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Emergent spin-1 trimerized valence bond crystal in the spin-12 Heisenberg model on the star lattice

Physical Review B 2018年第7期97卷 075146-075146页

作者： Shi-Ju Ran Wei Li Shou-Shu Gong Andreas Weichselbaum Jan von Delft Gang Su ICFO–Institut de Ciencies Fotoniques The Barcelona Institute of Science and Technology 08860 Castelldefels (Barcelona) Spain Department of Physics Key Laboratory of Micro-nano Measurement-Manipulation and Physics (Ministry of Education) and International Research Institute for Multidisciplinary Science Beihang University Beijing 100191 China National High Magnetic Field Laboratory Florida State University Tallahassee Florida 32310 USA Physics Department Arnold Sommerfeld Center for Theoretical Physics and Center for NanoScience Ludwig-Maximilians-University Munich 80333 Germany School of Physical Sciences and CAS Center for Excellence in Topological Quantum Computation University of Chinese Academy of Sciences Beijing 100049 China Kavli Institute for Theoretical Sciences University of Chinese Academy of Sciences Beijing 100190 China

We explore the frustrated spin-12 Heisenberg model on the star lattice with antiferromagnetic (AF) couplings inside each triangle and ferromagnetic (FM) intertriangle couplings (Je<0), and calculate its magnetic and thermodynamic properties. We show that the FM couplings do not sabotage the magnetic disordering of the ground state due to the frustration from the AF interactions inside each triangle, but trigger a fully gapped inversion-symmetry-breaking trimerized valence bond crystal (TVBC) with emergent spin-1 degrees of freedom. We discover that with strengthening Je, the system exhibits a universal scaling behavior either with or without a magnetic field h: the order parameter, the five critical fields that separate the Je−h ground-state phase diagram into six phases, and the excitation gap obtained by low-temperature specific heat, all depend exponentially on Je. Our work implies that the spin-1 VBCs can be stabilized by introducing small FM couplings in the geometrically frustrated spin-12 systems.

关键词： Frustrated magnetism Magnetic phase transitions 2-dimensional systems Density matrix renormalization group Heisenberg model Projected entangled pair states Spin lattice models Tensor network methods

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Binary Two-Dimensional Honeycomb Lattice with Strong Spin-Orbit Coupling and Electron-Hole Asymmetry

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Physical Review Letters 2018年第12期121卷 126801-126801页

作者： Jian Gou Bingyu Xia Hang Li Xuguang Wang Longjuan Kong Peng Cheng Hui Li Weifeng Zhang Tian Qian Hong Ding Yong Xu Wenhui Duan Kehui Wu Lan Chen Institute of Physics Chinese Academy of Sciences Beijing 100190 China School of Physics University of Chinese Academy of Sciences Beijing 100049 China State Key Laboratory of Low-Dimensional Quantum Physics Department of Physics Tsinghua University Beijing 100084 China Collaborative Innovation Center of Quantum Matter Beijing 100084/100871 China Beijing Advanced Innovation Center for Soft Matter Science and Engineering Beijing University of Chemical Technology Beijing 100029 China School of Physics and Electronics Henan University Kaifeng 475004 Henan Province China RIKEN Center for Emergent Matter Science (CEMS) Wako Saitama 351-0198 Japan Institute for Advanced Study Tsinghua University Beijing 100084 China CAS Center for Excellence in Topological Computation University of Chinese Academy of Sciences Beijing 1000190 China

Two-dimensional (2D) materials consisting of heavy atoms with particular arrangements may host exotic quantum properties. Here, we report a unique 2D semiconducting binary compound, a Sn2Bi atomic layer on Si(111), in which hexagons are formed by bonding Bi with a triangular network of Sn. Because of the unique honeycomb configuration, the heavy elements, and the energy-dependent hybridization between Sn and Bi, 2D Sn2Bi not only shows strong spin-orbit coupling effects but also exhibits high electron-hole asymmetry: Nearly free hole bands and dispersionless flat electron bands coexist in the same system. By tuning the Fermi level, it is possible to preserve both nearly free and strongly localized charge carriers in the same 2D material, which provides an ideal platform for the studies of strongly correlated phenomena and possible applications in nanodevices.

关键词： Spin-orbit coupling Surface reconstruction Surface states 2-dimensional systems Stanene Two-dimensional electron gas Angle-resolved photoemission spectroscopy Density functional theory Scanning tunneling microscopy

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Effect of Zn doping on the antiferromagnetism in kagome Cu4−xZnx(OH)6FBr

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Physical Review B 2018年第15期98卷 155127-155127页

作者： Zili Feng Yuan Wei Ran Liu Dayu Yan Yan-Cheng Wang Jianlin Luo Anatoliy Senyshyn Clarina dela Cruz Wei Yi Jia-Wei Mei Zi Yang Meng Youguo Shi Shiliang Li Beijing National Laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences Beijing 100190 China School of Physical Sciences University of Chinese Academy of Sciences Beijing 100190 China School of Physical Science and Technology China University of Mining and Technology Xuzhou 221116 China Collaborative Innovation Center of Quantum Matter Beijing 100190 China Heinz Maier-Leibnitz Zentrum (MLZ) Technische Universität München Garching D-85747 Germany Neutron Scattering Division Neutron Sciences Directorate Oak Ridge National Laboratory Oak Ridge Tennessee 37831 USA Semiconductor Device Materials Group National Institute for Materials Science 1-1 Namiki Tsukuba Ibaraki 305-0044 Japan Institute for Quantum Science and Engineering and Department of Physics Southern University of Science and Technology Shenzhen 518055 China CAS Center of Excellence in Topological Quantum Computation University of Chinese Academy of Sciences Beijing 100190 China

Barlowite Cu4(OH)6FBr shows three-dimensional (3D) long-range antiferromagnetism, which is fully suppressed in Cu3Zn(OH)6FBr with a kagome quantum spin liquid ground state. Here we report systematic studies on the evolution of magnetism in the Cu4−xZnx(OH)6FBr system as a function of x to bridge the two limits of Cu4(OH)6FBr(x=0) and Cu3Zn(OH)6FBr(x=1). Neutron-diffraction measurements reveal a hexagonal-to-orthorhombic structural change with decreasing temperature in the x=0 sample. While confirming the 3D antiferromagnetic nature of low-temperature magnetism, the magnetic moments on some Cu2+ sites on the kagome planes are found to be vanishingly small, suggesting strong frustration already exists in barlowite. Substitution of interlayer Cu2+ with Zn2+ with gradually increasing x completely suppresses the bulk magnetic order at around x=0.4 but leaves a local secondary magnetic order up to x∼0.8 with a slight decrease in its transition temperature. The high-temperature magnetic susceptibility and specific-heat measurements further suggest that the intrinsic magnetic properties of kagome spin liquid planes may already appear from x>0.3 samples. Our results reveal that the Cu4−xZnx(OH)6FBr may be the long-thought experimental playground for the systematic investigations of the quantum phase transition from a long-range antiferromagnet to a topologically ordered quantum spin liquid.

关键词： Antiferromagnetism Quantum spin liquid Kagome lattice DC susceptibility measurements Neutron diffraction Specific heat measurements

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Dynamical signature of symmetry fractionalization in frustrated magnets

arXiv

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arXiv 2018年

作者： Sun, Guang-Yu Wang, Yan-Cheng Fang, Chen Qi, Yang Cheng, Meng Meng, Zi Yang Beijing National Laboratory of Condensed Matter Physics and Institute of Physics Chinese Academy of Sciences Beijing100190 China School of Physical Sciences University of Chinese Academy of Sciences Beijing100190 China School of Physical Science and Technology China University of Mining and Technology Xuzhou221116 China CAS Center of Excellence in Topological Quantum Computation and School of Physical Sciences University of Chinese Academy of Sciences Beijing100190 China Center for Field Theory and Particle Physics Department of Physics Fudan University Shanghai200433 China State Key Laboratory of Surface Physics Fudan University Shanghai200433 China Collaborative Innovation Center of Advanced Microstructures Nanjing210093 China Department of Physics Yale University New HavenCT06520-8120 United States

The nontrivialness of quantum spin liquid (QSL) typically manifests in the non-local observables that signify their existence, however, this fact actually casts a shadow on detecting QSL with experimentally accessible probes. Here, we provide a solution by unbiasedly demonstrating dynamical signature of anyonic excitations and symmetry fractionalization in QSL. Employing large-scale quantum Monte Carlo simulation and stochastic analytic continuation, we investigate the extended XXZ model on the kagome lattice, and find out that across the phase transitions from Z2 QSLs to different symmetry breaking phases, spin spectral functions can reveal the presence and condensation of emergent anyonic spinon and vison excitations, in particular the translational symmetry fractionalization of the latter, which can be served as the dynamical signature of the seemingly ephemeral QSLs in spectroscopic techniques such as inelastic neutron or resonance (inelastic) X-ray scatterings. Copyright © 2018, The Authors. All rights reserved.

关键词： Monte Carlo methods

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Interface-Induced Zeeman-Protected Superconductivity in Ultrathin Crystalline Lead Films

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Physical Review X 2018年第2期8卷 021002-021002页

作者： Yi Liu Ziqiao Wang Xuefeng Zhang Chaofei Liu Yongjie Liu Zhimou Zhou Junfeng Wang Qingyan Wang Yanzhao Liu Chuanying Xi Mingliang Tian Haiwen Liu Ji Feng X. C. Xie Jian Wang International Center for Quantum Materials School of Physics Peking University Beijing 100871 China Collaborative Innovation Center of Quantum Matter Beijing 100871 China Wuhan National High Magnetic Field Center Huazhong University of Science and Technology Wuhan 430074 China Institute of Physics Chinese Academy of Sciences Beijing 100190 China High Magnetic Field Laboratory Chinese Academy of Sciences Hefei 230031 Anhui China Center for Advanced Quantum Studies Department of Physics Beijing Normal University Beijing 100875 China CAS Center for Excellence in Topological Quantum Computation University of Chinese Academy of Sciences Beijing 100190 China

Two-dimensional (2D) superconducting systems are of great importance for exploring exotic quantum physics. The recent development of fabrication techniques has stimulated studies of high-quality single-crystalline 2D superconductors, where intrinsic properties give rise to unprecedented physical phenomena. Here, we report the observation of Zeeman-type spin-orbit interaction protected superconductivity (Zeeman-protected superconductivity) in 4-monolayer (ML) to 6-ML crystalline Pb films grown on striped incommensurate Pb layers on Si(111) substrates by molecular beam epitaxy. An anomalously large in-plane critical field far beyond the Pauli limit is detected, which can be attributed to the Zeeman-protected superconductivity due to the in-plane inversion symmetry breaking at the interface. Our work demonstrates that, in superconducting heterostructures, the interface can induce Zeeman-type spin-orbit interactions and modulate the superconductivity.

关键词： Electrical conductivity First-principles calculations Spin-orbit coupling Superconductors Surface & interfacial phenomena Single crystal materials Solid-solid interfaces Ultrathin films Annealing Crystal growth Density functional theory Liquid helium cooling Molecular beam epitaxy Resistivity measurements Scanning tunneling microscopy Superconductivity

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Observation of momentum-space chiral edge currents in room-Temperature atoms

arXiv

引用

arXiv 2018年

作者： Cai, Han Liu, Jinhong Wu, Jinze He, Yanyan Zhu, Shi-Yao Zhang, Jun-Xiang Wang, Da-Wei Interdisciplinary Center of Quantum Information and Department of Physics Zhejiang University Hangzhou310027 State Key Laboratory of Quantum Optics and Quantum Optics Devices Institute of Opto-Electronics Shanxi University Taiyuan030006 China Synergetic Innovation Center of Quantum Information and Quantum Physics University of Science and Technology of China Hefei Anhui230026 Cas Center of Excellence in Topological Quantum Computation University of Chinese Academy of Sciences Beijing100190

Chiral edge currents play an important role in characterizing topological matter. In atoms, they have been observed at such a low temperature that the atomic motion can be measured. Here we report the first experimental observation of chiral edge currents in atoms at room temperature. Staggered magnetic uxes are induced by the spatial phase difference between two standing-wave light fields, which couple atoms to form a momentum-space zigzag superradiance lattice. The chiral edge currents have been measured by comparing the directional superradiant emissions of two timed Dicke states in the lattice. This work paves the way for quantum simulation of topological matter with hot atoms and facilitates the application of topological physics in real devices. Copyright © 2018, The Authors. All rights reserved.

关键词： Atoms

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Dimension engineering of narrow bandgap semiconductor inas nanostructures in wafer-scale

arXiv

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arXiv 2018年

作者： Pan, Dong Wang, Ji-Yin Zhang, Wei Zhu, Lujun Su, Xiaojun Huang, Shaoyun Sui, Manling Yartsev, Arkady Xu, H.Q. Zhao, Jianhua State Key Laboratory of Superlattices and Microstructures Institute of Semiconductors Chinese Academy of Sciences P.O. Box 912 Beijing100083 China Beijing Key Laboratory of Quantum Devices Key Laboratory for the Physics and Chemistry of Nanodevices Department of Electronics Peking University Beijing100871 China NanoLund and Division of Chemical Physics Lund University Box 124 Lund22100 Sweden Institute of Microstructure and Properties of Advanced Materials Beijing University of Technology Beijing100124 China College of Materials Science and Opto-Electronic Technology University of Chinese Academy of Sciences Beijing China CAS Center for Excellence in Topological Quantum Computation University of Chinese Academy of Sciences Beijing100190 China College of Physics and Information Technology Shaanxi Normal University Xi'an710062 China

Low-dimensional narrow bandgap III-V semiconductors are key building blocks for the next generation of high-performance nano-electronics, nano-photonics and quantum devices. To realize these various applications, it requires an efficient methodology that enables the material dimensional control during the synthesis process and the mass production of these materials with perfect crystallinity, reproducibility, low cost and outstanding optoelectronic properties. However, despite advances in one- and two-dimensional narrow bandgap III-V semiconductors synthesis, the progress towards reliable methods that can satisfy all of these requirements has been limited. Here, we demonstrate an approach that provides a precise control of the dimension of InAs from one-dimensional nanowires to wafer-scale free-standing two-dimensional nanosheets, which have a high degree of crystallinity and outstanding electrical and optical properties, using molecular-beam epitaxy by controlling catalyst alloy segregation. In our approach, two-dimensional InAs nanosheets can be obtained directly from one-dimensional InAs nanowires by silver-indium alloy segregation, which is much easier than all previously reported method, such as traditional buffering technique and select area epitaxial growth. Detailed transmission electron microscopy investigations provide a solid evidence that the catalyst alloy segregation is the origination of the InAs dimensional transformation from one-dimensional nanowires to two-dimensional nanosheets, and even to three-dimensional complex crosses. Using this method, we find that the wafer-scale free-standing InAs nanosheets can be grown on various substrates including Si, MgO, sapphire and GaAs etc. The InAs nanosheets grown at high temperature are pure phase single crystals and have a high electron mobility and a long time-resolved THz kinetics lifetime. Our work will open up a conceptually new and general technology route toward the effective controlling the dimensio

关键词： III-V semiconductors

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The πγ → ππ transition and the ρ radiative decay width from lattice QCD

arXiv

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arXiv 2018年

作者： Alexandrou, Constantia Leskovec, Luka Meinel, Stefan Negele, John Paul, Srijit Petschlies, Marcus Pochinsky, Andrew Rendon, Gumaro Syritsyn, Sergey Department Of Physics University Of Cyprus P.O. Box 20537 Nicosia1678 Cyprus Computation-based Science And Technology Research Center Cyprus Institute 20 Kavafi Str. Nicosia2121 Cyprus Department Of Physics University Of Arizona TucsonAZ85721 United States Riken Bnl Research Center Brookhaven National Laboratory UptonNY11973 United States Center For Theoretical Physics Laboratory For Nuclear Science Department Of Physics Massachusetts Institute Of Technology CambridgeMA02139 United States Helmholtz-Institut Für Strahlen- Und Kernphysik Rheinische Friedrich-Wilhelms-Universität Bonn Nußallee 14-16 BonnD-53115 Germany Department Of Physics And Astronomy Stony Brook University Stony BrookNY11794 United States

We report a lattice QCD determination of the πγ → ππ transition amplitude for the P-wave, I = 1 two-pion final state, as a function of the photon virtuality and ππ invariant mass. The calculation was performed with 2 + 1 flavors of clover fermions at a pion mass of approximately 320 MeV, on a 323× 96 lattice with L ≈ 3.6 fm. We construct the necessary correlation functions using a combination of smeared forward, sequential and stochastic propagators, and determine the finite-volume matrix elements for all ππ momenta up to |P| = √ 3 2π/L and all associated irreducible representations. In the mapping of the finite-volume to infinite-volume matrix elements using the Lellouch-Lüscher factor, we consider two different parametrizations of the ππ scattering phase shift. We fit the q2and s dependence of the infinite-volume transition amplitude in a model-independent way using series expansions, and compare multiple different truncations of this series. Through analytic continuation to the ρ resonance pole, we also determine the πγ → ρ resonant transition form factor and the ρ meson photocoupling, and obtain |Gρπγ| = 0.0802(32)(20). Copyright © 2018, The Authors. All rights reserved.

关键词： Hadrons

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Uncover topology by quantum quench dynamics

arXiv

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arXiv 2018年

作者： Sun, Wei Yi, Chang-Rui Wang, Bao-Zong Zhang, Wei-Wei Sanders, Barry C. Xu, Xiao-Tian Wang, Zong-Yao Schmiedmayer, Joerg Deng, Youjin Liu, Xiong-Jun Chen, Shuai Pan, Jian-Wei Shanghai Branch National Laboratory for Physical Sciences Microscale Department of Modern Physics University of Science and Technology of China Shanghai201315 China Chinese Academy of Sciences Center for Exellence: Quantum Information and Quantum Physics University of Science and Technology of China Hefei Anhui230326 China CAS-Alibaba Lab for quantum computation Shanghai201315 China International Center for Quantum Materials School of Physics Peking University Beijing100871 China Collaborative Innovation Center of Quantum Matter Beijing100871 China Centre for Engineered Quantum Systems School of Physics University of Sydney SydneyNSW2006 Australia Institute for Quantum Science and Technology University of Calgary CalgaryABT2N1N4 Canada Program in Quantum Information Science Canadian Institute for Advanced Research TorontoONM5G1Z8 Canada Vienna Center for Quantum Science and Technology Atominstitut TU Wien Stadionallee 2 Vienna1020 Austria

Topological quantum states are characterized by nonlocal invariants, and their detection is intrinsically challenging. Various strategies have been developed to study topological Hamiltonians through their equilibrium states. We present a fundamentally new, high-precision dynamical approach, revealing topology through the unitary evolution after a quench from a topological trivial initial state with a two-dimensional Chern band realized in an ultracold 87Rb atom gas. The emerging ring structure in the spin dynamics uniquely determines the Chern number for the post-quench band and enables probing the full phase diagram of the band topology with high precision. Besides, we also measure the topological band gap and the domain wall structure dynamically formed in the momentum space during the long-term evolution. Our dynamical approach provides a way towards observing a universal bulk-ring correspondence, and has broad applications in exploring topological quantum matter. Copyright © 2018, The Authors. All rights reserved.

关键词： Topology

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Epitaxial growth and magnetic properties of NiMnAs film on GaAs substrate

arXiv

引用

arXiv 2018年

作者： Ma, J.L. Wang, H.L. Zhang, X.M. Yan, S. Yan, W.S. Zhao, J.H. State Key Laboratory of Superlattices and Microstructures Institute of Semiconductors Chinese Academy of Sciences P. O. Box 912 Beijing100083 China College of Materials Science and Opto-Electronic Technology University of Chinese Academy of Sciences Beijing100049 China Shanghai Synchrotron Radiation Facility Institute of Applied Physics Chinese Academy of Sciences Shanghai201204 China National Synchrotron Radiation Laboratory University of Science and Technology of China Hefei230029 China CAS Center for Excellence in Topological Quantum Computation University of Chinese Academy of Sciences Beijing100190 China

Single-phase Ni0.46Mn0.54As films with strained C1b symmetry have been successfully grown on GaAs (001) substrates by molecular-beam epitaxy. The epitaxial relationship between the film and the substrate has been studied using synchrotron radiation, and a preferred configuration of (110)-orientated Ni0.46Mn0.54As on (001)-orientated GaAs was revealed. In addition, the magnetic properties of the films were found to be significantly influenced by the growth temperature. The optimized growth temperature is determined to be ~370 ℃, for which relatively high Curie temperature, large saturation magnetization and coercive field, as well as the pronounced in-plane magnetic anisotropy were obtained. According to the results of X-ray absorption spectroscopy, the above phenomenon can be attributed to the variation of the local electronic structure of the Mn atoms. Our work provides useful information for the further investigations of NiMnAs, which is theoretically predicted to host robust half-metallicity. Copyright © 2018, The Authors. All rights reserved.

关键词： Substrates

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