantum interferences may be used for electronic structure characterization of carbon nanotubes and the study of many-body effects in these model one-dimensional systems.
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Affiliation(s)
- Neda Lotfizadeh
- Department of Physics and Astronomy, University of Utah, Salt Lake City, Utah 84112, USA
| | - Mitchell J Senger
- Department of Physics, Oregon State University, Corvallis, Oregon 97331, USA
| | - Daniel R McCulley
- Department of Physics, Oregon State University, Corvallis, Oregon 97331, USA
| | - Ethan D Minot
- Department of Physics, Oregon State University, Corvallis, Oregon 97331, USA
| | - Vikram V Deshpande
- Department of Physics and Astronomy, University of Utah, Salt Lake City, Utah 84112, USA
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21
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Ma HY, Hu M, Li N, Liu J, Yao W, Jia JF, Liu J. Multifunctional antiferromagnetic materials with giant piezomagnetism and noncollinear spin current. Nat Commun 2021; 12:2846. [PMID: 33990597 PMCID: PMC8121910 DOI: 10.1038/s41467-021-23127-7] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2021] [Accepted: 04/16/2021] [Indexed: 11/09/2022] Open
Abstract
We propose a new type of spin-valley locking (SVL), named C-paired SVL, in antiferromagnetic systems, which directly connects the spin/valley space with the real space, and hence enables both static and dynamical controls of spin and valley to realize a multifunctional antiferromagnetic material. The new emergent quantum degree of freedom in the C-paired SVL is comprised of spin-polarized valleys related by a crystal symmetry instead of the time-reversal symmetry. Thus, both spin and valley can be accessed by simply breaking the corresponding crystal symmetry. Typically, one can use a strain field to induce a large net valley polarization/magnetization and use a charge current to generate a large noncollinear spin current. We predict the realization of the C-paired SVL in monolayer V2Se2O, which indeed exhibits giant piezomagnetism and can generate a large transverse spin current. Our findings provide unprecedented opportunities to integrate various controls of spin and valley with nonvolatile information storage in a single material, which is highly desirable for versatile fundamental research and device applications.
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Affiliation(s)
- Hai-Yang Ma
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, China
| | - Mengli Hu
- Department of Physics, The Hong Kong University of Science and Technology, Hong Kong, China
| | - Nana Li
- Department of Physics, The Hong Kong University of Science and Technology, Hong Kong, China
| | - Jianpeng Liu
- Department of Physics, The Hong Kong University of Science and Technology, Hong Kong, China
| | - Wang Yao
- Department of Physics and Center of Theoretical and Computational Physics, University of Hong Kong, Hong Kong, China
| | - Jin-Feng Jia
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, China.
- Tsung-Dao Lee Institute, Shanghai, China.
| | - Junwei Liu
- Department of Physics, The Hong Kong University of Science and Technology, Hong Kong, China.
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22
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Ronen Y, Werkmeister T, Haie Najafabadi D, Pierce AT, Anderson LE, Shin YJ, Lee SY, Lee YH, Johnson B, Watanabe K, Taniguchi T, Yacoby A, Kim P. Aharonov-Bohm effect in graphene-based Fabry-Pérot quantum Hall interferometers. NATURE NANOTECHNOLOGY 2021; 16:563-569. [PMID: 33633404 DOI: 10.1038/s41565-021-00861-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2020] [Accepted: 01/22/2021] [Indexed: 06/12/2023]
Abstract
Interferometers probe the wave-nature and exchange statistics of indistinguishable particles-for example, electrons in the chiral one-dimensional edge channels of the quantum Hall effect (QHE). Quantum point contacts can split and recombine these channels, enabling interference of charged particles. Such quantum Hall interferometers (QHIs) can unveil the exchange statistics of anyonic quasi-particles in the fractional quantum Hall effect (FQHE). Here, we present a fabrication technique for QHIs in van der Waals (vdW) materials and realize a tunable, graphene-based Fabry-Pérot (FP) QHI. The graphite-encapsulated architecture allows observation of FQHE at a magnetic field of 3T and precise partitioning of integer and fractional edge modes. We measure pure Aharonov-Bohm interference in the integer QHE, a major technical challenge in small FP interferometers, and find that edge modes exhibit high-visibility interference due to large velocities. Our results establish vdW heterostructures as a versatile alternative to GaAs-based interferometers for future experiments targeting anyonic quasi-particles.
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Affiliation(s)
- Yuval Ronen
- Department of Physics, Harvard University, Cambridge, MA, USA
| | - Thomas Werkmeister
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
| | | | - Andrew T Pierce
- Department of Physics, Harvard University, Cambridge, MA, USA
| | | | - Young Jae Shin
- Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, NY, USA
| | - Si Young Lee
- Center for Integrated Nanostructure Physics, Institute for Basic Science, Suwon, Republic of Korea
| | - Young Hee Lee
- Center for Integrated Nanostructure Physics, Institute for Basic Science, Suwon, Republic of Korea
| | - Bobae Johnson
- Department of Physics, Harvard University, Cambridge, MA, USA
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Japan
| | - Amir Yacoby
- Department of Physics, Harvard University, Cambridge, MA, USA
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
| | - Philip Kim
- Department of Physics, Harvard University, Cambridge, MA, USA.
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA.
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23
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de Leon NP, Itoh KM, Kim D, Mehta KK, Northup TE, Paik H, Palmer BS, Samarth N, Sangtawesin S, Steuerman DW. Materials challenges and opportunities for quantum computing hardware. Science 2021; 372:372/6539/eabb2823. [PMID: 33859004 DOI: 10.1126/science.abb2823] [Citation(s) in RCA: 65] [Impact Index Per Article: 21.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Quantum computing hardware technologies have advanced during the past two decades, with the goal of building systems that can solve problems that are intractable on classical computers. The ability to realize large-scale systems depends on major advances in materials science, materials engineering, and new fabrication techniques. We identify key materials challenges that currently limit progress in five quantum computing hardware platforms, propose how to tackle these problems, and discuss some new areas for exploration. Addressing these materials challenges will require scientists and engineers to work together to create new, interdisciplinary approaches beyond the current boundaries of the quantum computing field.
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Affiliation(s)
- Nathalie P de Leon
- Department of Electrical Engineering, Princeton University, Princeton, NJ 08544, USA
| | - Kohei M Itoh
- School of Fundamental Science and Technology, Keio University, Yokohama 223-8522, Japan
| | - Dohun Kim
- Department of Physics and Astronomy and Institute of Applied Physics, Seoul National University, Seoul 08826, Korea
| | - Karan K Mehta
- Department of Physics, Institute for Quantum Electronics, ETH Zürich, 8092 Zürich, Switzerland
| | - Tracy E Northup
- Institut für Experimentalphysik, Universität Innsbruck, 6020 Innsbruck, Austria
| | - Hanhee Paik
- IBM Quantum, IBM T. J. Watson Research Center, Yorktown Heights, NY 10598, USA.
| | - B S Palmer
- Laboratory for Physical Sciences, University of Maryland, College Park, MD 20740, USA.,Quantum Materials Center, University of Maryland, College Park, MD 20742, USA
| | - N Samarth
- Department of Physics, The Pennsylvania State University, University Park, PA 16802, USA
| | - Sorawis Sangtawesin
- School of Physics and Center of Excellence in Advanced Functional Materials, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand
| | - D W Steuerman
- Kavli Foundation, 5715 Mesmer Avenue, Los Angeles, CA 90230, USA
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24
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Tiwari P, Srivastav SK, Ray S, Das T, Bid A. Observation of Time-Reversal Invariant Helical Edge-Modes in Bilayer Graphene/WSe 2 Heterostructure. ACS NANO 2021; 15:916-922. [PMID: 33378173 DOI: 10.1021/acsnano.0c07524] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Topological insulators, along with Chern insulators and quantum Hall insulator phases, are considered as paradigms for symmetry protected topological phases of matter. This article reports the experimental realization of the time-reversal invariant helical edge-modes in bilayer graphene/monolayer WSe2-based heterostructures-a phase generally considered as a precursor to the field of generic topological insulators. Our observation of this elusive phase depended crucially on our ability to create mesoscopic devices comprising both a moiré superlattice potential and strong spin-orbit coupling; this resulted in materials whose electronic band structure could be tuned from trivial to topological by an external displacement field. We find that the topological phase is characterized by a bulk bandgap and by helical edge-modes with electrical conductance quantized exactly to 2e2/h in zero external magnetic field. We put the helical edge-modes on firm ground through supporting experiments, including the verification of predictions of the Landauer-Büttiker model for quantum transport in multiterminal mesoscopic devices. Our nonlocal transport properties measurements show that the helical edge-modes are dissipationless and equilibrate at the contact probes. We achieved the tunability of the different topological phases with electric and magnetic fields, which allowed us to achieve topological phase transitions between trivial and multiple, distinct topological phases. We also present results of a theoretical study of a realistic model which, in addition to replicating our experimental results, explains the origin of the topological insulating bulk and helical edge-modes. Our experimental and theoretical results establish a viable route to realizing the time-reversal invariant Z2 topological phase of matter.
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Affiliation(s)
- Priya Tiwari
- Department of Physics, Indian Institute of Science, Bangalore 560012, India
| | | | - Sujay Ray
- Department of Physics, Indian Institute of Science, Bangalore 560012, India
| | - Tanmoy Das
- Department of Physics, Indian Institute of Science, Bangalore 560012, India
| | - Aveek Bid
- Department of Physics, Indian Institute of Science, Bangalore 560012, India
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25
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Sinha S, Adak PC, Surya Kanthi RS, Chittari BL, Sangani LDV, Watanabe K, Taniguchi T, Jung J, Deshmukh MM. Bulk valley transport and Berry curvature spreading at the edge of flat bands. Nat Commun 2020; 11:5548. [PMID: 33144578 PMCID: PMC7641251 DOI: 10.1038/s41467-020-19284-w] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2020] [Accepted: 09/25/2020] [Indexed: 11/24/2022] Open
Abstract
2D materials based superlattices have emerged as a promising platform to modulate band structure and its symmetries. In particular, moiré periodicity in twisted graphene systems produces flat Chern bands. The recent observation of anomalous Hall effect (AHE) and orbital magnetism in twisted bilayer graphene has been associated with spontaneous symmetry breaking of such Chern bands. However, the valley Hall state as a precursor of AHE state, when time-reversal symmetry is still protected, has not been observed. Our work probes this precursor state using the valley Hall effect. We show that broken inversion symmetry in twisted double bilayer graphene (TDBG) facilitates the generation of bulk valley current by reporting experimental evidence of nonlocal transport in a nearly flat band system. Despite the spread of Berry curvature hotspots and reduced quasiparticle velocities of the carriers in these flat bands, we observe large nonlocal voltage several micrometers away from the charge current path - this persists when the Fermi energy lies inside a gap with large Berry curvature. The high sensitivity of the nonlocal voltage to gate tunable carrier density and gap modulating perpendicular electric field makes TDBG an attractive platform for valley-twistronics based on flat bands.
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Affiliation(s)
- Subhajit Sinha
- Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Mumbai, 400005, India
| | - Pratap Chandra Adak
- Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Mumbai, 400005, India.
| | - R S Surya Kanthi
- Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Mumbai, 400005, India
| | | | - L D Varma Sangani
- Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Mumbai, 400005, India
| | - Kenji Watanabe
- National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Takashi Taniguchi
- National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Jeil Jung
- Department of Physics, University of Seoul, Seoul, 02504, Korea
| | - Mandar M Deshmukh
- Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Mumbai, 400005, India.
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26
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de Vries FK, Zhu J, Portolés E, Zheng G, Masseroni M, Kurzmann A, Taniguchi T, Watanabe K, MacDonald AH, Ensslin K, Ihn T, Rickhaus P. Combined Minivalley and Layer Control in Twisted Double Bilayer Graphene. PHYSICAL REVIEW LETTERS 2020; 125:176801. [PMID: 33156662 DOI: 10.1103/physrevlett.125.176801] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Accepted: 09/03/2020] [Indexed: 06/11/2023]
Abstract
Control over minivalley polarization and interlayer coupling is demonstrated in double bilayer graphene twisted with an angle of 2.37°. This intermediate angle is small enough for the minibands to form and large enough such that the charge carrier gases in the layers can be tuned independently. Using a dual-gated geometry we identify and control all possible combinations of minivalley polarization via the population of the two bilayers. An applied displacement field opens a band gap in either of the two bilayers, allowing us to even obtain full minivalley polarization. In addition, the carriers, formerly separated by their minivalley character, are mixed by tuning through a Lifshitz transition, where the Fermi surface topology changes. The high degree of control over the minivalley character of the bulk charge transport in twisted double bilayer graphene offers new opportunities for realizing valleytronics devices such as valley valves, filters, and logic gates.
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Affiliation(s)
- Folkert K de Vries
- Laboratory for Solid State Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Jihang Zhu
- Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA
| | - Elías Portolés
- Laboratory for Solid State Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Giulia Zheng
- Laboratory for Solid State Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Michele Masseroni
- Laboratory for Solid State Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Annika Kurzmann
- Laboratory for Solid State Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Takashi Taniguchi
- National Institute for Material Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Kenji Watanabe
- National Institute for Material Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Allan H MacDonald
- Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA
| | - Klaus Ensslin
- Laboratory for Solid State Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Thomas Ihn
- Laboratory for Solid State Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Peter Rickhaus
- Laboratory for Solid State Physics, ETH Zürich, CH-8093 Zürich, Switzerland
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27
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Xu G, Zhou T, Scharf B, Žutić I. Optically Probing Tunable Band Topology in Atomic Monolayers. PHYSICAL REVIEW LETTERS 2020; 125:157402. [PMID: 33095598 DOI: 10.1103/physrevlett.125.157402] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2019] [Revised: 06/26/2020] [Accepted: 09/03/2020] [Indexed: 06/11/2023]
Abstract
In many atomically thin materials, their optical absorption is dominated by excitonic transitions. It was recently found that optical selection rules in these materials are influenced by the band topology near the valleys. We propose that gate-controlled band ordering in a single atomic monolayer, through changes in the valley winding number and excitonic transitions, can be probed in helicity-resolved absorption and photoluminescence. This predicted tunable band topology is confirmed by combining an effective Hamiltonian and a Bethe-Salpeter equation for an accurate description of excitons, with first-principles calculations suggesting its realization in Sb-based monolayers.
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Affiliation(s)
- Gaofeng Xu
- Department of Physics, University at Buffalo, State University of New York, Buffalo, New York 14260, USA
| | - Tong Zhou
- Department of Physics, University at Buffalo, State University of New York, Buffalo, New York 14260, USA
| | - Benedikt Scharf
- Institute for Theoretical Physics and Astrophysics and Würzburg-Dresden Cluster of Excellence ct.qmat, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Igor Žutić
- Department of Physics, University at Buffalo, State University of New York, Buffalo, New York 14260, USA
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28
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Li L, Shao L, Liu X, Gao A, Wang H, Zheng B, Hou G, Shehzad K, Yu L, Miao F, Shi Y, Xu Y, Wang X. Room-temperature valleytronic transistor. NATURE NANOTECHNOLOGY 2020; 15:743-749. [PMID: 32690885 DOI: 10.1038/s41565-020-0727-0] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Accepted: 06/03/2020] [Indexed: 06/11/2023]
Abstract
Valleytronics, based on the valley degree of freedom rather than charge, is a promising candidate for next-generation information devices beyond complementary metal-oxide-semiconductor (CMOS) technology1-4. Although many intriguing valleytronic properties have been explored based on excitonic injection or the non-local response of transverse current schemes at low temperature4-7, demonstrations of valleytronic building blocks similar to transistors in electronics, especially at room temperature, remain elusive. Here, we report a solid-state device that enables a full sequence of generating, propagating, detecting and manipulating valley information at room temperature. Chiral nanocrescent plasmonic antennae8 are used to selectively generate valley-polarized carriers in MoS2 through hot-electron injection under linearly polarized infrared excitation. These long-lived valley-polarized free carriers can be detected in a valley Hall configuration9-11 even without charge current, and can propagate over 18 μm by means of drift. In addition, electrostatic gating allows us to modulate the magnitude of the valley Hall voltage. The electrical valley Hall output could drive the valley manipulation of a cascaded stage, rendering the device able to serve as a transistor free of charge current with pure valleytronic input/output. Our results demonstrate the possibility of encoding and processing information by valley degree of freedom, and provide a universal strategy to study the Berry curvature dipole in quantum materials.
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Affiliation(s)
- Lingfei Li
- School of Electronic Science and Engineering, Nanjing University, Nanjing, China
- Colleges of ISEE and Microelectronics, ZJU-Hangzhou Global Scientific and Technological Innovation Center, ZJU-UIUC Institute, State Key Labs of Silicon Materials and Modern Optical Instruments, Zhejiang University, Hangzhou, China
| | - Lei Shao
- Beijing Computational Science Research Centre, Beijing, China
| | - Xiaowei Liu
- School of Physics, Nanjing University, Nanjing, China
| | - Anyuan Gao
- School of Physics, Nanjing University, Nanjing, China
| | - Hao Wang
- Beijing Computational Science Research Centre, Beijing, China
| | - Binjie Zheng
- School of Electronic Science and Engineering, Nanjing University, Nanjing, China
| | - Guozhi Hou
- School of Electronic Science and Engineering, Nanjing University, Nanjing, China
| | - Khurram Shehzad
- Colleges of ISEE and Microelectronics, ZJU-Hangzhou Global Scientific and Technological Innovation Center, ZJU-UIUC Institute, State Key Labs of Silicon Materials and Modern Optical Instruments, Zhejiang University, Hangzhou, China
| | - Linwei Yu
- School of Electronic Science and Engineering, Nanjing University, Nanjing, China
| | - Feng Miao
- School of Physics, Nanjing University, Nanjing, China
| | - Yi Shi
- School of Electronic Science and Engineering, Nanjing University, Nanjing, China
| | - Yang Xu
- Colleges of ISEE and Microelectronics, ZJU-Hangzhou Global Scientific and Technological Innovation Center, ZJU-UIUC Institute, State Key Labs of Silicon Materials and Modern Optical Instruments, Zhejiang University, Hangzhou, China.
| | - Xiaomu Wang
- School of Electronic Science and Engineering, Nanjing University, Nanjing, China.
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29
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Jiang L, Wang S, Zhao S, Crommie M, Wang F. Soliton-Dependent Electronic Transport across Bilayer Graphene Domain Wall. NANO LETTERS 2020; 20:5936-5942. [PMID: 32589430 DOI: 10.1021/acs.nanolett.0c01911] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Layer-stacking domain wall in bilayer graphene is one type of topological defects that can greatly affect the electronic properties of bilayer graphene and therefore lead to nontrivial transport behaviors. An outstanding question on the layer stacking domain wall is how the electrons hop between two adjacent stacking domains. Here we report the first experimental observation of electronic transport across bilayer graphene domain walls by combining near-field infrared nanoscopy and scanning voltage microscopy techniques. We observe markedly different electron transport behaviors across the tensile- and shear-type domain walls. The tensile-type domain wall is highly reflective of low-energy incident electrons, but becomes more transparent when the electron density and the Fermi energy are increased by electrostatic gating. In contrast, the shear-type domain wall is always highly transparent at different gate voltages. Such soliton-dependent electronic transport can open up new routes to engineer novel nanoelectronic devices based on layer-stacking domain walls in bilayer graphene.
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Affiliation(s)
- Lili Jiang
- Department of Physics, University of California at Berkeley, Berkeley, California 94720, United States
| | - Sheng Wang
- Department of Physics, University of California at Berkeley, Berkeley, California 94720, United States
- Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Sihan Zhao
- Department of Physics, University of California at Berkeley, Berkeley, California 94720, United States
| | - Michael Crommie
- Department of Physics, University of California at Berkeley, Berkeley, California 94720, United States
- Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
- Kavli Energy NanoSciences Institute at the University of California, Berkeley and the Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Feng Wang
- Department of Physics, University of California at Berkeley, Berkeley, California 94720, United States
- Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
- Kavli Energy NanoSciences Institute at the University of California, Berkeley and the Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
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30
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Zhao G, Mu H, Liu F, Wang Z. Folding Graphene into a Chern Insulator with Light Irradiation. NANO LETTERS 2020; 20:5860-5865. [PMID: 32658490 DOI: 10.1021/acs.nanolett.0c01758] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Recently, the precise folding of flexible graphene is reported experimentally [ Science, 2019, 365, 1036-1040], demonstrating an efficient approach to manipulate its electronic and optoelectronic properties. Here, we propose a light-induced high-Chern-number Chern insulator (CI) in the folded graphene. Along both armchair and zigzag folding directions, we demonstrate that there are two-handedness-dependent chiral interface states localized at the curved region. Physically, they can be attributed to the light-induced mass-term inversion across the folded graphene. Most remarkably, by rationally designing the folding processes, 2D and 3D CIs are also realizable in a single-wall carbon nanotube and periodic folded graphene, respectively, illustrating a high tunability of the folding degree of freedom. We envision that this intriguing form of "foldtronics" will provide a new platform for investigating the topological state in 2D materials to draw immediate experimental attention.
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Affiliation(s)
- Gan Zhao
- Hefei National Laboratory for Physical Sciences at the Microscale, CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Haimen Mu
- Hefei National Laboratory for Physical Sciences at the Microscale, CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Feng Liu
- Department of Materials Science and Engineering, University of Utah, Salt Lake City, Utah 84112, United States
| | - Zhengfei Wang
- Hefei National Laboratory for Physical Sciences at the Microscale, CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
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31
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Liang SJ, Cheng B, Cui X, Miao F. Van der Waals Heterostructures for High-Performance Device Applications: Challenges and Opportunities. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2020; 32:e1903800. [PMID: 31608514 DOI: 10.1002/adma.201903800] [Citation(s) in RCA: 117] [Impact Index Per Article: 29.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2019] [Revised: 08/22/2019] [Indexed: 06/10/2023]
Abstract
The discovery of two-dimensional (2D) materials with unique electronic, superior optoelectronic, or intrinsic magnetic order has triggered worldwide interest in the fields of material science, condensed matter physics, and device physics. Vertically stacking 2D materials with distinct electronic and optical as well as magnetic properties enables the creation of a large variety of van der Waals heterostructures. The diverse properties of the vertical heterostructures open unprecedented opportunities for various kinds of device applications, e.g., vertical field-effect transistors, ultrasensitive infrared photodetectors, spin-filtering devices, and so on, which are inaccessible in conventional material heterostructures. Here, the current status of vertical heterostructure device applications in vertical transistors, infrared photodetectors, and spintronic memory/transistors is reviewed. The relevant challenges for achieving high-performance devices are presented. An outlook into the future development of vertical heterostructure devices with integrated electronic and optoelectronic as well as spintronic functionalities is also provided.
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Affiliation(s)
- Shi-Jun Liang
- National Laboratory of Solid State Microstructures, School of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
| | - Bin Cheng
- National Laboratory of Solid State Microstructures, School of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
| | - Xinyi Cui
- State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing, 210046, China
| | - Feng Miao
- National Laboratory of Solid State Microstructures, School of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
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32
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Wang M, Zhou W, Bi L, Qiu C, Ke M, Liu Z. Valley-locked waveguide transport in acoustic heterostructures. Nat Commun 2020; 11:3000. [PMID: 32533082 PMCID: PMC7293314 DOI: 10.1038/s41467-020-16843-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Accepted: 05/28/2020] [Indexed: 11/24/2022] Open
Abstract
Valley pseudospin, labeling the pair of energy extrema in momentum space, has been attracting attention because of its potential as a new degree of freedom in manipulating electrons or classical waves. Recently, topological valley edge transport of sound, by virtue of the gapless valley-locked edge states, has been observed in the domain walls of sonic crystals. Here, by constructing a heterostructure with sonic crystals, a topological waveguide is realized. The waveguide states feature gapless dispersion, momentum-valley locking, immunity against defects, and a high capacity for energy transport. With a designable size, the heterostructures are more flexible for interfacing with the existing acoustic devices than the domain wall structures. Such heterostructures may serve as versatile new devices for acoustic wave manipulation, such as acoustic splitting, reflection-free guiding and converging. Here, by constructing a heterostructure with sonic crystals, a topological waveguide is realized by the authors. The waveguide states feature gapless dispersion, momentum-valley locking, immunity against defects, and a high capacity for energy transport.
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Affiliation(s)
- Mudi Wang
- Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education and School of Physics and Technology, Wuhan University, 430072, Wuhan, China
| | - Wenyi Zhou
- Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education and School of Physics and Technology, Wuhan University, 430072, Wuhan, China
| | - Liya Bi
- Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education and School of Physics and Technology, Wuhan University, 430072, Wuhan, China
| | - Chunyin Qiu
- Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education and School of Physics and Technology, Wuhan University, 430072, Wuhan, China
| | - Manzhu Ke
- Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education and School of Physics and Technology, Wuhan University, 430072, Wuhan, China
| | - Zhengyou Liu
- Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education and School of Physics and Technology, Wuhan University, 430072, Wuhan, China. .,Institute for Advanced Studies, Wuhan University, 430072, Wuhan, China.
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33
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Piezoelectricity and topological quantum phase transitions in two-dimensional spin-orbit coupled crystals with time-reversal symmetry. Nat Commun 2020; 11:2290. [PMID: 32385246 PMCID: PMC7210280 DOI: 10.1038/s41467-020-16058-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Accepted: 04/09/2020] [Indexed: 11/08/2022] Open
Abstract
Finding new physical responses that signal topological quantum phase transitions is of both theoretical and experimental importance. Here, we demonstrate that the piezoelectric response can change discontinuously across a topological quantum phase transition in two-dimensional time-reversal invariant systems with spin-orbit coupling, thus serving as a direct probe of the transition. We study all gap closing cases for all 7 plane groups that allow non-vanishing piezoelectricity, and find that any gap closing with 1 fine-tuning parameter between two gapped states changes either the Z2 invariant or the locally stable valley Chern number. The jump of the piezoelectric response is found to exist for all these transitions, and we propose the HgTe/CdTe quantum well and BaMnSb2 as two potential experimental platforms. Our work provides a general theoretical framework to classify topological quantum phase transitions, and reveals their ubiquitous relation to the piezoelectric response. The linear response and topological electronic properties of a material both depend on the underlying crystal symmetry. Here the authors study how topological phase transitions in two-dimensional materials manifest themselves in the piezoelectric response.
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34
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Yang Y, Jia Z, Wu Y, Xiao RC, Hang ZH, Jiang H, Xie XC. Gapped topological kink states and topological corner states in honeycomb lattice. Sci Bull (Beijing) 2020; 65:531-537. [PMID: 36659184 DOI: 10.1016/j.scib.2020.01.024] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2019] [Revised: 12/30/2019] [Accepted: 01/15/2020] [Indexed: 01/21/2023]
Abstract
Based on the tight-binding calculations on honeycomb lattice and photonic experimental visualization on artificial graphene (AG), we report the domain-wall-induced gapped topological kink states and topological corner states. In honeycomb lattice, domain walls (DWs) with gapless topological kink states could be induced either by sublattice symmetry breaking or by lattice deformation. We find that the coexistence of these two mechanisms will induce DWs with gapped topological kink states. Significantly, the intersection of these two types of DWs gives rise to topological corner state localized at the crossing point. Through the manipulation of the DWs, we show AG with honeycomb lattice structure not only a versatile platform supporting multiple topological corner modes in a controlled manner, but also possessing promising applications such as fabricating topological quantum dots composed of gapped topological kink states and topological corner states.
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Affiliation(s)
- Yuting Yang
- School of Physical Science and Technology, Soochow University, Suzhou 215006, China
| | - Ziyuan Jia
- School of Physical Science and Technology, Soochow University, Suzhou 215006, China
| | - Yijia Wu
- International Center for Quantum Materials, Peking University, Beijing 100871, China
| | - Rui-Chun Xiao
- School of Physical Science and Technology, Soochow University, Suzhou 215006, China
| | - Zhi Hong Hang
- School of Physical Science and Technology, Soochow University, Suzhou 215006, China; Institute for Advanced Study, Soochow University, Suzhou 215006, China.
| | - Hua Jiang
- School of Physical Science and Technology, Soochow University, Suzhou 215006, China; Institute for Advanced Study, Soochow University, Suzhou 215006, China.
| | - X C Xie
- International Center for Quantum Materials, Peking University, Beijing 100871, China; Beijing Academy of Quantum Information Sciences, Beijing 100193, China; CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100190, China
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35
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Li SY, Su Y, Ren YN, He L. Valley Polarization and Inversion in Strained Graphene via Pseudo-Landau Levels, Valley Splitting of Real Landau Levels, and Confined States. PHYSICAL REVIEW LETTERS 2020; 124:106802. [PMID: 32216392 DOI: 10.1103/physrevlett.124.106802] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2019] [Revised: 12/04/2019] [Accepted: 02/19/2020] [Indexed: 06/10/2023]
Abstract
It is quite easy to control spin polarization and the spin direction of a system via magnetic fields. However, there is no such direct and efficient way to manipulate the valley pseudospin degree of freedom. Here, we demonstrate experimentally that it is possible to realize valley polarization and valley inversion in graphene by using both strain-induced pseudomagnetic fields and real magnetic fields. Pseudomagnetic fields, which are quite different from real magnetic fields, point in opposite directions at the two distinct valleys of graphene. Therefore, the coexistence of pseudomagnetic fields and real magnetic fields leads to imbalanced effective magnetic fields at two distinct valleys of graphene. This allows us to control the valley in graphene as conveniently as the electron spin. In this work, we report a consistent observation of valley polarization and inversion in strained graphene via pseudo-Landau levels, splitting of real Landau levels, and valley splitting of confined states using scanning tunneling spectroscopy. Our results highlight a pathway to valleytronics in strained graphene-based platforms.
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Affiliation(s)
- Si-Yu Li
- Center for Advanced Quantum Studies, Department of Physics, Beijing Normal University, Beijing 100875, People's Republic of China
| | - Ying Su
- Theoretical Division, T-4 and CNLS, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Ya-Ning Ren
- Center for Advanced Quantum Studies, Department of Physics, Beijing Normal University, Beijing 100875, People's Republic of China
| | - Lin He
- Center for Advanced Quantum Studies, Department of Physics, Beijing Normal University, Beijing 100875, People's Republic of China
- State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, 865 Changning Road, Shanghai 200050, People's Republic of China
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36
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Chen H, Zhou P, Liu J, Qiao J, Oezyilmaz B, Martin J. Gate controlled valley polarizer in bilayer graphene. Nat Commun 2020; 11:1202. [PMID: 32139694 PMCID: PMC7058031 DOI: 10.1038/s41467-020-15117-y] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2019] [Accepted: 02/19/2020] [Indexed: 11/19/2022] Open
Abstract
Sign reversal of Berry curvature across two oppositely gated regions in bilayer graphene can give rise to counter-propagating 1D channels with opposite valley indices. Considering spin and sub-lattice degeneracy, there are four quantized conduction channels in each direction. Previous experimental work on gate-controlled valley polarizer achieved good contrast only in the presence of an external magnetic field. Yet, with increasing magnetic field the ungated regions of bilayer graphene will transit into the quantum Hall regime, limiting the applications of valley-polarized electrons. Here we present improved performance of a gate-controlled valley polarizer through optimized device geometry and stacking method. Electrical measurements show up to two orders of magnitude difference in conductance between the valley-polarized state and gapped states. The valley-polarized state displays conductance of nearly 4e2/h and produces contrast in a subsequent valley analyzer configuration. These results pave the way to further experiments on valley-polarized electrons in zero magnetic field.
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Affiliation(s)
- Hao Chen
- Centre for Advanced 2D Materials, National University of Singapore, 6 Science Drive 2, 117546, Singapore, Singapore
- Department of Physics, National University of Singapore, 2 Science Drive 3, 117551, Singapore, Singapore
| | - Pinjia Zhou
- Centre for Advanced 2D Materials, National University of Singapore, 6 Science Drive 2, 117546, Singapore, Singapore
| | - Jiawei Liu
- Centre for Advanced 2D Materials, National University of Singapore, 6 Science Drive 2, 117546, Singapore, Singapore
- Department of Physics, National University of Singapore, 2 Science Drive 3, 117551, Singapore, Singapore
| | - Jiabin Qiao
- Centre for Advanced 2D Materials, National University of Singapore, 6 Science Drive 2, 117546, Singapore, Singapore
| | - Barbaros Oezyilmaz
- Centre for Advanced 2D Materials, National University of Singapore, 6 Science Drive 2, 117546, Singapore, Singapore
- Department of Physics, National University of Singapore, 2 Science Drive 3, 117551, Singapore, Singapore
| | - Jens Martin
- Centre for Advanced 2D Materials, National University of Singapore, 6 Science Drive 2, 117546, Singapore, Singapore.
- Department of Physics, National University of Singapore, 2 Science Drive 3, 117551, Singapore, Singapore.
- Leibniz Institut für Kristallzüchtung, Max-Born-Strasse 2, 12489, Berlin, Germany.
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37
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Yu ZM, Guan S, Sheng XL, Gao W, Yang SA. Valley-Layer Coupling: A New Design Principle for Valleytronics. PHYSICAL REVIEW LETTERS 2020; 124:037701. [PMID: 32031831 DOI: 10.1103/physrevlett.124.037701] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Indexed: 06/10/2023]
Abstract
The current valleytronics research is based on the paradigm of time-reversal-connected valleys in two-dimensional (2D) hexagonal materials, which forbids the fully electric generation of valley polarization by a gate field. Here, we go beyond the existing paradigm to explore 2D systems with a novel valley-layer coupling (VLC) mechanism, where the electronic states in the emergent valleys have a valley-contrasted layer polarization. The VLC enables a direct coupling between a valley and a gate electric field. We analyze the symmetry requirements for a system to host VLC, demonstrate our idea via first-principles calculations and model analysis of a concrete 2D material example, and show that an electric, continuous, wide-range, and switchable control of valley polarization can be achieved by VLC. Furthermore, we find that systems with VLC can exhibit other interesting physics, such as valley-contrasting linear dichroism and optical selection of the valley and the electric polarization of interlayer excitons. Our finding opens a new direction for valleytronics and 2D materials research.
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Affiliation(s)
- Zhi-Ming Yu
- 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, Beijing 100081, China
- Research Laboratory for Quantum Materials, Singapore University of Technology and Design, Singapore 487372, Singapore
| | - Shan Guan
- Research Laboratory for Quantum Materials, Singapore University of Technology and Design, Singapore 487372, Singapore
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
| | - Xian-Lei Sheng
- Research Laboratory for Quantum Materials, Singapore University of Technology and Design, Singapore 487372, Singapore
- Department of Physics, Key Laboratory of Micro-nano Measurement-Manipulation and Physics (Ministry of Education), Beihang University, Beijing 100191, China
| | - Weibo Gao
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
- The Photonics Institute and Centre for Disruptive Photonic Technologies, Nanyang Technological University, Singapore 637371, Singapore
| | - Shengyuan A Yang
- Research Laboratory for Quantum Materials, Singapore University of Technology and Design, Singapore 487372, Singapore
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Li J, Fu H, Yin Z, Watanabe K, Taniguchi T, Zhu J. Metallic Phase and Temperature Dependence of the ν=0 Quantum Hall State in Bilayer Graphene. PHYSICAL REVIEW LETTERS 2019; 122:097701. [PMID: 30932549 DOI: 10.1103/physrevlett.122.097701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Indexed: 06/09/2023]
Abstract
The ν=0 quantum Hall state of bilayer graphene is a fertile playground to realize many-body ground states with various broken symmetries. Here we report the experimental observations of a previously unreported metallic phase. The metallic phase resides in the phase space between the previously identified layer polarized state at large transverse electric field and the canted antiferromagnetic state at small transverse electric field. We also report temperature dependence studies of the quantum spin Hall state of ν=0. Complex nonmonotonic behavior reveals concomitant bulk and edge conductions and excitations. These results provide a timely experimental update to understand the rich physics of the ν=0 state.
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Affiliation(s)
- Jing Li
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Hailong Fu
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Zhenxi Yin
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - 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
| | - Jun Zhu
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
- Center for 2-Dimensional and Layered Materials, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
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