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

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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Topological corner states in graphene by bulk and edge engineering

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Physical Review B 2022年第20期106卷 L201407-L201407页

作者： Junjie Zeng Chen Chen Yafei Ren Zheng Liu Wei Ren Zhenhua Qiao CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics and Department of Physics University of Science and Technology of China Hefei Anhui 230026 China Chongqing Key Laboratory for Strongly Coupled Physics and Institute for Structure and Function Department of Physics Chongqing University Chongqing 401331 China International Center for Quantum and Molecular Structures Materials Genome Institute Physics Department and Shanghai Key Laboratory of High Temperature Superconductors Shanghai University Shanghai 200444 China Department of Materials Science and Engineering University of Washington Seattle Washington 98195 USA ICQD Hefei National Laboratory for Physical Sciences at Microscale University of Science and Technology of China Hefei Anhui 230026 China

Two-dimensional higher-order topology is usually studied in (nearly) particle-hole symmetric models, so that an edge gap can be opened within the bulk one. But more often the edge anticrossing deviates even into the bulk, where corner states are difficult to pinpoint. We address this problem in a graphene-based Z2 topological insulator with spin-orbit coupling and in-plane magnetization both originating from substrates through a Slater-Koster multiorbital model. The gapless helical edge modes cross inside the bulk, where the magnetization-induced edge gap is also located. After demonstrating its second-order nontriviality in bulk topology by a series of evidence, we show that a difference in bulk-edge on-site energy can adiabatically tune the position of the crossing/anticrossing of the edge modes to be inside the bulk gap. This can help unambiguously identify two pairs of topological corner states with nonvanishing energy degeneracy for a rhombic flake. We further find that the obtuse-angle pair is more stable than the acute-angle one.

关键词： Edge states Spin-orbit coupling Topological phases of matter Graphene Topological insulators

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

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Quantum Frontiers 2024年第1期3卷 1-21页

作者： Zhan, Fangyang Chen, Rui Ning, Zhen Ma, Da-Shuai Wang, Ziming Xu, Dong-Hui Wang, Rui Institute for Structure and Function & amp Department of Physics & amp Chongqing Key Laboratory for Strongly Coupled Physics Chongqing University Chongqing 400044 China Center of Quantum Materials and Devices Chongqing University Chongqing 400044 China Department of Physics Hubei University Wuhan 430062 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. © The Author(s) 2024.

关键词： Effective models First-principles calculations Floquet engineering Topological states

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Circularly polarized light irradiated ferromagnetic MnBi2Te4: A possible ideal Weyl semimetal

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Physical Review B 2024年第12期110卷 125204页

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

The interaction between light and nontrivial 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 (WPs) in systems without time-reversal symmetry. More importantly, in FM MnBi2Te4 with an 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 the 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 an in-plane easy magnetization axis, the system becomes a type-I Weyl semimetal under CPL irradiation. With controllable band dispersion, the length of the Fermi arc, and a minimum number of WPs, our results indicate that CPL-irradiated FM MnBi2Te4 is an ideal platform for the study of novel transport phenomena in Weyl semimetals with distinct band dispersion.

关键词： Electronic structure First-principles calculations Topological materials Weyl semimetal

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Obstructed atomic insulators with robust corner modes

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Physical Review B 2023年第10期108卷 L100101-L100101页

作者： Da-Shuai Ma Kejun Yu Xiao-Ping Li Xiaoyuan Zhou 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 Center of Quantum materials and devices Chongqing University Chongqing 400044 People's Republic of China 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 Lab of Nanophotonics and Ultrafine Optoelectronic Systems School of Physics Beijing Institute of Technology Beijing 100081 China School of Physical Science and Technology Inner Mongolia University Hohhot 010021 China

Higher-order topological insulators (HOTIs), that are classified as obstructed atomic insulators (OAIs) in the topological quantum chemistry (TQC) theory, attract great interest owning to the lower-dimensional topological boundary states. However, the boundary states in HOTIs reported so far are often fragile, manifested as strongly depending on crystalline symmetries and cleavage terminations in the disk or cylinder geometry. Here, using the TQC theory, we propose an intuitive strategy to establish the connection between the obstructed Wannier charge centers of OAIs and the emergence of robust corner states in two-dimensional systems. Based on first-principles calculations and real space invariant theory, we extend the concept of OAIs to phonon systems and thereby predict that the robust corner states can be realized in the phonon spectra of MX3 (M = Bi, Sb, As, Sc, Y; X = I, Br, Cl) monolayers. The phonon corner modes in different shapes of nanodisks are investigated, and their robustness facilitates the detection in experiments and further applications. This work suggests a promising avenue to explore more attractive features of higher-order band topology beyond the existing paradigm.

关键词： Edge states First-principles calculations Phonons Topological materials Topological phases of matter 2-dimensional systems Topological insulators High-throughput calculations Wannier function methods

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Temperature-dependent and magnetism-controlled Fermi surface changes in magnetic Weyl semimetals

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Physical Review Research 2023年第2期5卷 L022013-L022013页

作者： Nan Zhang Xianyong Ding Fangyang Zhan Houpu Li Hongyu Li Kaixin Tang Yingcai Qian Senyang Pan Xiaoliang Xiao Jinglei Zhang Rui Wang Ziji Xiang Xianhui 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 and Center for Quantum Materials and Devices Chongqing University Chongqing 400044 China High Magnetic Field Laboratory Chinese Academy of Sciences Hefei Anhui 230031 China Collaborative Innovation Center of Advanced Microstructures Nanjing University Nanjing 210093 China

The coupling between band structure and magnetism can lead to intricate Fermi surface modifications. Here we report on the comprehensive study of the Shubnikov–de Haas (SdH) effect in two rare-earth-based magnetic Weyl semimetals, NdAlSi and CeAlSi0.8Ge0.2. The results show that the temperature evolution of topologically nontrivial Fermi surfaces strongly depends on magnetic configurations. In NdAlSi, the SdH frequencies vary with temperature in both the paramagnetic state and the magnetically ordered state with a chiral spin texture, but become temperature independent in the high-field fully polarized state. In CeAlSi0.8Ge0.2, SdH frequencies are temperature dependent only in the ferromagnetic state with magnetic fields applied along the axis. First-principles calculations suggest that the notable temperature and magnetic-configuration dependence of Fermi surface morphology can be attributed to strong exchange coupling between the conduction electrons and local magnetic moments.

关键词： Fermi surface First-principles calculations High magnetic fields Landau levels Magnetotransport Topological materials Transport phenomena Ferromagnets Weyl semimetal Quantum oscillation techniques Resistivity measurements Shubnikov-de Haas effect

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Hourglass phonons jointly protected by symmorphic and nonsymmorphic symmetries

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Physical Review B 2021年第6期104卷 L060301-L060301页

作者： Baobing Zheng Fangyang Zhan Xiaozhi Wu Rui Wang Jing Fan College of Physics and Optoelectronic Technology & Advanced Titanium Alloys and Functional Coatings Cooperative Innovation Center Baoji University of Arts and Sciences Baoji 721016 People's Republic of China 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 Center for Quantum Materials and Devices 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

Hourglass dispersion is generally believed to be solely protected by nonsymmorphic symmetries, because these symmetries can introduce high-dimensional projective representations. Here, based on symmetry arguments, we propose that the hourglass dispersion can be jointly protected by symmorphic and nonsymmorphic symmetries, instead of the conventional nonsymmorphic symmetry. Moreover, using first-principles calculations, we realize our proposal in the phonon spectra of realistic materials that share an antiperovskite structure with space group P4/nmm. Importantly, the neck points of these hourglass dispersions trace out two nodal rings tangential to four nodal lines, forming a unique hourglass nodal cage in the bulk Brillouin zone. The Berry phase analysis reveals the nontrivial topology of these nodal rings and nodal lines. Furthermore, nontrivial surface states and isofrequency surface arcs are visible, facilitating their experimental confirmation of such exotic quasiparticles. work not only offers different insights into the hourglass dispersion, but also expands aspects for studying promising topological quasiparticles in condensed-matter systems.

关键词： Electronic structure Lattice dynamics Phonons Symmetry protected topological states Node-line semimetals First-principles calculations

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Electronic structure and effective mass of pristine and Cl-doped CsPbBr_(3)

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Chinese physics B 2024年第5期33卷 167-171页

作者：魏志远魏愉昊徐申东彭舒婷 Makoto Hashimoto 路东辉潘旭匡泯泉肖正国何俊峰 Department of Physics and CAS Key Laboratory of Strongly-coupled Quantum Matter Physics University of Science and Technology of ChinaHefei 230026China Chongqing Key Laboratory of Micro & Nano Structure Optoelectronics and School of Physical Science and TechnologySouthwest UniversityChongqing 400715China Key Laboratory of Photovoltaic and Energy Conservation Materials Institute of Applied TechnologyHefei Institutes of Physical ScienceChinese Academy of SciencesHefei 230031China Stanford Synchrotron Radiation Lightsource and Stanford Institute for Materials and Energy Sciences SLAC National Accelerator LaboratoryMenlo ParkCalifornia 94025USA

Organic–inorganic lead halide perovskites(LHPs) have attracted great interest owing to their outstanding optoelectronic ***,the underlying electronic structure would determinate the physical properties of *** as for now,limited studies have been done to reveal the underlying electronic structure of this material system,comparing to the huge amount of investigations on the material *** effective mass of the valance band is one of the most important physical parameters which plays a dominant role in charge transport and photovoltaic *** pristine CsPbBr_(3),the Fr?hlich polarons associated with the Pb–Br stretching modes are proposed to be responsible for the effective mass *** this regard,it would be very interesting to explore the electronic structure in doped ***,we report high-resolution angle-resolved photoemission spectroscopy(ARPES) studies on both pristine and Cl-doped CsPbBr_(3).The experimental band dispersions are extracted from ARPES spectra along both ■ and ■ high symmetry *** calculations are performed and directly compared with the ARPES *** results have revealed the band structure of Cl-doped CsPbBr_(3) for the first time,which have also unveiled the effective mass renormalization in the Cl-doped CsPbBr_(3) *** dependent measurements indicate that the chlorine doping could moderately tune the renormalization *** results will help understand the physical properties of LHPs as a function of doping.

关键词： lead halide perovskites electronic structure effective mass

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

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Physical Review Letters 2024年第24期133卷 246606-246606页

作者： Zhen Ning Da-Shuai Ma Junjie Zeng 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 and Center of Quantum Materials and Devices Chongqing University Chongqing 400044 People’s Republic of 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 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 transitions arise from the simultaneous creations (or annihilations) of valley pairs, which are attributed to the intertwining with magnetic symmetry, superconductivity, and topology. Our findings provide a feasible approach for achieving the Floquet chiral topological superconductivity with flexible tunability, which would draw extensive attention in experiments.

关键词： Antiferromagnetism

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Rationally Design of Near Infrared Light Responsive Micro-Photoelectrodes for In Vivo Sensing of Neurotransmitter Molecules in Mouse Brain

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Chinese Journal of Chemistry 2020年第3期38卷 275-281页

作者： Yina Zhao Wenlong Wu Baihe Fu Liyong Gan Zhonghai Zhang Shanghai Key Laboratory of Green Chemistry and Chemical Processes School of Chemistry and Molecular EngineeringEast China Normal University500 Dongchuan RoadShanghai 200241China Institute for Structure and Function and Deportment of Physics Chongqing UniversityChongqing 400030China

The accurate quantification of neurotransmitter molecules is an indispensable means to reveal the physiological mechanisms of neuro movement in molecular ***,existing detection strategies cannot fully meet practical needs,and the on-site and in vivo detection of neurotransmitters in brain remains a great ***,we report the development of a near infrared light responsive photo-electrochemical(PEC)detection method for in vivo quantification of neurotransmitter dopamine in mouse *** guidance of density function theory calculations,a combination strategy of non-metal cation doping and defect engineering is introduced to rationally design the micro-photoelec-trodes with excellent biocompatibility and stability and implements the in vivo PEC detection of dopamine in mouse *** opens up a new way for the accurate in vivo detection of biomolecules and allows researchers to make novel inquiries for long-standing questions in a new way.

关键词： Infrared Rational vivo

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