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Symmetry dictionary on charge and spin nonlinear responses for all magnetic point groups with nontrivial topological nature

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National Science Review 2023年第11期10卷 103-109页

作者： Zhi-Fan Zhang Zhen-gang Zhu gang su School of Physical Sciences University of Chinese Academy of Sciences School of Electronic Electrical and Communication EngineeringUniversity of Chinese Academy of Sciences CAS Center for Excellence in Topological Quantum Computation University of Chinese Academy of Sciences Kavli Institute for Theoretical Sciences University of Chinese Academy of Sciences

Recently, charge or spin nonlinear transport with nontrivial topological properties in crystal materials has attracted much attention. In this paper, we perform a comprehensive symmetry analysis for all 122 magnetic point groups(MPGs) and provide a useful dictionary for charge and spin nonlinear transport from the Berry curvature dipole, Berry connection polarizability and Drude term with nontrivial topological *** results are obtained by conducting a full symmetry investigation of the matrix representations of six nonlinear response tensors. We further identify every MPG that can accommodate two or three of the nonlinear tensors. The present work gives a solid theoretical basis for an overall understanding of the second-order nonlinear responses in realistic materials.

关键词： nonlinear response magnetic point group matrix representation

Spin manipulations through electrical and thermoelectrical transport in magnetic tunnel junctions

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Science China(Physics,Mechanics & Astronomy) 2013年第1期56卷 166-183页

作者： ZHU Zhengang su gang School of Electronics Eletrical and Communication EngineeringUniversity of Chinese Academy of Sciences Institut fr Physik Martin-Luther-UniversittHalle-Wittenberg Nanotechnikum-WeinbergHeinrich-Damerow-Strasse 4 D-06120 Halle(Saale)Germany School of Physics University of Chinese Academy of Sciences

A brief review is presented,which includes the direct current,alternate current,electrical and thermoelectrical transport as well as spin transfer effect in a variety of spin-based nanostructures such as the magnetic tunnel junction(MTJ),ferromagnet(FM)-quantum dot(QD)/FM-FM,double barrier MTJ,FM-marginal Fermi liquid-FM,FM-unconventional superconductor-FM(FUSF),quantum ring and optical spin-field-effect *** magnetoresistances in those structures,spin accumulation effect in FM-QD-FM and FUSF systems,spin injection and spin filter into semiconductor,spin transfer effect,photon-assisted spin transport,magnonassisted tunneling,electron-electron interaction effect on spin transport,laser-controlled spin dynamics,and thermoelectrical spin transport are discussed.

关键词： spintronics magnetic tunnel junction spin transport magnetoresistance spin transfer torque spin injection spin filter spin-valve spin-orbit

The p-orbital magnetic topological states on a square lattice

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National Science Review 2022年第4期9卷 84-91页

作者： Jing-Yang You Bo Gu gang su Kavli Institute for Theoretical Sciences and CAS Center for Excellence in Topological Quantum ComputationUniversity of Chinese Academy of Sciences Department of Physics Faculty of ScienceNational University of Singapore Physical Science Laboratory Huairou National Comprehensive Science Center School of Physical Sciences University of Chinese Academy of Sciences

Honeycomb or triangular lattices were extensively studied and thought to be proper platforms for realizing the quantum anomalous Hall effect（QAHE）, where magnetism is usually caused by d orbitals of transition metals. Here we propose that a square lattice can host three magnetic topological states, including the fully spin-polarized nodal loop semimetal, QAHE and the topologically trivial ferromagnetic semiconductor, in terms of the symmetry and k · p model analyses that are material independent. A phase diagram is presented. We further show that the above three magnetic topological states can indeed be implemented in the two-dimensional（2 D） materials Sc Li Cl5, Li Sc Z5（Z=Cl, Br） and Sc Li Br5, *** ferromagnetism in these 2 D materials is microscopically revealed from p electrons of halogen atoms. This present study opens a door to explore the exotic topological states as well as quantum magnetism from p-orbital electrons by means of the material-independent approach.

关键词： p-orbital magnetism square lattice topological states

High temperature ferrimagnetic semiconductors by spin-dependent doping in high temperature antiferromagnets

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npj Computational Materials 2024年第1期10卷 1116-1125页

作者： Jia-Wen Li gang su Bo Gu Kavli Institute for Theoretical Sciences University of Chinese Academy of SciencesBeijngChina CAS Center for Excellence in Topological Quantum Computation University of Chinese Academy of SciencesBeijngChina Physical Science Laboratory Huairou National Comprehensive Science CenterBeijingChina School of Physical Sciences University of Chinese Academy of SciencesBeijngChina

To realize room temperature ferromagnetic(FM)semiconductors is still a challenge in *** antiferromagnetic(AFM)insulators and semiconductors with high Neel temperature TN are obtained in experiments,such as LaFeO_(3),BiFeO_(3),*** concentrations of magnetic impurities can be doped into these AFM materials,but AFM state with very tiny net magnetic moments was obtained in experiments because the magnetic impurities were equally doped into the spin up and down sublattices of the AFM ***,we propose that the effective magnetic field provided by a FM substrate could guarantee the spin-dependent doping in AFM materials,where the doped magnetic impurities prefer one sublattice of spins,and the ferrimagnetic(FIM)materials are *** demonstrate this proposal,we study the Mn-doped AFM insulator LaFeO_(3)with FM substrate of Fe metal by the density functional theory(DFT)calculations.

关键词： materials. magnetic high

The Generalized West Decomposition of Operators and Other Compact Perturbation Problems

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Acta Mathematica Sinica,English Series 2006年第2期22卷 515-522页

作者： Wei gang su Huai Jie ZHONG School of Mathematics and Computer Science Fujian Normal University

This paper introduces the concept of the generalized Riesz operators and the concept of the generalized West decomposition of a general operator which generalizes the definition of the West decomposition of Riesz operators, and proves that the following three statements are equivalent on a general Banach space：（a） Every generalized Riesz operator has the generalized West decomposition; （b） Every operator makes strong Stampfli theorem true; Every operator has Apostol＇s compact correction.

关键词： correction Banach space generalized Riesz operator generalized West decomposition compact

Magnetization Reversal of Single-Molecular Magnets by a Spin-Polarized Current

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Chinese Physics Letters 2020年第8期37卷 108-113页

作者： Chao Yang Zheng-Chuan Wang gang su School of Physical Sciences University of Chinese Academy of SciencesBeijng 100049China Kavli Institute for Theoretical Physics CAS Center for Excellence in Topological Quantum ComputationUniversity of Chinese Academy of SciencesBeijing 100190China

We study the magnetization reversal of single-molecular magnets by a spin-polarized current in the framework of the spinor Boltzmann *** of the spin–orbit coupling,the spin-polarized current will impose a non-zero spin transfer torque on the single-molecular magnets,which will induce the magnetization switching of the *** the s–d exchange interaction between the conducting electrons and single-molecular magnets,we can investigate the magnetization dynamics of single-molecular *** demonstrate the dynamics of the magnetization based on the spin diffusion equation and the Heisenberg-like *** results show that when the current is large enough,the magnetization of the single-molecular magnets can be *** also calculate the critical current density required for the magnetization reversal under different anisotropy and external magnetic fields,which is helpful for the corresponding experimental design.

关键词： magnetization magnets reversed

A versatile model with three-dimensional triangular lattice for unconventional transport and various topological effects

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National Science Review 2024年第1期11卷 204-214页

作者： Jing-Yang You gang su Yuan Ping Feng Department of Physics National University of Singapore Kavli Institute for Theoretical Sciences and CAS Center for Excellence in Topological Quantum Computation University of Chinese Academy of Sciences Centre for Advanced 2D Materials National University of Singapore

The finite Berry curvature in topological materials can induce many subtle phenomena, such as the anomalous Hall effect(AHE), spin Hall effect(SHE), anomalous Nernst effect(ANE), non-linear Hall effect(NLHE) and bulk photovoltaic effects. To explore these novel physics as well as their connection and coupling, a precise and effective model should be developed. Here, we propose such a versatile model—a 3D triangular lattice with alternating hopping parameters, which can yield various topological phases,including kagome bands, triply degenerate fermions, double Weyl semimetals and so on. We reveal that this special lattice can present unconventional transport due to its unique topological surface states and the aforementioned topological phenomena, such as AHE, ANE, NLHE and the topological photocurrent effect. In addition, we also provide a number of material candidates that have been synthesized experimentally with this lattice, and discuss two materials, including a non-magnetic triangular system for SHE, NLHE and the shift current, and a ferromagnetic triangular lattice for AHE and ANE. Our work provides an excellent platform, including both the model and materials, for the study of Berry-curvature-related physics.

关键词： three-dimensional triangular lattice different topological phases various topological effects Berry curvature

The atlas of ferroicity in two-dimensional MGeX_(3) family:Room-temperature ferromagnetic half metals and unexpected ferroelectricity and ferroelasticity

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Nano Research 2021年第12期14卷 4732-4739页

作者： Kuan-Rong Hao Xing-Yu Ma Hou-Yi Lyu Zhen-gang Zhu Qing-Bo Yan gang su School of Physical Sciences University of Chinese Academy of SciencesBeijing100049China School of Electronic Electrical and Communication EngineeringUniversity of Chinese Academy of SciencesBeijing100049China Center of Materials Science and Optoelectronics Engineering College of Materials Science and Optoelectronic TechnologyUniversity of Chinese Academy of SciencesBeijing100049China Kavli Institute for Theoretical Sciences and CAS Center of Excellence in Topological Quantum ComputationUniversity of Chinese Academy of SciencesBeijing100190China

Two-dimensional(2D)ferromagnetic and ferroelectric materials attract unprecedented attention due to the spontaneous-symmetry-breaking induced novel properties and multifarious potential *** we systematically investigate a large family(148)of 2D MGeX3(M=metal elements,X=O/S/Se/Te)by means of the high-throughput first-principles calculations,and focus on their possible ferroic properties including ferromagnetism,ferroelectricity,and *** discover eight stable 2D ferromagnets including five semiconductors and three half-metals,212D antiferromagnets,and 11 stable 2D ferroelectric semiconductors including two multiferroic ***,MnGeSe3 and MnGeTe3 are predicted to be room-temperature 2D ferromagnetic half metals with Tc of 490 and 308 K,*** is probably for the first time that ferroelectricity is uncovered in 2D MGeX3 family,which derives from the spontaneous symmetry breaking induced by unexpected displacements of Ge-Ge atomic pairs,and we also reveal that the electric polarizations are in proportion to the ratio of electronegativity of X and M atoms,and IVB group metal elements are highly favored for 2D *** tunnel junction and water-splitting photocatalyst based on 2D ferroic MGeX3 are proposed as examples of wide potential *** atlas of ferroicity in 2D MGeX3 materials will spur great interest in experimental studies and would lead to diverse applications.

关键词： two-dimensional materials ferroicity ferroelectricity ferroelasticity ferromagnetic half metal

An Analytical Approach to Thermal and Electrical Transport in a Mesoscopic Conductor

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Communications in Theoretical Physics 2005年第4X期44卷 735-742页

作者： WANG Zheng-Chuan su gang LI Ling GAO Jie Department of Physics Graduate School of the Chinese Academy of Sciences Beijing 100049 China Department of Physics Sichuan University Chengdu 610018 China

In order to consider the thermal and electrical coherent transport in a mesoscopic conductor under the influence of electron-electron interaction, in this paper, we establish a method in terms of which one can analytically obtain the Hartree self-consistent potential instead of computing it by the numerical iterative procedure as usual, which is convenient for us to describe the thermal and electric current flow through a mesoscopic conductor. If we study the electron-electron interaction at the Hartree approximation level, the Hartree potential satisfies the Poisson equation and Schroedinger equation, so when we expand the action function S（x） by Planck constant h, the self-consistent potential and the wavefunction can be solved analytically order by order, and the thermal and electrical conductance can thus be obtained readily. However, we just show the quantum corrections up to the second order.

关键词： mesoscopic conductor thermal and electrical transport