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Theory for superconductivity in alkali chromium arsenides A2Cr3As3 (A = K, Rb, Cs)

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Science Bulletin 2017年第3期62卷 208-211页

作者： Yi Zhou Chao Cao fu-chun zhang Department of Physics Zhejiang University Hangzhou 310027 China Collaborative Innovation Center of Advanced Microstructures Nanjing 210093 China Department of Physics Hangzhou Normal University Hangzhou 310036 China

Recently,CrAs based superconductors have attracted much *** itself is a 3D antiferromagnet(AFM),which becomes superconducting(SC)under modest pressure with T_C^2 K[1].Subsequently,a new family of quasi-lD superconductors A_2Cr_3As_3(A=K,Rb,Cs)has been discovered at ambient pressure with T_c up to 6.1 K[2-4].The key building block of

关键词：氧化物高温超导体 Rb Cs 砷化物环境压力铬碱 AFM

Hexagonal warping effect on Majorana zero modes at the ends of superconducting vortex lines in doped strong 3D topological insulators

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Science China(Physics,Mechanics & Astronomy) 2019年第11期62卷 125-134页

作者： Chuang Li Lun-Hui Hu fu-chun zhang Department of Physics Zhejiang UniversityHangzhou 310027China Kavli Institute for Theoretical Sciences University of Chinese Academy of SciencesBeijing 100190China Department of Physics University of CaliforniaSan Diego CA 92093USA CAS Center for Excellence in Topological Quantum Computation University of Chinese Academy of SciencesBeijing 100190China Collaborative Innovation Center of Advanced Microstructures Nanjing UniversityNanjing 210093China

In a superconducting topological insulator, a superconducting vortex line can trap a one-dimensional topological band with localized Majorana zero modes at the ends. Here, we study the effect of hexagonal warping and its corresponding symmetry-breaking effect on vortex phase transition. We perform both analytical calculations based on a semiclassical formula and numerical calculations based on full quantum mechanics using the Bogoliubov-de Gennes equation. We find that the hexagonal warping term extends the topological region of the vortex line as the chemical potential changes and leads to MZMs, even in the absence of topological surface states.

关键词： topological insulator topological superconductor vortex phase transition Majorana zero modes hexagonal warping

The preface: Toward higher-Tc superconductivity under lower pressure——from binary to ternary superhydrides

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National Science Review 2024年第7期11卷 7-8页

作者： fu-chun zhang Ho-kwang Mao Xin-Cheng Xie Kavli Institute for Theoretical Sciences University of Chinese Academy of Sciences Shanghai Advanced Research in Physical Sciences Center for High Pressure Science and Technology Advanced Research International Center for Quantum Materials School of Physics Peking University

Superconductivity——the phenomenon of complete vanishing of electrical resistance and expulsion of magnetic field——is the paramount electromagnetic property for technological advancement that is only shackled by th...

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The preface: Interplay of topological and magnetic orders in the Mn-Bi-Te family

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National Science Review 2024年第2期11卷 6-7页

作者： fu-chun zhang Hai-Zhou Lu X.C.Xie Kavli Institute for Theoretical Sciences University of Chinese Academy of Sciences Department of Physics Southern University of Science and Technology (SUSTech) International Center for Quantum Materials School of Physics Peking University

The discovery and synthesis of MnBi2Te4in 2013 initially garnered little attention [1]. Yet, the revelation of its topological properties in 2019 [2–6] sparked a surge of research into the MnBiTe family. These extensive studies are primarily driven by two objectives:the realization of a high-temperature quantum anomalous Hall effect （QAHE） and the exploration of exotic phases born from the interplay of topological and magnetic orders,

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Topological vortex phase transitions in iron-based superconductors

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Science Bulletin 2019年第17期64卷 1207-1214页

作者： Shengshan Qin Lunhui Hu Xianxin Wu Xia Dai Chen Fang fu-chun zhang Jiangping Hu Kavli Institute of Theoretical Sciences University o f Chinese Academy of Sciences Beijing 100049 China Beijing National Research Center for Condensed Matter Physics and Institute o f Physics Chinese Academy of Sciences Beijing 100190 China Department of Physics University of California San Diego CA 92093 USA Institute for Theoretical Physics and Astrophysics Julius-Maximilians University o f Wurzburg Am Hubland D-97074 Wurzburg Germany CAS Center for Excellence in Topological Quantum Computation University of Chinese Academy of Sciences Beijing 100049 China Collaborative Innovation Center of Quantum Matter Beijing 100049 China

We study topological vortex phases in iron-based superconductors. Besides the previously known vortex end Majorana zero modes(MZMs) phase stemming from the existence of a three dimensional(3 D) strong topological insulator state, we show that there is another topologically nontrivial phase as iron-based superconductors can be doped superconducting 3 D weak topological insulators(WTIs). The vortex bound states in a superconducting 3 D WTI exhibit two different types of quantum states, a robust nodal superconducting phase with pairs of bulk MZMs and a full-gap topologically nontrivial superconducting phase which has single vortex end MZM in a certain range of doping level. Moreover, we predict and summarize various topological phases in iron-based superconductors, and find that carrier doping and interlayer coupling can drive systems to have phase transitions between these different topological phases.

关键词： Weak topological insulators Vortex bound states Majorana modes Iron-based superconductors

Iron-based high transition temperature superconductors

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National Science Review 2014年第3期1卷 371-395页

作者： Xianhui Chen Pengcheng Dai Donglai Feng Tao Xiang fu-chun zhang Department of Physics University of Science and Technology of China Department of Physics and Astronomy Rice University Institute of Physics Chinese Academy of Sciences Department of Physics Fudan University Collaborative Innovation Center of Quantum Matter Department of Physics Zhejiang University

In a superconductor electrons form pairs and electric transport becomes dissipation-less at low temperatures. Recently discovered iron-based superconductors have the highest superconducting transition temperature next to copper oxides. In this article, we review material aspects and physical properties of iron-based superconductors. We discuss the dependence of transition temperature on the crystal structure,the interplay between antiferromagnetism and superconductivity by examining neutron scatering experiments, and the electronic properties of these compounds obtained by angle-resolved photoemission spectroscopy in link with some results from scanning tunneling microscopy/spectroscopy *** microscopic model for this class of compounds is discussed from a strong coupling point of view.

关键词： superconductivity angle-resolved photoemission spectroscopy iron-based superconductors

Controllable Majorana vortex states in iron-based superconducting nanowires

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National Science Review 2022年第9期9卷 195-203页

作者： Chuang Li Xun-Jiang Luo Li Chen Dong E.Liu fu-chun zhang Xin Liu School of Physics and Institute for Quantum Science and Engineering Huazhong University of Science and Technology Wuhan National High Magnetic Field Center and Hubei Key Laboratory of Gravitation and Quantum Physics State Key Laboratory of Low Dimensional Quantum Physics Department of Physics Tsinghua University Kavli Institute for Theoretical Sciences and CAS Center for Excellence in Topological Quantum Computing University of Chinese Academy of Sciences Collaborative Innovation Center of Advanced Microstructures Nanjing University

To reve al the non-Abelian braiding statistics of Major ana zero modes(MZMs),it is crucial to design a Majorana platform,in which MZMs can be easily manipulated in a broad topological nontrivial parameter *** is also an essential step to confirm their *** this study,we propose an iron-based superconducting nanowire system with Majorana vortex states to satisfy desirable *** system has a radius-induced topological phase transition,giving a lower bound for the nanowire *** the topological phase,the iron-based superconducting nanowires have only one pair of MZMs over a wide range of radii,chemical potential and external magnetic *** wave function of MZMs has a sizable distribution at the side edge of the *** property enables the control of the interaction of MZMs in neighboring vortex nanowires and paves the way for Majorana fusion and braiding.

关键词： iron-based superconductor topological phase transition superconducting vortex Majorana zero modes nanowire

Preface: special topic on topological matter

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National Science Review 2019年第2期6卷 195-195页

作者： fu-chun zhang Kavli Institute for Theoretical Sciences University of Chinese Academy of Sciences NSR

Topological matter has now become a very broad field in frontier of condensed-matter physics and beyond. Initial study of quantum matter started about four decades ago when the quantum Hall effect was discovered. A quantum Hall state is characterized by a Chern number, which leads to the observed quantized transverse conductance in a 2D electron system under perpendicular high magnetic fields. Explosive development of the present topic of quantum matter was largely due to

关键词： Preface special topic on topological matter

Designing of spin filter devices based on zigzag zinc oxide nanoribbon modified by edge defect

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Chinese Physics B 2019年第10期28卷 585-589页

作者： Bao-Rui Huang fu-chun zhang Yan-Ning Yang Zhi-Yong zhang Wei-Guo Wang School of Information Science Technology Northwest UniversityXi’an 710127China School of Physics and Electronic Information Yan’an UniversityYan’an 716000China

The spin-dependent electronic transport properties of a zigzag zinc oxide(ZnO) nanoribbon are studied by using density functional theory with non-equilibrium Green's functions. We calculate the spin-polarized band structure, projected density of states, Bloch states, and transmission spectrum of the ZnO nanoribbon. It is determined that all Bloch states are located at the edge of the ZnO nanoribbon. The spin-up transmission eigenchannels are contributed from Zn 4s orbital,whereas the spin-down transmission eigenchannels are contributed from Zn 4s and O 2p orbitals. By analyzing the current-voltage curves for the opposite spins of the ZnO nanoribbon device, negative differential resistance(NDR) and spin filter effect are observed. Moreover, by constructing the ZnO nanoribbon modified by the Zn-edge defect, the spin-up current is severely suppressed because of the destruction of the spin-up transmission eigenchannels. However, the spin-down current is preserved, thus resulting in the perfect spin filter effect. Our results indicate that the ZnO nanoribbon modulated by the edge defect is a practical design for a spin filter.

关键词： ZnO nanoribbon spin-dependent transport nonequilibrium Green's functions transmission eigenchannels spin filtering efficiency