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One-dimensional chiral anomaly and its disorder response

Physical Review B 2023年第19期108卷 195103-195103页

作者： Zheng Qin Dong-Hui Xu Zhen Ning 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 400044 People's Republic of China Center of Quantum Materials and Devices Chongqing University Chongqing 400044 People's Republic of China

The condensed-matter realization of chiral anomaly has attracted tremendous interest in exploring unexpected phenomena of quantum field theory. Here, we show that one-dimensional (1D) chiral anomaly (i.e., 1D nonconservational chiral current under a background electromagnetic field) can be realized in a generalized Su-Schrieffer-Heeger model where a single gapless Dirac cone occurs. Based on the topological Thouless pump and anomalous dynamics of chiral displacement, we elucidate that such a system possesses the half-integer quantization of the winding number. Moreover, we investigate the evolution of 1D chiral anomaly with respect to two typical types of disorder, i.e., on-site disorder and bond disorder. The results show that the on-site disorder tends to smear the gapless Dirac cone. However, we propose a strategy to stabilize the half-integer quantization, facilitating its experimental detection. Furthermore, we demonstrate that the bond disorder causes a unique crossover with disorder-enhanced topological charge pumping, driving the system into a topological Anderson insulator phase.

关键词： Electronic structure Topological phase transition Topological phases of matter 1-dimensional systems Dirac semimetal Second quantization Tight-binding model k dot p method

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From atomic semimetal to topological nontrivial insulator

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Physical Review B 2022年第16期105卷 165135-165135页

作者： Xiao-Ping Li Da-Shuai Ma Cheng-Cheng Liu Zhi-Ming Yu Yugui Yao Centre for Quantum Physics Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE) School of Physics Beijing Institute of Technology Beijing 100081 China Beijing Key Laboratory of Nanophotonics and Ultrafine Optoelectronic Systems School of Physics Beijing Institute of Technology Beijing 100081 China Chongqing Key Laboratory for Strongly Coupled Physics and Institute for Structure and Function Department of Physics Chongqing University Chongqing 401331 China

Topological band insulators and (semi-)metals can arise out of atomic insulators when the hopping strength between electrons increases. Such topological phases are separated from the atomic insulator by a bulk gap closing. In this paper, we show that in many (magnetic) space groups, the crystals with certain Wyckoff positions and atomic orbitals being occupied must be semimetals in the atomic limit, e.g., the hopping strength between electrons is infinitesimal but not vanishing, which then are termed atomic semimetals (ASMs). We derive a sufficient condition for realizing ASMs in both spinless and spinful systems. Remarkably, with both symmetries and electron fillings of system preserved, increasing the hopping strength between electrons may transform an ASM into an insulator, and the induced insulators inevitably are topologically nontrivial. Particularly, using silicon as an example, we show the ASM criterion can discover the obstructed atomic insulators (OAIs) that are marked as trivial insulators on the topological quantum chemistry website. Our paper not only establishes an efficient way to identify and design topologically nontrivial insulators, but also predicts that the group-IV elemental semiconductors are ideal candidate materials for OAI.

关键词： Electronic structure Surface states Topological materials

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The One-dimensional Chiral Anomaly and its Disorder Response

arXiv

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arXiv 2023年

作者： Qin, Zheng Xu, Dong-Hui Ning, Zhen Wang, Rui Institute for Structure and Function Department of Physics Chongqing University Chongqing400044 China Chongqing Key Laboratory for Strongly Coupled Physics Chongqing400044 China Center of Quantum Materials and Devices Chongqing University Chongqing400044 China

The condensed-matter realization of chiral anomaly has attracted tremendous interest in exploring unexpected phenomena of quantum field theory. Here, we show that one-dimensional (1D) chiral anomaly (i.e., 1D nonconservational chiral current under a background electromagnetic field) can be realized in a generalized Su-Schrieffer-Heeger model where a single gapless Dirac cone occurs. Based on the topological Thouless pump and anomalous dynamics of chiral displacement, we elucidate that such a system possesses the half-integer quantization of winding number. Moreover, we investigate the evolution of 1D chiral anomaly with respect to two typical types of disorder, i.e., on-site disorder and bond disorder. The results show that the on-site disorder tends to smear the gapless Dirac cone. However, we propose a strategy to stabilize the half-integer quantization, facilitating its experimental detection. Furthermore, we demonstrate that the bond disorder causes a unique crossover with disorder-enhanced topological charge pumping, driving the system into a topological Anderson insulator phase. Copyright © 2023, The Authors. All rights reserved.

关键词： Topology

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Precise determination of the top-quark on-shell mass Mt via its scale-invariant perturbative relation to the top-quark MS mass m_(t)(m_(t))

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Chinese physics C 2024年第5期48卷 180-193页

作者：黄旭东吴兴刚郑绪昌闫江吴知非马鸿浩 Institute of High Energy Physics Chinese Academy of SciencesBeijing 100049China Department of Physics Chongqing Key Laboratory for Strongly Coupled PhysicsChongqing UniversityChongqing 401331China Department of Physics Guangxi Normal UniversityGuilin 541004China

The principle of maximum conformality(PMC)provides a systematic approach to solve the conventional renormalization scheme and scale ***-fixed predictions of physical observables using the PMC are independent of the choice of renormalization scheme–a key requirement for renormalization group *** this paper,we derive new degeneracy relations based on the renormalization group equations that involve both the usualβ-function and the quark mass anomalous dimensionγ*** new degeneracy relations enable improved PMC scale-setting procedures for correct magnitudes of the strong coupling constant and MS¯-running quark mass to be determined *** using these improved PMC scale-setting procedures,the renormalization scale dependence of the MS¯-on-shell quark mass relation can be eliminated ***,the top-quark on-shell(or MS¯)mass can be determined without conventional renormalization scale *** the top-quark MS¯mass m¯t(m¯t)=162.5+2.1−1.5 GeV as the input,we obtain Mt≃172.41+2.21−1.57 ***,the uncertainties arise from errors combined with those fromΔαs(MZ)and the approximate uncertainty resulting from the uncalculated five-loop terms predicted through the Padéapproximation approach.

关键词： perturbative QCD top quark mass renormalization

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Chiral-Flux-Phase-Based Topological Superconductivity in Kagome Systems with Mixed Edge Chiralities

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Physical Review Letters 2023年第8期131卷 086601-086601页

作者： Junjie Zeng Qingming Li Xun Yang Dong-Hui Xu 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 Department of Physics Shijiazhuang University Shijiazhuang Hebei 050035 People’s Republic of China Center of Quantum materials and devices Chongqing University Chongqing 400044 People’s Republic of China

Recent studies have attracted intense attention on the quasi-2D kagome superconductors AV3Sb5 (A=K, Rb, and Cs) where the unexpected chiral flux phase (CFP) associates with the spontaneous time-reversal symmetry breaking in charge density wave states. Here, commencing from the 2-by-2 charge density wave phases, we bridge the gap between topological superconductivity and time-reversal asymmetric CFP in kagome systems. Several chiral topological superconductor (TSC) states featuring distinct Chern numbers emerge for an s-wave or a d-wave superconducting pairing symmetry. Importantly, these CFP-based TSC phases possess unique gapless edge modes with mixed chiralities (i.e., both positive and negative chiralities), but with the net chiralities consistent with the Bogoliubov–de Gennes Chern numbers. We further study the transport properties of a two-terminal junction, using Chern insulator or normal metal leads via atomic Green’s function method with Landauer-Büttiker formalism. In both cases, the normal electron tunneling and the crossed Andreev reflection oscillate as the chemical potential changes, but together contribute to plateau transmissions (1 and 32, respectively) that exhibit robustness against disorder. These behaviors can be regarded as the signature of a TSC hosting edge states with mixed chiralities.

关键词： Andreev reflection Charge density waves Edge states Spin-orbit coupling Spin-singlet pairing Superconductivity Topological phases of matter Topological superconductors 2-dimensional systems Bogoliubov-de Gennes equations Green's function methods Landauer formula Second quantization Tight-binding model

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Intrinsically large effective mass and multi-valley band characteristics of n-type Bi_(2)eBi_(2)Te_(3)superlattice-like films

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Journal of Materiomics 2024年第3期10卷 716-724页

作者： Yujie Ouyang Min Zhang Fangyang Zhan Chunxia Li Xianda Li Fan Yan Sen Xie Qiwei Tong Haoran Ge Yong Liu Rui Wang Wei Liu Xinfeng Tang State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of TechnologyWuhan430070China International School of Materials Science and Engineering Wuhan University of TechnologyWuhan430070China Institute for Structure and Function&Department of Physics Chongqing UniversityChongqing400044China School of Physics and Technology and the Key Laboratory of Artificial Micro/Nano Structures of Ministry of Education Wuhan UniversityWuhan430072China

Thermoelectric superlattices are expected to decouple the strong correlation between various thermo-electric parameters,and are an important strategy for excellent thermoelectric *** superlattices of(Bi_(2))m(Bi_(2)Te_(3))n homologous series are well-known for low lattice thermal conductivity and intriguing topological surface ***,the impacts of electronic structure on the thermo-electric performance were still not well-understood in(Bi_(2))m(Bi_(2)Te_(3))*** cope with this issue,Bi_(2)eBi_(2)Te_(3)superlattice-like films with adjustable Bi_(2)/(Bi_(2)+Bi_(2)Te_(3))molar ratio(R)were successfully fabricated by the molecular beam epitaxy ***-resolved photoemission spectroscopy measurements com-bined with theoretical calculations revealed the conduction band evolution from single-valley to multi-valley as R≥0.30,leading to intrinsically high carrier effective mass and improved thermoelectric power ***,the superlattice film(R=0.46)with the structure close to Bi_(4)Te_(3)possesses the topological surface state feature around the high symmetry *** a result of the high effective mass of 3.9 m0 and very high electron density of_(2).31×10^(21)cm^(-3),the film with R=0.46 acquired the highest power factor of 1.49 mW·m^(-1)·K^(-2)at 420 K,outperforming that of other(Bi_(2))m(Bi_(2)Te_(3))n *** work lays an essential foundation on understanding the electronic structure and further improving thermoelectric performances of(Bi_(2))m(Bi_(2)Te_(3))n homologous series.

关键词： Bi_(2)eBi_(2)Te_(3)superlattice Molecular beam epitaxy Band structure Thermoelectric performance

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Photoinduced high-Chern-number quantum anomalous Hall effect from higher-order topological insulators

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Physical Review B 2024年第8期109卷 085148-085148页

作者： Xiaolin Wan Zhen Ning Dong-Hui Xu Rui Wang Baobing Zheng 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 College of Physics and Optoelectronic Technology Baoji University of Arts and Sciences Baoji 721016 People's Republic of 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. Here, we propose a dynamic approach for achieving high-Chern-number QAH phases in periodically driven two-dimensional higher-order topological insulators (HOTIs) irradiated by circularly polarized light (CPL). 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 numbers 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. Remarkably, the irradiation of CPL does not destroy the quantized quadruple moment in periodically driven HOTIs, leading to an exotic mixed phase harboring both high Chern numbers and higher-order topology. 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.

关键词： Edge states First-principles calculations Photoinduced effect Topological insulators Topological materials Topological phase transition Topological phases of matter Bloch-Floquet theorem Density functional theory Second quantization Tight-binding model Wannier function methods k dot p method

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Perspective: Floquet engineering topological states from effective models towards realistic materials

arXiv

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arXiv 2024年

作者： Zhan, Fangyang Chen, Rui Ning, Zhen Ma, Da-Shuai Wang, Ziming Xu, Dong-Hui 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 Department of Physics Hubei University Wuhan430062 China

With significant advances in classifying and cataloguing topological matter, the focus of topological physics has shifted towards quantum control, particularly the creation and manipulation of topological phases of matter. Floquet engineering, the concept of tailoring a system by periodic fields, offers a powerful tool to manipulate electronic properties of condensed systems, and even to create exotic non-equilibrium topological states that are impossibly present in equilibrium scenarios. In this perspective, we give a brief review of recent progress in theoretical investigations of Floquet engineering topological states from effective models towards realistic materials. We show that light irradiation can realize various desired topological states through the introduction of symmetry breaking, such as first- and higher-order Weyl fermions, quadrupole topological insulator with periodic driving and disorder, quantum anomalous Hall effects with a tunable Chern number, as well as beyond. Moreover, based on first-principles calculations and Floquet theorem, we show several realistic material candidates proposed as potential hosts for promising Floquet topological states, facilitating their verification in experiments. We believe that our perspective on Floquet engineering of topological states will advance further studies of rich exotic light-induced phenomena in condensed matter physics. Copyright © 2024, The Authors. All rights reserved.

关键词： Electronic properties

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Stability and thermoelectric performance of the two-dimensional rare-earth compounds RTeCl (R=La,Pr,Nd)

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Physical Review Applied 2024年第5期21卷 054026-054026页

作者： Haoran Wei Xin Jin Xiaoliang Xiao Li Shi Yuanhao Duan Jing Fan Rui Wang Xiaozhi Wu Institute for Structure and Function & Department of Physics Chongqing University Chongqing 400044 China College of Physics and Electronic Engineering Chongqing Normal University Chongqing 401331 China Center for Computational Science and Engineering Southern University of Science and Technology Shenzhen 518055 China Center of Quantum Materials and Devices Chongqing University Chongqing 400044 China Chongqing Key Laboratory for Strongly Coupled Physics Chongqing 400044 China

Thermoelectric conversion technology is increasingly important for sustainable energy, particularly in transforming waste heat into electricity. In this study, we explore the thermoelectric properties of three novel two-dimensional materials, monolayer RTeCl (with R=La,Pr,Nd), using density-functional theory and semiclassical Boltzmann transport theory. These materials are stable and can be easily exfoliated from bulk structures due to their low cleavage energy. Notably, monolayer RTeCl materials have high power factors ((2.04--4.48)×104μWm−1K−2), attributed to multiple valleys in their valence-band maximum. Their complex crystal structures and the presence of two heavy elements contribute to an ultralow lattice thermal conductivity ((2.42--4.58)Wm−1K−1) at room temperature. Impressively, the figure of merit (ZT) values of monolayer RTeCl range from 0.4 to 1.2 at 300 K. Across the temperature range of 300 to 700 K, the average ZT value and thermoelectric conversion efficiency reach 1.32--2.75 and 15.3%--22.6%, respectively. Our results indicate that monolayer RTeCl is a promising candidate for nanoelectronics and low-dimensional thermoelectric devices, offering a new avenue for high-performance thermoelectric materials.

关键词： Phonons Thermoelectric effects 2-dimensional systems Semiconductor compounds Thermoelectrics Ab initio molecular dynamics Boltzmann theory Density functional calculations

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Complete topological phase diagram and realization of minimum Weyl nodes in a sheared chiral crystal of elemental tellurium

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Physical Review B 2023年第23期108卷 235211-235211页

作者： Shuai Fan Botao Fu Da-Shuai Ma Rui Wang Institute for Structure and Function & Department of Physics & Chongqing Key Laboratory for Strongly Coupled Physics Chongqing University Chongqing 400044 People's Republic of China College of Physics and Electronic Engineering Center for Computational Sciences Sichuan Normal University Chengdu 610068 People's Republic of China Center of Quantum Materials and Devices Chongqing University Chongqing 400044 People's Republic of China

Ideal Weyl semimetals, with minimum Weyl nodes located far away from each other in reciprocal space and near the Fermi level in the energy space, are considered to be crucial for revealing the intrinsic physical properties of Weyl semimetals. Based on first-principles calculations, we demonstrate that elemental tellurium, under application of a broad range of shear strain, is a candidate for realizing ideal Weyl semimetals. Particularly, the sheared elemental tellurium has only four Weyl nodes in the Brillioun zone, which is the minimum number of Weyl nodes that can be achieved by a system with time-reversal symmetry. More importantly, by adjusting the strength of the strain, we obtain abundant topological phases, i.e., Weyl semimetals, strong topological insulators, composite Weyl semimetals, and weak topological insulators in elemental tellurium. Notably, this paper proposes implementing a weak topological insulator phase in a space group with only time-reversal symmetry. The complete topological phase diagram of sheared tellurium is given and the topological properties of different topological nontrivial phases are characterized, respectively.

关键词： Electronic structure First-principles calculations Topological materials Topological phase transition

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