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Coexistence of electronic and phononic higher-order band topology in group III-V monolayers

Physical Review B 2025年第16期111卷 165205-165205页

作者： Xijian Zhu Kanghan Zackery Ye Fangyang Zhan Xianyong Ding Da-Shuai Ma Rui Wang Institute for Structure and Function Department of Physics and Chongqing Key Laboratory for Strongly Coupled Physics Chongqing University Chongqing 400044 People's Republic of China Foreign Language School Attached to Sichuan International Studies University Chongqing 400039 People's Republic of China Center of Quantum Materials and Devices Chongqing University Chongqing 400044 People's Republic of China

The coexistence of electronic and phononic higher-order band topology has been largely unexplored. Based on first-principles calculations and symmetry arguments, we demonstrate that III-V monolayers XY (X = B, Al, Ga, In; Y = N, P, As, Sb), with planar and low-buckled honeycomb structures, exhibit both electronic and phononic higher-order band topology. We show the explicit existence of hallmark corner states with quantized fractional charge, which are linked to nontrivial topological indices, i.e., rotation topological invariants associated with threefold rotation symmetry. Moreover, we further verify by first-principles calculations and effective model analysis that the variation of atomic masses in III-V monolayers can induce phonon band inversion, leading to different quantized fractional charges. Our work reveals the coexistence of electronic and phononic higher-order band topology in experimentally accessible monolayers, which has profound implications for advancing our fundamental understanding of the topological properties of matter and related experiments and applications.

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Semiconducting behaviors at epitaxial Ca0.5TaO3 interfaces

arXiv

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arXiv 2025年

作者： Nie, Guangdong Han, Guanghui Huang, Shengpu Wu, Huiyin Wang, Deshun Liu, Kangxi Ding, Hao Tang, Fangdong Peng, Licong Ma, Dashuai Sun, Young Liu, Changjiang Hong, Deshun Department of Applied Physics Chongqing University Chongqing401331 China Center of Quantum Materials and Devices Chongqing University Chongqing401331 China School of Materials Science and Engineering Peking University Beijing100871 China Institute for Structure and Function Department of Physics Chongqing Key Laboratory for Strongly Coupled Physics Chongqing University Chongqing400044 China Department of Physics University at Buffalo SUNY BuffaloNY14260 United States

Emergent phenomena take place in symmetry-breaking systems, notably the recently discovered two-dimensional electron gas and its tunable superconductivities near the KTaO3 interfaces. Here, we synthesized perovskite Ca0.5TaO3 films along both [001] and [111] orientations. Different from the KTaO3 system, Ca0.5TaO3 films show semiconducting behaviors when capped with LaAlO3 films in both [001] and [111] orientations. By growing films at higher temperatures, more oxygen vacancies can be introduced, and the carrier density can be tuned from ~ 1014 cm-2 to ~ 1016 cm-2. Another difference is that the superconducting transition temperature Tc in KTaO3 (111) increases linearly along with its carrier density, while the Ca0.5TaO3 (111) remains semiconducting when carrier density ranges from ~ 1014 cm-2 to ~ 1016 cm-2. Based on the density function theory calculation, Ca0.5TaO3 and KTaO3 show similar electronic band structures. According to the energy-dispersive X-ray spectroscopy, we found heavy Sr diffusion from the substrate to the Ca0.5TaO3 layer, which may destroy the interfacial conductivity. Our work demonstrates that besides the oxygen vacancies, electronic transport is sensitive to the atomic intermixing near the interface in tantulates. © 2025, CC BY.

关键词： Perovskite

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Modification of the Peierls-Nabarro model for misfit dislocation

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Chinese physics B 2020年第5期29卷 392-399页

作者： Shujun Zhang Shaofeng Wang Department of Physics and Institute for Structure and Function Chongqing UniversityChongqing 400030China

For a misfit dislocation,the balance equations satisfied by the displacement fields are modified,and an extra term proportional to the second-order derivative appears in the resulting misfit equation compared with the equation derived by Yao et *** second-order derivative describes the lattice discreteness effect that arises from the surface *** core structure of a misfit dislocation and the change in interfacial spacing that it induces are investigated theoretically in the framework of an improved Peierls-Nabarro equation in which the effect of discreteness is fully taken into *** an application,the structure of the misfit dislocation for a honeycomb structure in a two-dimensional heterostructure is presented.

关键词： interfacial misfit dislocation the energy of misfit dislocation

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Higher-order band topology in a twisted bilayer kagome lattice

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Physical Review B 2025年第8期111卷 085137-085137页

作者： Xiaolin Wan Junjie Zeng Ruixiang Zhu Dong-Hui Xu Baobing Zheng Rui Wang Institute for Structure and Function 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 College of Physics and Optoelectronic Technology Baoji University of Arts and Sciences Baoji 721016 People's Republic of China Lanzhou Center for Theoretical Physics Key Laboratory of Theoretical Physics of Gansu Province and Key Laboratory of Quantum Theory and Applications of MoE Lanzhou University Lanzhou Gansu 730000 China Center of Quantum Materials and Devices Chongqing University Chongqing 400044 People's Republic of China

Topologically protected corner states serve as a key indicator for two-dimensional higher-order topological insulators, yet they have not been experimentally identified in realistic materials. Here, by utilizing the effective tight-binding model and symmetry arguments, we establish a connection between higher-order topological insulators and twisted bilayer kagome lattices. We find that the topologically nontrivial bulk band gap arises in the twisted bilayer kagome lattice system due to twist-induced intervalley scattering, leading to the emergence of higher-order topological insulators with a range of commensurate twist angles, and the higher-order band topology is verified by the second Stiefel-Whitney number and fractionally quantized corner charges. Moreover, we investigate the influence of disorder and charge density wave order on the stability of higher-order topological insulator phases. The results show that the corner states of twisted bilayer kagome lattice systems are robust with respect to disorder and charge density wave. Our paper not only provides a feasible approach to realize the readily controllable higher-order topological insulator phases by employing a simple twist technique but also demonstrates that the twisted bilayer kagome lattice systems exhibit the robustness of higher-order band topology, making it feasible to check above prediction in experiments.

关键词： Topological insulators

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Controllable Weyl nodes and Fermi arcs from Floquet engineering triple fermions

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Physical Review B 2024年第12期110卷 L121118页

作者： Shengpu Huang Fangyang Zhan Xianyong Ding Dong-Hui Xu Da-Shuai Ma Rui Wang Institute for Structure and Function Department of Physics and Chongqing Key Laboratory for Strongly Coupled Physics Center of Quantum Materials and Devices

Floquet engineering with periodic driving as a powerful tool for designing desirable topological states has been the subject of intense recent studies. Here, we present the application of Floquet engineering to investigate the evolution of topological triple fermions under irradiation of circularly polarized light (CPL), a phenomenon that currently remains a mystery. By using first-principles calculations and Floquet theorem, we demonstrate that WC-type TiO and its analogs are promising candidates for Floquet engineering of triple fermions. The symmetry analysis reveals that the electric field of CPL can break the specific symmetries, such as the time-reversal symmetry and its combination of spatial symmetries, inducing a transition to a flexibly controllable Weyl semimetallic phase. The survived spatial symmetry, controlled by light, guarantees that the Weyl nodes are located along the high-symmetry line or in high-symmetry planes in momentum space. Our findings focusing on Floquet engineering in realistic materials featured by triple fermions would facilitate both theoretical and experimental interest.

关键词： Electronic structure Topological phases of matter Semimetals First-principles calculations

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Dislocation neutralizing in a self-organized array of dislocation and anti-dislocation

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Chinese physics B 2019年第11期28卷 251-257页

作者： Feng-Lin Deng Xiang-Sheng Hu Shao-Feng Wang Department of Physics and Institute for Structure and Function Chongqing UniversityChongqing 400030China Department of Mechanics Huazhong University of Science and TechnologyWuhan 430074China

A one-dimensional(1 D) self-organized array composed of dislocation and anti-dislocation is analytically investigated in the frame of Peierls theory. From the exact solution of the Peierls equation, it is found that there exists strong neutralizing effect that makes the Burgers vector of each individual dislocation in the equilibrium array smaller than that of an isolated dislocation. This neutralizing effect is not negligible even though dislocations are well separated. For example, when the distance between the dislocation and the anti-dislocation is as large as ten times of the dislocation width, the actual Burgers vector is only about 80% of an isolated dislocation. The neutralizing effect originates physically from the power-law asymptotic behavior that enables two dislocations interfere even though they are well separated.

关键词： dislocation array neutralizing exact solution

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Half-metallic ferromagneticWeyl fermions related to dynamic correlations in the zinc-blende compound VAs

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Chinese physics B 2024年第9期33卷 528-533页

作者： Xianyong Ding Haoran Wei Ruixiang Zhu Xiaoliang Xiao Xiaozhi Wu Rui Wang Institute for Structure and Function&Department of Physics&Chongqing Key Laboratory forStrongly Coupled Physics Chongqing UniversityChongqing 400044China Center of Quantum Materials and Devices Chongqing UniversityChongqing 400044China

The realization of 100%polarized topologicalWeyl fermions in half-metallic ferromagnets is of particular importance for fundamental research and spintronic ***,we theoretically investigate the electronic and topological properties of the zinc-blende compound VAs,which was deemed as a half-metallic ferromagnet related to dynamic *** on the combination of density functional theory and dynamical mean field theory,we uncover that the half-metallic ferromagnet VAs exhibits attractive Weyl semimetallic behaviors which are very close to the Fermi level in the DFT+U regime with effect U values ranging from 1.5 eV to 2.5 ***,we also investigate the magnetization-dependent topological properties;the results show that the change of magnetization directions only slightly affects the positions of Weyl points,which is attributed to the weak spin–orbital coupling *** topological surface states of VAs projected on semi-infinite(001)and(111)surfaces are *** Fermi arcs of all Weyl points are clearly visible on the projected Fermi *** findings suggest that VAs is a fully spin-polarized Weyl semimetal with many-body correlated effects in the effective U values range from 1.5 eV to 2.5 eV.

关键词： density functional theory Weyl semimetal dynamical mean field theory half metallic ferromagnet

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Orbital Order Triggered Out-of-Plane Ferroelectricity in Magnetic Transition Metal di-halide Monolayers

arXiv

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arXiv 2025年

作者： Luo, Xiao-Feng He, Xu Wang, Rui Xiang, Hongjun Zhao, Jin-Zhu Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials School of Physics South China Normal University Guangzhou510006 China Guangdong-Hong Kong Joint Laboratory of Quantum Matter South China Normal University Guangzhou510006 China Theoretical Materials Physics Q-MAT CESAM Université de Liège LiègeB-4000 Belgium 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 Center for Computational Science and Engineering Southern University of Science and Technology Shenzhen518055 China Institute of Computational Physical Sciences Department of Physics Fudan University Shanghai200433 China Shanghai Qi Zhi Institution Shanghai200030 China National Laboratory of Solid State Microstructures Nanjing University Nanjing210093 China

Although multiferroics have undergone extensive examination for several decades, the occurrence of ferroelectricity induced by orbital order is only scarcely documented. In this study, we propose the existence of spontaneous ferroelectric states featuring a finite out-of-plane polarization in monolayer compounds of magnetic transition metal di-halides. Our first principles analysis reveals that partially occupied d-orbital states within octahedra exhibit a preference for spatial orbital order within a two-dimensional lattice. The absence of inversion symmetry, arising from orbital order, serves as the driving force introducing additional electric polarization along the out-of-plane direction. Unlike previous reported orbital orders arising from metal states in lattice, the non-colinear ones we studied in this work relate to the transition between two insulator states. The resultant asymmetric Jahn-Teller distortions are accompanied as the consequence producing additional ionic polarization. Importantly, our findings indicate that this mechanism is not confined to a specific material but is a shared characteristic among a series of monolayer transition metal magnetic di-halides, proposing an innovative form of intrinsic two-dimensional multiferroic physics. © 2025, CC BY-NC-ND.

关键词： Metal halides

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Robustness of half-integer quantized Hall conductivity against disorder in an anisotropic Dirac semimetal with parity anomaly

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Physical Review B 2023年第4期108卷 L041104-L041104页

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

Two-dimensional Dirac semimetals with a single massless Dirac cone exhibit a parity anomaly. Usually, such a kind of anomalous topological semimetallic phase in real materials is unstable where any amount of disorder can drive it into a diffusive metal and destroy the half-integer quantized Hall conductivity as an indicator of parity anomaly. Here, based on a low-energy effective model, we propose an anisotropic Dirac semimetal which explicitly breaks time-reversal symmetry and carries half-integer quantized Hall conductivity. This topological semimetallic phase can be realized on a deformed honeycomb lattice subjected to a magnetic flux. Moreover, we perceptively investigate the disorder correction to the Hall conductivity. The results show that the effects of disorder can be strongly suppressed and thereby the nearly half-integer quantization of Hall conductivity can exist in a wide region of disorder, indicating that our proposed anisotropic Dirac semimetal is an exciting platform to investigate the parity anomaly phenomena.

关键词： Density of states Electrical conductivity Topological phases of matter Disordered systems Two-dimensional electron system Green's function methods Lattice models in condensed matter Tight-binding model k dot p method

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Weyl nodes with higher-order topology in an optically driven nodal-line semimetal

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Physical Review B 2022年第8期105卷 L081102-L081102页

作者： Xiu-Li Du Rui Chen Rui Wang Dong-Hui Xu Department of Physics Hubei University Wuhan 430062 China Shenzhen Institute for Quantum Science and Engineering and Department of Physics Southern University of Science and Technology (SUSTech) Shenzhen 518055 China Institute for Structure and Function and Department of Physics Chongqing University Chongqing 400044 China Chongqing Key Laboratory for Strongly Coupled Physics Chongqing 400044 China Center for Quantum Materials and Devices Chongqing University Chongqing 400044 China

Creating and manipulating topological states is a key goal of condensed matter physics. Periodic driving offers a powerful method to manipulate electronic states, and even to create topological states in solids. Here, we investigate the tunable Floquet states in a periodically driven higher-order nodal-line semimetal with both spatial inversion and time-reversal symmetries. We found that the Floquet Weyl semimetal states, which support both one-dimensional hinge Fermi arc and two-dimensional surface Fermi arc states, can be induced in the higher-order nodal-line semimetal by shining circularly polarized light. Moreover, we show that the location of Weyl nodes and the curvature of surface Fermi arcs can be tuned by adjusting the propagation direction and incident angle of light.

关键词： Topological phase transition Topological phases of matter Floquet systems Bloch-Floquet theorem

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