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arXiv 2021年

作者： Liu, Wei-Xin Wang, Tao Zhang, Xue-Feng Li, Wei-Dong Institute of Theoretical Physics Department of Physics State Key Laboratory of Quantum Optics and Quantum Optics Devices Collaborative Innovation Center of Extreme Optics Shanxi University Taiyuan030006 China Department of Physics Center of Quantum Materials and Devices Chongqing University Chongqing401331 China Chongqing Key Laboratory for Strongly Coupled Physics Chongqing401331 China Shenzhen Key Laboratory of Ultraintense Laser and Advanced Material Technology Center for Advanced Material Diagnostic Technology College of Engineering Physics Shenzhen Technology University Shenzhen518118 China

The interference between a sequence of Landau-Zener (LZ) transitions can produce Rabi oscillations (LZROs). This phenomenon is a kind of time-domain Landau-Zener-Stückelberg-Majorana (LZSM) interference. However, experimental demonstrations of this LZSM interference induced Rabi oscillation are extremely hard due to the short coherence time of the driven quantum system. Here, we study theoretically the time-domain LZSM interference between the clock transition in one-dimensional (1D) 87Sr optical lattice clock (OLC) system. With the help of both the adiabatic-impulse model and Floquet numerical simulation method, the LZROs with special step-like structure are clearly found both in fast- and slow-passage limit in the real experiment parameter regions. In addition, the dephasing effect caused by the system temperature can be suppressed with destructive interference in the slow-passage limit. Finally, we discuss the possible Bloch-Siegert shift while the pulse time is away from the half-integer and integer periods. Our work provides a clear roadmap to observe the LZROs on the OLC platform. © 2021, CC BY.

关键词： Numerical methods

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Improved light-cone harmonic oscillator model for the pionic leading-twist distribution amplitude

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Physical Review D 2021年第1期104卷 016021-016021页

作者： Tao Zhong Zhi-Hao Zhu Hai-Bing Fu Xing-Gang Wu Tao Huang Department of Physics Guizhou Minzu University Guiyang 550025 P.R. China College of Physics and Materials Science Henan Normal University Xinxiang 453007 P.R. China Department of Physics Chongqing University Chongqing 401331 P.R. China Chongqing Key Laboratory for Strongly Coupled Physics Chongqing 401331 P.R. China Institute of High Energy Physics and Theoretical Physics Center for Science Facilities Chinese Academy of Sciences Beijing 100049 P.R. China

In this paper, we study the pion leading-twist distribution amplitude (DA) ϕ2;π(x,μ) by improving the traditional light-cone harmonic oscillator model within the reconstruction of the function φ2;π(x). In order to constrain the model parameters, we calculate its moments ⟨ξn⟩2;π|μ in the framework of the QCD background field theory sum rule up to tenth order. Considering the fact that the sum rule of the zeroth moment ⟨ξ0⟩2;π|μ cannot be normalized, we suggest a more reasonable sum rule formula for ⟨ξn⟩2;π|μ. Then, we obtain the values of ⟨ξn⟩2;π|μ0 with n=(2,4,6,8,10) at the initial scale μ0=1 GeV. The first two moments are ⟨ξ2⟩2;π|μ0=0.271±0.013 and ⟨ξ4⟩2;π|μ0=0.138±0.010, and the corresponding Gegenbauer moments are a22;π(μ0)=0.206±0.038 and a42;π(μ0)=0.047±0.011, respectively. After fitting the moments ⟨ξn⟩2;π|μ, we obtain the appropriate model parameters by using the least squares method. The resultant behavior for the twist-2 pion DA is closer to the AdS/QCD and lattice results, but narrower than that obtained using the Dyson-Schwinger equation. Furthermore, we calculate the pion-photon transition form factors (TFFs) and B→π TFFs within the light-cone sum rule approach, which conform with experimental and theoretical results.

关键词： Pions

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Three-Dimensional Dirac Phonons with Inversion Symmetry

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Physical Review Letters 2021年第18期126卷 185301-185301页

作者： Z. J. Chen R. Wang B. W. Xia B. B. Zheng Y. J. Jin Yu-Jun Zhao H. Xu Department of Physics South China University of Technology Guangzhou 510640 People’s Republic of China Department of Physics and Institute for Quantum Science and Engineering Southern University of Science and Technology Shenzhen 518055 People’s Republic of China Guangdong Provincial Key Laboratory of Computational Science and Material Design Southern University of Science and Technology Shenzhen 518055 People’s Republic of China Institute for Structure and Function and Department of Physics and Center for Quantum Materials and Devices Chongqing University Chongqing 400044 People’s Republic of China

Dirac semimetals associated with bulk Dirac fermions are well known in topological electronic systems. In sharp contrast, three-dimensional (3D) Dirac phonons in crystalline solids are still unavailable. Here we perform symmetry arguments and first-principles calculations to systematically investigate 3D Dirac phonons in all space groups with inversion symmetry. The results show that there are two categories of 3D Dirac phonons depending on their protection mechanisms and positions in momentum space. The first category originates from the four-dimensional irreducible representations at the high symmetry points. The second category arises from the phonon branch inversion, and the symmetry guarantees Dirac points to be located along the high symmetry lines. Furthermore, we reveal that nonsymmorphic symmetries and the combination of inversion and time-reversal symmetries play essential roles in the emergence of 3D Dirac phonons. Our work not only offers a comprehensive understanding of 3D Dirac phonons but also provides significant guidance for exploring Dirac bosons in both phononic and photonic systems.

关键词： Acoustic phonons Phonons Symmetry protected topological states Topological phases of matter Dirac semimetal Topological materials First-principles calculations k dot p method

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Three-Dimensional Charge Density Wave and Surface-Dependent Vortex-Core States in a Kagome Superconductor CsV3Sb5

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Physical Review X 2021年第3期11卷 031026-031026页

作者： Zuowei Liang Xingyuan Hou Fan Zhang Wanru Ma Ping Wu Zongyuan Zhang Fanghang Yu J.-J. Ying Kun Jiang Lei Shan Zhenyu Wang X.-H. Chen Department of Physics and Chinese Academy of Sciences Key laboratory of Strongly-coupled Quantum Matter Physics University of Science and Technology of China Hefei Anhui 230026 China Information Materials and Intelligent Sensing Laboratory of Anhui Province Institutes of Physical Science and Information Technology Anhui University Hefei 230601 China Beijing National Laboratory for Condensed Matter Physics and Institute of Physics Chinese Academy of Sciences Beijing 100190 China Key Laboratory of Structure and Functional Regulation of Hybrid Materials of Ministry of Education Anhui University Hefei 230601 China CAS Center for Excellence in Quantum Information and Quantum Physics Hefei Anhui 230026 China Collaborative Innovation Center of Advanced Microstructures Nanjing 210093 China

The transition-metal-based kagome metals provide a versatile platform for correlated topological phases hosting various electronic instabilities. While superconductivity is rare in layered kagome compounds, its interplay with nontrivial topology could offer an engaging space to realize exotic excitations of quasiparticles. Here, we use scanning tunneling microscopy to study a newly discovered Z2 topological kagome metal CsV3Sb5 with a superconducting ground state. We observe charge modulation associated with the opening of an energy gap near the Fermi level. When across single-unit-cell surface step edges, the intensity of this charge modulation exhibits a π-phase shift, suggesting a three-dimensional 2×2×2 charge density wave ordering. Interestingly, while conventional Caroli–de Gennes–Matricon bound states are observed inside the superconducting vortex on the Sb surfaces, a robust zero-bias conductance peak emerges that does not split in a large distance when moving away from the vortex center on the Cs 2×2 surfaces, resembling the Majorana bound states arising from the superconducting Dirac surface states in Bi2Te3/NbSe2 heterostructures. Our findings establish CsV3Sb5 as a promising candidate for realizing exotic excitations at the confluence of nontrivial lattice geometry, topology and multiple electronic orders.

关键词： Charge density waves Local density of states Majorana bound states Topological materials Topological superconductors

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Three-dimensional dirac phonons with inversion symmetry

arXiv

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arXiv 2021年

作者： Chen, Z.J. Wang, R. Xia, B.W. Zheng, B.B. Jin, Y.J. Zhao, Yu-Jun Xu, H. Department of Physics South China University of Technology Guangzhou510640 China Department of Physics & Institute for Quantum Science and Engineering Southern University of Science and Technology Shenzhen518055 China Guangdong Provincial Key Laboratory of Computational Science and Material Design Southern University of Science and Technology China Institute for Structure and Function Department of physics & Center for Quantum Materials and Devices Chongqing University Chongqing400044 China

Dirac semimetals associated with bulk Dirac fermions are well-known in topological electronic systems. In sharp contrast, three-dimensional (3D) Dirac phonons in crystalline solids are still unavailable. Here we perform symmetry arguments and first-principles calculations to systematically investigate 3D Dirac phonons in all space groups with inversion symmetry. The results show that there are two categories of 3D Dirac phonons depending on their protection mechanisms and positions in momentum space. The first category originates from the four-dimensional irreducible representations at the high symmetry points. The second category arises from the phonon branch inversion, and the symmetry guarantees Dirac points to be located along the high symmetry lines. Furthermore, we reveal that non-symmorphic symmetries and the combination of inversion and time-reversal symmetries play essential roles in the emergence of 3D Dirac phonons. Our work not only offers a comprehensive understanding of 3D Dirac phonons but also provides significant guidance for exploring Dirac bosons in both phononic and photonic systems. Copyright © 2021, The Authors. All rights reserved.

关键词： Phonons

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Tunable double Weyl phonons driven by chiral point group symmetry

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Physical Review B 2021年第10期103卷 104101-104101页

作者： Y. J. Jin Z. J. Chen X. L. Xiao H. Xu Department of Physics & Institute for Quantum Science and Engineering Southern University of Science and Technology Shenzhen 518055 People's Republic of China Department of Physics the University of Hong Kong Pokfulam Road Hong Kong People's Republic of China Department of Physics South China University of Technology Guangzhou 510640 People's Republic of China Institute for Structure and Function & Department of physics Chongqing University Chongqing 400044 People's Republic of China Guangdong Provincial Key Laboratory of Computational Science and Material Design & Shenzhen Key Laboratory for Advanced Quantum Functional Materials and Devices Southern University of Science and Technology Shenzhen 518055 People's Republic of China

Different from spin-12 Weyl points which are robust due to the protection of topology, the unconventional chiral quasiparticles usually require extra crystalline symmetries for their existence, indicating that such quasiparticles are sensitive to perturbation. Herein, we present that the spin-1 Weyl can transform into quadratic Weyl phonons depending on symmetry variation. Specifically, the spin-1 Weyl nodes arisen from three-dimensional (3D) irreducible representations (IRs) of chiral point groups, O(432) or T(23), are verified to split into quadratic Weyl points if symmetry breaking decomposes 3D IRs into two-dimensional IRs. Symmetry analysis and low-energy effective models are performed to identify the splitting mechanisms. The evolution of Berry curvature and surface states driven by symmetry breaking is obtained in real materials. Our work not only builds the connection between double Weyl phonons but also offers guidance for exploring the transition among unconventional quasiparticles.

关键词： Phonons Topological phase transition Topological materials Weyl semimetal First-principles calculations k dot p method

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Higher-Order Band Topology in Twisted Moiré Superlattice

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Physical Review Letters 2021年第6期126卷 066401-066401页

作者： Bing Liu Lede Xian Haimen Mu Gan Zhao Zhao Liu Angel Rubio Z. F. Wang Hefei National Laboratory for Physical Sciences at the Microscale CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics Department of Physics University of Science and Technology of China Hefei Anhui 230026 China Max Planck Institute for the Structure and Dynamics of Matter Center for Free Electron Laser Science Luruper Chaussee 149 22761 Hamburg Germany Center for Computational Quantum Physics Simons Foundation Flatiron Institute New York New York 10010 USA Nano-Bio Spectroscopy Group Departamento de Fisica de Materiales Universidad del País Vasco UPV/EHU-20018 San Sebastián Spain

The two-dimensional (2D) twisted bilayer materials with van der Waals coupling have ignited great research interests, paving a new way to explore the emergent quantum phenomena by twist degree of freedom. Generally, with the decreasing of twist angle, the enhanced interlayer coupling will gradually flatten the low-energy bands and isolate them by two high-energy gaps at zero and full filling, respectively. Although the correlation and topological physics in the low-energy flat bands have been intensively studied, little information is available for these two emerging gaps. In this Letter, we predict a 2D second-order topological insulator (SOTI) for twisted bilayer graphene and twisted bilayer boron nitride in both zero and full filling gaps. Employing a tight-binding Hamiltonian based on first-principles calculations, three unique fingerprints of 2D SOTI are identified, that is, nonzero bulk topological index, gapped topological edge state, and in-gap topological corner state. Most remarkably, the 2D SOTI exists in a wide range of commensurate twist angles, which is robust to microscopic structure disorder and twist center, greatly facilitating the possible experimental measurement. Our results not only extend the higher-order band topology to massless and massive twisted moiré superlattice, but also demonstrate the importance of high-energy bands for fully understanding the nontrivial electronics.

关键词： Electronic structure Topological materials Van der Waals systems

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A High-Capacity Ammonium Vanadate Cathode for Zinc-Ion Battery

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Nano-Micro Letters 2020年第5期12卷 153-164页

作者： Qifei Li Xianhong Rui Dong Chen Yuezhan Feng Ni Xiao Liyong Gan Qi Zhang Yan Yu Shaoming Huang Guangzhou Key Laboratory of Low-Dimensional Materials and Energy Storage Devices School of Materials and EnergyGuangdong University of TechnologyGuangzhou 510006People’s Republic of China Hefei National Laboratory for Physical Sciences at the Microscale Department of Materials Science and EngineeringCAS Key Laboratory of Materials for Energy ConversionUniversity of Science and Technology of ChinaHefei 230026People’s Republic of China Key Laboratory of Materials Processing and Mold(Zhengzhou University) Ministry of EducationZhengzhou UniversityZhengzhou 450002People’s Republic of China Aviation Fuel Research and Development Center China National Aviation Fuel Group LimitedBeijing 102603People’s Republic of China Department Institute for Structure and Function and of Physics Chongqing UniversityChongqing 400030People’s Republic of China Dalian National Laboratory for Clean Energy(DNL) Chinese Academy of SciencesDalian 116023LiaoningPeople’s Republic of China State Key Laboratory of Fire Science University of Science and Technology of ChinaHefei 230026People’s Republic of China

Given the advantages of being abundant in resources,environmental benign and highly safe,rechargeable zinc-ion batteries(ZIBs)enter the global spotlight for their potential utilization in large-scale energy *** their preliminary success,zinc-ion storage that is able to deliver capacity>400 mAh g^-1 remains a great ***,we demonstrate the viability of NH4V4O10(NVO)as high-capacity cathode that breaks through the bottleneck of ZIBs in limited *** first-principles calculations reveal that layered NVO is a good host to provide fast Zn^2+ions diffusion channel along its[010]direction in the interlayer *** the other hand,to further enhance Zn^2+ion intercalation kinetics and long-term cycling stability,a three-dimensional(3D)flower-like architecture that is self-assembled by NVO nanobelts(3D-NVO)is rationally designed and fabricated through a microwave-assisted hydrothermal *** a result,such 3D-NVO cathode possesses high capacity(485 mAh g^-1)and superior long-term cycling performance(3000 times)at 10 A g^-1(~50 s to full discharge/charge).Additionally,based on the excellent 3D-NVO cathode,a quasi-solid-state ZIB with capacity of 378 mAh g^-1is developed.

关键词： Zinc-ion battery Ammonium vanadate NH4V4O10

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Evolution of magnetic field induced ordering in the layered quantum Heisenberg triangular-lattice antiferromagnet Ba3CoSb2O9

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Physical Review B 2021年第18期103卷 184425-184425页

作者： N. A. Fortune Q. Huang T. Hong J. Ma E. S. Choi S. T. Hannahs Z. Y. Zhao X. F. Sun Y. Takano H. D. Zhou Department of Physics Smith College Northampton Massachusetts 01063 USA Department of Physics and Astronomy University of Tennessee Knoxville Tennessee 37996-1200 USA Neutron Scattering Division Oak Ridge National Laboratory Oak Ridge Tennessee 37831 USA Laboratory of Artificial Structures and Quantum Control School of Physics and Astronomy Shanghai Jiao Tong University Shanghai 200240 China Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China National High Magnetic Field Laboratory Florida State University Tallahassee Florida 32310-3706 USA State Key Laboratory of Structure Chemistry Fujian Institute of Research on the Structure of Matter Chinese Academy of Sciences Fuzhou Fujian 350002 China Department of Physics Hefei National Laboratory for Physical Sciences at Microscale and Key Laboratory of Strongly-Coupled Quantum Matter Physics (CAS) University of Science and Technology of China Hefei Anhui 230026 China Institute of Physical Science and Information Technology Anhui University Hefei Anhui 230601 China Department of Physics University of Florida Gainesville Florida 32611-8440 USA

Quantum fluctuations in the effective spin-12 layered triangular-lattice quantum Heisenberg antiferromagnet Ba3CoSb2O9 lift the classical degeneracy of the antiferromagnetic ground state in magnetic field, producing a series of novel spin structures for magnetic fields applied within the crystallographic ab plane, including a celebrated collinear “up-up-down” spin ordering with magnetization equal to 1/3 of the saturation magnetization over an extended field range. Theoretically unresolved, however, are the effects of interlayer antiferromagnetic coupling and transverse magnetic fields on the ground states of this system. Additional magnetic field induced phase transitions are theoretically expected and in some cases have been experimentally observed, but details regarding their number, location, and physical character appear inconsistent with the predictions of existing models. Conversely, an absence of experimental measurements as a function of magnetic-field orientation has left other key predictions of these models untested. To address these issues, we have used specific heat, neutron diffraction, thermal conductivity, and magnetic torque measurements to map out the phase diagram as a function of magnetic field intensity and orientation relative to the crystallographic ab plane. For H||ab, we have discovered an additional magnetic field induced phase transition at low temperature and an unexpected tetracritical point in the high-field phase diagram, which coupled with the apparent second-order nature of the phase transitions eliminates several theoretically proposed spin structures for the high-field phases. Our calorimetric measurements as a function of magnetic field orientation are in general agreement with theory for field-orientation angles close to plane parallel (H||a) but diverge at angles near plane perpendicular; a predicted convergence of two phase boundaries at finite angle and a corresponding change in the order of the field induced phase transition

关键词： Antiferromagnetism Frustrated magnetism Magnetic interactions Magnetic phase transitions Magnetization measurements Neutron scattering Specific heat measurements Thermal techniques

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A new class of bilayer kagome lattice compounds with Dirac nodal lines and pressure-induced superconductivity

arXiv

引用

arXiv 2021年

作者： Shi, Mengzhu Yu, Fanghang Yang, Ye Meng, Fanbao Lei, Bin Luo, Yang Sun, Zhe He, Junfeng Wang, Rui Jiang, Zhicheng Liu, Zhengtai Shen, Dawei Wu, Tao Wang, Zhenyu Xiang, Ziji Ying, Jianjun Chen, Xianhui Hefei National Laboratory for Physical Sciences at Microscale Department of Physics Key Laboratory of Strongly-Couple Quantum Matter Physics Chinese Academy of Sciences University of Science and Technology of China Anhui Hefei230026 China National Synchrotron Radiation Laboratory University of Science and Technology of China Anhui Hefei230029 China Institute for Structure and Function Department of Physics Center for Quantum Materials and Devices Chongqing University Chongqing400044 China State Key Laboratory of Functional Materials for Informatics Shanghai Institute of Microsystem and Information Technology Chinese Academy of Sciences Shanghai200050 China Shanghai200050 China CAS Center for Excellence in Quantum Information and Quantum Physics Anhui Hefei230026 China Collaborative Innovation Center of Advanced Microstructures Nanjing University Nanjing210093 China

Kagome lattice composed of transition-metal ions provides a great opportunity to explore the intertwining between geometry, electronic orders and band topology. The discovery of multiple competing orders that connect intimately with the underlying topological band structure in nonmagnetic kagome metals AV3Sb5 (A = K, Rb, Cs) further pushes this topic to the quantum frontier. Here we report a new class of vanadium-based compounds with kagome bilayers, namely AV6Sb6 (A = K, Rb, Cs) and V6Sb4, which, together with AV3Sb5, compose a series of kagome compounds with a generic chemical formula (Am-1Sb2m)(V3Sb)n (m = 1, 2;n = 1, 2). Theoretical calculations combined with angle-resolved photoemission measurements reveal that these compounds feature Dirac nodal lines in close vicinity to the Fermi level. Pressure-induced superconductivity in AV6Sb6 further suggests promising emergent phenomena in these materials. The establishment of a new family of layered kagome materials paves the way for designer of fascinating kagome systems with diverse topological nontrivialities and collective ground states. Copyright © 2021, The Authors. All rights reserved.

关键词： Topology

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