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Tailoring quadrupole topological insulators with periodic driving and disorder

Physical Review B 2022年第20期105卷 L201114-L201114页

作者： Zhen Ning Bo Fu Dong-Hui Xu Rui Wang Institute for Structure and Function and Department of Physics Chongqing University Chongqing 400044 People's Republic of China Chongqing Key Laboratory for Strongly Coupled Physics Chongqing University Chongqing 400044 People's Republic of China Department of Physics The University of Hong Kong Pokfulam Road Hong Kong China Center of Quantum Materials and Devices Chongqing University Chongqing 400044 People's Republic of China

The quadrupole topological insulator (QTI) has attracted intense studies as a prototype of symmetry-protected higher-order topological phases of matter with a quantized quadrupole moment. The realization of QTIs has been reported in various static settings with periodic structures. Here, we theoretically investigate topological phase transitions and establish the QTI phase in a periodically driven system with disorder. In the clean limit, the Floquet QTI phase emerges from a topologically trivial band structure driven by elliptically polarized irradiation. More strikingly, starting from a pure and static system with trivial topology, we unveil an intriguing QTI phase which necessitates the simultaneous presence of disorder and periodic driving. Furthermore, we reveal that particle-hole symmetry is sufficient to protect the QTI. Our work not only establishes a strategy to design QTIs but also enriches the symmetry-protected mechanism of higher-order topology.

关键词： Symmetry protected topological states Topological insulators Topological phases of matter

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Controllable Weyl nodes and Fermi arcs in a light-irradiated carbon allotrope

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Physical Review B 2023年第20期108卷 205139-205139页

作者： Ruoning Ji Xianyong Ding Fangyang Zhan Xiaoliang Xiao Jing Fan Zhen Ning Rui Wang Institute for Structure and Function and Department of Physics and Chongqing Key Laboratory for Strongly Coupled Physics Chongqing University Chongqing 400044 People's Republic of China Center for Computational Science and Engineering Southern University of Science and Technology Shenzhen 518055 People's Republic of China Center of Quantum Materials and Devices Chongqing University Chongqing 400044 People's Republic of China

The precise control of Weyl physics in realistic materials offers a promising avenue to construct accessible topological quantum systems, and thus draws widespread attention in condensed-matter physics. Here, based on first-principles calculations, the maximally localized Wannier function based tight-binding model, and Floquet theorem, we study the light-manipulated evolution of Weyl physics in a carbon allotrope C6 crystallizing a face-centered orthogonal structure (fco-C6), an ideal Weyl semimetal with two pairs of Weyl nodes, under irradiation of a linearly polarized light. We show that the positions of Weyl nodes and Fermi arcs can be accurately controlled by changing the light intensity. Moreover, we employ a low-energy effective k·p model to understand light-controllable Weyl physics. The results indicate that the symmetry of light-irradiated fco-C6 can be selectively preserved, which guarantees that the light-manipulated Weyl nodes can only move in the high-symmetry plane in momentum space. Our work not only demonstrates the efficacy of employing periodic driving light fields as an efficient approach to manipulate the Weyl physics, but also paves a reliable pathway for designing accessible topological states under light irradiation.

关键词： Electrical properties Electronic structure First-principles calculations Photoinduced effect Topological materials Weyl semimetal Bloch-Floquet theorem Density functional theory Tight-binding model Wannier function methods

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Tailoring Quadrupole Topological Insulators with Periodic Driving and Disorder

arXiv

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arXiv 2022年

作者： Ning, Zhen Fu, Bo Xu, Dong-Hui Wang, Rui Institute for Structure and Function Department of Physics Chongqing University Chongqing400044 China Chongqing Key Laboratory for Strongly Coupled Physics Chongqing University Chongqing400044 China Department of Physics The University of Hong Kong Pokfulam Road Hong Kong Department of Physics Hubei University Wuhan430062 China Chongqing Key Laboratory for Strongly Coupled Physics Chongqing400044 China Center of Quantum Materials and Devices Chongqing University Chongqing400044 China

The quadrupole topological insulator (QTI) has attracted intense studies as a prototype of symmetry-protected higher-order topological phases of matter with a quantized quadrupole moment. The realization of QTIs has been reported in various static settings with periodic structures. Here, we theoretically investigate topological phase transitions and establish the QTI phase in a periodically driven system with disorder. In the clean limit, the Floquet QTI phase emerges from a topologically trivial band structure driven by elliptically polarized irradiation. More strikingly, starting from a pure and static system with trivial topology, we unveil an intriguing QTI phase which necessitates the simultaneous presence of disorder and periodic driving. Furthermore, we reveal that particle-hole symmetry is sufficient to protect the QTI. Our work not only establishes a new strategy to design QTIs but also enriches the symmetry-protected mechanism of higher-order topology. Copyright © 2022, The Authors. All rights reserved.

关键词： Topological insulators

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Berry-Curvature Engineering for Nonreciprocal Directional Dichroism in Two-Dimensional Antiferromagnets

arXiv

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arXiv 2023年

作者： Liang, Wenhao Zeng, Junjie Qiao, Zhenhua Gao, Yang Niu, Qian International Centre for Quantum Design of Functional Materials CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics Department of Physics University of Science and Technology of China Anhui Hefei230026 China Institute for Structure and Function Department of Physics Chongqing Key Laboratory for Strongly Coupled Physics Chongqing University Chongqing400044 China Hefei National Laboratory University of Science and Technology of China Hefei230088 China

In two-dimensional antiferromagnets, we identify the mixed Berry curvature as the geometrical origin of the nonreciprocal directional dichroism (NDD), which refers to the difference in light absorption with the propagation direction flipped. Such a Berry curvature is strongly tied to the uniaxial strain in accordance with the symmetry constraint, leading to a highly tunable NDD, whose sign and magnitude can be manipulated via the strain direction. As a concrete example, we demonstrate such a phenomenon in a lattice model of MnBi2Te4. The coupling between the mixed Berry curvature and strain also suggests the magnetic quadrupole of the Bloch wave packet as the macroscopic order parameter probed by the NDD in two dimensions, distinct from the multiferroic order P × M or the spin toroidal and quadrupole order within a unit cell in previous studies. Our work paves the way of the Berry-curvature engineering for optical nonreciprocity in two-dimensional antiferromagnets. Copyright © 2023, The Authors. All rights reserved.

关键词： Dichroism

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Topological insulator path toward efficient hydrogen evolution catalysts in the Li2Pt family

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Physical Review B 2023年第23期107卷 235414-235414页

作者： Yu-Hao Wei Da-Shuai Ma Hong-Kuan Yuan Xiaotian Wang Min-Quan Kuang Chongqing Key Laboratory of Micro & Nano Structure Optoelectronics and School of Physical Science and Technology Southwest University Chongqing 400715 People's Republic of China Institute for Structure and Function & Department of Physics & Chongqing Key Laboratory for Strongly Coupled Physics Chongqing University Chongqing 400044 People's Republic of China Center of Quantum materials and devices Chongqing University Chongqing 400044 People's Republic of China Institute for Superconducting and Electronic Materials (ISEM) University of Wollongong Wollongong 2500 Australia

Topological materials, such as topological semimetals and topological insulators, with robust topological surface states have bright application prospects in electrochemical catalysis. Here, the first-principles calculations indicate the strong topological insulator Li2Pt family promotes efficient catalytic response to the hydrogen evolution reaction. For Li2Pt and Li2Pd, the calculated Gibbs free energy ΔGH* of the bridge site is 0.054 eV and 0.041 eV, while that for the top site is 0.187 eV and 0.641 eV, respectively. The better hydrogen evolution reaction performance of the bridge site can ascribe to H hybridizes with the dxy+dx2−y2 orbital, which donates the nontrivial topological surface states, while H hybridizes with the dz2 orbital that withholds contribution to topological surface states for the top site. Noticeably, the ΔGH* of the bridge site for Li2Pt (0.054 eV) and Li2Pd (0.041 eV) is nearly half of the value of Pt (0.09 eV), indicating an excellent hydrogen evolution reaction activity. This work uncovers the hybridization between adsorbate and topological surface states plays a vital role in enhancing the hydrogen evolution reaction performance and provides a promising route to design topological quantum catalysts.

关键词： Chemical kinetics, dynamics & catalysis Electronic structure Hydrogen energy Topological insulators First-principles calculations

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Symmetry-protected Dirac nodal lines and large spin Hall effect in a V6Sb4 kagome bilayer

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Physical Review B 2022年第15期105卷 155102-155102页

作者： Y. Yang R. Wang M.-Z. Shi Z. Wang Z. Xiang X.-H. Chen CAS Key Laboratory of Strongly-coupled Quantum Matter Physics Department of Physics University of Science and Technology of China Hefei Anhui 230026 China Institute for Structure and Function & Department of Physics Chongqing University Chongqing 400044 China Center of Quantum Materials and Devices Chongqing University Chongqing 400044 China Chongqing Key Laboratory for Strongly Coupled Physics Chongqing University Chongqing 400044 China CAS Center for Excellence in Superconducting Electronics (CENSE) Shanghai 200050 China CAS Center for Excellence in Quantum Information and Quantum Physics Hefei Anhui 230026 China Collaborative Innovation Center of Advanced Microstructures Nanjing University Nanjing 210093 China

Recently, a family of nonmagnetic kagome metals AV3Sb5 (A=K, Rb, and Cs) has attracted significant attention for realizing the intertwining of quantum order and nontrivial topology. However, these compounds have been identified to host complex band structures. Therefore, it is desirable to design and synthesize novel kagome materials with a simple band topology and good transport properties. In this study, using first-principles calculations, we present the electronic properties and the intrinsic spin Hall effect of V6Sb4, the latest experimentally synthesized vanadium-based compounds that form a kagome bilayer. In the absence of spin-orbital coupling (SOC), this compound is a Dirac nodal line semimetal with symmetry-protected nodal rings near the Fermi level. Within the SOC, the spin-rotation symmetry breaks the gaps of the nodal rings with a small band gap. Furthermore, based on the Wannier tight-binding approach and the Kubo formula, we reveal a large spin Hall effect in V6Sb4, which intrinsically originates from the spin Berry curvature. Our work further expands nonmagnetic kagome compounds for applications in spintronics accompanied by exotic quantum order.

关键词： Electrical conductivity First-principles calculations Topological materials Topological phases of matter Node-line semimetals Wannier function methods

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Disorder and quantum transport of the helical quantum Hall phase in graphene

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Physical Review B 2023年第12期108卷 125409-125409页

作者： Yue-Ran Ding Dong-Hui Xu Chui-Zhen Chen Institute for Advanced Study and School of Physical Science and Technology Soochow University Suzhou 215006 China Department of Physics Chongqing University Chongqing 400044 China Chongqing Key Laboratory for Strongly Coupled Physics Chongqing University Chongqing 400044 China

Recently, an exotic quantum Hall ferromagnet with spin-filtered helical edge modes was observed in monolayer graphene on a high-dielectric constant substrate at moderate magnetic fields, withstanding temperatures of up to 110 Kelvin [L. Veyrat et al., Science 367, 781 (2020)]. However, the characteristic quantized longitudinal resistance mediated by these edge modes departs from quantization with decreasing temperature. In this work, we investigate the transport properties of helical edge modes in a graphene nanoribbon under a perpendicular magnetic field using the Landauer-Büttiker transport formalism. We find that the departure of quantization of longitudinal conductance is due to the helical-edge gap opened by the Rashba spin-orbital coupling. The quantization can be restored by weak nonmagnetic Anderson disorder at low temperature, increasing the localization length, or by raising temperature at weak disorder, through thermal broadening. The resulted conductance is very close to the quantized value 2e2/h, which is qualitatively consistent with the experimental results. Furthermore, we suggest that the helical quantum Hall phase in graphene could be a promising platform for creating Majorana zero modes by introducing superconductivity.

关键词： Quantum Hall effect Transport phenomena Graphene Green's function methods Landauer formula Tight-binding model Transfer matrix method

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Photoinduced High-Chern-Number Quantum Anomalous Hall Effect from Higher-Order Topological Insulators

arXiv

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arXiv 2023年

作者： Wan, Xiaolin Ning, Zhen Xu, Dong-Hui Zheng, Baobing Wang, Rui Institute for Structure and Function Department of Physics Chongqing Key Laboratory for Strongly Coupled Physics Chongqing University Chongqing400044 China Center of Quantum Materials and Devices Chongqing University Chongqing400044 China College of Physics and Optoelectronic Technology Baoji University of Arts and Sciences Baoji721016 China

Quantum anomalous Hall (QAH) insulators with high Chern number host multiple dissipationless chiral edge channels, which are of fundamental interest and promising for applications in spintronics and quantum computing. However, only a limited number of high-Chern-number QAH insulators have been reported to date. Here, we propose a dynamic approach for achieving high-Chern-number QAH phases in periodically driven two-dimensional higher-order topological insulators (HOTIs). In particular, we consider two representative kinds of HOTIs which are characterized by a quantized quadruple moment and the second Stiefel-Whitney number, respectively. Using the Floquet formalism for periodically driven systems, we demonstrate that QAH insulators with tunable Chern number up to four can be achieved. Moreover, we show by first-principles calculations that the monolayer graphdiyne, a realistic HOTI, is an ideal material candidate. Our work not only establishes a strategy for designing high-Chern-number QAH insulators in periodically driven HOTIs, but also provides a powerful approach to investigate exotic topological states in nonequilibrium cases. Copyright © 2023, The Authors. All rights reserved.

关键词： Electric insulators

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Ferroelectric order in hybrid organic-inorganic perovskite NH_(4)PbI_(3) with non-polar molecules and small tolerance factor

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npj Computational Materials 2023年第1期9卷 1726-1731页

作者： Jia-Bin Li Zhi-Kang Jiang Rui Wang Jin-Zhu Zhao Ruiqiang Wang Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials School of Physics and Telecommunication EngineeringSouth China Normal UniversityGuangzhou 510006PR China Guangdong-Hong Kong Joint Laboratory of Quantum Matter South China Normal UniversityGuangzhou 510006PR China Foshan(Southern China)Institute for New Materials Foshan 528300PR China Institute for Structure and Function and Department of Physics Chongqing UniversityChongqing 400044PR China Center of Quantum Materials and Devices Chongqing UniversityChongqing 400044PR China Center for Computational Science and Engineering Southern University of Science and TechnologyShenzhen 518055PR China

The appropriate theoretical picture of describing the ferroelectric order in hybrid organic-inorganic perovskite remains attractive and under intense *** rationalize the interaction between organic molecule sublattice and inorganic frame from *** systematic investigations on the NH_(4)PbI_(3),we show that the non-polar octahedral rotation dominates the process of stabilizing of the lattice with small value of tolerance *** direct coupling between molecules is *** the help of hydrogen bonding to the inorganic cage,molecule sublattice will eventually build long-range ferroelectric or anti-ferroelectric order under the constrain of the inorganic cage and further polarize the inorganic frame as the *** results also clarify that to build ferroelectricity the polar molecule is helpful but not *** the general rule for hybrid organic-inorganic perovskite,we identified the fundamental mechanism that can be considered as a critical pre-step forward to further controlling the related physics in functional materials.

关键词： inorganic ferroelectric polar

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Single pair of charge-2 high-fold fermions with surface type-II Van Hove singularities in ultralight chiral crystals

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Physical Review B 2024年第16期109卷 165136-165136页

作者： Xiaoliang Xiao Yuanjun Jin Da-Shuai Ma Haoran Wei Jing Fan Rui Wang Xiaozhi Wu Institute for Structure and Function & Department of Physics Chongqing University Chongqing 400044 China Guangdong Basic Research Center of Excellence for Structure and Fundamental Interactions of Matter Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials School of Physics South China Normal University Guangzhou 510006 China Center of Quantum Materials and Devices Chongqing University Chongqing 400044 China Center for Computational Science and Engineering Southern University of Science and Technology Shenzhen 518055 China Chongqing Key Laboratory for Strongly Coupled Physics Chongqing 400044 China

The realization of the single-pair fermions in electronic systems remains challenging in topology physics, especially for the systems with larger chiral charges C. In this work, based on the symmetry analysis, low-energy effective models, and first-principles calculations, we identify the single-pair charge-two chiral fermions in cubic lattices. We first derive the minimal lattice model that exhibits a single pair of Weyl points with the opposite chiral charges of C=±2. Furthermore, we show the ultralight chiral crystal P4332-type LiC2 and its mirror enantiomer as high-quality candidate materials, which exhibit large energy windows to surmount the interruption of irrelevant bands. Since two enantiomers are connected by the mirror symmetry, we observe the opposite chiral charges C and the reversal of Fermi-arc connections, showing the correspondence of chirality in the momentum space and the real space. In addition, we also reveal type-II van Hove singularities on the helicoid surfaces, which may induce chirality-locked charge density waves on the crystal surface. Our work not only provides a promising platform for controlling the sign of chiral charge through structural chirality but also facilitates the exploration of electronic correlations on the surface of ultralight chiral crystals.

关键词： Crystal symmetry Fermions Symmetry protected topological states 3-dimensional systems Crystal structures Electronic structure Weyl semimetal High-throughput calculations Tight-binding model Wannier function methods k dot p method

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