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Chinese physics B 2022年第8期31卷 517-529页

作者： Hao Xiang Rui Wang Feng-Lin Deng Shao-Feng Wang Department of Physics and Institute for Structure and Function Chongqing UniversityChongqing 401331China CAS Key Laboratory of Magnetic Materials and Devices Ningbo Institute of Materials Technology and EngineeringChinese Academy of SciencesNingbo 315201China Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology Ningbo Institute of Materials Technology and EngineeringChinese Academy of SciencesNingbo 315201China

The core structure,Peierls stress and core energy,*** comprehensively investigated for the 90°dislocation and the 60°dislocation in metal aluminum using the fully discrete Peierls model,and in particular thermal effects are included for temperature range 0≤T≤900 *** the 90°dislocation,the core clearly dissociates into two partial dislocations with the separating distance D~12?,and the Peierls stress is very smallσp<1 k *** nearly vanishing Peierls stress results from the large characteristic width and a small step length of the 90°*** 60°dislocation dissociates into 30°and 90°partial dislocations with the separating distance D~*** Peierls stress of the 60°dislocation grows up from1 MPa to 2 MPa as the temperature increases from 0 K to 900 *** influence on the core structures is weak for both the 90°dislocation and the 60°*** core structures theoretically predicted at T=0 K are also confirmed by the first principle simulations.

关键词： dislocation temperature effect aluminum

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

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Physical Review Letters 2023年第25期131卷 256901-256901页

作者： Wenhao Liang Junjie Zeng Zhenhua Qiao Yang Gao Qian Niu International Centre for Quantum Design of Functional Materials CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics and Department of Physics University of Science and Technology of China Hefei Anhui 230026 China Institute for Structure and Function Department of Physics and Chongqing Key Laboratory for Strongly Coupled Physics Chongqing University Chongqing 400044 China Hefei National Laboratory University of Science and Technology of China Hefei 230088 China

In two-dimensional antiferromagnets, we find that the mixed Berry curvature can be attributed as the geometrical origin of the nonreciprocal directional dichroism (NDD), which refers to the difference in light absorption between opposite propagation directions. This Berry curvature is closely related to the uniaxial strain in accordance with the symmetry constraint, leading to a highly tunable NDD, whose sign and strength can be tuned via strain direction. We choose the lattice model of MnBi2Te4 as a concrete example. The coupling between 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, which is 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 for the Berry-curvature engineering for optical nonreciprocity in two-dimensional antiferromagnets.

关键词： Geometric & topological phases Non-reciprocal transmission Bilayer films Tight-binding model

Multiple PD sources separation of oil-paper insulation using S transform based similarity

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Multiple PD sources separation of oil-paper insulation using...

2012 International Conference on High Voltage Engineering and Application, ICHVE 2012

作者： Wang, Ke Liao, Ruijin Yang, Lijun Li, Shaorong Qi, Chaoliang State Key Laboratory of Power Transmission Equipment and System Security and New Technology Chongqing University Chongqing China Institute for Structure and Function Department of Physics Chongqing University Chongqing China

ISBN: (纸本)9781467347464

A new algorithm for multiple partial discharge sources separation is proposed in this paper. ST is firstly employed to obtain the time-frequency representation of original PD pulses. Then, PD pulses similarity matrix is computed based on ST amplitude matrix. By using the pulses similarity matrix, affinity propagation clustering is applied to perform the automatic separation of PD pulses. The proposed algorithm is tested by multiple PD sources generated by manually combining pulses from different single sources. It is shown that the successful rates of pulses separation 99.63% and 98.35% are obtained in two application cases. Results demonstrate that it is feasible to apply ST and APC to realize multiple PD source separation. © 2012 IEEE.

关键词： Partial discharges

Design of Antiferromagnetic Second-order Band Topology with Rotation Topological Invariants in Two Dimensions

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arXiv 2023年

作者： Zhan, Fangyang Qin, Zheng Xu, Dong-Hui Zhou, Xiaoyuan Ma, Da-Shuai 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

The existence of fractionally quantized topological corner states serves as a key indicator for two-dimensional second-order topological insulators (SOTIs), yet has not been experimentally observed in realistic materials. Here, based on effective model analysis and symmetry arguments, we propose a strategy for achieving SOTI phases with in-gap corner states in two dimensional systems with antiferromagnetic (AFM) order. We uncover by a minimum lattice model that the band topology originates from the interplay between intrinsic spin-orbital coupling and interlayer AFM exchange interactions. Using first principles calculations, we show that the 2D AFM SOTI phases can be realized in (MnBi2Te4)(Bi2Te3)m films. Moreover, we demonstrate that the nontrivial corner states are linked to rotation topological invariants under three-fold rotation symmetry C3, resulting in C3-symmetric SOTIs with corner charges fractionally quantized to 3n |e| (mod e). Due to the great recent achievements in (MnBi2Te4)(Bi2Te3)m systems, our results providing reliable material candidates for experimentally accessible AFM higher-order band topology would draw intense attentions. Copyright © 2023, The Authors. All rights reserved.

关键词： Topology

Pressure-induced superconductivity and nontrivial band topology in compressed γ-InSe

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Physical Review B 2022年第21期105卷 214506-214506页

作者： Shiqiu Liu Ye Yang Fanghang Yu Xikai Wen Zhigang Gui Kunling Peng Rui Wang Jianjun Ying Department of Physics and CAS Key Laboratory of Strongly-coupled Quantum Matter Physics University of Science and Technology of China Hefei Anhui 230026 China Institute for Structure and Function & Department of physics & Center for Quantum Materials and Devices Chongqing University Chongqing 400044 China

We performed high-pressure electrical transport and Raman measurements on a two-dimensional rhombohedral semiconductor γ-InSe. Our results confirm two structural phase transitions at high pressure. More interestingly, a domelike superconducting transition with maximum Tc around 2.3 K is discovered when the compound transforms to the cubic CsCl phase above 40 GPa. Our first-principles calculations indicate that the high-pressure superconducting phase possesses nontrivial topological band structure in the vicinity of the Fermi level. These results show that the physical properties in this material strongly depend on its structure, which provides insights into the interplay between superconductivity and topological physics. Our work suggests promising emergent phenomena in this material and other related III-VI semiconductors under high-pressure conditions.

关键词： Pressure effects Superconductivity Layered semiconductors Topological materials

Flexible Control of Chiral Superconductivity in Optically Driven Nodal Point Superconductors with Antiferromagnetism

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arXiv 2024年

作者： Ning, Zhen Zeng, Junjie Ma, Da-Shuai 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

Recent studies have attracted widespread attention on magnet-superconductor hybrid systems with emergent topological superconductivity. Here, we present the Floquet engineering of realistic two-dimensional topological nodal-point superconductors that are composed of antiferromagnetic monolayers in proximity to an s-wave superconductor. We show that Floquet chiral topological superconductivity arises naturally due to light-induced breaking of the effective time-reversal symmetry. More strikingly, we find that the Floquet chiral topological superconducting phases can be flexibly controlled by irradiating elliptically polarized light, with the photon-dressed quasienergy spectrum carrying different Chern numbers. Such optically switchable topological transition is attributed to the simultaneous creations (or annihilations) of valley pairs. Our findings provide a feasible approach for achieving the Floquet chiral topological superconductivity with flexible tunability, which would draw extensive attention in experiments. Copyright © 2024, The Authors. All rights reserved.

关键词： Superconducting materials

Realization of kagome lattice and superconductivity in topological electrides

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Physical Review B 2024年第5期110卷 054511-054511页

作者： Yu-Hao Wei Hao-Dong Liu Da-Shuai Ma Hong-Kuan Yuan Bao-Tian Wang Min-Quan Kuang Chongqing Key Laboratory of Micro & Nano Structure Optoelectronics and School of Physical Science and Technology Chinese Academy of Sciences Beijing 100049 People's Republic of China Dongguan 523803 People's Republic of China Institute for Structure and Function & Department of Physics & Chongqing Key Laboratory for Strongly Coupled Physics Center of Quantum Materials and Devices

Realization of kagome lattice, and hence achieving specific performance, is a challenging issue in condensed matter physics. The corner-sharing triangles of kagome lattice are normally comprised of real atoms occupying certain Wyckoff sites. Here, we propose that the excess electrons in layered electrides Mg3N and Mg3O build the two-dimensional kagome lattices. The interstitial electrons further contribute to the nontrivial band topology, i.e., the Dirac points and the Dirac nodal lines in Mg3N and Mg3O. Further, the in-plane coupling between the electronic orbitals and the atomic vibrational modes dominate the electron-phonon coupling, and yield superconducting critical temperatures approaching 2.0 and 2.2 K for Mg3N and Mg3O, respectively. This work proposes a feasible scheme to construct kagome lattices by interstitial quasiatoms and provides a promising platform to explore the superconductivity and nontrivial band topology in kagome electrides.

关键词： Superconductivity Kagome lattice Topological materials First-principles calculations

Circularly polarized light irradiated ferromagnetic MnBi2Te4: the long-sought ideal Weyl semimetal

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arXiv 2024年

作者： Fan, Shuai Huang, Shengpu Chen, Zhuo Zhan, Fangyang Ding, Xian-Yong Ma, Da-Shuai 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

The interaction between light and non-trivial energy band topology allows for the precise manipulation of topological quantum states, which has attracted intensive interest in condensed matter physics. In this work, using first-principles calculations, we studied the topological transition of ferromagnetic (FM) MnBi2Te4 upon irradiation with circularly polarized light (CPL). We revealed that the MnBi2Te4 can be driven from an FM insulator to a Weyl semimetal with a minimum number of Weyl points, i.e., two Weyl points in systems without time-reversal symmetry. More importantly, in FM MnBi2Te4 with out-of-plane easy magnetization axis, we found that the band dispersion of the WP evolves from Type-II to Type-III and finally to Type-I when the light intensity increases. Moreover, we show that the profile of the characteristic Fermi arc of Weyl semimetal phase is sensitive to changes in light intensity, which enables efficient manipulation of the Fermi arc length of FM MnBi2Te4 in experiments. In addition, for FM MnBi2Te4 with in-plane easy magnetization axis, the system becomes a type I Weyl semimetal under CPL irradiation. With controllable band dispersion, length of Fermi arc, and minimum number of WPs, our results indicate that CPL-irradiated FM MnBi2Te4 is an ideal platform to study novel transport phenomena in Weyl semimetals with distinct band dispersion. Copyright © 2024, The Authors. All rights reserved.

关键词： Dispersions

Robustness of Half-Integer Quantized Hall Conductivity against Disorder in an Anisotropic Dirac Semimetal with Parity Anomaly

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arXiv 2023年

作者： Ning, Zhen Ding, Xianyong 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

Two-dimensional Dirac semimetals with a single massless Dirac cone exhibit the 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 low-energy effective model, we propose an anisotropic Dirac semimetal which explicitly breaks time-reversal symmetry and carries a 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. Copyright © 2023, The Authors. All rights reserved.

关键词： Topology

Controllable Weyl Nodes and Fermi Arcs from Floquet Engineering Triple Fermions

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arXiv 2024年

作者： Huang, Shengpu Zhan, Fangyang Ding, Xianyong Xu, Dong-Hui Ma, Da-Shuai 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

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 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 analogues 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. © 2024, CC BY.

关键词： Topology