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Wang J, Li Z, Zhao K, Dong S, Wu D, Meng W, Zhang J, Hou Y, Lu Y, Lu Q. Isolated scan unit and scanning tunneling microscope for stable imaging in ultra-high magnetic fields. Ultramicroscopy 2024; 261:113960. [PMID: 38547811 DOI: 10.1016/j.ultramic.2024.113960] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2023] [Revised: 02/19/2024] [Accepted: 03/20/2024] [Indexed: 04/22/2024]
Abstract
The high resolution of a scanning tunneling microscope (STM) relies on the stability of its scan unit. In this study, we present an isolated scan unit featuring non-magnetic design and ultra-high stability, as well as bidirectional movement capability. Different types of piezoelectric motors can be incorporated into the scan unit to create a highly stable STM. The standalone structure of scan unit ensures a stable atomic imaging process by decreasing noise generated by motor. The non-magnetic design makes the scan unit work stable in high magnetic field conditions. Moreover, we have successfully constructed a novel STM based on the isolated scan unit, in which two inertial piezoelectric motors act as the coarse approach actuators. The exceptional performance of homebuilt STM is proved by the high-resolution atomic images and dI/dV spectrums on NbSe2 surface at varying temperatures, as well as the raw-data images of graphite obtained at ultra-high magnetic fields of 23 T. According to the literature research, no STM has previously reported the atomic image at extreme conditions of 2 K low temperature and 23 T ultra-high magnetic field. Additionally, we present the ultra-low drift rates between the tip and sample at varying temperatures, as well as when raising the magnetic fields from 0 T to 23 T, indicating the ultra-high stability of the STM in high magnetic field conditions. The outstanding performance of our stable STM hold great potential for investigating the materials in ultra-high magnetic fields.
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Affiliation(s)
- Jihao Wang
- Anhui Key Laboratory of Low-Energy Quantum Materials and Devices, High Magnetic Field Laboratory, HFIPS, Chinese Academy of Sciences, Hefei 230031, Anhui, China; The High Magnetic Field Laboratory of Anhui Province, Hefei 230031, Anhui, China
| | - Zihao Li
- Anhui Key Laboratory of Low-Energy Quantum Materials and Devices, High Magnetic Field Laboratory, HFIPS, Chinese Academy of Sciences, Hefei 230031, Anhui, China; The High Magnetic Field Laboratory of Anhui Province, Hefei 230031, Anhui, China; Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230026, Anhui, China
| | - Kesen Zhao
- Anhui Key Laboratory of Low-Energy Quantum Materials and Devices, High Magnetic Field Laboratory, HFIPS, Chinese Academy of Sciences, Hefei 230031, Anhui, China; The High Magnetic Field Laboratory of Anhui Province, Hefei 230031, Anhui, China
| | - Shuai Dong
- Anhui Key Laboratory of Low-Energy Quantum Materials and Devices, High Magnetic Field Laboratory, HFIPS, Chinese Academy of Sciences, Hefei 230031, Anhui, China; The High Magnetic Field Laboratory of Anhui Province, Hefei 230031, Anhui, China
| | - Dan Wu
- Anhui Key Laboratory of Low-Energy Quantum Materials and Devices, High Magnetic Field Laboratory, HFIPS, Chinese Academy of Sciences, Hefei 230031, Anhui, China; The High Magnetic Field Laboratory of Anhui Province, Hefei 230031, Anhui, China
| | - Wenjie Meng
- Anhui Key Laboratory of Low-Energy Quantum Materials and Devices, High Magnetic Field Laboratory, HFIPS, Chinese Academy of Sciences, Hefei 230031, Anhui, China; The High Magnetic Field Laboratory of Anhui Province, Hefei 230031, Anhui, China
| | - Jing Zhang
- Anhui Key Laboratory of Low-Energy Quantum Materials and Devices, High Magnetic Field Laboratory, HFIPS, Chinese Academy of Sciences, Hefei 230031, Anhui, China; The High Magnetic Field Laboratory of Anhui Province, Hefei 230031, Anhui, China
| | - Yubin Hou
- Anhui Key Laboratory of Low-Energy Quantum Materials and Devices, High Magnetic Field Laboratory, HFIPS, Chinese Academy of Sciences, Hefei 230031, Anhui, China; The High Magnetic Field Laboratory of Anhui Province, Hefei 230031, Anhui, China.
| | - Yalin Lu
- Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230026, Anhui, China; Anhui Laboratory of Advanced Photon Science and Technology, University of Science and Technology of China, Hefei Anhui 230026, China
| | - Qingyou Lu
- Anhui Key Laboratory of Low-Energy Quantum Materials and Devices, High Magnetic Field Laboratory, HFIPS, Chinese Academy of Sciences, Hefei 230031, Anhui, China; The High Magnetic Field Laboratory of Anhui Province, Hefei 230031, Anhui, China; Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230026, Anhui, China; Anhui Laboratory of Advanced Photon Science and Technology, University of Science and Technology of China, Hefei Anhui 230026, China; Hefei Science Center, Chinese Academy of Sciences, Hefei 230031, China.
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2
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Zhuo D, Zhou L, Zhao YF, Zhang R, Yan ZJ, Wang AG, Chan MHW, Liu CX, Chen CZ, Chang CZ. Engineering Plateau Phase Transition in Quantum Anomalous Hall Multilayers. NANO LETTERS 2024; 24:6974-6980. [PMID: 38829211 DOI: 10.1021/acs.nanolett.4c01313] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2024]
Abstract
The plateau phase transition in quantum anomalous Hall (QAH) insulators corresponds to a quantum state wherein a single magnetic domain gives way to multiple domains and then reconverges back to a single magnetic domain. The layer structure of the sample provides an external knob for adjusting the Chern number C of the QAH insulators. Here, we employ molecular beam epitaxy to grow magnetic topological insulator multilayers and realize the magnetic field-driven plateau phase transition between two QAH states with odd Chern number change ΔC. We find that critical exponents extracted for the plateau phase transitions with ΔC = 1 and ΔC = 3 in QAH insulators are nearly identical. We construct a four-layer Chalker-Coddington network model to understand the consistent critical exponents for the plateau phase transitions with ΔC = 1 and ΔC = 3. This work will motivate further investigations into the critical behaviors of plateau phase transitions with different ΔC in QAH insulators.
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Affiliation(s)
- Deyi Zhuo
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Lingjie Zhou
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Yi-Fan Zhao
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Ruoxi Zhang
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Zi-Jie Yan
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Annie G Wang
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Moses H W Chan
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Chao-Xing Liu
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Chui-Zhen Chen
- Institute for Advanced Study and School of Physical Science and Technology, Soochow University, Suzhou 215006, China
| | - Cui-Zu Chang
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
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3
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Wang S, Zhang Z, Li H, Sanborn C, Zhao W, Wang S, Watanabe K, Taniguchi T, Crommie MF, Chen G, Wang F. Chern Insulator States with Tunable Chern Numbers in a Graphene Moiré Superlattice. NANO LETTERS 2024; 24:6838-6843. [PMID: 38825784 DOI: 10.1021/acs.nanolett.3c05145] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2024]
Abstract
Moiré superlattices, constituted by two-dimensional materials, demonstrate a variety of strongly correlated and topological phenomena including correlated insulators, superconductivity, and integer/fractional Chern insulators. In the realm of topological nontrivial Chern insulators within specific moiré superlattices, previous studies usually observe a single Chern number at a given filling factor in a device. Here we present the observation of gate-tunable Chern numbers within the Chern insulator state of an ABC-stacked trilayer graphene/hexagonal boron nitride moiré superlattice device. Near quarter filling, the moiré superlattice exhibits spontaneous valley polarization and distinct ferromagnetism associated with the Chern insulator states over a range of the displacement field. Surprisingly we find a transition of the Chern number from C = 3 to 4 as the displacement field is increased. Our observation of gate-tunable correlated Chern insulators suggests new ways to control and manipulate topological states in a moiré superlattice device.
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Affiliation(s)
- Shaoxin Wang
- Department of Physics, University of California at Berkeley, Berkeley, California 94720, United States
| | - Zuocheng Zhang
- Department of Physics, University of California at Berkeley, Berkeley, California 94720, United States
| | - Hongyuan Li
- Department of Physics, University of California at Berkeley, Berkeley, California 94720, United States
| | - Collin Sanborn
- Department of Physics, University of California at Berkeley, Berkeley, California 94720, United States
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Wenyu Zhao
- Department of Physics, University of California at Berkeley, Berkeley, California 94720, United States
| | - Siqi Wang
- Department of Applied Phyiscs, Yale University, New Haven, Connecticut 06511, 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
| | - Michael F Crommie
- Department of Physics, University of California at Berkeley, Berkeley, California 94720, United States
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
- Kavli Energy NanoScience Institute, University of California at Berkeley, Berkeley, California 94720, United States
| | - Guorui Chen
- Department of Physics, University of California at Berkeley, Berkeley, California 94720, United States
| | - Feng Wang
- Department of Physics, University of California at Berkeley, Berkeley, California 94720, United States
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
- Kavli Energy NanoScience Institute, University of California at Berkeley, Berkeley, California 94720, United States
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4
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Lu H, Chen BB, Wu HQ, Sun K, Meng ZY. Thermodynamic Response and Neutral Excitations in Integer and Fractional Quantum Anomalous Hall States Emerging from Correlated Flat Bands. PHYSICAL REVIEW LETTERS 2024; 132:236502. [PMID: 38905653 DOI: 10.1103/physrevlett.132.236502] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2023] [Revised: 04/26/2024] [Accepted: 05/14/2024] [Indexed: 06/23/2024]
Abstract
Integer and fractional Chern insulators have been extensively explored in correlated flat band models. Recently, the prediction and experimental observation of fractional quantum anomalous Hall (FQAH) states with spontaneous time-reversal symmetry breaking have garnered attention. While the thermodynamics of integer quantum anomalous Hall (IQAH) states have been systematically studied, our theoretical knowledge on thermodynamic properties of FQAH states has been severely limited. Here, we delve into the general thermodynamic response and collective excitations of both IQAH and FQAH states within the paradigmatic flat Chern-band model with remote band considered. Our key findings include (i) in both ν=1 IQAH and ν=1/3 FQAH states, even without spin fluctuations, the charge-neutral collective excitations would lower the onset temperature of these topological states, to a value significantly smaller than the charge gap, due to band mixing and multiparticle scattering; (ii) by employing large-scale thermodynamic simulations in FQAH states in the presence of strong interband mixing between C=±1 bands, we find that the lowest collective excitations manifest as the zero-momentum excitons in the IQAH state, whereas in the FQAH state, they take the form of magnetorotons with finite momentum; (iii) the unique charge oscillations in FQAH states are exhibited with distinct experimental signatures, which we propose to detect in future experiments.
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5
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Han X, Liu Q, Wang Y, Niu R, Qu Z, Wang Z, Li Z, Han C, Watanabe K, Taniguchi T, Song Z, Liu J, Mao J, Han Z, Chittari BL, Jung J, Gan Z, Lu J. Engineering the Band Topology in a Rhombohedral Trilayer Graphene Moiré Superlattice. NANO LETTERS 2024; 24:6286-6295. [PMID: 38747346 DOI: 10.1021/acs.nanolett.4c00948] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2024]
Abstract
Moiré superlattices have become a fertile playground for topological Chern insulators, where the displacement field can tune the quantum geometry and Chern number of the topological band. However, in experiments, displacement field engineering of spontaneous symmetry-breaking Chern bands has not been demonstrated. Here in a rhombohedral trilayer graphene moiré superlattice, we use a thermodynamic probe and transport measurement to monitor the Chern number evolution as a function of the displacement field. At a quarter filling of the moiré band, a novel Chern number of three is unveiled to compete with the well-established number of two upon turning on the electric field and survives when the displacement field is sufficiently strong. The transition can be reconciled by a nematic instability on the Fermi surface due to the pseudomagnetic vector field potentials associated with moiré strain patterns. Our work opens more opportunities to active control of Chern numbers in van der Waals moiré systems.
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Affiliation(s)
- Xiangyan Han
- State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China
| | - Qianling Liu
- State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China
| | - Yijie Wang
- International Center for Quantum Materials, Peking University, Beijing 100871, China
| | - Ruirui Niu
- State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China
| | - Zhuangzhuang Qu
- State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China
| | - Zhiyu Wang
- State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China
| | - Zhuoxian Li
- State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China
| | - Chunrui Han
- Institute of Microelectronics, Chinese Academy of Sciences, Beijing, 100029, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - 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
| | - Zhida Song
- International Center for Quantum Materials, Peking University, Beijing 100871, China
| | - Jianpeng Liu
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 200031, China
- ShanghaiTech Laboratory for Topological Physics, ShanghaiTech University, Shanghai 200031, China
| | - Jinhai Mao
- School of Physical Sciences and CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Zheng Han
- State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Optoelectronics, Shanxi University, Taiyuan 030006, China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China
| | - Bheema Lingam Chittari
- Department of Physical Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur 741246, West Bengal, India
| | - Jeil Jung
- Department of Physics, University of Seoul, Seoul 02504, Korea
- Department of Smart Cities, University of Seoul, Seoul 02504, Korea
| | - Zizhao Gan
- State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China
| | - Jianming Lu
- State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China
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6
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Hoke JC, Li Y, May-Mann J, Watanabe K, Taniguchi T, Bradlyn B, Hughes TL, Feldman BE. Uncovering the spin ordering in magic-angle graphene via edge state equilibration. Nat Commun 2024; 15:4321. [PMID: 38773076 PMCID: PMC11109299 DOI: 10.1038/s41467-024-48385-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2024] [Accepted: 04/30/2024] [Indexed: 05/23/2024] Open
Abstract
The flat bands in magic-angle twisted bilayer graphene (MATBG) provide an especially rich arena to investigate interaction-driven ground states. While progress has been made in identifying the correlated insulators and their excitations at commensurate moiré filling factors, the spin-valley polarizations of the topological states that emerge at high magnetic field remain unknown. Here we introduce a technique based on twist-decoupled van der Waals layers that enables measurement of their electronic band structure and-by studying the backscattering between counter-propagating edge states-the determination of the relative spin polarization of their edge modes. We find that the symmetry-broken quantum Hall states that extend from the charge neutrality point in MATBG are spin unpolarized at even integer filling factors. The measurements also indicate that the correlated Chern insulator emerging from half filling of the flat valence band is spin unpolarized and suggest that its conduction band counterpart may be spin polarized.
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Affiliation(s)
- Jesse C Hoke
- Department of Physics, Stanford University, Stanford, CA, 94305, USA
- Geballe Laboratory for Advanced Materials, Stanford, CA, 94305, USA
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA, 94025, USA
| | - Yifan Li
- Department of Physics, Stanford University, Stanford, CA, 94305, USA
- Geballe Laboratory for Advanced Materials, Stanford, CA, 94305, USA
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA, 94025, USA
| | - Julian May-Mann
- Department of Physics, Stanford University, Stanford, CA, 94305, USA
- Department of Physics and Institute for Condensed Matter Theory, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, 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
| | - Barry Bradlyn
- Department of Physics and Institute for Condensed Matter Theory, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Taylor L Hughes
- Department of Physics and Institute for Condensed Matter Theory, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Benjamin E Feldman
- Department of Physics, Stanford University, Stanford, CA, 94305, USA.
- Geballe Laboratory for Advanced Materials, Stanford, CA, 94305, USA.
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA, 94025, USA.
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7
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Zhang XW, Wang C, Liu X, Fan Y, Cao T, Xiao D. Polarization-driven band topology evolution in twisted MoTe 2 and WSe 2. Nat Commun 2024; 15:4223. [PMID: 38762554 PMCID: PMC11102499 DOI: 10.1038/s41467-024-48511-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2023] [Accepted: 05/02/2024] [Indexed: 05/20/2024] Open
Abstract
Motivated by recent experimental observations of opposite Chern numbers in R-type twisted MoTe2 and WSe2 homobilayers, we perform large-scale density-functional-theory calculations with machine learning force fields to investigate moiré band topology across a range of twist angles in both materials. We find that the Chern numbers of the moiré frontier bands change sign as a function of twist angle, and this change is driven by the competition between moiré ferroelectricity and piezoelectricity. Our large-scale calculations, enabled by machine learning methods, reveal crucial insights into interactions across different scales in twisted bilayer systems. The interplay between atomic-level relaxation effects and moiré-scale electrostatic potential variation opens new avenues for the design of intertwined topological and correlated states, including the possibility of mimicking higher Landau level physics in the absence of magnetic field.
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Affiliation(s)
- Xiao-Wei Zhang
- Department of Materials Science and Engineering, University of Washington, Seattle, WA, 98195, USA
| | - Chong Wang
- Department of Materials Science and Engineering, University of Washington, Seattle, WA, 98195, USA
| | - Xiaoyu Liu
- Department of Materials Science and Engineering, University of Washington, Seattle, WA, 98195, USA
| | - Yueyao Fan
- Department of Materials Science and Engineering, University of Washington, Seattle, WA, 98195, USA
| | - Ting Cao
- Department of Materials Science and Engineering, University of Washington, Seattle, WA, 98195, USA.
| | - Di Xiao
- Department of Materials Science and Engineering, University of Washington, Seattle, WA, 98195, USA.
- Department of Physics, University of Washington, Seattle, WA, 98195, USA.
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8
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Xiong R, Brantly SL, Su K, Nie JH, Zhang Z, Banerjee R, Ruddick H, Watanabe K, Taniguchi T, Tongay SA, Xu C, Jin C. Tunable exciton valley-pseudospin orders in moiré superlattices. Nat Commun 2024; 15:4254. [PMID: 38762501 PMCID: PMC11102517 DOI: 10.1038/s41467-024-48725-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2023] [Accepted: 05/13/2024] [Indexed: 05/20/2024] Open
Abstract
Excitons in two-dimensional (2D) semiconductors have offered an attractive platform for optoelectronic and valleytronic devices. Further realizations of correlated phases of excitons promise device concepts not possible in the single particle picture. Here we report tunable exciton "spin" orders in WSe2/WS2 moiré superlattices. We find evidence of an in-plane (xy) order of exciton "spin"-here, valley pseudospin-around exciton filling vex = 1, which strongly suppresses the out-of-plane "spin" polarization. Upon increasing vex or applying a small magnetic field of ~10 mT, it transitions into an out-of-plane ferromagnetic (FM-z) spin order that spontaneously enhances the "spin" polarization, i.e., the circular helicity of emission light is higher than the excitation. The phase diagram is qualitatively captured by a spin-1/2 Bose-Hubbard model and is distinct from the fermion case. Our study paves the way for engineering exotic phases of matter from correlated spinor bosons, opening the door to a host of unconventional quantum devices.
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Affiliation(s)
- Richen Xiong
- Department of Physics, University of California at Santa Barbara, Santa Barbara, CA, USA
| | - Samuel L Brantly
- Department of Physics, University of California at Santa Barbara, Santa Barbara, CA, USA
| | - Kaixiang Su
- Department of Physics, University of California at Santa Barbara, Santa Barbara, CA, USA
| | - Jacob H Nie
- Department of Physics, University of California at Santa Barbara, Santa Barbara, CA, USA
| | - Zihan Zhang
- Department of Physics, University of California at Santa Barbara, Santa Barbara, CA, USA
| | - Rounak Banerjee
- School for Engineering of Matter, Transport, and Energy, Arizona State University, Tempe, AZ, USA
| | - Hayley Ruddick
- School for Engineering of Matter, Transport, and Energy, Arizona State University, Tempe, AZ, 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
| | - Seth Ariel Tongay
- School for Engineering of Matter, Transport, and Energy, Arizona State University, Tempe, AZ, USA
| | - Cenke Xu
- Department of Physics, University of California at Santa Barbara, Santa Barbara, CA, USA
| | - Chenhao Jin
- Department of Physics, University of California at Santa Barbara, Santa Barbara, CA, USA.
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9
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Chang C, Zhang X, Li W, Guo Q, Feng Z, Huang C, Ren Y, Cai Y, Zhou X, Wang J, Tang Z, Ding F, Wei W, Liu K, Xu X. Remote epitaxy of single-crystal rhombohedral WS 2 bilayers. Nat Commun 2024; 15:4130. [PMID: 38755189 PMCID: PMC11099013 DOI: 10.1038/s41467-024-48522-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2024] [Accepted: 05/03/2024] [Indexed: 05/18/2024] Open
Abstract
Compared to transition metal dichalcogenide (TMD) monolayers, rhombohedral-stacked (R-stacked) TMD bilayers exhibit remarkable electrical performance, enhanced nonlinear optical response, giant piezo-photovoltaic effect and intrinsic interfacial ferroelectricity. However, from a thermodynamics perspective, the formation energies of R-stacked and hexagonal-stacked (H-stacked) TMD bilayers are nearly identical, leading to mixed stacking of both H- and R-stacked bilayers in epitaxial films. Here, we report the remote epitaxy of centimetre-scale single-crystal R-stacked WS2 bilayer films on sapphire substrates. The bilayer growth is realized by a high flux feeding of the tungsten source at high temperature on substrates. The R-stacked configuration is achieved by the symmetry breaking in a-plane sapphire, where the influence of atomic steps passes through the lower TMD layer and controls the R-stacking of the upper layer. The as-grown R-stacked bilayers show up-to-30-fold enhancements in carrier mobility (34 cm2V-1s-1), nearly doubled circular helicity (61%) and interfacial ferroelectricity, in contrast to monolayer films. Our work reveals a growth mechanism to obtain stacking-controlled bilayer TMD single crystals, and promotes large-scale applications of R-stacked TMD.
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Affiliation(s)
- Chao Chang
- Guangdong Basic Research Center of Excellence for Structure and Fundamental Interactions of Matter, Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials, School of Physics, South China Normal University, Guangzhou, 510006, China
- Guangdong-Hong Kong Joint Laboratory of Quantum Matter, Frontier Research Institute for Physics, South China Normal University, Guangzhou, 510006, China
| | - Xiaowen Zhang
- Guangdong Basic Research Center of Excellence for Structure and Fundamental Interactions of Matter, Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials, School of Physics, South China Normal University, Guangzhou, 510006, China
- Guangdong-Hong Kong Joint Laboratory of Quantum Matter, Frontier Research Institute for Physics, South China Normal University, Guangzhou, 510006, China
| | - Weixuan Li
- Guangdong Basic Research Center of Excellence for Structure and Fundamental Interactions of Matter, Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials, School of Physics, South China Normal University, Guangzhou, 510006, China
- Guangdong-Hong Kong Joint Laboratory of Quantum Matter, Frontier Research Institute for Physics, South China Normal University, Guangzhou, 510006, China
| | - Quanlin Guo
- State Key Laboratory for Mesoscopic Physics, Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, 100871, Beijing, China
| | - Zuo Feng
- State Key Laboratory for Mesoscopic Physics, Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, 100871, Beijing, China
| | - Chen Huang
- State Key Laboratory for Mesoscopic Physics, Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, 100871, Beijing, China
| | - Yunlong Ren
- Guangdong Basic Research Center of Excellence for Structure and Fundamental Interactions of Matter, Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials, School of Physics, South China Normal University, Guangzhou, 510006, China
- Guangdong-Hong Kong Joint Laboratory of Quantum Matter, Frontier Research Institute for Physics, South China Normal University, Guangzhou, 510006, China
- Songshan Lake Materials Laboratory, Institute of Physics, Chinese Academy of Sciences, Dongguan, 523808, China
| | - Yingying Cai
- Guangdong Basic Research Center of Excellence for Structure and Fundamental Interactions of Matter, Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials, School of Physics, South China Normal University, Guangzhou, 510006, China
- Guangdong-Hong Kong Joint Laboratory of Quantum Matter, Frontier Research Institute for Physics, South China Normal University, Guangzhou, 510006, China
| | - Xu Zhou
- Guangdong Basic Research Center of Excellence for Structure and Fundamental Interactions of Matter, Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials, School of Physics, South China Normal University, Guangzhou, 510006, China
- Guangdong-Hong Kong Joint Laboratory of Quantum Matter, Frontier Research Institute for Physics, South China Normal University, Guangzhou, 510006, China
| | - Jinhuan Wang
- Guangdong Basic Research Center of Excellence for Structure and Fundamental Interactions of Matter, Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials, School of Physics, South China Normal University, Guangzhou, 510006, China
- Guangdong-Hong Kong Joint Laboratory of Quantum Matter, Frontier Research Institute for Physics, South China Normal University, Guangzhou, 510006, China
| | - Zhilie Tang
- Guangdong Basic Research Center of Excellence for Structure and Fundamental Interactions of Matter, Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials, School of Physics, South China Normal University, Guangzhou, 510006, China
- Guangdong-Hong Kong Joint Laboratory of Quantum Matter, Frontier Research Institute for Physics, South China Normal University, Guangzhou, 510006, China
| | - Feng Ding
- Faculty of Materials Science and Engineering/Institute of Technology for Carbon Neutrality, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Wenya Wei
- Guangdong Basic Research Center of Excellence for Structure and Fundamental Interactions of Matter, Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials, School of Physics, South China Normal University, Guangzhou, 510006, China.
- Guangdong-Hong Kong Joint Laboratory of Quantum Matter, Frontier Research Institute for Physics, South China Normal University, Guangzhou, 510006, China.
| | - Kaihui Liu
- State Key Laboratory for Mesoscopic Physics, Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, 100871, Beijing, China.
- Songshan Lake Materials Laboratory, Institute of Physics, Chinese Academy of Sciences, Dongguan, 523808, China.
- Interdisciplinary Institute of Light-Element Quantum Materials and Research Centre for Light-Element Advanced Materials, Peking University, 100871, Beijing, China.
| | - Xiaozhi Xu
- Guangdong Basic Research Center of Excellence for Structure and Fundamental Interactions of Matter, Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials, School of Physics, South China Normal University, Guangzhou, 510006, China.
- Guangdong-Hong Kong Joint Laboratory of Quantum Matter, Frontier Research Institute for Physics, South China Normal University, Guangzhou, 510006, China.
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10
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Graham AJ, Park H, Nguyen PV, Nunn J, Kandyba V, Cattelan M, Giampietri A, Barinov A, Watanabe K, Taniguchi T, Andreev A, Rudner M, Xu X, Wilson NR, Cobden DH. Conduction Band Replicas in a 2D Moiré Semiconductor Heterobilayer. NANO LETTERS 2024; 24:5117-5124. [PMID: 38629940 DOI: 10.1021/acs.nanolett.3c04866] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2024]
Abstract
Stacking monolayer semiconductors creates moiré patterns, leading to correlated and topological electronic phenomena, but measurements of the electronic structure underpinning these phenomena are scarce. Here, we investigate the properties of the conduction band in moiré heterobilayers of WS2/WSe2 using submicrometer angle-resolved photoemission spectroscopy with electrostatic gating. We find that at all twist angles the conduction band edge is the K-point valley of the WS2, with a band gap of 1.58 ± 0.03 eV. From the resolved conduction band dispersion, we deduce an effective mass of 0.15 ± 0.02 me. Additionally, we observe replicas of the conduction band displaced by reciprocal lattice vectors of the moiré superlattice. We argue that the replicas result from the moiré potential modifying the conduction band states rather than final-state diffraction. Interestingly, the replicas display an intensity pattern with reduced 3-fold symmetry, which we show implicates the pseudo vector potential associated with in-plane strain in moiré band formation.
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Affiliation(s)
- Abigail J Graham
- Department of Physics, University of Warwick, Coventry CV4 7AL, U.K
| | - Heonjoon Park
- Department of Physics, University of Washington, Seattle, Washington 98195, United States
| | - Paul V Nguyen
- Department of Physics, University of Washington, Seattle, Washington 98195, United States
| | - James Nunn
- Department of Physics, University of Warwick, Coventry CV4 7AL, U.K
| | - Viktor Kandyba
- Elettra - Sincrotrone Trieste, S.C.p.A, Basovizza (TS), Friuli-Venezia Giulia 34149, Italy
| | - Mattia Cattelan
- Elettra - Sincrotrone Trieste, S.C.p.A, Basovizza (TS), Friuli-Venezia Giulia 34149, Italy
| | - Alessio Giampietri
- Elettra - Sincrotrone Trieste, S.C.p.A, Basovizza (TS), Friuli-Venezia Giulia 34149, Italy
| | - Alexei Barinov
- Elettra - Sincrotrone Trieste, S.C.p.A, Basovizza (TS), Friuli-Venezia Giulia 34149, Italy
| | - Kenji Watanabe
- Research Center for Electronic and Optical Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Anton Andreev
- Department of Physics, University of Washington, Seattle, Washington 98195, United States
| | - Mark Rudner
- Department of Physics, University of Washington, Seattle, Washington 98195, United States
| | - Xiaodong Xu
- Department of Physics, University of Washington, Seattle, Washington 98195, United States
- Department of Materials Science and Engineering, University of Washington, Seattle, Washington 98195, United States
| | - Neil R Wilson
- Department of Physics, University of Warwick, Coventry CV4 7AL, U.K
| | - David H Cobden
- Department of Physics, University of Washington, Seattle, Washington 98195, United States
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11
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Ma Y, Du Y, Wu W, Shi Z, Meng X, Yuan X. Synthesis and Characterization of 2D Ternary Compound TMD Materials Ta 3VSe 8. MICROMACHINES 2024; 15:591. [PMID: 38793164 PMCID: PMC11123142 DOI: 10.3390/mi15050591] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2024] [Revised: 04/24/2024] [Accepted: 04/25/2024] [Indexed: 05/26/2024]
Abstract
Two-dimensional (2D) transition metal dichalcogenides (TMDs) are garnering considerable scientific interest, prompting discussion regarding their prospective applications in the fields of nanoelectronics and spintronics while also fueling groundbreaking discoveries in phenomena such as the fractional quantum anomalous Hall effect (FQAHE) and exciton dynamics. The abundance of binary compound TMDs, such as MX2 (M = Mo, W; X = S, Se, Te), has unlocked myriad avenues of exploration. However, the exploration of ternary compound TMDs remains relatively limited, with notable examples being Ta2NiS5 and Ta2NiSe5. In this study, we report the synthesis of a new 2D ternary compound TMD materials, Ta3VSe8, employing the chemical vapor transport (CVT) method. The as-grown bulk crystal is shiny and can be easily exfoliated. The crystal quality and structure are verified by X-ray diffraction (XRD), while the surface morphology, stoichiometric ratio, and uniformity are determined by scanning electron microscopy (SEM). Although the phonon property is found stable at different temperatures, magneto-resistivity evolves. These findings provide a possible approach for the realization and exploration of ternary compound TMDs.
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Affiliation(s)
- Yuanji Ma
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200241, China
| | - Yuhan Du
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200241, China
| | - Wenbin Wu
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200241, China
| | - Zeping Shi
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200241, China
| | - Xianghao Meng
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200241, China
| | - Xiang Yuan
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200241, China
- Shanghai Center of Brain-Inspired Intelligent Materials and Devices, Department of Electronics, East China Normal University, Shanghai 200241, China
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12
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Foutty BA, Kometter CR, Devakul T, Reddy AP, Watanabe K, Taniguchi T, Fu L, Feldman BE. Mapping twist-tuned multiband topology in bilayer WSe 2. Science 2024; 384:343-347. [PMID: 38669569 DOI: 10.1126/science.adi4728] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2023] [Accepted: 03/19/2024] [Indexed: 04/28/2024]
Abstract
Semiconductor moiré superlattices have been shown to host a wide array of interaction-driven ground states. However, twisted homobilayers have been difficult to study in the limit of large moiré wavelengths, where interactions are most dominant. In this study, we conducted local electronic compressibility measurements of twisted bilayer WSe2 (tWSe2) at small twist angles. We demonstrated multiple topological bands that host a series of Chern insulators at zero magnetic field near a "magic angle" around 1.23°. Using a locally applied electric field, we induced a topological quantum-phase transition at one hole per moiré unit cell. Our work establishes the topological phase diagram of a generalized Kane-Mele-Hubbard model in tWSe2, demonstrating a tunable platform for strongly correlated topological phases.
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Affiliation(s)
- Benjamin A Foutty
- Geballe Laboratory for Advanced Materials, Stanford, CA 94305, USA
- Department of Physics, Stanford University, Stanford, CA 94305, USA
| | - Carlos R Kometter
- Geballe Laboratory for Advanced Materials, Stanford, CA 94305, USA
- Department of Physics, Stanford University, Stanford, CA 94305, USA
| | - Trithep Devakul
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Aidan P Reddy
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, 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
| | - Liang Fu
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Benjamin E Feldman
- Geballe Laboratory for Advanced Materials, Stanford, CA 94305, USA
- Department of Physics, Stanford University, Stanford, CA 94305, USA
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA
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13
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Kim J, Park J, Choi H, Kim T, Cha S, Lee Y, Watanabe K, Taniguchi T, Kim J, Jo MH, Choi H. Correlation-driven nonequilibrium exciton site transition in a WSe 2/WS 2 moiré supercell. Nat Commun 2024; 15:3312. [PMID: 38632336 PMCID: PMC11024152 DOI: 10.1038/s41467-024-47768-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2023] [Accepted: 04/10/2024] [Indexed: 04/19/2024] Open
Abstract
Moiré superlattices of transition metal dichalcogenides offer a unique platform to explore correlated exciton physics with optical spectroscopy. Whereas the spatially modulated potentials evoke that the exciton resonances are distinct depending on a site in a moiré supercell, there have been no clear demonstration how the moiré excitons trapped in different sites dynamically interact with the doped carriers; so far the exciton-electron dynamic interactions were presumed to be site-dependent. Thus, the transient emergence of nonequilibrium correlations are open questions, but existing studies are limited to steady-state optical measurements. Here we report experimental fingerprints of site-dependent exciton correlations under continuous-wave as well as ultrashort optical excitations. In near-zero angle-aligned WSe2/WS2 heterobilayers, we observe intriguing polarization switching and strongly enhanced Pauli blocking near the Mott insulating state, dictating the dominant correlation-driven effects. When the twist angle is near 60°, no such correlations are observed, suggesting the strong dependence of atomic registry in moiré supercell configuration. Our studies open the door to largely unexplored nonequilibrium correlations of excitons in moiré superlattices.
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Affiliation(s)
- Jinjae Kim
- Department of Physics, Seoul National University, Seoul, 08826, Korea
- Institute of Applied Physics, Seoul National University, Seoul, 08826, Korea
| | - Jiwon Park
- Department of Physics, Seoul National University, Seoul, 08826, Korea
- Institute of Applied Physics, Seoul National University, Seoul, 08826, Korea
| | - Hyojin Choi
- Department of Physics, Seoul National University, Seoul, 08826, Korea
- Institute of Applied Physics, Seoul National University, Seoul, 08826, Korea
| | - Taeho Kim
- Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang, 37673, Korea
- Center for van der Waals Quantum Solids, Institute for Basic Science (IBS), Pohang, 37673, Korea
| | - Soonyoung Cha
- Department of Physics and Astronomy, University of California, Riverside, CA, 92521, USA
| | - Yewon Lee
- Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang, 37673, Korea
- Center for van der Waals Quantum Solids, Institute for Basic Science (IBS), Pohang, 37673, Korea
| | - Kenji Watanabe
- Advanced Materials Laboratory, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Takashi Taniguchi
- Advanced Materials Laboratory, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Jonghwan Kim
- Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang, 37673, Korea
- Center for van der Waals Quantum Solids, Institute for Basic Science (IBS), Pohang, 37673, Korea
| | - Moon-Ho Jo
- Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang, 37673, Korea
- Center for van der Waals Quantum Solids, Institute for Basic Science (IBS), Pohang, 37673, Korea
| | - Hyunyong Choi
- Department of Physics, Seoul National University, Seoul, 08826, Korea.
- Institute of Applied Physics, Seoul National University, Seoul, 08826, Korea.
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14
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Wu K, Wang H, Yang M, Liu L, Sun Z, Hu G, Song Y, Han X, Guo J, Wu K, Feng B, Shen C, Huang Y, Shi Y, Cheng Z, Yang H, Bao L, Pantelides ST, Gao HJ. Gold-Template-Assisted Mechanical Exfoliation of Large-Area 2D Layers Enables Efficient and Precise Construction of Moiré Superlattices. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024:e2313511. [PMID: 38597395 DOI: 10.1002/adma.202313511] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2023] [Revised: 04/07/2024] [Indexed: 04/11/2024]
Abstract
Moiré superlattices, consisting of rotationally aligned 2D atomically thin layers, provide a highly novel platform for the study of correlated quantum phenomena. However, reliable and efficient construction of moiré superlattices is challenging because of difficulties to accurately angle-align small exfoliated 2D layers and the need to shun wet-transfer processes. Here, efficient and precise construction of various moiré superlattices is demonstrated by picking up and stacking large-area 2D mono- or few-layer crystals with predetermined crystal axes, made possible by a gold-template-assisted mechanical exfoliation method. The exfoliated 2D layers are semiconductors, superconductors, or magnets and their high quality is confirmed by photoluminescence and Raman spectra and by electrical transport measurements of fabricated field-effect transistors and Hall devices. Twisted homobilayers with angle-twisting accuracy of ≈0.3°, twisted heterobilayers with sub-degree angle-alignment accuracy, and multilayer superlattices are precisely constructed and characterized by their moiré patterns, interlayer excitons, and second harmonic generation. The present study paves the way for exploring emergent phenomena in moiré superlattices.
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Affiliation(s)
- Kang Wu
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, P. R. China
- School of Physical Sciences and CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
| | - Hao Wang
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, P. R. China
- School of Physical Sciences and CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
| | - Meng Yang
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, P. R. China
- School of Physical Sciences and CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
| | - Li Liu
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, P. R. China
| | - Zhenyu Sun
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, P. R. China
- School of Physical Sciences and CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
| | - Guojing Hu
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, P. R. China
| | - Yanpeng Song
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, P. R. China
| | - Xin Han
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, P. R. China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Science, Beijing, 100049, P. R. China
| | - Jiangang Guo
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, P. R. China
| | - Kehui Wu
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, P. R. China
- School of Physical Sciences and CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
| | - Baojie Feng
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, P. R. China
- School of Physical Sciences and CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
| | - Chengmin Shen
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, P. R. China
- School of Physical Sciences and CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
| | - Yuan Huang
- Advanced Research Institute of Multidisciplinary Science, Beijing Institute of Technology, Beijing, 100081, P. R. China
| | - Youguo Shi
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, P. R. China
- School of Physical Sciences and CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Science, Beijing, 100049, P. R. China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong, 523808, P. R. China
| | - Zhigang Cheng
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, P. R. China
- School of Physical Sciences and CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong, 523808, P. R. China
| | - Haitao Yang
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, P. R. China
- School of Physical Sciences and CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
- Hefei National Laboratory, Hefei, Anhui, 230088, P. R. China
| | - Lihong Bao
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, P. R. China
- School of Physical Sciences and CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
- Hefei National Laboratory, Hefei, Anhui, 230088, P. R. China
| | - Sokrates T Pantelides
- School of Physical Sciences and CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
- Department of Physics and Astronomy & Department of Electrical and Computer Engineering, Vanderbilt University, Nashville, TN, 37235, USA
| | - Hong-Jun Gao
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, P. R. China
- School of Physical Sciences and CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
- Hefei National Laboratory, Hefei, Anhui, 230088, P. R. China
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15
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Fumega AO, Lado JL. Nature of the Unconventional Heavy-Fermion Kondo State in Monolayer CeSiI. NANO LETTERS 2024; 24:4272-4278. [PMID: 38394370 PMCID: PMC11010227 DOI: 10.1021/acs.nanolett.4c00619] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2024] [Revised: 02/14/2024] [Accepted: 02/15/2024] [Indexed: 02/25/2024]
Abstract
CeSiI has been recently isolated in the ultrathin limit, establishing CeSiI as the first intrinsic two-dimensional van der Waals heavy-fermion material up to 85 K. We show that, due to the strong spin-orbit coupling, the local moments develop a multipolar real-space magnetic texture, leading to local pseudospins with a nearly vanishing net moment. To elucidate its Kondo-screened regime, we extract from first-principles the parameters of the Kondo lattice model describing this material. We develop a pseudofermion methodology in combination with ab initio calculations to reveal the nature of the heavy-fermion state in CeSiI. We analyze the competing magnetic interactions leading to an unconventional heavy-fermion order as a function of the magnetic exchange between the localized f-electrons and the strength of the Kondo coupling. Our results show that the magnetic exchange interactions promote an unconventional momentum-dependent Kondo-screened phase, establishing the nature of the heavy-fermion state observed in CeSiI.
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Affiliation(s)
- Adolfo O. Fumega
- Department of Applied
Physics, Aalto University, 02150 Espoo, Finland
| | - Jose L. Lado
- Department of Applied
Physics, Aalto University, 02150 Espoo, Finland
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16
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Liu X, He Y, Wang C, Zhang XW, Cao T, Xiao D. Gate-Tunable Antiferromagnetic Chern Insulator in Twisted Bilayer Transition Metal Dichalcogenides. PHYSICAL REVIEW LETTERS 2024; 132:146401. [PMID: 38640385 DOI: 10.1103/physrevlett.132.146401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2023] [Revised: 01/19/2024] [Accepted: 03/10/2024] [Indexed: 04/21/2024]
Abstract
A series of recent experimental works on twisted MoTe_{2} homobilayers have unveiled an abundance of exotic states in this system. Valley-polarized quantum anomalous Hall states have been identified at hole doping of ν=-1, and the fractional quantum anomalous Hall effect is observed at ν=-2/3 and ν=-3/5. In this Letter, we investigate the electronic properties of AA-stacked twisted bilayer MoTe_{2} at ν=-2 by k-space Hartree-Fock calculations. We identify a series of phases, among which a noteworthy phase is the antiferromagnetic Chern insulator, stabilized by an external electric field. We attribute the existence of this Chern insulator to an antiferromagnetic instability at a topological phase transition between the quantum spin hall phase and a band insulator phase. Our research proposes the potential of realizing a Chern insulator beyond ν=-1, and contributes fresh perspectives on the interplay between band topology and electron-electron correlations in moiré superlattices.
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Affiliation(s)
- Xiaoyu Liu
- Department of Materials Science and Engineering, University of Washington, Seattle, Washington 98195, USA
| | - Yuchi He
- Rudolf Peierls Centre for Theoretical Physics, Clarendon Laboratory, Parks Road, Oxford OX1 3PU, United Kingdom
| | - Chong Wang
- Department of Materials Science and Engineering, University of Washington, Seattle, Washington 98195, USA
| | - Xiao-Wei Zhang
- Department of Materials Science and Engineering, University of Washington, Seattle, Washington 98195, USA
| | - Ting Cao
- Department of Materials Science and Engineering, University of Washington, Seattle, Washington 98195, USA
| | - Di Xiao
- Department of Materials Science and Engineering, University of Washington, Seattle, Washington 98195, USA
- Department of Physics, University of Washington, Seattle, Washington 98195, USA
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17
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Liang J, Liu Z, Yang Z, Huang Y, Wurstbauer U, Dean CR, West KW, Pfeiffer LN, Du L, Pinczuk A. Evidence for chiral graviton modes in fractional quantum Hall liquids. Nature 2024; 628:78-83. [PMID: 38538799 DOI: 10.1038/s41586-024-07201-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2023] [Accepted: 02/16/2024] [Indexed: 04/01/2024]
Abstract
Exotic physics could emerge from interplay between geometry and correlation. In fractional quantum Hall (FQH) states1, novel collective excitations called chiral graviton modes (CGMs) are proposed as quanta of fluctuations of an internal quantum metric under a quantum geometry description2-5. Such modes are condensed-matter analogues of gravitons that are hypothetical spin-2 bosons. They are characterized by polarized states with chirality6-8 of +2 or -2, and energy gaps coinciding with the fundamental neutral collective excitations (namely, magnetorotons9,10) in the long-wavelength limit. However, CGMs remain experimentally inaccessible. Here we observe chiral spin-2 long-wavelength magnetorotons using inelastic scattering of circularly polarized lights, providing strong evidence for CGMs in FQH liquids. At filling factor v = 1/3, a gapped mode identified as the long-wavelength magnetoroton emerges under a specific polarization scheme corresponding to angular momentum S = -2, which persists at extremely long wavelength. Remarkably, the mode chirality remains -2 at v = 2/5 but becomes the opposite at v = 2/3 and 3/5. The modes have characteristic energies and sharp peaks with marked temperature and filling-factor dependence, corroborating the assignment of long-wavelength magnetorotons. The observations capture the essentials of CGMs and support the FQH geometrical description, paving the way to unveil rich physics of quantum metric effects in topological correlated systems.
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Affiliation(s)
- Jiehui Liang
- School of Physics, National Laboratory of Solid State Microstructures, and Collaborative Innovation Center for Advanced Microstructures, Nanjing University, Nanjing, China
| | - Ziyu Liu
- Department of Physics, Columbia University, New York, NY, USA
| | - Zihao Yang
- School of Physics, National Laboratory of Solid State Microstructures, and Collaborative Innovation Center for Advanced Microstructures, Nanjing University, Nanjing, China
| | - Yuelei Huang
- School of Physics, National Laboratory of Solid State Microstructures, and Collaborative Innovation Center for Advanced Microstructures, Nanjing University, Nanjing, China
| | | | - Cory R Dean
- Department of Physics, Columbia University, New York, NY, USA
| | - Ken W West
- Department of Electrical Engineering, Princeton University, Princeton, NJ, USA
| | - Loren N Pfeiffer
- Department of Electrical Engineering, Princeton University, Princeton, NJ, USA
| | - Lingjie Du
- School of Physics, National Laboratory of Solid State Microstructures, and Collaborative Innovation Center for Advanced Microstructures, Nanjing University, Nanjing, China.
- Shishan Laboratory, Suzhou Campus of Nanjing University, Suzhou, China.
| | - Aron Pinczuk
- Department of Physics, Columbia University, New York, NY, USA
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, NY, USA
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18
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Kang K, Shen B, Qiu Y, Zeng Y, Xia Z, Watanabe K, Taniguchi T, Shan J, Mak KF. Evidence of the fractional quantum spin Hall effect in moiré MoTe 2. Nature 2024; 628:522-526. [PMID: 38509375 DOI: 10.1038/s41586-024-07214-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2023] [Accepted: 02/20/2024] [Indexed: 03/22/2024]
Abstract
Quantum spin Hall (QSH) insulators are two-dimensional electronic materials that have a bulk band gap similar to an ordinary insulator but have topologically protected pairs of edge modes of opposite chiralities1-6. So far, experimental studies have found only integer QSH insulators with counter-propagating up-spins and down-spins at each edge leading to a quantized conductance G0 = e2/h (with e and h denoting the electron charge and Planck's constant, respectively)7-14. Here we report transport evidence of a fractional QSH insulator in 2.1° twisted bilayer MoTe2, which supports spin-Sz conservation and flat spin-contrasting Chern bands15,16. At filling factor ν = 3 of the moiré valence bands, each edge contributes a conductance3 2 G 0 with zero anomalous Hall conductivity. The state is probably a time-reversal pair of the even-denominator 3/2-fractional Chern insulators. Furthermore, at ν = 2, 4 and 6, we observe a single, double and triple QSH insulator with each edge contributing a conductance G0, 2G0 and 3G0, respectively. Our results open up the possibility of realizing time-reversal symmetric non-abelian anyons and other unexpected topological phases in highly tunable moiré materials17-19.
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Affiliation(s)
- Kaifei Kang
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY, USA.
| | - Bowen Shen
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY, USA
| | - Yichen Qiu
- Department of Physics, Cornell University, Ithaca, NY, USA
| | - Yihang Zeng
- Department of Physics, Cornell University, Ithaca, NY, USA
| | - Zhengchao Xia
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY, USA
| | - Kenji Watanabe
- National Institute for Materials Science, Tsukuba, Japan
| | | | - Jie Shan
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY, USA.
- Department of Physics, Cornell University, Ithaca, NY, USA.
- Kavli Institute at Cornell for Nanoscale Science, Ithaca, NY, USA.
| | - Kin Fai Mak
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY, USA.
- Department of Physics, Cornell University, Ithaca, NY, USA.
- Kavli Institute at Cornell for Nanoscale Science, Ithaca, NY, USA.
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19
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Tang J, Ding TS, Chen H, Gao A, Qian T, Huang Z, Sun Z, Han X, Strasser A, Li J, Geiwitz M, Shehabeldin M, Belosevich V, Wang Z, Wang Y, Watanabe K, Taniguchi T, Bell DC, Wang Z, Fu L, Zhang Y, Qian X, Burch KS, Shi Y, Ni N, Chang G, Xu SY, Ma Q. Dual quantum spin Hall insulator by density-tuned correlations in TaIrTe 4. Nature 2024; 628:515-521. [PMID: 38509374 DOI: 10.1038/s41586-024-07211-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2023] [Accepted: 02/20/2024] [Indexed: 03/22/2024]
Abstract
The convergence of topology and correlations represents a highly coveted realm in the pursuit of new quantum states of matter1. Introducing electron correlations to a quantum spin Hall (QSH) insulator can lead to the emergence of a fractional topological insulator and other exotic time-reversal-symmetric topological order2-8, not possible in quantum Hall and Chern insulator systems. Here we report a new dual QSH insulator within the intrinsic monolayer crystal of TaIrTe4, arising from the interplay of its single-particle topology and density-tuned electron correlations. At charge neutrality, monolayer TaIrTe4 demonstrates the QSH insulator, manifesting enhanced nonlocal transport and quantized helical edge conductance. After introducing electrons from charge neutrality, TaIrTe4 shows metallic behaviour in only a small range of charge densities but quickly goes into a new insulating state, entirely unexpected on the basis of the single-particle band structure of TaIrTe4. This insulating state could arise from a strong electronic instability near the van Hove singularities, probably leading to a charge density wave (CDW). Remarkably, within this correlated insulating gap, we observe a resurgence of the QSH state. The observation of helical edge conduction in a CDW gap could bridge spin physics and charge orders. The discovery of a dual QSH insulator introduces a new method for creating topological flat minibands through CDW superlattices, which offer a promising platform for exploring time-reversal-symmetric fractional phases and electromagnetism2-4,9,10.
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Affiliation(s)
- Jian Tang
- Department of Physics, Boston College, Chestnut Hill, MA, USA
| | | | - Hongyu Chen
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore
| | - Anyuan Gao
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA
| | - Tiema Qian
- Department of Physics and Astronomy and California NanoSystems Institute, University of California Los Angeles, Los Angeles, CA, USA
| | - Zumeng Huang
- Department of Physics, Boston College, Chestnut Hill, MA, USA
| | - Zhe Sun
- Department of Physics, Boston College, Chestnut Hill, MA, USA
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA
| | - Xin Han
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, China
| | - Alex Strasser
- Department of Materials Science and Engineering, Texas A&M University, College Station, TX, USA
| | - Jiangxu Li
- Department of Physics and Astronomy, University of Tennessee, Knoxville, TN, USA
- Min H. Kao Department of Electrical Engineering and Computer Science, University of Tennessee, Knoxville, TN, USA
| | - Michael Geiwitz
- Department of Physics, Boston College, Chestnut Hill, MA, USA
| | | | | | - Zihan Wang
- Department of Physics, Boston College, Chestnut Hill, MA, USA
| | - Yiping Wang
- Department of Physics, Boston College, Chestnut Hill, MA, USA
| | - Kenji Watanabe
- Research Center for Electronic and Optical Materials, National Institute for Materials Science, Tsukuba, Japan
| | - Takashi Taniguchi
- Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Japan
| | - David C Bell
- Harvard John A. Paulson School of Engineering and Applied Sciences and The Center for Nanoscale Systems, Harvard University, Cambridge, MA, USA
| | - Ziqiang Wang
- Department of Physics, Boston College, Chestnut Hill, MA, USA
| | - Liang Fu
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Yang Zhang
- Department of Physics and Astronomy, University of Tennessee, Knoxville, TN, USA
- Min H. Kao Department of Electrical Engineering and Computer Science, University of Tennessee, Knoxville, TN, USA
| | - Xiaofeng Qian
- Department of Materials Science and Engineering, Texas A&M University, College Station, TX, USA
| | - Kenneth S Burch
- Department of Physics, Boston College, Chestnut Hill, MA, USA
| | - Youguo Shi
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, China
| | - Ni Ni
- Department of Physics and Astronomy and California NanoSystems Institute, University of California Los Angeles, Los Angeles, CA, USA
| | - Guoqing Chang
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore.
| | - Su-Yang Xu
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA
| | - Qiong Ma
- Department of Physics, Boston College, Chestnut Hill, MA, USA.
- CIFAR Azrieli Global Scholars program, CIFAR, Toronto, Ontario, Canada.
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20
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Garisto D. Weird new electron behaviour in stacked graphene thrills physicists. Nature 2024; 628:16-17. [PMID: 38528157 DOI: 10.1038/d41586-024-00832-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/27/2024]
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21
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Zhou H, Liang K, Bi L, Shi Y, Wang Z, Li S. Spotlight: Visualization of Moiré Quantum Phenomena in Transition Metal Dichalcogenide with Scanning Tunneling Microscopy. ACS APPLIED ELECTRONIC MATERIALS 2024; 6:1530-1541. [PMID: 38558951 PMCID: PMC10976882 DOI: 10.1021/acsaelm.3c01328] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/21/2023] [Revised: 01/09/2024] [Accepted: 01/10/2024] [Indexed: 04/04/2024]
Abstract
Transition metal dichalcogenide (TMD) moiré superlattices have emerged as a significant area of study in condensed matter physics. Thanks to their superior optical properties, tunable electronic band structure, strong Coulomb interactions, and quenched electron kinetic energy, they offer exciting avenues to explore correlated quantum phenomena, topological properties, and light-matter interactions. In recent years, scanning tunneling microscopy (STM) has made significant impacts on the study of these fields by enabling intrinsic surface visualization and spectroscopic measurements with unprecedented atomic scale detail. Here, we spotlight the key findings and innovative developments in imaging and characterization of TMD heterostructures via STM, from its initial implementation on the in situ grown sample to the latest photocurrent tunneling microscopy. The evolution in sample design, progressing from a conductive to an insulating substrate, has not only expanded our control over TMD moiré superlattices but also promoted an understanding of their structures and strongly correlated properties, such as the structural reconstruction and formation of generalized two-dimensional Wigner crystal states. In addition to highlighting recent advancements, we outline upcoming challenges, suggest the direction of future research, and advocate for the versatile use of STM to further comprehend and manipulate the quantum dynamics in TMD moiré superlattices.
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Affiliation(s)
- Hao Zhou
- Department
of Chemistry and Biochemistry, University
of California, San Diego, La Jolla, California 92093-0309, United States
- Program
in Materials Science and Engineering, University
of California, San Diego, La Jolla, California 92093-0418, United States
| | - Kangkai Liang
- Department
of Chemistry and Biochemistry, University
of California, San Diego, La Jolla, California 92093-0309, United States
- Program
in Materials Science and Engineering, University
of California, San Diego, La Jolla, California 92093-0418, United States
| | - Liya Bi
- Department
of Chemistry and Biochemistry, University
of California, San Diego, La Jolla, California 92093-0309, United States
- Program
in Materials Science and Engineering, University
of California, San Diego, La Jolla, California 92093-0418, United States
| | - Yueqing Shi
- Department
of Chemistry and Biochemistry, University
of California, San Diego, La Jolla, California 92093-0309, United States
| | - Zihao Wang
- Department
of Chemistry and Biochemistry, University
of California, San Diego, La Jolla, California 92093-0309, United States
- School
of Physics, Nankai University, Tianjin 300071, China
| | - Shaowei Li
- Department
of Chemistry and Biochemistry, University
of California, San Diego, La Jolla, California 92093-0309, United States
- Program
in Materials Science and Engineering, University
of California, San Diego, La Jolla, California 92093-0418, United States
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22
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Xie B, Wu J, Mei J, Zhu S, Zhang R, Gu F, Watanabe K, Taniguchi T, Cai X. Resonant Tunneling-Enhanced Photoresponsivity in a Twisted Graphene van der Waals Heterostructure. NANO LETTERS 2024; 24:2870-2875. [PMID: 38407933 DOI: 10.1021/acs.nanolett.3c05131] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/27/2024]
Abstract
Leveraging its ultrahigh carrier mobility, zero-bandgap linear dispersion, and extremely short response time, graphene exhibits remarkable potential in ultrafast broad-band photodetection. Nonetheless, the inherently low responsivity of graphene photodetectors, due to the low photogenerated carrier density, significantly impedes the development of practical devices. In this study, we present an improved photoresponse within a graphene-hexagonal boron nitride-graphene vertical tunnel junction device, where the crystallographic orientation of the two graphene electrodes is aligned. Through meticulous device structure design and the adjustment of bias and gate voltages, we observe a 2 orders of magnitude increase in tunneling photocurrent, which is attributed to the momentum-conserving resonant electron tunneling. The enhanced external photoresponsivity is evident across a wide temperature and spectral range and achieves 0.7 A/W for visible light excitation. This characteristic, coupled with the device's negative differential conductance, suggests a novel avenue for highly efficient photodetection and high-frequency, logic-based optoelectronics using van der Waals heterostructures.
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Affiliation(s)
- Binghe Xie
- National Key Laboratory of Advanced Micro and Nano Manufacture Technology, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
- Department of Micro/Nano Electronics, School of Electronic Information and Electrical Engineering, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
| | - Jiaxin Wu
- National Key Laboratory of Advanced Micro and Nano Manufacture Technology, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
- Department of Micro/Nano Electronics, School of Electronic Information and Electrical Engineering, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
| | - Junning Mei
- National Key Laboratory of Advanced Micro and Nano Manufacture Technology, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
- Department of Micro/Nano Electronics, School of Electronic Information and Electrical Engineering, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
| | - Shuangxing Zhu
- National Key Laboratory of Advanced Micro and Nano Manufacture Technology, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
- Department of Micro/Nano Electronics, School of Electronic Information and Electrical Engineering, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
| | - Ruan Zhang
- Department of Micro/Nano Electronics, School of Electronic Information and Electrical Engineering, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
- Key Laboratory of Thin Film and Microfabrication Technology (Ministry of Education), Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
| | - Feifan Gu
- National Key Laboratory of Advanced Micro and Nano Manufacture Technology, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
- Key Laboratory of Thin Film and Microfabrication Technology (Ministry of Education), Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
| | - Kenji Watanabe
- National Institute for Materials Science, Tsukuba, Ibaraki 305-00044, Japan
| | - Takashi Taniguchi
- National Institute for Materials Science, Tsukuba, Ibaraki 305-00044, Japan
| | - Xinghan Cai
- National Key Laboratory of Advanced Micro and Nano Manufacture Technology, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
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23
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Morales-Durán N, Wei N, Shi J, MacDonald AH. Magic Angles and Fractional Chern Insulators in Twisted Homobilayer Transition Metal Dichalcogenides. PHYSICAL REVIEW LETTERS 2024; 132:096602. [PMID: 38489616 DOI: 10.1103/physrevlett.132.096602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2023] [Accepted: 02/12/2024] [Indexed: 03/17/2024]
Abstract
We explain the appearance of magic angles and fractional Chern insulators in twisted K-valley homobilayer transition metal dichalcogenides by mapping their continuum model to a Landau level problem. Our approach relies on an adiabatic approximation for the quantum mechanics of valence band holes in a layer-pseudospin field that is valid for sufficiently small twist angles and on a lowest Landau level approximation that is valid for sufficiently large twist angles. It provides a simple qualitative explanation for the nearly ideal quantum geometry of the lowest moiré miniband at particular twist angles, predicts that topological flat bands occur only when the valley-dependent moiré potential is sufficiently strong compared to the interlayer tunneling amplitude, and provides a convenient starting point for the study of interactions.
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Affiliation(s)
| | - Nemin Wei
- Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA
| | - Jingtian Shi
- Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA
| | - Allan H MacDonald
- Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA
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24
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Huang K, Li L, Zhao W, Wang X. Magnetization direction-controlled topological band structure in TlTiX (X = Si, Ge) monolayers. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2024; 36:225702. [PMID: 38382124 DOI: 10.1088/1361-648x/ad2bda] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2023] [Accepted: 02/21/2024] [Indexed: 02/23/2024]
Abstract
The quantum anomalous Hall (QAH) insulator is a vital material for the investigation of emerging topological quantum effects, but its extremely low working temperature limits experiments. Apart from the temperature challenge, effective regulation of the topological state of QAH insulators is another crucial concern. Here, by first-principles calculations, we find a family of stable two-dimensional materials TlTiX (X = Si, Ge) are large-gap QAH insulators. Their extremely robust ferromagnetic (FM) ground states are determined by both the direct- and super-exchange FM coupling. In the absence of spin-orbit coupling (SOC), there exist a spin-polarized crossing point located at eachKandK' points, respectively. The SOC effect results in the spontaneous breaking ofC2symmetry and introduces a mass term, giving rise to a QAH state with sizable band gap. The tiny magnetocrystalline anisotropic energy (MAE) implies that an external magnetic field can be easily used to align magnetization deviating fromzdirection to thex-yplane, thereby leading to a transformation of the electronic state from the QAH state to the Weyl half semimetals state, which indicate monolayers TlTiX (X = Si, Ge) exhibit a giant magneto topological band effect. Finally, we examined the impact of stress on the band gap and MAE, which underlies the reasons for the giant magneto topological band effect attributed to the crystal field. These findings present novel prospects for the realization of large-gap QAH states with the characteristic of easily modifiable topological states.
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Affiliation(s)
- Keer Huang
- Frontiers Science Center for Flexible Electronics (FSCFE) & Institute of Flexible Electronics (IFE), Northwestern Polytechnical University, Xi'an 710072, People's Republic of China
| | - Lei Li
- Frontiers Science Center for Flexible Electronics (FSCFE) & Institute of Flexible Electronics (IFE), Northwestern Polytechnical University, Xi'an 710072, People's Republic of China
- MIIT Key Laboratory of Flexible Electronics (KLoFE), Northwestern Polytechnical University, Xi'an 710072, People's Republic of China
- Shaanxi Key Laboratory of Flexible Electronics (KLoFE), Northwestern Polytechnical University, Xi'an 710072, People's Republic of China
| | - Wu Zhao
- School of Information Science and Technology, Northwest University, Xi'an 710072, People's Republic of China
| | - Xuewen Wang
- Frontiers Science Center for Flexible Electronics (FSCFE) & Institute of Flexible Electronics (IFE), Northwestern Polytechnical University, Xi'an 710072, People's Republic of China
- MIIT Key Laboratory of Flexible Electronics (KLoFE), Northwestern Polytechnical University, Xi'an 710072, People's Republic of China
- Shaanxi Key Laboratory of Flexible Electronics (KLoFE), Northwestern Polytechnical University, Xi'an 710072, People's Republic of China
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25
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Fractional quantum Hall effect at zero magnetic field observed in an unexpected material. Nature 2024:10.1038/d41586-024-00067-y. [PMID: 38383643 DOI: 10.1038/d41586-024-00067-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2024]
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26
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Xu C, Li J, Xu Y, Bi Z, Zhang Y. Maximally localized Wannier functions, interaction models, and fractional quantum anomalous Hall effect in twisted bilayer MoTe 2. Proc Natl Acad Sci U S A 2024; 121:e2316749121. [PMID: 38349878 PMCID: PMC10895274 DOI: 10.1073/pnas.2316749121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2023] [Accepted: 01/04/2024] [Indexed: 02/15/2024] Open
Abstract
We investigate the moiré band structures and the strong correlation effects in twisted bilayer MoTe[Formula: see text] for a wide range of twist angles, employing a combination of various techniques. Using large-scale first-principles calculations, we pinpoint realistic continuum modeling parameters, subsequently deriving the maximally localized Wannier functions for the top three moiré bands. Simplifying our model with reasonable assumptions, we obtain a minimal two-band model, encompassing Coulomb repulsion, correlated hopping, and spin exchange. Our minimal interaction models pave the way for further exploration of the rich many-body physics in twisted MoTe[Formula: see text]. Furthermore, we explore the phase diagrams of the system through Hartree-Fock approximation and exact diagonalization (ED). Our two-band ED analysis underscores significant band-mixing effects in this system, which enlarge the optimal twist angle for fractional quantum anomalous Hall states.
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Affiliation(s)
- Cheng Xu
- Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996
- Department of Physics, Tsinghua University, Beijing 100084, China
| | - Jiangxu Li
- Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996
| | - Yong Xu
- Department of Physics, Tsinghua University, Beijing 100084, China
| | - Zhen Bi
- Department of Physics, The Pennsylvania State University, University Park, PA 16802
| | - Yang Zhang
- Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996
- Min H. Kao Department of Electrical Engineering and Computer Science, University of Tennessee, Knoxville, TN 37996
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27
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Lu Z, Han T, Yao Y, Reddy AP, Yang J, Seo J, Watanabe K, Taniguchi T, Fu L, Ju L. Fractional quantum anomalous Hall effect in multilayer graphene. Nature 2024; 626:759-764. [PMID: 38383622 DOI: 10.1038/s41586-023-07010-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2023] [Accepted: 12/21/2023] [Indexed: 02/23/2024]
Abstract
The fractional quantum anomalous Hall effect (FQAHE), the analogue of the fractional quantum Hall effect1 at zero magnetic field, is predicted to exist in topological flat bands under spontaneous time-reversal-symmetry breaking2-6. The demonstration of FQAHE could lead to non-Abelian anyons that form the basis of topological quantum computation7-9. So far, FQAHE has been observed only in twisted MoTe2 at a moiré filling factor v > 1/2 (refs. 10-13). Graphene-based moiré superlattices are believed to host FQAHE with the potential advantage of superior material quality and higher electron mobility. Here we report the observation of integer and fractional QAH effects in a rhombohedral pentalayer graphene-hBN moiré superlattice. At zero magnetic field, we observed plateaus of quantized Hall resistance [Formula: see text] at v = 1, 2/3, 3/5, 4/7, 4/9, 3/7 and 2/5 of the moiré superlattice, respectively, accompanied by clear dips in the longitudinal resistance Rxx. Rxy equals [Formula: see text] at v = 1/2 and varies linearly with v, similar to the composite Fermi liquid in the half-filled lowest Landau level at high magnetic fields14-16. By tuning the gate-displacement field D and v, we observed phase transitions from composite Fermi liquid and FQAH states to other correlated electron states. Our system provides an ideal platform for exploring charge fractionalization and (non-Abelian) anyonic braiding at zero magnetic field7-9,17-19, especially considering a lateral junction between FQAHE and superconducting regions in the same device20-22.
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Affiliation(s)
- Zhengguang Lu
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Tonghang Han
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Yuxuan Yao
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Aidan P Reddy
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Jixiang Yang
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Junseok Seo
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Kenji Watanabe
- Research Center for Electronic and Optical Materials, National Institute for Materials Science, Tsukuba, Japan
| | - Takashi Taniguchi
- Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Japan
| | - Liang Fu
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Long Ju
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA.
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28
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Kuang X, Pantaleón Peralta PA, Angel Silva-Guillén J, Yuan S, Guinea F, Zhan Z. Optical properties and plasmons in moiré structures. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2024; 36:173001. [PMID: 38232397 DOI: 10.1088/1361-648x/ad1f8c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2023] [Accepted: 01/17/2024] [Indexed: 01/19/2024]
Abstract
The discoveries of numerous exciting phenomena in twisted bilayer graphene (TBG) are stimulating significant investigations on moiré structures that possess a tunable moiré potential. Optical response can provide insights into the electronic structures and transport phenomena of non-twisted and twisted moiré structures. In this article, we review both experimental and theoretical studies of optical properties such as optical conductivity, dielectric function, non-linear optical response, and plasmons in moiré structures composed of graphene, hexagonal boron nitride (hBN), and/or transition metal dichalcogenides. Firstly, a comprehensive introduction to the widely employed methodology on optical properties is presented. After, moiré potential induced optical conductivity and plasmons in non-twisted structures are reviewed, such as single layer graphene-hBN, bilayer graphene-hBN and graphene-metal moiré heterostructures. Next, recent investigations of twist-angle dependent optical response and plasmons are addressed in twisted moiré structures. Additionally, we discuss how optical properties and plasmons could contribute to the understanding of the many-body effects and superconductivity observed in moiré structures.
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Affiliation(s)
- Xueheng Kuang
- Yangtze Delta Industrial Innovation Center of Quantum Science and Technology, Suzhou 215000, People's Republic of China
| | | | - Jose Angel Silva-Guillén
- Instituto Madrileño de Estudios Avanzados, IMDEA Nanociencia, Calle Faraday 9, 28049 Madrid, Spain
| | - Shengjun Yuan
- Key Laboratory of Artificial Micro- and Nano-structures of the Ministry of Education and School of Physics and Technology, Wuhan University, Wuhan 430072, People's Republic of China
- Wuhan Institute of Quantum Technology, Wuhan 430206, People's Republic of China
| | - Francisco Guinea
- Instituto Madrileño de Estudios Avanzados, IMDEA Nanociencia, Calle Faraday 9, 28049 Madrid, Spain
- Donostia International Physics Center, Paseo Manuel de Lardizábal 4, 20018 San Sebastián, Spain
| | - Zhen Zhan
- Instituto Madrileño de Estudios Avanzados, IMDEA Nanociencia, Calle Faraday 9, 28049 Madrid, Spain
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29
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Wu H, Yang L, Zhang G, Jin W, Xiao B, Zhang W, Chang H. Robust Magnetic Proximity Induced Anomalous Hall Effect in a Room Temperature van der Waals Ferromagnetic Semiconductor Based 2D Heterostructure. SMALL METHODS 2024:e2301524. [PMID: 38295050 DOI: 10.1002/smtd.202301524] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2023] [Revised: 01/04/2024] [Indexed: 02/02/2024]
Abstract
Developing novel high-temperature van der Waals ferromagnetic semiconductor materials and investigating their interface coupling effects with 2D topological semimetals are pivotal for advancing next-generation spintronic and quantum devices. However, most van der Waals ferromagnetic semiconductors exhibit ferromagnetism only at low temperatures, limiting the proximity research on their interfaces with topological semimetals. Here, an intrinsic, van der Waals layered room-temperature ferromagnetic semiconductor crystal, FeCr0.5 Ga1.5 Se4 (FCGS), is reported with a Curie temperature (TC ) as high as 370 K, setting a new record for van der Waals ferromagnetic semiconductors. The saturation magnetization at low temperature (2 K) and room temperature (300 K) reaches 8.2 and 2.7 emu g-1 , respectively. Furthermore, FCGS possesses a bandgap of ≈1.2 eV, which is comparable to the widely used commercial silicon. The FCGS/graphene 2D heterostructure exhibits an impeccably smooth and gapless interface, thereby inducing a robust van der Waals magnetic proximity coupling effect between FCGS and graphene. After the proximity coupling, graphene undergoes a charge carrier transition from electrons to holes, accompanied by a transition from non-magnetic to ferromagnetic transport behavior with robust anomalous Hall effect (AHE). Notably, the van der Waals magnetic proximity-induced AHE remains robust even up to 400 K.
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Affiliation(s)
- Hao Wu
- Center for Joining and Electronic Packaging, State Key Laboratory of Material Processing and Die & Mold Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology (HUST), Wuhan, 430074, China
- Institute for Quantum Science and Engineering, Huazhong University of Science and Technology (HUST), Wuhan, 430074, China
| | - Li Yang
- Center for Joining and Electronic Packaging, State Key Laboratory of Material Processing and Die & Mold Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology (HUST), Wuhan, 430074, China
| | - Gaojie Zhang
- Center for Joining and Electronic Packaging, State Key Laboratory of Material Processing and Die & Mold Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology (HUST), Wuhan, 430074, China
- Institute for Quantum Science and Engineering, Huazhong University of Science and Technology (HUST), Wuhan, 430074, China
- Shenzhen R&D Center of Huazhong University of Science and Technology (HUST), Shenzhen, 518000, China
| | - Wen Jin
- Center for Joining and Electronic Packaging, State Key Laboratory of Material Processing and Die & Mold Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology (HUST), Wuhan, 430074, China
| | - Bichen Xiao
- Center for Joining and Electronic Packaging, State Key Laboratory of Material Processing and Die & Mold Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology (HUST), Wuhan, 430074, China
| | - Wenfeng Zhang
- Shenzhen R&D Center of Huazhong University of Science and Technology (HUST), Shenzhen, 518000, China
| | - Haixin Chang
- Shenzhen R&D Center of Huazhong University of Science and Technology (HUST), Shenzhen, 518000, China
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30
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Moll PJW. All-electric writing of a chiral quantum memory. NATURE MATERIALS 2024; 23:35-36. [PMID: 38110513 DOI: 10.1038/s41563-023-01751-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2023]
Affiliation(s)
- Philip J W Moll
- Max Planck Institute for the Structure and Dynamics of Matter, Hamburg, Germany.
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31
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Wu YH, Tu HH, Cheng M. Continuous Phase Transitions between Fractional Quantum Hall States and Symmetry-Protected Topological States. PHYSICAL REVIEW LETTERS 2023; 131:256502. [PMID: 38181355 DOI: 10.1103/physrevlett.131.256502] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2023] [Revised: 10/11/2023] [Accepted: 11/28/2023] [Indexed: 01/07/2024]
Abstract
We study quantum phase transitions in Bose-Fermi mixtures driven by interspecies interaction in the quantum Hall regime. In the absence of such an interaction, the bosons and fermions form their respective fractional quantum Hall (FQH) states at certain filling factors. A symmetry-protected topological (SPT) state is identified as the ground state for strong interspecies interaction. The phase transitions between them are proposed to be described by Chern-Simons-Higgs field theories. For a simple microscopic Hamiltonian, we present numerical evidence for the existence of the SPT state and a continuous transition to the FQH state. It is also found that the entanglement entropy between the bosons and fermions exhibits scaling behavior in the vicinity of this transition.
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Affiliation(s)
- Ying-Hai Wu
- School of Physics and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Hong-Hao Tu
- Institut für Theoretische Physik, Technische Universität Dresden, 01062 Dresden, Germany
| | - Meng Cheng
- Department of Physics, Yale University, New Haven, Connecticut 06511-8499, USA
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Törmä P. Essay: Where Can Quantum Geometry Lead Us? PHYSICAL REVIEW LETTERS 2023; 131:240001. [PMID: 38181149 DOI: 10.1103/physrevlett.131.240001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2023] [Indexed: 01/07/2024]
Abstract
Quantum geometry defines the phase and amplitude distances between quantum states. The phase distance is characterized by the Berry curvature and thus relates to topological phenomena. The significance of the full quantum geometry, including the amplitude distance characterized by the quantum metric, has started to receive attention in the last few years. Various quantum transport and interaction phenomena have been found to be critically influenced by quantum geometry. For example, quantum geometry allows counterintuitive flow of supercurrent in a flat band where single electrons are immobile. In this Essay, I will discuss my view of the important open problems and future applications of this research topic and will try to inspire the reader to come up with further ideas. At its best, quantum geometry can open a new chapter in band theory and lead to breakthroughs as transformative as room-temperature superconductivity. However, first, more experiments directly showing the effect of quantum geometry are needed. We also have to integrate quantum geometry analysis in our most advanced numerical methods. Further, the ramifications of quantum geometry should be studied in a wider range, including electric and electromagnetic responses and interaction phenomena in free- and correlated-electron materials, bosonic systems, optics, and other fields. Part of a series of Essays which concisely present author visions for the future of their field.
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Affiliation(s)
- Päivi Törmä
- Department of Applied Physics, Aalto University School of Science, FI-00076 Aalto, Finland
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Zeng Y, Xia Z, Kang K, Zhu J, Knüppel P, Vaswani C, Watanabe K, Taniguchi T, Mak KF, Shan J. Thermodynamic evidence of fractional Chern insulator in moiré MoTe 2. Nature 2023; 622:69-73. [PMID: 37494955 DOI: 10.1038/s41586-023-06452-3] [Citation(s) in RCA: 23] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2023] [Accepted: 07/18/2023] [Indexed: 07/28/2023]
Abstract
Chern insulators, which are the lattice analogues of the quantum Hall states, can potentially manifest high-temperature topological orders at zero magnetic field to enable next-generation topological quantum devices1-3. Until now, integer Chern insulators have been experimentally demonstrated in several systems at zero magnetic field3-8, whereas fractional Chern insulators have been reported in only graphene-based systems under a finite magnetic field9,10. The emergence of semiconductor moiré materials11, which support tunable topological flat bands12,13, provides an opportunity to realize fractional Chern insulators13-16. Here we report thermodynamic evidence of both integer and fractional Chern insulators at zero magnetic field in small-angle twisted bilayer MoTe2 by combining the local electronic compressibility and magneto-optical measurements. At hole filling factor ν = 1 and 2/3, the system is incompressible and spontaneously breaks time-reversal symmetry. We show that they are integer and fractional Chern insulators, respectively, from the dispersion of the state in the filling factor with an applied magnetic field. We further demonstrate electric-field-tuned topological phase transitions involving the Chern insulators. Our findings pave the way for the demonstration of quantized fractional Hall conductance and anyonic excitation and braiding17 in semiconductor moiré materials.
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Affiliation(s)
- Yihang Zeng
- Department of Physics, Cornell University, Ithaca, NY, USA
| | - Zhengchao Xia
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY, USA
| | - Kaifei Kang
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY, USA
| | - Jiacheng Zhu
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY, USA
| | - Patrick Knüppel
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY, USA
| | - Chirag Vaswani
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY, USA
| | - Kenji Watanabe
- National Institute for Materials Science, Tsukuba, Japan
| | | | - Kin Fai Mak
- Department of Physics, Cornell University, Ithaca, NY, USA.
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY, USA.
- Kavli Institute at Cornell for Nanoscale Science, Ithaca, NY, USA.
| | - Jie Shan
- Department of Physics, Cornell University, Ithaca, NY, USA.
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY, USA.
- Kavli Institute at Cornell for Nanoscale Science, Ithaca, NY, USA.
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Dong J, Wang J, Ledwith PJ, Vishwanath A, Parker DE. Composite Fermi Liquid at Zero Magnetic Field in Twisted MoTe_{2}. PHYSICAL REVIEW LETTERS 2023; 131:136502. [PMID: 37832017 DOI: 10.1103/physrevlett.131.136502] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2023] [Accepted: 08/25/2023] [Indexed: 10/15/2023]
Abstract
The pursuit of exotic phases of matter outside of the extreme conditions of a quantizing magnetic field is a long-standing quest of solid state physics. Recent experiments have observed spontaneous valley polarization and fractional Chern insulators in zero magnetic field in twisted bilayers of MoTe_{2}, at partial filling of the topological valence band (ν=-2/3 and -3/5). We study the topological valence band at half filling, using exact diagonalization and density matrix renormalization group calculations. We discover a composite Fermi liquid (CFL) phase even at zero magnetic field that covers a large portion of the phase diagram near twist angle ∼3.6°. The CFL is a non-Fermi liquid phase with metallic behavior despite the absence of Landau quasiparticles. We discuss experimental implications including the competition between the CFL and a Fermi liquid, which can be tuned with a displacement field. The topological valence band has excellent quantum geometry over a wide range of twist angles and a small bandwidth that is, remarkably, reduced by interactions. These key properties stabilize the exotic zero field quantum Hall phases. Finally, we present an optical signature involving "extinguished" optical responses that detects Chern bands with ideal quantum geometry.
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Affiliation(s)
- Junkai Dong
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Jie Wang
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
- Center of Mathematical Sciences and Applications, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Patrick J Ledwith
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Ashvin Vishwanath
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Daniel E Parker
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
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Qiu G, Yang HY, Chong SK, Cheng Y, Tai L, Wang KL. Manipulating Topological Phases in Magnetic Topological Insulators. NANOMATERIALS (BASEL, SWITZERLAND) 2023; 13:2655. [PMID: 37836296 PMCID: PMC10574534 DOI: 10.3390/nano13192655] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2023] [Revised: 09/21/2023] [Accepted: 09/25/2023] [Indexed: 10/15/2023]
Abstract
Magnetic topological insulators (MTIs) are a group of materials that feature topological band structures with concurrent magnetism, which can offer new opportunities for technological advancements in various applications, such as spintronics and quantum computing. The combination of topology and magnetism introduces a rich spectrum of topological phases in MTIs, which can be controllably manipulated by tuning material parameters such as doping profiles, interfacial proximity effect, or external conditions such as pressure and electric field. In this paper, we first review the mainstream MTI material platforms where the quantum anomalous Hall effect can be achieved, along with other exotic topological phases in MTIs. We then focus on highlighting recent developments in modulating topological properties in MTI with finite-size limit, pressure, electric field, and magnetic proximity effect. The manipulation of topological phases in MTIs provides an exciting avenue for advancing both fundamental research and practical applications. As this field continues to develop, further investigations into the interplay between topology and magnetism in MTIs will undoubtedly pave the way for innovative breakthroughs in the fundamental understanding of topological physics as well as practical applications.
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Affiliation(s)
- Gang Qiu
- Department of Electrical and Computer Engineering, University of California, Los Angeles, CA 90095, USA; (H.-Y.Y.); (S.K.C.); (Y.C.); (L.T.)
- Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN 55455, USA
| | - Hung-Yu Yang
- Department of Electrical and Computer Engineering, University of California, Los Angeles, CA 90095, USA; (H.-Y.Y.); (S.K.C.); (Y.C.); (L.T.)
| | - Su Kong Chong
- Department of Electrical and Computer Engineering, University of California, Los Angeles, CA 90095, USA; (H.-Y.Y.); (S.K.C.); (Y.C.); (L.T.)
- Beijing Academy of Quantum Information Sciences, Beijing 100193, China
| | - Yang Cheng
- Department of Electrical and Computer Engineering, University of California, Los Angeles, CA 90095, USA; (H.-Y.Y.); (S.K.C.); (Y.C.); (L.T.)
| | - Lixuan Tai
- Department of Electrical and Computer Engineering, University of California, Los Angeles, CA 90095, USA; (H.-Y.Y.); (S.K.C.); (Y.C.); (L.T.)
| | - Kang L. Wang
- Department of Electrical and Computer Engineering, University of California, Los Angeles, CA 90095, USA; (H.-Y.Y.); (S.K.C.); (Y.C.); (L.T.)
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