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Designing topological and correlated 2D magnetic states via superatomic lattice constructions of zirconium dichloride

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Nano Research 2023年第12期16卷 13509-13515页

作者： Yang Song Wen-Han Dong Kuan-Rong Hao Shixuan Du Lizhi Zhang Laboratory of Theoretical and Computational Nanoscience National Center for Nanoscience and TechnologyBeijing 100190China Beijing National Laboratory for Condensed Matter Physics and Institute of Physics Chinese Academy of SciencesBeijing 100190China State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics Tsinghua UniversityBeijing 100084China

Magnetic materials could realize the intriguing quantum anomalous Hall effect and metal-to-insulator transition when combined with band topology or electronic correlation,which have broad prospects in quantum information,spintronics,and valleytronics.Here,we propose the approach of designing novel two-dimensional(2D)magnetic states via d-orbital-based superatomic lattices.Specifically,we chose triangular zirconium dichloride disks as superatoms to construct the honeycomb superatomic lattices.Using first-principles calculations,we identified a series of 2D magnetic states with varying sizes of superatoms.We found the non-uniform stoichiometries and geometric effect of superatomic lattice give rise to spin-polarized charges arranged in different magnetic configurations,containing ferromagnetic coloring triangles,antiferromagnetic honeycomb,and ferromagnetic kagome lattices.Attractively,these magnetic states are endowed with nontrivial band topology or strong correlation,forming an ideal chern insulator or antiferromagnetic Dirac Mott insulator.Our work not only reveals the potential of d-orbital-based superatoms for generating unusual magnetic configurations,but also supplies a new avenue for material engineering at the nanoscale.

关键词： topological state chern insulator Dirac Mott insulator zirconium dichloride superatomic lattice kagome lattice

A gauge theory for two-band model of chern insulators and induced topological defects

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Communications in Theoretical Physics 2022年第1期74卷 124-133页

作者： Zhi-Wen Chang Wei-Chang Hao Xin Liu Institute of Theoretical Physics Faculty of SciencesBeijing University of TechnologyBeijing 100124China School of Physics Beihang UniversityBeijing 100191China

In this paper a gauge theory is proposed for the two-band model of chern insulators.Based on the so-calle't Hooft monopole model,a U(1)Maxwell electromagnetic sub-field is constructed from an SU(2)gauge field,from which arise two types of topological defects,monopoles and e2 merons.We focus on the topological number in the Hall conductance σ_(xy)=e^(2)/hC,where C is the chern number.It is discovered that in the monopole case C is indeterminate,while in the meron case C takes different values,due to a varying on-site energy m.As a typical example,we apply this method to the square lattice and compute the winding numbers(topological charges)of the defects;the C-evaluations we obtain reproduce the results of the usual literature.Furthermore,based on the gauge theory we propose a new model to obtain the high chern numbers|C|=2,4.

关键词： chern insulator chern number monopole meron

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High-chern-number and high-temperature quantum Hall effect without Landau levels

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National Science Review 2020年第8期7卷 1280-1287页

作者： Jun Ge Yanzhao Liu Jiaheng Li Hao Li Tianchuang Luo Yang Wu Yong Xu Jian Wang International Center for Quantum Materials School of Physics Peking University State Key Laboratory of Low Dimensional Quantum Physics Department of Physics Tsinghua University School of Materials Science and Engineering Tsinghua University Tsinghua-Foxconn Nanotechnology Research Center and Department of Physics Tsinghua University Department of Mechanical Engineering Tsinghua University Frontier Science Center for Quantum Information CAS Center for Excellence in Topological Quantum Computation University of Chinese Academy of Sciences

The quantum Hall effect（QHE） with quantized Hall resistance of h/νe;started the research on topological quantum states and laid the foundation of topology in physics. Since then, Haldane proposed the QHE without Landau levels, showing nonzero chern number |C| = 1, which has been experimentally observed at relatively low temperatures. For emerging physics and low-power-consumption electronics, the key issues are how to increase the working temperature and realize high chern numbers（C > 1）. Here, we report the experimental discovery of high-chern-number QHE（C = 2） without Landau levels and C = 1 chern insulator state displaying a nearly quantized Hall resistance plateau above the Néel temperature in MnBi;Te;devices. Our observations provide a new perspective on topological matter and open new avenues for exploration of exotic topological quantum states and topological phase transitions at higher temperatures.

关键词： quantum Hall effect without Landau levels chern insulator topological matter topological quantum states high chern number high temperature

Revealing chern number from quantum metric

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Chinese Physics B 2022年第4期31卷 73-77页

作者：张安伟 Department of Physics The Chinese University of Hong KongShatinNew TerritoriesHong KongChina Department of Physics Ajou UniversitySuwon 16499Korea

chern number is usually characterized by Berry curvature.Here,by investigating the Dirac model of even-dimensional chern insulator,we give the general relation between Berry curvature and quantum metric,which indicates that the chern number can be encoded in quantum metric as well as the surface area of the Brillouin zone on the hypersphere embedded in Euclidean parameter space.We find that there is a corresponding relationship between the quantum metric and the metric on such a hypersphere.We give the geometrical property of quantum metric.Besides,we give a protocol to measure the quantum metric in the degenerate system.

关键词： quantum metric chern insulator topological physics

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