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Zhang XX, Nagaosa N. Surface spectroscopy and surface-bulk hybridization of Weyl semimetals. Proc Natl Acad Sci U S A 2024; 121:e2313488121. [PMID: 38513104 PMCID: PMC10990132 DOI: 10.1073/pnas.2313488121] [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: 08/05/2023] [Accepted: 01/30/2024] [Indexed: 03/23/2024] Open
Abstract
Weyl semimetal showing open-arc surface states is a prominent example of topological quantum matter in three dimensions. With the bulk-boundary correspondence present, nontrivial surface-bulk hybridization is inevitable but less understood. Spectroscopies have been often limited to verifying the existence of surface Fermi arcs, whereas its spectral shape related to the hybridization profile in energy-momentum space is not well studied. We present an exactly solvable formalism at the surface for a wide range of prototypical Weyl semimetals. The resonant surface state and the bulk influence coexist as a surface-bulk hybrid and are treated in a unified manner. Directly accessible to angle-resolved photoemission spectroscopy, we analytically reveal universal information about the system obtained from the spectroscopy of resonant topological states. We systematically find inhomogeneous and anisotropic singular responses around the surface-bulk merging borderline crossing Weyl points, highlighting its critical role in the Weyl topology. The response in scanning tunneling spectroscopy is also discussed. The results will provide much-needed insight into the surface-bulk-coupled physical properties and guide in-depth spectroscopic investigation of the nontrivial hybrid in many topological semimetal materials.
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Affiliation(s)
- Xiao-Xiao Zhang
- Wuhan National High Magnetic Field Center and School of Physics, Huazhong University of Science and Technology, Wuhan430074, China
- RIKEN Center for Emergent Matter Science (CEMS), Saitama351-0198, Japan
| | - Naoto Nagaosa
- RIKEN Center for Emergent Matter Science (CEMS), Saitama351-0198, Japan
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2
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Tian M, Velkovsky I, Chen T, Sun F, He Q, Gadway B. Manipulation of Weyl Points in Reciprocal and Nonreciprocal Mechanical Lattices. PHYSICAL REVIEW LETTERS 2024; 132:126602. [PMID: 38579212 DOI: 10.1103/physrevlett.132.126602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2023] [Accepted: 02/22/2024] [Indexed: 04/07/2024]
Abstract
We introduce feedback-measurement technologies to achieve flexible control of Weyl points and conduct the first experimental demonstration of Weyl type I-II transition in mechanical systems. We demonstrate that non-Hermiticity can expand the Fermi arc surface states from connecting Weyl points to Weyl rings, and lead to a localization transition of edge states influenced by the interplay between band topology and the non-Hermitian skin effect. Our findings offer valuable insights into the design and manipulation of Weyl points in mechanical systems, providing a promising avenue for manipulating topological modes in non-Hermitian systems.
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Affiliation(s)
- Mingsheng Tian
- State Key Laboratory for Mesoscopic Physics, School of Physics, Frontiers Science Center for Nano-optoelectronics, & Collaborative Innovation Center of Quantum Matter, Peking University, Beijing 100871, China
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801-3080, USA
| | - Ivan Velkovsky
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801-3080, USA
| | - Tao Chen
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801-3080, USA
| | - Fengxiao Sun
- State Key Laboratory for Mesoscopic Physics, School of Physics, Frontiers Science Center for Nano-optoelectronics, & Collaborative Innovation Center of Quantum Matter, Peking University, Beijing 100871, China
| | - Qiongyi He
- State Key Laboratory for Mesoscopic Physics, School of Physics, Frontiers Science Center for Nano-optoelectronics, & Collaborative Innovation Center of Quantum Matter, Peking University, Beijing 100871, China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China
- Hefei National Laboratory, Hefei, 230088, China
| | - Bryce Gadway
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801-3080, USA
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3
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Chung PF, Venkatesan B, Su CC, Chang JT, Cheng HK, Liu CA, Yu H, Chang CS, Guan SY, Chuang TM. Design and performance of an ultrahigh vacuum spectroscopic-imaging scanning tunneling microscope with a hybrid vibration isolation system. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2024; 95:033701. [PMID: 38426899 DOI: 10.1063/5.0189100] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2023] [Accepted: 02/06/2024] [Indexed: 03/02/2024]
Abstract
A spectroscopic imaging-scanning tunneling microscope (SI-STM) allows for the atomic scale visualization of the surface electronic and magnetic structure of novel quantum materials with a high energy resolution. To achieve the optimal performance, a low vibration facility is required. Here, we describe the design and performance of an ultrahigh vacuum STM system supported by a hybrid vibration isolation system that consists of a pneumatic passive and a piezoelectric active vibration isolation stage. We present the detailed vibrational noise analysis of the hybrid vibration isolation system, which shows that the vibration level can be suppressed below 10-8 m/sec/√Hz for most frequencies up to 100 Hz. Combined with a rigid STM design, vibrational noise can be successfully removed from the tunneling current. We demonstrate the performance of our STM system by taking high resolution spectroscopic maps and topographic images on several quantum materials. Our results establish a new strategy to achieve an effective vibration isolation system for high-resolution STM and other scanning probe microscopies to investigate the nanoscale quantum phenomena.
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Affiliation(s)
- Pei-Fang Chung
- Institute of Physics, Academia Sinica, Taipei 11529, Taiwan
| | - Balaji Venkatesan
- Institute of Physics, Academia Sinica, Taipei 11529, Taiwan
- Department of Physics, National Taiwan University, Taipei 10617, Taiwan
- Nano Science and Technology Program, Taiwan International Graduate Program, Academia Sinica and National Taiwan University, Taipei 11529, Taiwan
| | - Chih-Chuan Su
- Institute of Physics, Academia Sinica, Taipei 11529, Taiwan
| | - Jen-Te Chang
- Institute of Physics, Academia Sinica, Taipei 11529, Taiwan
| | - Hsu-Kai Cheng
- Institute of Physics, Academia Sinica, Taipei 11529, Taiwan
| | - Che-An Liu
- Institute of Physics, Academia Sinica, Taipei 11529, Taiwan
| | - Henry Yu
- Institute of Physics, Academia Sinica, Taipei 11529, Taiwan
| | - Chia-Seng Chang
- Institute of Physics, Academia Sinica, Taipei 11529, Taiwan
- Department of Physics, National Taiwan University, Taipei 10617, Taiwan
- Nano Science and Technology Program, Taiwan International Graduate Program, Academia Sinica and National Taiwan University, Taipei 11529, Taiwan
| | - Syu-You Guan
- Institute of Physics, Academia Sinica, Taipei 11529, Taiwan
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4
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Lin CL, Kawakami N, Arafune R, Minamitani E, Takagi N. Scanning tunneling spectroscopy studies of topological materials. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:243001. [PMID: 32069440 DOI: 10.1088/1361-648x/ab777d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Topological materials have become promising materials for next-generation devices by utilizing their exotic electronic states. Their exotic states caused by spin-orbital coupling usually locate on the surfaces or at the edges. Scanning tunneling spectroscopy (STS) is a powerful tool to reveal the local electronic structures of condensed matters. Therefore, STS provides us with an almost perfect method to access the exotic states of topological materials. In this topical review, we report the current investigations by several methods based on the STS technique for layered topological material from transition metal dichalcogenide Weyl semimetals (WTe2 and MoTe2) to two dimensional topological insulators (layered bismuth and silicene). The electronic characteristics of these layered topological materials are experimentally identified.
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Affiliation(s)
- Chun-Liang Lin
- Department of Electrophysics, National Chiao Tung University, Hsinchu, Taiwan, Republic of China
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5
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Wang R, Jin Y, Xia B, Xu H. Topological Quantum States in Magnetic Oxides. J Phys Chem Lett 2020; 11:4036-4042. [PMID: 32364393 DOI: 10.1021/acs.jpclett.9b03467] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The realization of topological quantum states in devices is an important subject. According to whether or not the time-reversal symmetry is broken, topological materials can be classified into magnetic and nonmagnetic ones. In particular, magnetic topological materials are of importance, in which the coexistence of nontrivial band topology and magnetic orders gives exotic spintronics-related applications. However, experimental observations of magnetic topological quantum states are extremely difficult. In this Perspective, we review the recent progress to explore and design magnetic topological oxides such as topological semimetals and three-dimensional quantum anomalous Hall insulators, which are robustly stable against oxidation at ambient conditions. Most of these materials possess high Curie temperatures and are widely used in industrial applications, stimulating considerable experimental interest. Moreover, further discussions related to the topological classification and topological transitions are also present.
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Affiliation(s)
- Rui Wang
- Department of Physics & Institute for Structure and Function & Center for Quantum Materials and Devices, Chongqing University, Chongqing 400044, P. R. China
| | - Yuanjun Jin
- Department of Physics & Institute for Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, P. R. China
- Guangdong Provincial Key Laboratory of Computational Science and Material Design, Southern University of Science and Technology, Shenzhen 518055, P. R. China
| | - Bowen Xia
- Department of Physics & Institute for Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, P. R. China
- Guangdong Provincial Key Laboratory of Computational Science and Material Design, Southern University of Science and Technology, Shenzhen 518055, P. R. China
| | - Hu Xu
- Department of Physics & Institute for Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, P. R. China
- Guangdong Provincial Key Laboratory of Computational Science and Material Design, Southern University of Science and Technology, Shenzhen 518055, P. R. China
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6
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Xing Y, Shao Z, Ge J, Luo J, Wang J, Zhu Z, Liu J, Wang Y, Zhao Z, Yan J, Mandrus D, Yan B, Liu XJ, Pan M, Wang J. Surface superconductivity in the type II Weyl semimetal TaIrTe 4. Natl Sci Rev 2020; 7:579-587. [PMID: 34692077 PMCID: PMC8288950 DOI: 10.1093/nsr/nwz204] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Revised: 11/27/2019] [Accepted: 11/28/2019] [Indexed: 11/13/2022] Open
Abstract
The search for unconventional superconductivity in Weyl semimetal materials is currently an exciting pursuit, since such superconducting phases could potentially be topologically non-trivial and host exotic Majorana modes. The layered material TaIrTe4 is a newly predicted time-reversal invariant type II Weyl semimetal with the minimum number of Weyl points. Here, we report the discovery of surface superconductivity in Weyl semimetal TaIrTe4. Our scanning tunneling microscopy/spectroscopy (STM/STS) visualizes Fermi arc surface states of TaIrTe4 that are consistent with the previous angle-resolved photoemission spectroscopy results. By a systematic study based on STS at ultralow temperature, we observe uniform superconducting gaps on the sample surface. The superconductivity is further confirmed by electrical transport measurements at ultralow temperature, with an onset transition temperature (T c) up to 1.54 K being observed. The normalized upper critical field h*(T/T c) behavior and the stability of the superconductivity against the ferromagnet indicate that the discovered superconductivity is unconventional with the p-wave pairing. The systematic STS, and thickness- and angular-dependent transport measurements reveal that the detected superconductivity is quasi-1D and occurs in the surface states. The discovery of the surface superconductivity in TaIrTe4 provides a new novel platform to explore topological superconductivity and Majorana modes.
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Affiliation(s)
- Ying Xing
- Department of Materials Science and Engineering, College of New Energy and Materials, China University of Petroleum, Beijing 102249, China
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Zhibin Shao
- School of Physics and Information Technology, Shaanxi Normal University, Xi’an 710119, China
| | - Jun Ge
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Jiawei Luo
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Jinhua Wang
- School of Physics, Huazhong University of Science and Technology, Wuhan 430074, China
- Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Zengwei Zhu
- School of Physics, Huazhong University of Science and Technology, Wuhan 430074, China
- Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Jun Liu
- Center of Electron Microscopy, State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, China
| | - Yong Wang
- Center of Electron Microscopy, State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, China
| | - Zhiying Zhao
- Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN 37996, USA
- Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996, USA
| | - Jiaqiang Yan
- Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN 37996, USA
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - David Mandrus
- Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN 37996, USA
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Binghai Yan
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Xiong-Jun Liu
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
- CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100190, China
- Beijing Academy of Quantum Information Sciences, Beijing 100193, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100871, China
| | - Minghu Pan
- School of Physics and Information Technology, Shaanxi Normal University, Xi’an 710119, China
- School of Physics, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Jian Wang
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
- CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100190, China
- Beijing Academy of Quantum Information Sciences, Beijing 100193, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100871, China
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7
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Deng Y, Lai Y, Zhao X, Wang X, Zhu C, Huang K, Zhu C, Zhou J, Zeng Q, Duan R, Fu Q, Kang L, Liu Y, Pennycook SJ, Wang XR, Liu Z. Controlled Growth of 3R Phase Tantalum Diselenide and Its Enhanced Superconductivity. J Am Chem Soc 2020; 142:2948-2955. [DOI: 10.1021/jacs.9b11673] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Ya Deng
- School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore
| | - Yuanming Lai
- School of Physical and Mathematical Sciences & School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798, Singapore
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, China
| | - Xiaoxu Zhao
- Department of Materials Science and Engineering, National University of Singapore, Singapore 117575, Singapore
| | - Xiaowei Wang
- School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore
| | - Chao Zhu
- School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore
| | - Ke Huang
- School of Physical and Mathematical Sciences & School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798, Singapore
| | - Chao Zhu
- School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore
| | - Jiadong Zhou
- School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore
| | - Qingsheng Zeng
- School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore
| | - Ruihuan Duan
- School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore
| | - Qundong Fu
- School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore
| | - Lixing Kang
- School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore
| | - Yang Liu
- School of Computer Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore
| | - Stephen J. Pennycook
- Department of Materials Science and Engineering, National University of Singapore, Singapore 117575, Singapore
| | - X. Renshaw Wang
- School of Physical and Mathematical Sciences & School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798, Singapore
| | - Zheng Liu
- School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore
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8
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Yuan QQ, Zhou L, Rao ZC, Tian S, Zhao WM, Xue CL, Liu Y, Zhang T, Tang CY, Shi ZQ, Jia ZY, Weng H, Ding H, Sun YJ, Lei H, Li SC. Quasiparticle interference evidence of the topological Fermi arc states in chiral fermionic semimetal CoSi. SCIENCE ADVANCES 2019; 5:eaaw9485. [PMID: 32064310 PMCID: PMC6989308 DOI: 10.1126/sciadv.aaw9485] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2019] [Accepted: 10/29/2019] [Indexed: 05/29/2023]
Abstract
Chiral fermions in solid state feature "Fermi arc" states, connecting the surface projections of the bulk chiral nodes. The surface Fermi arc is a signature of nontrivial bulk topology. Unconventional chiral fermions with an extensive Fermi arc traversing the whole Brillouin zone have been theoretically proposed in CoSi. Here, we use scanning tunneling microscopy/spectroscopy to investigate quasiparticle interference at various terminations of a CoSi single crystal. The observed surface states exhibit chiral fermion-originated characteristics. These reside on (001) and (011) but not (111) surfaces with p-rotation symmetry, spiral with energy, and disperse in a wide energy range from ~-200 to ~+400 mV. Owing to the high-energy and high-space resolution, a spin-orbit coupling-induced splitting of up to ~80 mV is identified. Our observations are corroborated by density functional theory and provide strong evidence that CoSi hosts the unconventional chiral fermions and the extensive Fermi arc states.
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Affiliation(s)
- Qian-Qian Yuan
- National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Liqin Zhou
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Zhi-Cheng Rao
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Shangjie Tian
- Department of Physics and Beijing Key Laboratory of Optoelectronic Functional Materials and Micro-Nano Devices, Renmin University of China, Beijing 100872, China
| | - Wei-Min Zhao
- National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Cheng-Long Xue
- National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Yixuan Liu
- Department of Physics and Beijing Key Laboratory of Optoelectronic Functional Materials and Micro-Nano Devices, Renmin University of China, Beijing 100872, China
| | - Tiantian Zhang
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Cen-Yao Tang
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Zhi-Qiang Shi
- National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Zhen-Yu Jia
- National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Hongming Weng
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100190, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China
| | - Hong Ding
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100190, China
| | - Yu-Jie Sun
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100190, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China
| | - Hechang Lei
- Department of Physics and Beijing Key Laboratory of Optoelectronic Functional Materials and Micro-Nano Devices, Renmin University of China, Beijing 100872, China
| | - Shao-Chun Li
- National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
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9
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Shi ZQ, Li H, Yuan QQ, Song YH, Lv YY, Shi W, Jia ZY, Gao L, Chen YB, Zhu W, Li SC. Van der Waals Heteroepitaxial Growth of Monolayer Sb in a Puckered Honeycomb Structure. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2019; 31:e1806130. [PMID: 30515884 DOI: 10.1002/adma.201806130] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2018] [Revised: 10/30/2018] [Indexed: 06/09/2023]
Abstract
Atomically thin 2D crystals have gained tremendous attention owing to their potential impact on future electronics technologies, as well as the exotic phenomena emerging in these materials. Monolayers of α-phase Sb (α-antimonene), which shares the same puckered structure as black phosphorous, are predicted to be stable with precious properties. However, the experimental realization still remains challenging. Here, high-quality monolayerα-antimonene is successfully grown, with the thickness finely controlled. The α-antimonene exhibits great stability upon exposure to air. Combining scanning tunneling microscopy, density functional theory calculations, and transport measurements, it is found that the electron band crossing the Fermi level exhibits a linear dispersion with a fairly small effective mass, and thus a good electrical conductivity. All of these properties make the α-antimonene promising for future electronic applications.
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Affiliation(s)
- Zhi-Qiang Shi
- National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing, 210093, China
| | - Huiping Li
- International Center for Quantum Design of Functional Materials (ICQD), Hefei National Laboratory for Physical Sciences at the Microscale, and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui, 230026, China
- Key Laboratory of Strongly-Coupled Quantum Matter Physics, Chinese Academy of Sciences, School of Physical Sciences, University of Science and Technology of China, Hefei, Anhui, 230026, China
| | - Qian-Qian Yuan
- National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing, 210093, China
| | - Ye-Heng Song
- National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing, 210093, China
| | - Yang-Yang Lv
- National Laboratory of Solid State Microstructures, Department of Materials Science and Engineering, Nanjing University, Nanjing, 210093, China
| | - Wei Shi
- National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing, 210093, China
| | - Zhen-Yu Jia
- National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing, 210093, China
| | - Libo Gao
- National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing, 210093, China
| | - Yan-Bin Chen
- National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing, 210093, China
| | - Wenguang Zhu
- International Center for Quantum Design of Functional Materials (ICQD), Hefei National Laboratory for Physical Sciences at the Microscale, and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui, 230026, China
- Key Laboratory of Strongly-Coupled Quantum Matter Physics, Chinese Academy of Sciences, School of Physical Sciences, University of Science and Technology of China, Hefei, Anhui, 230026, China
| | - Shao-Chun Li
- National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing, 210093, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
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10
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Zhu L, Li QY, Lv YY, Li S, Zhu XY, Jia ZY, Chen YB, Wen J, Li SC. Superconductivity in Potassium-Intercalated T d-WTe 2. NANO LETTERS 2018; 18:6585-6590. [PMID: 30226053 DOI: 10.1021/acs.nanolett.8b03180] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
To realize a topological superconductor is one of the most attracting topics because of its great potential in quantum computation. In this study, we successfully intercalate potassium (K) into the van der Waals gap of type II Weyl semimetal WTe2 and discover the superconducting state in K xWTe2 through both electrical transport and scanning tunneling spectroscopy measurements. The superconductivity exhibits an evident anisotropic behavior. Moreover, we also uncover the coexistence of superconductivity and the positive magnetoresistance state. Structural analysis substantiates the negligible lattice expansion induced by the intercalation, therefore suggesting K-intercalated WTe2 still hosts the topological nontrivial state. These results indicate that the K-intercalated WTe2 may be a promising candidate to explore the topological superconductor.
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Affiliation(s)
- Li Zhu
- National Laboratory of Solid State Microstructures, School of Physics , Nanjing University , Nanjing 210093 , China
| | - Qi-Yuan Li
- National Laboratory of Solid State Microstructures, School of Physics , Nanjing University , Nanjing 210093 , China
| | - Yang-Yang Lv
- National Laboratory of Solid State Microstructures, Department of Materials Science and Engineering , Nanjing University , Nanjing 210093 , China
| | - Shichao Li
- National Laboratory of Solid State Microstructures, School of Physics , Nanjing University , Nanjing 210093 , China
| | - Xin-Yang Zhu
- National Laboratory of Solid State Microstructures, School of Physics , Nanjing University , Nanjing 210093 , China
| | - Zhen-Yu Jia
- National Laboratory of Solid State Microstructures, School of Physics , Nanjing University , Nanjing 210093 , China
| | - Y B Chen
- National Laboratory of Solid State Microstructures, School of Physics , Nanjing University , Nanjing 210093 , China
- Collaborative Innovation Center of Advanced Microstructures , Nanjing University , Nanjing 210093 , China
| | - Jinsheng Wen
- National Laboratory of Solid State Microstructures, School of Physics , Nanjing University , Nanjing 210093 , China
- Collaborative Innovation Center of Advanced Microstructures , Nanjing University , Nanjing 210093 , China
| | - Shao-Chun Li
- National Laboratory of Solid State Microstructures, School of Physics , Nanjing University , Nanjing 210093 , China
- Collaborative Innovation Center of Advanced Microstructures , Nanjing University , Nanjing 210093 , China
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11
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Zhu Z, Chang TR, Huang CY, Pan H, Nie XA, Wang XZ, Jin ZT, Xu SY, Huang SM, Guan DD, Wang S, Li YY, Liu C, Qian D, Ku W, Song F, Lin H, Zheng H, Jia JF. Quasiparticle interference and nonsymmorphic effect on a floating band surface state of ZrSiSe. Nat Commun 2018; 9:4153. [PMID: 30297777 PMCID: PMC6175950 DOI: 10.1038/s41467-018-06661-9] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2018] [Accepted: 09/18/2018] [Indexed: 11/09/2022] Open
Abstract
Non-symmorphic crystals are generating great interest as they are commonly found in quantum materials, like iron-based superconductors, heavy-fermion compounds, and topological semimetals. A new type of surface state, a floating band, was recently discovered in the nodal-line semimetal ZrSiSe, but also exists in many non-symmorphic crystals. Little is known about its physical properties. Here, we employ scanning tunneling microscopy to measure the quasiparticle interference of the floating band state on ZrSiSe (001) surface and discover rotational symmetry breaking interference, healing effect and half-missing-type anomalous Umklapp scattering. Using simulation and theoretical analysis we establish that the phenomena are characteristic properties of a floating band surface state. Moreover, we uncover that the half-missing Umklapp process is derived from the glide mirror symmetry, thus identify a non-symmorphic effect on quasiparticle interferences. Our results may pave a way towards potential new applications of nanoelectronics.
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Affiliation(s)
- Zhen Zhu
- School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Tay-Rong Chang
- Department of Physics, National Cheng Kung University, Tainan, 701, Taiwan
| | - Cheng-Yi Huang
- Institute of Physics, Academia Sinica, Taipei City, 11529, Taiwan
| | - Haiyang Pan
- College of Physics, Nanjing University, Nanjing, 210093, China
| | - Xiao-Ang Nie
- School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Xin-Zhe Wang
- School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Zhe-Ting Jin
- School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Su-Yang Xu
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Shin-Ming Huang
- Department of Physics, National Sun Yat-Sen University, Kaohsiung, 80424, Taiwan
| | - Dan-Dan Guan
- School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, 200240, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
| | - Shiyong Wang
- School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, 200240, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
| | - Yao-Yi Li
- School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, 200240, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
| | - Canhua Liu
- School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, 200240, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
| | - Dong Qian
- School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, 200240, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
| | - Wei Ku
- School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, 200240, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
| | - Fengqi Song
- College of Physics, Nanjing University, Nanjing, 210093, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
| | - Hsin Lin
- Institute of Physics, Academia Sinica, Taipei City, 11529, Taiwan
| | - Hao Zheng
- School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, 200240, China.
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China.
| | - Jin-Feng Jia
- School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, 200240, China.
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China.
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12
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Li Y, Gu Q, Chen C, Zhang J, Liu Q, Hu X, Liu J, Liu Y, Ling L, Tian M, Wang Y, Samarth N, Li S, Zhang T, Feng J, Wang J. Nontrivial superconductivity in topological MoTe 2-x S x crystals. Proc Natl Acad Sci U S A 2018; 115:9503-9508. [PMID: 30166451 PMCID: PMC6156667 DOI: 10.1073/pnas.1801650115] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Topological Weyl semimetals (TWSs) with pairs of Weyl points and topologically protected Fermi arc states have broadened the classification of topological phases and provide superior platform for study of topological superconductivity. Here we report the nontrivial superconductivity and topological features of sulfur-doped Td -phase MoTe2 with enhanced Tc compared with type-II TWS MoTe2 It is found that Td -phase S-doped MoTe2 (MoTe2-x S x , x ∼ 0.2) is a two-band s-wave bulk superconductor (∼0.13 meV and 0.26 meV), where the superconducting behavior can be explained by the s+- pairing model. Further, measurements of the quasi-particle interference (QPI) patterns and a comparison with band-structure calculations reveal the existence of Fermi arcs in MoTe2-x S x More interestingly, a relatively large superconducting gap (∼1.7 meV) is detected by scanning tunneling spectroscopy on the sample surface, showing a hint of topological nontrivial superconductivity based on the pairing of Fermi arc surface states. Our work demonstrates that the Td -phase MoTe2-x S x is not only a promising topological superconductor candidate but also a unique material for study of s+- superconductivity.
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Affiliation(s)
- Yanan Li
- International Center for Quantum Materials, School of Physics, Peking University, 100871 Beijing, China
- Collaborative Innovation Center of Quantum Matter, 100871 Beijing, China
- Department of Physics, Pennsylvania State University, University Park, PA 16802
| | - Qiangqiang Gu
- International Center for Quantum Materials, School of Physics, Peking University, 100871 Beijing, China
- Collaborative Innovation Center of Quantum Matter, 100871 Beijing, China
| | - Chen Chen
- Department of Physics, State Key Laboratory of Surface Physics, Fudan University, 200433 Shanghai, China
- Laboratory of Advanced Materials, Fudan University, 200433 Shanghai, China
| | - Jun Zhang
- Department of Physics, State Key Laboratory of Surface Physics, Fudan University, 200433 Shanghai, China
- Laboratory of Advanced Materials, Fudan University, 200433 Shanghai, China
| | - Qin Liu
- Department of Physics, State Key Laboratory of Surface Physics, Fudan University, 200433 Shanghai, China
- Laboratory of Advanced Materials, Fudan University, 200433 Shanghai, China
- Science and Technology on Surface Physics and Chemistry Laboratory, 621908 Mianyang, China
| | - Xiyao Hu
- International Center for Quantum Materials, School of Physics, Peking University, 100871 Beijing, China
| | - Jun Liu
- High Magnetic Field Laboratory, Chinese Academy of Sciences, 230031 Hefei, Anhui, China
| | - Yi Liu
- International Center for Quantum Materials, School of Physics, Peking University, 100871 Beijing, China
- Collaborative Innovation Center of Quantum Matter, 100871 Beijing, China
| | - Langsheng Ling
- High Magnetic Field Laboratory, Chinese Academy of Sciences, 230031 Hefei, Anhui, China
| | - Mingliang Tian
- High Magnetic Field Laboratory, Chinese Academy of Sciences, 230031 Hefei, Anhui, China
| | - Yong Wang
- Department of Materials Science and Engineering, State Key Laboratory of Silicon Materials, Center of Electron Microscopy, Zhejiang University, 310027 Hangzhou, China
| | - Nitin Samarth
- Department of Physics, Pennsylvania State University, University Park, PA 16802
| | - Shiyan Li
- Department of Physics, State Key Laboratory of Surface Physics, Fudan University, 200433 Shanghai, China
- Laboratory of Advanced Materials, Fudan University, 200433 Shanghai, China
- Collaborative Innovation Center of Advanced Microstructures, 210093 Nanjing, China
| | - Tong Zhang
- Department of Physics, State Key Laboratory of Surface Physics, Fudan University, 200433 Shanghai, China;
- Laboratory of Advanced Materials, Fudan University, 200433 Shanghai, China
- Collaborative Innovation Center of Advanced Microstructures, 210093 Nanjing, China
| | - Ji Feng
- International Center for Quantum Materials, School of Physics, Peking University, 100871 Beijing, China;
- Collaborative Innovation Center of Quantum Matter, 100871 Beijing, China
- Chinese Academy of Science Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, 100190 Beijing, China
| | - Jian Wang
- International Center for Quantum Materials, School of Physics, Peking University, 100871 Beijing, China;
- Collaborative Innovation Center of Quantum Matter, 100871 Beijing, China
- Chinese Academy of Science Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, 100190 Beijing, China
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13
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Qin C, Liu Q, Wang B, Lu P. Photonic Weyl phase transition in dynamically modulated brick-wall waveguide arrays. OPTICS EXPRESS 2018; 26:20929-20943. [PMID: 30119400 DOI: 10.1364/oe.26.020929] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Accepted: 07/23/2018] [Indexed: 06/08/2023]
Abstract
We investigate the topological phase transition between Type-I and Type-II Weyl points (WPs) in a composite three-dimensional lattice composed of a two-dimensional brick-wall waveguide array and a synthetic frequency dimension created by dynamic modulation. By imposing different modulation amplitudes and phases in the two sublattices, we can break either parity or time-reversal symmetry and realize the phase transition between Type-I and Type-II WPs. As the array is truncated to have two edges, two Fermi-arc surface states will emerge, which propagate in opposite directions for Type-I WPs while in same directions for Type-II WPs, accompanied by bidirectional and unidirectional frequency shifts for the optical modes. Particularly at the phase transition point, we find that one of two bands becomes flat with a vanished group velocity along frequency axis in the vicinity of WPs. The study paves a way towards realizing different topological phases in the same photonic structure, which offers new opportunities to control wave transportation both in spatial and frequency domains.
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14
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Lin CL, Arafune R, Minamitani E, Kawai M, Takagi N. Quasiparticle scattering in type-II Weyl semimetal MoTe 2. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:105703. [PMID: 29447120 DOI: 10.1088/1361-648x/aaab95] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The electronic structure of type-II Weyl semimetal molybdenum ditelluride (MoTe2) is studied by using scanning tunneling microscopy and density functional theory calculations. Through measuring energy-dependent quasiparticle interference (QPI) patterns with a cryogenic scanning tunneling microscope, several characteristic features are found in the QPI patterns. Two of them arise from the Weyl semimetal nature; one is the topological Fermi arc surface state and the other can be assigned to be a Weyl point. The remaining structures are derived from the scatterings relevant to the bulk electronic states. The findings lead to further understanding of the topological electronic structure of type-II Weyl semimetal MoTe2.
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Affiliation(s)
- Chun-Liang Lin
- Department of Advanced Materials Science, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561, Japan
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15
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Lin CL, Arafune R, Liu RY, Yoshimura M, Feng B, Kawahara K, Ni Z, Minamitani E, Watanabe S, Shi Y, Kawai M, Chiang TC, Matsuda I, Takagi N. Visualizing Type-II Weyl Points in Tungsten Ditelluride by Quasiparticle Interference. ACS NANO 2017; 11:11459-11465. [PMID: 29061038 DOI: 10.1021/acsnano.7b06179] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Weyl semimetals (WSMs) are classified into two types, type I and II, according to the topology of the Weyl point, where the electron and hole pockets touch each other. Tungsten ditelluride (WTe2) has garnered a great deal of attention as a strong candidate to be a type-II WSM. However, the Weyl points for WTe2 are located above the Fermi level, which has prevented us from identifying the locations and the connection to the Fermi arc surface states by using angle-resolved photoemission spectroscopy. Here, we present experimental proof that WTe2 is a type-II WSM. We measured energy-dependent quasiparticle interference patterns with a cryogenic scanning tunneling microscope, revealing the position of the Weyl point and its connection with the Fermi arc surface states, in agreement with prior theoretical predictions. Our results provide an answer to this crucial question and stimulate further exploration of the characteristics of WSMs.
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Affiliation(s)
- Chun-Liang Lin
- Department of Advanced Materials Science, The University of Tokyo , 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561, Japan
| | - Ryuichi Arafune
- International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science , 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
| | - Ro-Ya Liu
- Institute for Solid State Physics, The University of Tokyo , 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561, Japan
| | - Masato Yoshimura
- Department of Advanced Materials Science, The University of Tokyo , 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561, Japan
| | - Baojie Feng
- Institute for Solid State Physics, The University of Tokyo , 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561, Japan
| | - Kazuaki Kawahara
- Department of Advanced Materials Science, The University of Tokyo , 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561, Japan
| | - Zeyuan Ni
- Department of Materials Engineering, The University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Emi Minamitani
- Department of Materials Engineering, The University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Satoshi Watanabe
- Department of Materials Engineering, The University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Youguo Shi
- Institute of Physics, Chinese Academy of Sciences , Beijing 100190, China
| | - Maki Kawai
- Department of Advanced Materials Science, The University of Tokyo , 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561, Japan
| | - Tai-Chang Chiang
- Department of Physics, University of Illinois , Urbana, Illinois 61801, United States
| | - Iwao Matsuda
- Institute for Solid State Physics, The University of Tokyo , 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561, Japan
| | - Noriaki Takagi
- Department of Advanced Materials Science, The University of Tokyo , 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561, Japan
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16
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Zheng H, Chang G, Huang SM, Guo C, Zhang X, Zhang S, Yin J, Xu SY, Belopolski I, Alidoust N, Sanchez DS, Bian G, Chang TR, Neupert T, Jeng HT, Jia S, Lin H, Hasan MZ. Mirror Protected Dirac Fermions on a Weyl Semimetal NbP Surface. PHYSICAL REVIEW LETTERS 2017; 119:196403. [PMID: 29219493 DOI: 10.1103/physrevlett.119.196403] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Indexed: 06/07/2023]
Abstract
The first Weyl semimetal was recently discovered in the NbP class of compounds. Although the topology of these novel materials has been identified, the surface properties are not yet fully understood. By means of scanning tunneling spectroscopy, we find that NbP's (001) surface hosts a pair of Dirac cones protected by mirror symmetry. Through our high-resolution spectroscopic measurements, we resolve the quantum interference patterns arising from these novel Dirac fermions and reveal their electronic structure, including the linear dispersions. Our data, in agreement with our theoretical calculations, uncover further interesting features of the Weyl semimetal NbP's already exotic surface. Moreover, we discuss the similarities and distinctions between the Dirac fermions here and those in topological crystalline insulators in terms of symmetry protection and topology.
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Affiliation(s)
- Hao Zheng
- Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
| | - Guoqing Chang
- Centre for Advanced 2D Materials and Graphene Research Centre National University of Singapore, 6 Science Drive 2, Singapore 117546, Singapore
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542, Singapore
| | - Shin-Ming Huang
- Department of Physics, National Sun Yat-sen University, Kaohsiung 80424, Taiwan
| | - Cheng Guo
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Xiao Zhang
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Songtian Zhang
- Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
| | - Jiaxin Yin
- Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
| | - Su-Yang Xu
- Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
| | - Ilya Belopolski
- Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
| | - Nasser Alidoust
- Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
| | - Daniel S Sanchez
- Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
| | - Guang Bian
- Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
| | - Tay-Rong Chang
- Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Titus Neupert
- Department of Physics, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Horng-Tay Jeng
- Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Shuang Jia
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100871, China
| | - Hsin Lin
- Centre for Advanced 2D Materials and Graphene Research Centre National University of Singapore, 6 Science Drive 2, Singapore 117546, Singapore
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542, Singapore
| | - M Zahid Hasan
- Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
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17
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Mukherjee SP, Carbotte JP. Optical response in Weyl semimetal in model with gapped Dirac phase. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:425301. [PMID: 28749377 DOI: 10.1088/1361-648x/aa82a7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We study the optical properties of Weyl semimetal (WSM) in a model which features, in addition to the usual term describing isolated Dirac cones proportional to the Fermi velocity v F, a gap term m and a Zeeman spin-splitting term b with broken time reversal symmetry. Transport is treated within Kubo formalism and particular attention is payed to the modifications that result from a finite m and b. We consider how these modifications change when a finite residual scattering rate [Formula: see text] is included. For [Formula: see text] the A.C. conductivity as a function of photon energy [Formula: see text] continues to display the two quasilinear energy regions of the clean limit for [Formula: see text] below the onset of the second electronic band which is gapped at ([Formula: see text]). For [Formula: see text] of the order m little trace of two distinct linear energy scales remain and the optical response has evolved towards that for [Formula: see text]. Although some quantitative differences remain there are no qualitative differences. The magnitude of the D.C. conductivity [Formula: see text] at zero temperature ([Formula: see text]) and chemical potential ([Formula: see text]) is altered. While it remains proportional to [Formula: see text] it becomes inversely dependent on an effective Fermi velocity out of the Weyl nodes equal to [Formula: see text] which decreases strongly as the phase boundary between Weyl semimetal and gapped Dirac phase (GDSM) is approached at [Formula: see text]. The leading term in the approach to [Formula: see text] for finite [Formula: see text], [Formula: see text] and [Formula: see text] is found to be quadratic. The coefficient of these corrections tracks closely the [Formula: see text] dependence of the [Formula: see text] limit with differences largest near to the WSM-GDSM boundary.
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Affiliation(s)
- S P Mukherjee
- Department of Physics and Astronomy, McMaster University, Hamiltion, Ontario, L8S 4M1, Canada
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18
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Signatures of the topological s +- superconducting order parameter in the type-II Weyl semimetal T d-MoTe 2. Nat Commun 2017; 8:1082. [PMID: 29057874 PMCID: PMC5651900 DOI: 10.1038/s41467-017-01066-6] [Citation(s) in RCA: 79] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2017] [Accepted: 08/13/2017] [Indexed: 11/08/2022] Open
Abstract
In its orthorhombic Td polymorph, MoTe2 is a type-II Weyl semimetal, where the Weyl fermions emerge at the boundary between electron and hole pockets. Non-saturating magnetoresistance and superconductivity were also observed in Td-MoTe2. Understanding the superconductivity in Td-MoTe2, which was proposed to be topologically non-trivial, is of eminent interest. Here, we report high-pressure muon-spin rotation experiments probing the temperature-dependent magnetic penetration depth in Td-MoTe2. A substantial increase of the superfluid density and a linear scaling with the superconducting critical temperature Tc is observed under pressure. Moreover, the superconducting order parameter in Td-MoTe2 is determined to have 2-gap s-wave symmetry. We also exclude time-reversal symmetry breaking in the superconducting state with zero-field μSR experiments. Considering the strong suppression of Tc in MoTe2 by disorder, we suggest that topologically non-trivial s+− state is more likely to be realized in MoTe2 than the topologically trivial s++ state. Understanding the superconductivity in topological materials is of eminent interest. Here, Guguchia et al. report temperature-dependent magnetic penetration depth in the superconducting state of Td-MoTe2 under pressure, suggesting a topologically nontrivial s+− order parameter.
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19
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Zhan L, Wan W, Zhu Z, Zhao Z, Zhang Z, Shih TM, Cai W. A visualization method for probing grain boundaries of single layer graphene via molecular beam epitaxy. NANOTECHNOLOGY 2017; 28:305601. [PMID: 28590942 DOI: 10.1088/1361-6528/aa77ec] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Graphene, a member of layered two-dimensional (2D) materials, possesses high carrier mobility, mechanical flexibility, and optical transparency, as well as enjoying a wide range of promising applications in electronics. Adopting the chemical vaporization deposition method, the majority of investigators have ubiquitously grown single layer graphene (SLG), which inevitably involves polycrystalline properties. Here we demonstrate a simple method for the direct visualization of arbitrarily large-size SLG domains by synthesizing one-hundred-nm-scale MoS2 single crystals via a high-vacuum molecular beam epitaxy process. The present study based on epitaxial growth provides a guide for probing the grain boundaries of various 2D materials and implements higher potentials for the next-generation electronic devices.
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Affiliation(s)
- Linjie Zhan
- Department of Physics, State Key Laboratory of Physical Chemistry of Solid Surfaces, Xiamen University, 361005, People's Republic of China
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20
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Chen J, Wang G, Tang Y, Tian H, Xu J, Dai X, Xu H, Jia J, Ho W, Xie M. Quantum Effects and Phase Tuning in Epitaxial Hexagonal and Monoclinic MoTe 2 Monolayers. ACS NANO 2017; 11:3282-3288. [PMID: 28225590 DOI: 10.1021/acsnano.7b00556] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Monolayer (ML) transition-metal dichalcogenides exist in different phases, such as hexagonal (2H) and monoclinic (1T') structures. They show very different properties: semiconducting for 2H-MoTe2 and semimetallic for 1T'-MoTe2. The formation energy difference between 2H- and 1T'-phase MoTe2 is small, so there is a high chance of tuning the structures of MoTe2 and thereby introducing applications of phase-change electronics. In this paper, we report the growth of both 2H- and 1T'-MoTe2 MLs by molecular-beam epitaxy (MBE) and demonstrate its tenability by changing the conditions of MBE. We attribute the latter to an effect of Te adsorption. By scanning tunneling microscopy and spectroscopy, we reveal not only the atomic structures and intrinsic electronic properties of the two phases of MoTe2 but also quantum confinement and quantum interference effects in the 2H- and 1T'-MoTe2 domains, respectively, as effected by domain boundaries in the samples.
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Affiliation(s)
- Jinglei Chen
- Physics Department, The University of Hong Kong , Pokfulam Road, Hong Kong, China
| | - Guanyong Wang
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Department of Physics and Astronomy, Shanghai Jiaotong University , 800 Dongchuan Road, Shanghai 200240, China
- Innovation Center of Advanced Microstructures , Nanjing 210023, China
| | - Yanan Tang
- College of Physics and Electronic Engineering, Henan Normal University , Xinxiang, Henan 453007, China
- School of Physics and Electronic Engineering, Zhengzhou Normal University , Zhengzhou, Henan 450044, China
| | - Hao Tian
- Physics Department, The University of Hong Kong , Pokfulam Road, Hong Kong, China
- Physics Department, South University of Science and Technology of China , Shenzhen 518055, China
| | - Jinpeng Xu
- Physics Department, The University of Hong Kong , Pokfulam Road, Hong Kong, China
| | - Xianqi Dai
- College of Physics and Electronic Engineering, Henan Normal University , Xinxiang, Henan 453007, China
- School of Physics and Electronic Engineering, Zhengzhou Normal University , Zhengzhou, Henan 450044, China
| | - Hu Xu
- Physics Department, South University of Science and Technology of China , Shenzhen 518055, China
| | - Jinfeng Jia
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Department of Physics and Astronomy, Shanghai Jiaotong University , 800 Dongchuan Road, Shanghai 200240, China
- Innovation Center of Advanced Microstructures , Nanjing 210023, China
| | - Wingkin Ho
- Physics Department, The University of Hong Kong , Pokfulam Road, Hong Kong, China
| | - Maohai Xie
- Physics Department, The University of Hong Kong , Pokfulam Road, Hong Kong, China
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