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Wu M, Weng M, Chi Z, Qi Y, Li H, Zhao Q, Meng Y, Zhou J. Observing Relative Homotopic Degeneracy Conversions with Circuit Metamaterials. PHYSICAL REVIEW LETTERS 2024; 132:016605. [PMID: 38242672 DOI: 10.1103/physrevlett.132.016605] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2023] [Accepted: 12/04/2023] [Indexed: 01/21/2024]
Abstract
Making nodal lines (NLs) deterministic is quite challenging because directly probing them requires bulk momentum resolution. Here, based on the general scattering theory, we show that the Bloch modes of the circuit metamaterials can be selectively excited with a proper source. Consequently, the transport measurement for characterizing the circuit band structure is momentum resolved. Facilitated by this bulk resolution, we systematically demonstrate the degeneracy conversions ruled by the relative homotopy, including the conversions between Weyl points (WPs) and NLs, and between NLs. It is experimentally shown that two WPs with opposite chirality in a two-band model surprisingly convert into an NL rather than annihilating. And the multiband anomaly (due to the delicate property) in the NL-to-NL conversions is also observed, which in fact is captured by the non-Abelian relative homotopy. Additionally, the physical effects owing to the conversions, like the Fermi arc connecting NLs and the parallel transport of eigenstates, are discussed as well. Other types of degeneracy conversions, such as those induced by spin-orbit coupling or symmetry breaking, are directly amenable to the proposed circuit platform.
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Affiliation(s)
- Maopeng Wu
- State Key Laboratory of Tribology in Advanced Equipment, Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China
| | - Mingze Weng
- State Key Laboratory of Tribology in Advanced Equipment, Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China
| | - Zhonghai Chi
- State Key Laboratory of Tribology in Advanced Equipment, Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China
| | - Yingyi Qi
- State Key Laboratory of Tribology in Advanced Equipment, Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China
| | - Hui Li
- State Key Laboratory of Tribology in Advanced Equipment, Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China
| | - Qian Zhao
- State Key Laboratory of Tribology in Advanced Equipment, Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China
| | - Yonggang Meng
- State Key Laboratory of Tribology in Advanced Equipment, Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China
| | - Ji Zhou
- State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China
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2
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Zhang K, Chen M, Wang D, Lv H, Wu X, Yang J. Nodal-loop half metallicity in a two-dimensional Fe 4N 2 pentagon crystal with room-temperature ferromagnetism. NANOSCALE 2021; 13:19493-19499. [PMID: 34796890 DOI: 10.1039/d1nr06033c] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Two-dimensional (2D) materials with fully spin-polarized nodal-loop band crossing are a class of topological magnetic materials, holding promise for high-speed low-dissipation spintronic devices. Recently, several 2D nodal-loop materials have been reported in theory and experiment, such as Cu2Si, Be2C, CuSe, and Cr2S3 monolayers, adopting triangular, tetragonal, hexagonal, or complex lattices. However, a 2D nodal-loop half metal with room-temperature magnetism is still less reported. Here, we report that the 2D Fe4N2 pentagon crystal is a nodal-loop half metal with room-temperature magnetism over 428 K and a global minimum structure via first-principles calculations and global structure search. The Dirac nodal lines in Fe4N2 form a flat nodal loop at the Fermi level and a spin-polarized type-II nodal-loop above the Fermi level, which are protected by mirror symmetry. Our results establish Fe4N2 as a platform to obtain nodal-loop half metallicity in the 2D pentagon lattice and provide opportunities to build high-speed low-dissipation spintronics in the nanoscale.
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Affiliation(s)
- Kai Zhang
- School of Chemistry and Materials Sciences, CAS Key Laboratory of Materials for Energy Conversion, Synergetic Innovation of Quantum Information & Quantum Technology, and CAS Center for Excellence in Nanoscience, University of Science and Technology of China, Hefei, Anhui 230026, China.
- Hefei National Laboratory of Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Minglong Chen
- School of Chemistry and Materials Sciences, CAS Key Laboratory of Materials for Energy Conversion, Synergetic Innovation of Quantum Information & Quantum Technology, and CAS Center for Excellence in Nanoscience, University of Science and Technology of China, Hefei, Anhui 230026, China.
| | - Dayong Wang
- School of Chemistry and Materials Sciences, CAS Key Laboratory of Materials for Energy Conversion, Synergetic Innovation of Quantum Information & Quantum Technology, and CAS Center for Excellence in Nanoscience, University of Science and Technology of China, Hefei, Anhui 230026, China.
| | - Haifeng Lv
- School of Chemistry and Materials Sciences, CAS Key Laboratory of Materials for Energy Conversion, Synergetic Innovation of Quantum Information & Quantum Technology, and CAS Center for Excellence in Nanoscience, University of Science and Technology of China, Hefei, Anhui 230026, China.
- Hefei National Laboratory of Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Xiaojun Wu
- School of Chemistry and Materials Sciences, CAS Key Laboratory of Materials for Energy Conversion, Synergetic Innovation of Quantum Information & Quantum Technology, and CAS Center for Excellence in Nanoscience, University of Science and Technology of China, Hefei, Anhui 230026, China.
- Hefei National Laboratory of Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Jinlong Yang
- School of Chemistry and Materials Sciences, CAS Key Laboratory of Materials for Energy Conversion, Synergetic Innovation of Quantum Information & Quantum Technology, and CAS Center for Excellence in Nanoscience, University of Science and Technology of China, Hefei, Anhui 230026, China.
- Hefei National Laboratory of Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026, China
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3
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Wang D, Yang B, Guo Q, Zhang RY, Xia L, Su X, Chen WJ, Han J, Zhang S, Chan CT. Intrinsic in-plane nodal chain and generalized quaternion charge protected nodal link in photonics. LIGHT, SCIENCE & APPLICATIONS 2021; 10:83. [PMID: 33859166 PMCID: PMC8050084 DOI: 10.1038/s41377-021-00523-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Revised: 03/15/2021] [Accepted: 03/30/2021] [Indexed: 05/31/2023]
Abstract
Nodal lines are degeneracies formed by crossing bands in three-dimensional momentum space. Interestingly, these degenerate lines can chain together via touching points and manifest as nodal chains. These nodal chains are usually embedded in two orthogonal planes and protected by the corresponding mirror symmetries. Here, we propose and demonstrate an in-plane nodal chain in photonics, where all chained nodal lines coexist in a single mirror plane instead of two orthogonal ones. The chain point is stabilized by the intrinsic symmetry that is specific to electromagnetic waves at the Г point of zero frequency. By adding another mirror plane, we find a nodal ring that is constructed by two higher bands and links with the in-plane nodal chain. The nodal link in momentum space exhibits non-Abelian characteristics on a C2T - invariant plane, where admissible transitions of the nodal link structure are determined by generalized quaternion charges. Through near-field scanning measurements of bi-anisotropic metamaterials, we experimentally mapped out the in-plane nodal chain and nodal link in such systems.
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Affiliation(s)
- Dongyang Wang
- Department of Physics, Hong Kong University of Science and Technology, Hong Kong, China
| | - Biao Yang
- Department of Physics, Hong Kong University of Science and Technology, Hong Kong, China
- College of Advanced Interdisciplinary Studies, National University of Defense Technology, Changsha, China
| | - Qinghua Guo
- Department of Physics, Hong Kong University of Science and Technology, Hong Kong, China
- Institute for Advanced Study, Hong Kong University of Science and Technology, Hong Kong, China
| | - Ruo-Yang Zhang
- Department of Physics, Hong Kong University of Science and Technology, Hong Kong, China
| | - Lingbo Xia
- Key Laboratory for Micro-Nano Optoelectronic Devices of Ministry of Education, School of Physics and Electronics, Hunan University, Changsha, China
| | - Xiaoqiang Su
- Institute of Solid State Physics and Department of Physics, Shanxi Datong University, Datong, China
| | - Wen-Jie Chen
- School of Physics & State Key Laboratory of Optoelectronic Materials and Technologies, Sun Yat-Sen University, Guangzhou, China
| | - Jiaguang Han
- Center for Terahertz Waves and College of Precision Instrument and Optoelectronics Engineering, Tianjin University and the Key Laboratory of Optoelectronics Information and Technology (Ministry of Education), Tianjin, China.
| | - Shuang Zhang
- School of Physics & Astronomy, University of Birmingham, Birmingham, UK.
| | - C T Chan
- Department of Physics, Hong Kong University of Science and Technology, Hong Kong, China.
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4
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Yang E, Yang B, You O, Chan HC, Mao P, Guo Q, Ma S, Xia L, Fan D, Xiang Y, Zhang S. Observation of Non-Abelian Nodal Links in Photonics. PHYSICAL REVIEW LETTERS 2020; 125:033901. [PMID: 32745405 DOI: 10.1103/physrevlett.125.033901] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2019] [Accepted: 06/19/2020] [Indexed: 06/11/2023]
Abstract
In crystals, two bands may cross each other and form degeneracies along a closed loop in the three-dimensional momentum space, which is called nodal line. Nodal line degeneracy can be designed to exhibit various configurations such as nodal rings, chains, links, and knots. Very recently, non-Abelian band topology was proposed in nodal link systems, where the nodal lines formed by consecutive pairs of bands exhibit interesting braiding structures and the underlying topological charges are described by quaternions. Here, we experimentally demonstrate non-Abelian nodal links in a biaxial hyperbolic metamaterial. The linked nodal lines threading through each other are formed by the crossings between three adjacent bands. Based on the non-Abelian charges, we further analyze various admissible nodal link configurations for the three-band system. On the interface between the metamaterial and air, surface bound states in the continuum are observed, which serves as the symmetry-enforced derivative of drumhead surface states from the linked nodal lines. Our work serves as a direct observation of the global topological structures of nodal links, and provides a platform for studying non-Abelian topological charge in the momentum space.
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Affiliation(s)
- Erchan Yang
- International Collaborative Laboratory of 2D Materials for Optoelectronic Science & Technology of Ministry of Education, Institute of Microscale Optoelectronics (IMO), Shenzhen University, Shenzhen 518060, China
- School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - Biao Yang
- College of Advanced Interdisciplinary Studies, National University of Defense Technology, Changsha 410073, China
| | - Oubo You
- International Collaborative Laboratory of 2D Materials for Optoelectronic Science & Technology of Ministry of Education, Institute of Microscale Optoelectronics (IMO), Shenzhen University, Shenzhen 518060, China
- School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - Hsun-Chi Chan
- International Collaborative Laboratory of 2D Materials for Optoelectronic Science & Technology of Ministry of Education, Institute of Microscale Optoelectronics (IMO), Shenzhen University, Shenzhen 518060, China
- School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - Peng Mao
- School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - Qinghua Guo
- Department of Physics and Institute for Advanced Study, The Hong Kong University of Science and Technology, Hong Kong, China
| | - Shaojie Ma
- International Collaborative Laboratory of 2D Materials for Optoelectronic Science & Technology of Ministry of Education, Institute of Microscale Optoelectronics (IMO), Shenzhen University, Shenzhen 518060, China
- School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - Lingbo Xia
- School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - Dianyuan Fan
- International Collaborative Laboratory of 2D Materials for Optoelectronic Science & Technology of Ministry of Education, Institute of Microscale Optoelectronics (IMO), Shenzhen University, Shenzhen 518060, China
| | - Yuanjiang Xiang
- School of Physics and Electronics, Hunan University, Changsha 410082, China
| | - Shuang Zhang
- School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, United Kingdom
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5
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Yang Z, Chiu CK, Fang C, Hu J. Jones Polynomial and Knot Transitions in Hermitian and non-Hermitian Topological Semimetals. PHYSICAL REVIEW LETTERS 2020; 124:186402. [PMID: 32441967 DOI: 10.1103/physrevlett.124.186402] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Revised: 03/18/2020] [Accepted: 03/20/2020] [Indexed: 06/11/2023]
Abstract
Topological nodal line semimetals host stable chained, linked, or knotted line degeneracies in momentum space protected by symmetries. In this Letter, we use the Jones polynomial as a general topological invariant to capture the global knot topology of the oriented nodal lines. We show that every possible change in Jones polynomial is attributed to the local evolutions around every point where two nodal lines touch. As an application of our theory, we show that nodal chain semimetals with four touching points can evolve to a Hopf link. We extend our theory to 3D non-Hermitian multiband exceptional line semimetals. Our work provides a recipe to understand the transition of the knot topology for protected nodal lines.
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Affiliation(s)
- Zhesen Yang
- 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
| | - Ching-Kai Chiu
- Kavli Institute for Theoretical Sciences and CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100190, China
| | - Chen Fang
- Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Jiangping Hu
- Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- Kavli Institute for Theoretical Sciences and CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100190, China
- South Bay Interdisciplinary Science Center, Dongguan, Guangdong Province, China
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6
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Zhou J, Xie Y, Zhang S, Chen Y. Critical topological nodal points and nodal lines/rings in Kagome graphene. Phys Chem Chem Phys 2020; 22:8713-8718. [PMID: 32270831 DOI: 10.1039/d0cp00190b] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Critical topological phases, possessing flat bands, provide a platform to study unique topological properties and transport phenomena under a many-body effect. Here, we propose that critical nodal points and nodal lines or rings can be found in Kagome lattices. After the C3 rotation symmetry of a single-layer Kagome lattice is eliminated, a quadratic nodal point splits into two critical nodal points. When the layered Kagome lattices are stacked into a three-dimensional (3D) structure, critical nodal lines or rings can be generated by tuning the interlayer coupling. Furthermore, we use Kagome graphene as an example to identify that these critical phases could be obtained in real materials. We also discuss flat-band-induced ferromagnetism. It is found that the flat band splits into two spin-polarized bands by hole-doping, and as a result the Dirac-type critical phases evolve into Weyl-type phases.
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Affiliation(s)
- Jun Zhou
- School of Physics and Optoelectronics, Xiangtan University, Xiangtan, 411105, Hunan, China and Faculty of Science, Jiangsu University, Zhenjiang, 212013, Jiangsu, China.
| | - Yuee Xie
- School of Physics and Optoelectronics, Xiangtan University, Xiangtan, 411105, Hunan, China and Faculty of Science, Jiangsu University, Zhenjiang, 212013, Jiangsu, China.
| | - Shengbai Zhang
- Department of Physics, Applied Physics, and Astronomy Rensselaer Polytechnic Institute, Troy, New York 12180, USA
| | - Yuanping Chen
- School of Physics and Optoelectronics, Xiangtan University, Xiangtan, 411105, Hunan, China and Faculty of Science, Jiangsu University, Zhenjiang, 212013, Jiangsu, China.
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7
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Zhang RW, Zhang Z, Liu CC, Yao Y. Nodal Line Spin-Gapless Semimetals and High-Quality Candidate Materials. PHYSICAL REVIEW LETTERS 2020; 124:016402. [PMID: 31976722 DOI: 10.1103/physrevlett.124.016402] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2019] [Indexed: 06/10/2023]
Abstract
Spin-gapless semimetals (SGSMs), which generate 100% spin polarization, are viewed as promising semi-half-metals in spintronics with high speed and low consumption. We propose and characterize a new Z_{2} class of topological nodal line (TNL) in SGSMs. The proposed TNLSGSMs are protected by space-time inversion symmetry or glide mirror symmetry with two-dimensional (2D) fully spin-polarized nearly flat surface states. Based on first-principles calculations and effective model analysis, a series of high-quality materials with R3[over ¯]c and R3c space groups are predicted to realize such TNLSGSMs (chainlike). The 2D fully spin-polarized nearly flat surface states may provide a route to achieving equal spin pairing topological superconductivity as well as topological catalysts.
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Affiliation(s)
- Run-Wu Zhang
- Key Lab of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), Beijing Key Lab of Nanophotonics, and Ultrafine Optoelectronic Systems, and School of Physics, Beijing Institute of Technology, Beijing 100081, China
| | - Zeying Zhang
- Key Lab of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), Beijing Key Lab of Nanophotonics, and Ultrafine Optoelectronic Systems, and School of Physics, Beijing Institute of Technology, Beijing 100081, China
| | - Cheng-Cheng Liu
- Key Lab of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), Beijing Key Lab of Nanophotonics, and Ultrafine Optoelectronic Systems, and School of Physics, Beijing Institute of Technology, Beijing 100081, China
| | - Yugui Yao
- Key Lab of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), Beijing Key Lab of Nanophotonics, and Ultrafine Optoelectronic Systems, and School of Physics, Beijing Institute of Technology, Beijing 100081, China
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8
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Wu Q, Soluyanov AA, Bzdušek T. Non-Abelian band topology in noninteracting metals. Science 2019; 365:1273-1277. [DOI: 10.1126/science.aau8740] [Citation(s) in RCA: 96] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Accepted: 08/14/2019] [Indexed: 01/25/2023]
Affiliation(s)
- QuanSheng Wu
- Institute of Physics, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
- National Centre for Computational Design and Discovery of Novel Materials MARVEL, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Alexey A. Soluyanov
- Physik-Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
- Department of Physics, St. Petersburg State University, St. Petersburg, 199034 Russia
| | - Tomáš Bzdušek
- Department of Physics, McCullough Building, Stanford University, Stanford, CA 94305, USA
- Stanford Center for Topological Quantum Physics, Stanford University, Stanford, CA 94305, USA
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9
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Yokomizo K, Yamada H, Murakami S. Nodal-line semimetal superlattices. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:505301. [PMID: 30457120 DOI: 10.1088/1361-648x/aaeabe] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Spatial modulations, such as superlattices, to realize topological materials have recently been studied in theoretical and experimental works. In this paper, we investigate properties of the superlattices of the nodal-line semimetal and the normal insulator. We consider two types of superlattices, with the stacking direction being perpendicular or parallel to the plane where the nodal line lies. In particular, we show that when the stacking direction is parallel to the plane, the nodal lines remain but they change their shapes because of the folding of the Brillouin zone. We also study the superlattices with magnetization. One can expect that the quantum anomalous Hall (QAH) phase emerges in some cases, depending on the direction of the magnetization. If the magnetization is along the C 2-invariant axis, the superlattice becomes the Weyl semimetal phase if the C 2-invariant axis intersects the nodal lines, and otherwise it becomes the QAH phase.
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Affiliation(s)
- Kazuki Yokomizo
- Department of Physics, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo, 152-8551, Japan
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10
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Ahn J, Kim D, Kim Y, Yang BJ. Band Topology and Linking Structure of Nodal Line Semimetals with Z_{2} Monopole Charges. PHYSICAL REVIEW LETTERS 2018; 121:106403. [PMID: 30240267 DOI: 10.1103/physrevlett.121.106403] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2018] [Revised: 07/06/2018] [Indexed: 06/08/2023]
Abstract
We study the band topology and the associated linking structure of topological semimetals with nodal lines carrying Z_{2} monopole charges, which can be realized in three-dimensional systems invariant under the combination of inversion P and time reversal T when spin-orbit coupling is negligible. In contrast to the well-known PT-symmetric nodal lines protected only by the π Berry phase, in which a single nodal line can exist, the nodal lines with Z_{2} monopole charges should always exist in pairs. We show that a pair of nodal lines with Z_{2} monopole charges is created by a double band inversion process and that the resulting nodal lines are always linked by another nodal line formed between the two topmost occupied bands. It is shown that both the linking structure and the Z_{2} monopole charge are the manifestation of the nontrivial band topology characterized by the second Stiefel-Whitney class, which can be read off from the Wilson loop spectrum. We show that the second Stiefel-Whitney class can serve as a well-defined topological invariant of a PT-invariant two-dimensional insulator in the absence of Berry phase. Based on this, we propose that pair creation and annihilation of nodal lines with Z_{2} monopole charges can mediate a topological phase transition between a normal insulator and a three-dimensional weak Stiefel-Whitney insulator. Moreover, using first-principles calculations, we predict ABC-stacked graphdiyne as a nodal line semimetal (NLSM) with Z_{2} monopole charges having the linking structure. Finally, we develop a formula for computing the second Stiefel-Whitney class based on parity eigenvalues at inversion-invariant momenta, which is used to prove the quantized bulk magnetoelectric response of NLSMs with Z_{2} monopole charges under a T-breaking perturbation.
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Affiliation(s)
- Junyeong Ahn
- Department of Physics and Astronomy, Seoul National University, Seoul 08826, Korea
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul 08826, Korea
- Center for Theoretical Physics (CTP), Seoul National University, Seoul 08826, Korea
| | - Dongwook Kim
- Department of Physics, Sungkyunkwan University, Suwon 16419, Korea
| | - Youngkuk Kim
- Department of Physics, Sungkyunkwan University, Suwon 16419, Korea
| | - Bohm-Jung Yang
- Department of Physics and Astronomy, Seoul National University, Seoul 08826, Korea
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul 08826, Korea
- Center for Theoretical Physics (CTP), Seoul National University, Seoul 08826, Korea
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11
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Sun XQ, Zhang SC, Bzdušek T. Conversion Rules for Weyl Points and Nodal Lines in Topological Media. PHYSICAL REVIEW LETTERS 2018; 121:106402. [PMID: 30240246 DOI: 10.1103/physrevlett.121.106402] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2018] [Indexed: 06/08/2023]
Abstract
According to a widely held paradigm, a pair of Weyl points with opposite chirality mutually annihilate when brought together. In contrast, we show that such a process is strictly forbidden for Weyl points related by a mirror symmetry, provided that an effective two-band description exists in terms of orbitals with opposite mirror eigenvalue. Instead, such a pair of Weyl points convert into a nodal loop inside a symmetric plane upon the collision. Similar constraints are identified for systems with multiple mirrors, facilitating previously unreported nodal-line and nodal-chain semimetals that exhibit both Fermi-arc and drumhead surface states. We further find that Weyl points in systems symmetric under a π rotation composed with time reversal are characterized by an additional integer charge that we call helicity. A pair of Weyl points with opposite chirality can annihilate only if their helicities also cancel out. We base our predictions on topological crystalline invariants derived from relative homotopy theory, and we test our predictions on simple tight-binding models. The outlined homotopy description can be directly generalized to systems with multiple bands and other choices of symmetry.
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Affiliation(s)
- Xiao-Qi Sun
- Department of Physics, McCullough Building, Stanford University, Stanford, California 94305-4045, USA
- Stanford Center for Topological Quantum Physics, Stanford University, Stanford, California 94305-4045, USA
| | - Shou-Cheng Zhang
- Department of Physics, McCullough Building, Stanford University, Stanford, California 94305-4045, USA
- Stanford Center for Topological Quantum Physics, Stanford University, Stanford, California 94305-4045, USA
| | - Tomáš Bzdušek
- Department of Physics, McCullough Building, Stanford University, Stanford, California 94305-4045, USA
- Stanford Center for Topological Quantum Physics, Stanford University, Stanford, California 94305-4045, USA
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12
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Cai J, Xie Y, Chang PY, Kim HS, Chen Y. Nodal-chain network, intersecting nodal rings and triple points coexisting in nonsymmorphic Ba 3Si 4. Phys Chem Chem Phys 2018; 20:21177-21183. [PMID: 30083674 DOI: 10.1039/c8cp02810a] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Coexistence of topological elements in topological metals/semimetals (TMs) has gradually attracted attention. However, non-topological factors always interfere with the Fermi surface and cover interesting topological properties. Here, we find that Ba3Si4 is a "clean" TM which contains coexisting nodal-chain networks, intersecting nodal rings (INRs) and triple points, in the absence of spin-orbit coupling (SOC). Moreover, the nodal rings in the topological phase exhibit diverse types: from type-I and type-II to type-III rings according to band dispersions. All of the topological elements are generated by crossings of three energy bands, and thus they are correlated rather than mutually independent. When some structural symmetries are eliminated by an external strain, the topological phase evolves into another phase including a Hopf link, a one-dimensional nodal chain and new INRs.
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Affiliation(s)
- Jin Cai
- School of Physics and Optoelectronics, Xiangtan University, Xiangtan, Hunan 411105, China.
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13
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Gao Y, Xie Y, Chen Y, Gu J, Chen Z. Spindle nodal chain in three-dimensional α′ boron. Phys Chem Chem Phys 2018; 20:23500-23506. [PMID: 30183022 DOI: 10.1039/c8cp03874k] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A three-dimensional 3D-α′ boron is proposed and a novel spindle nodal chain is found in this material.
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Affiliation(s)
- Yan Gao
- School of Physics and Optoelectronics
- Xiangtan University
- Xiangtan
- China
| | - Yuee Xie
- School of Physics and Optoelectronics
- Xiangtan University
- Xiangtan
- China
| | - Yuanping Chen
- School of Physics and Optoelectronics
- Xiangtan University
- Xiangtan
- China
| | - Jinxing Gu
- Department of Chemistry
- University of Puerto Rico
- Rio Piedras Campus
- San Juan
- USA
| | - Zhongfang Chen
- Department of Chemistry
- University of Puerto Rico
- Rio Piedras Campus
- San Juan
- USA
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