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Z2classification for a novel antiferromagnetic topological insulating phase in three-dimensional topological Kondo insulator

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arXiv 2018年

作者： Li, Huan Zhong, Yin Liu, Yu Luo, Hong-Gang Song, Hai-Feng College of Science Guilin University of Technology Guilin541004 China Center for Interdisciplinary Studies Key Laboratory for Magnetism and Magnetic Materials of the MoE Lanzhou University Lanzhou730000 China Institute of Applied Physics and Computational Mathematics Beijing100088 China Software Center for High Performance Numerical Simulation China Academy of Engineering Physics Beijing100088 China Beijing Computational Science Research Center Beijing100084 China

Antiferromagnetic topological insulator (AFTI) is a topological matter that breaks time-reversal symmetry. Since its proposal, explorations of AFTI in strong-correlated systems are still lacking. In this paper, we show for the first time that a novel AFTI phase can be realized in three-dimensional topological Kondo insulator (TKI). In a wide parameter region, the ground states of TKI undergo a second-order transition to antiferromagnetic insulating phases which conserve a combined symmetry of time reversal and a lattice translation, allowing us to derive a Z2-classification formula for these states. By calculating the Z2index, the antiferromagnetic insulating states are classified into (AFTI) or non-topological antiferromagnetic insulator (nAFI) in different parameter regions. On the antiferromagnetic surfaces in AFTI, we find topologically protected gapless Dirac cones inside the bulk gap, leading to metallic Fermi rings exhibiting helical spin texture with weak spin-momentum locking. Depending on model parameters, the magnetic transitions take place either between AFTI and strong topological insulator, or between nAFI and weak topological insulator. By varying some model parameters, we find a topological transition between AFTI and nAFI, driving by closing of bulk gap. Our work may account for the pressure-induced magnetism in TKI compound SmB6, and helps to explore richer AFTI phases in heavyfermion systems as well as in other strong-correlated systems. Copyright © 2018, The Authors. All rights reserved.

关键词： Antiferromagnetism

Universality of the dynamic characteristic relationship of electron correlation in the two-photon double ionization process of a helium-like system

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arXiv 2020年

作者： Li, Fei Yang, Yu-Jun Chen, Jing Liu, Xiao-Jun Wei, Zhi-Yi Wang, Bing-Bing Laboratory of Optical Physics Beijing National Laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences Beijing100190 China Institute of Atomic and Molecular Physics Jilin University Changchun130012 China Institute of Applied Physics and Computational Mathematics P. O. Box 8009 Beijing100088 China HEDPS Center for Applied Physics and Technology Peking University Beijing100084 China State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics Wuhan Institute of Physics and Mathematics Innovation Academy for Precision Measurement Science and Technology Chinese Academy of Science Wuhan430071 China University of Chinese Academy of Sciences Beijing100049 China

Universality of the dynamic characteristic relationship between the characteristic time tc and the two-electron Coulomb interaction energy V 12 of the ground state in the two-photon double ionization process is investigated through changing the parameters of the two-electron atomic system and the corresponding laser conditions. The numerical results show that the product tcV 12 keeps constant around 4.1 in the cases of changing the nucleus charge, the electron charge, the electron mass, and changing simultaneously the nucleus charge and the electron charge. These results demonstrate that the dynamic characteristic relationship in the two-photon double ionization process is universal. This work sheds more light on the the dynamic characteristic relationship in ultrafast processes and may find its application in the measurement of attosecond pulses. Copyright © 2020, The Authors. All rights reserved.

关键词： Helium

A verification approach for Web service compositions based on epistemic model checking

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Jisuanji Xuebao/Chinese Journal of Computers 2011年第6期34卷 1041-1061页

作者： Luo, Xiang-Yu Tan, Zheng Su, Kai-Le Wu, Li-Jun College of Computer Science and Technology Huaqiao University Xiamen Fujian 361021 China School of Software Tsinghua University Beijing 100084 China No 504 Plant China National Nuclear Corporation Lanzhou 730065 China Key Laboratory of High Confidence Software Technologies of Ministry of Education Peking University Beijing 100871 China College of Mathematics Physics and Information Engineering Zhejiang Normal University Jinhua Zhejiang 321004 China School of Computer Science and Engineering University of Electronic Science and Technology Chengdu 410073 China

In recent years, the formal verification of Web service compositions is gradually becoming a hot research area. As a mainstream technique for formal verification, model checking is able to not only overcome the shortcoming of traditional software test techniques that they cannot generate the complete set of test cases, but also automatizes the verification process. In this paper, the authors propose and implement an epistemic model checking approach for the verification of Web service compositions by modeling them as multi-agent systems. After analyzing the BPEL control flow, the authors first propose a formal model for the BPEL activities and give the semantics of the implementation of the BPEL activities. By taking the so-call transition seven-tuple as the intermediate form, the authors further develop two automatic transform algorithms, one converts the BPEL process to the set of seven-tuples and the other converts this set of seven-tuples to the input language of MCTK (a model checker for multi-agent systems developed by the authors), such that can finally implement the verification by MCTK. The experimental results show that the proposed algorithms can effectively verify not only the temporal logical specifications, but also the temporal epistemic logical specifications, which are proper to multi-agent systems.

关键词： Model checking

Critical climate issues toward carbon neutrality targets

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Fundamental Research 2022年第3期2卷 396-400页

作者： Gang Huang Zhenhao Xu Xia Qu Junji Cao Shangmin Long Kai Yang Hongyu Hou Ya Wang Xiaofan Ma State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China Laboratory for Regional Oceanography and NumericalModeling Qingdao National Laboratory for Marine Science and TechnologyQingdao 266237China College of Earth and Planetary Sciences University of Chinese Academy of SciencesBeijing 100049China Institute of Atmospheric Physics Chinese Academy of SciencesBeijing 100029China International Polar Environment Research Laboratory College of OceanographyHohai UniversityNanjing 210098China

In 2020,China announced the"emission peak,carbon neutrality"policy,that is,China aims to have CO2 emissions peak before 2030 and achieve carbon neutrality before *** scenario of carbon neutrality will be significantly distinguished from the scenario we experienced since the industrial ***,instrumental data are unavailable in the future carbon-neutral *** system models and climate dynamics theory are needed to comprehend and project the climate *** this paper,we illustrate our perspective of the issues related to"emission peak,carbon neutrality",including climate dynamics,climate-carbon feedback,interaction between China and global climate and carbon emissions and solutions,*** highlight that climate change has profoundly affected human production and *** frequent occurrence of extreme weather disasters in recent years,together with the impact of epidemics,make the future"carbon peak&carbon-neutral"scenario more *** is whopping uncertainty but also a massive challenge to the scientific ***,carbon neutrality is closely related to domestic production and lives,and there is little time left for *** believe that we will make a breakthrough in climate dynamics in the context of carbon neutrality with our joint efforts,which will serve our country’s carbon emission policy at different stages.

关键词： Carbon neutrality Climate dynamics Climate-carbon feedback Diplomacy Possible solutions Future prospect

Subspace method based on neural networks for eigenvalue problems

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arXiv 2024年

作者： Dai, Xiaoying Fan, Yunying Sheng, Zhiqiang LSEC Institute of Computational Mathematics and Scientific/Engineering Computing Academy of Mathematics and Systems Science Chinese Academy of Sciences Beijing100190 China School of Mathematical Sciences University of Chinese Academy of Sciences Beijing100049 China National Key Laboratory of Computational Physics Institute of Applied Physics and Computational Mathematics Beijing100088 China HEDPS Center for Applied Physics and Technology College of Engineering Peking University Beijing100871 China

With the rapid development of machine learning, numerical discretization methods based on deep neural networks have been widely used in many fields, especially in solving high-dimensional problems where traditional methods face bottlenecks. However, for low-dimensional problems, existing machine learning methods are not as accurate and efficient as traditional methods. In this paper, we propose a subspace method based on neural networks for eigenvalue problems with high accuracy and low cost. Our basic idea is to use neural network based basis functions to span a subspace, then calculate the parameters of the neural network based basis functions through appropriate training, and finally calculate the Galerkin projection of the eigenvalue problem onto the subspace and obtain an approximate solution. In addition, we reduce the dimension of the subspace by applying some dimensionality reduction technique, which can improve the accuracy of the approximate solution in further. numerical experiments show that we can obtain approximate eigenvalues with accuracy of 10−11 but with less then 400 epochs, which is significantly superior to other existing neural network based *** Codes 65N25, 65L15, 68T07 Copyright © 2024, The Authors. All rights reserved.

关键词：

Dynamics and pattern formation of ring dark solitons in a two-dimensional binary Bose-Einstein condensate with tunable interactions

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Physical Review E 2019年第6期99卷 062216-062216页

作者： Zhang-Ming He L. Wen Ya-Jun Wang G. P. Chen R.-B. Tan C.-Q. Dai Xiao-Fei Zhang College of Science Hunan University of Technology Zhuzhou 412007 China College of Physics and Electronic Engineering Chongqing Normal University Chongqing 400047 China Key Laboratory of Time and Frequency Primary Standards National Time Service Center Chinese Academy of Sciences Xi'an 710600 China School of Astronomy and Space Science University of Chinese Academy of Sciences Beijing 100049 China School of Physics and Mechtronic Engineering Sichuan University of Art and Science Dazhou 635000 China College of Mathematics and Physics Chongqing University of Science and Technology Chongqing 401331 China School of Sciences Zhejiang A&F University Lin'an Zhejiang 311300 China

We investigate the dynamics and pattern formation of two ring dark solitons in a two-dimensional binary Bose-Einstein condensate with tunable intercomponent interaction via numerical simulation of the time-dependent Gross-Pitaevskii equation. Both the black and gray ring dark solitons are considered for cases where the modulation frequency of the intercomponent interaction is resonant or nonresonant with the one of the trapping potential. Our results show that in the presence of periodic modulation of the intercomponent interaction not only are the lifetimes of the ring dark solitons largely extended but also their decaying dynamics are dramatically affected. Before snaking instability sets in, new ring dark solitons are formed, and both the numbers and depths of the ring dark solitons exhibit collective oscillations. With the development of instability, the system exhibits different decaying processes, and a variety of decay profiles, such as vortex necklace, distorted octagon, vortex-antivortex ring, and cross, are formed, showing a strong dependence on the modulation frequency of the intercomponent interaction and the initial depth of the ring dark soliton.

关键词： Bose-Einstein condensates Cold atoms & matter waves Quantum control Ultracold collisions

Performance study of complex application programs on tens of thousands cores

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Ruan Jian Xue Bao/Journal of Software 2011年第SUPPL. 2期22卷 157-162页

作者： Gao, Xing-Yu Cao, Xiao-Lin Zhao, Wei-Bo Zhang, Ai-Qing Mo, Ze-Yao High Performance Computing Center Institute of Applied Physics and Computational Mathematics Beijing 100094 China Key Laboratory of Science and Technology for National Defense Institute of Applied Physics and Computational Mathematics Beijing 100094 China

Oriented to the large-scale computation on tens of thousands cores, the parallel software infrastructure named JASMIN has released a new version which has improved the enabling techniques and numerical algorithms. With downward compatible programming interfaces, the new version can enhance the scalability of the programs free of application users' effort. To investigate the scalability of the programs based on JASMIN, we test and analyze the performance of five complex application programs on tens of thousands cores of TH-1A supercomputer. These programs were developed for the high-performance computation arising from inertial confinement fusion, material science as well as the high-power microwave. It is shown that four programs achieve a parallel efficiency of over 60% on 42,000 cores and three ones achieve a parallel efficiency of over 45% on 84,000 cores. ©2011 Journal of Software.

关键词： Application programs

Spin-Triplet Excitonic Insulator: The Case of Semihydrogenated Graphene

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Physical Review Letters 2020年第16期124卷 166401-166401页

作者： Zeyu Jiang Wenkai Lou Yu Liu Yuanchang Li Haifeng Song Kai Chang Wenhui Duan Shengbai Zhang State Key Laboratory of Low-Dimensional Quantum Physics and Collaborative Innovation Center of Quantum Matter Department of Physics Tsinghua University Beijing 100084 China SKLSM Institute of Semiconductors Chinese Academy of Sciences P.O. Box 912 Beijing 100083 China Laboratory of Computational Physics Institute of Applied Physics and Computational Mathematics Beijing 100088 China Key Lab of advanced optoelectronic quantum architecture and measurement (MOE) and Advanced Research Institute of Multidisciplinary Science Beijing Institute of Technology Beijing 100081 China CAEP Software Center for High Performance Numerical Simulation Beijing 100088 China Beijing Academy of Quantum Information Sciences Beijing 100193 China Institute for Advanced Study Tsinghua University Beijing 100084 China Department of Physics Applied Physics and Astronomy Rensselaer Polytechnic Institute Troy New York 12180 USA

While various excitonic insulators have been studied in the literature, due to the perceived too-small spin splitting, spin-triplet excitonic insulator is rare. In two-dimensional systems such as a semihydrogenated graphene (known as graphone), however, it is possible, as revealed by first-principles calculations coupled with Bethe-Salpeter equation. The critical temperature, given by an effective Hamiltonian, is 11.5 K. While detecting excitonic insulators is still a daunting challenge, the condensation of triplet excitons will result in spin superfluidity, which can be directly measured by a transport experiment. Nonlocal dielectric screening also leads to an unexpected phenomenon, namely, an indirect-to-direct transition crossover between single-particle band and exciton dispersion in the semihydrogenated graphene, which offers yet another test by experiment.

关键词： Excitons Graphene First-principles calculations

The role of plasma beta in global coronal models: Bringing balance back to the force

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arXiv 2023年

作者： Brchnelova, Michaela Kuźma, Blażej Zhang, Fan Lani, Andrea Poedts, Stefaan Centre for Mathematical Plasma Astrophysics KU Leuven Celestijnenlaan 200B Leuven3001 Belgium Shenzhen Key Laboratory of Numerical Prediction for Space Storm Institute of Space Science and Applied Technology Harbin Institute of Technology Shenzhen518055 China Key Laboratory of Solar Activity and Space Weather National Space Science Center Chinese Academy of Sciences Beijing100190 China Institute of Physics University of Maria Curie-Sklodowska ul. Radziszewskiego 10 Lublin20-031 Poland

Context. COolfluid COrona uNstrUcTured (COCONUT) is a global coronal magnetohydrodynamic (MHD) model that has been recently developed and will soon be integrated into the ESA Virtual Space Weather Modelling Centre (VSWMC). In order to achieve robustness and fast convergence to steady-state for numerical simulations with COCONUT, several assumptions and simplifications have been made during its development, such as prescribing filtered photospheric magnetic maps for representing the magnetic field conditions in the lower corona. This filtering leads to smoothing and lower magnetic field values at the inner boundary (i.e., the solar surface), resulting in an unrealistically high plasma β (more than 1 in a large portion of the domain). Aims. In this paper, we examine the effects of prescribing such filtered/smoothed magnetograms in global coronal simulations and formulate a method for achieving more realistic plasma β values and improving the resolution of electromagnetic features without losing computational performance. Methods. We make use of the newly developed COCONUT solver to demonstrate the effects of the highly pre-processed magnetic maps set at the inner boundary and the resulting high plasma β on the features in the computational domain. Then, in our new approach, we shift the inner boundary to 2 R☉ from the original 1.01 R☉ and preserve the prescribed highly filtered magnetic map. With the shifted boundary, naturally, the boundary density and pressure are also adjusted to better represent the considered physical location. This effectively reduces the prescribed plasma β and leads to a more realistic setup. The method is applied on a magnetic dipole, a minimum (2008) and a maximum (2012) solar activity case, to demonstrate its effects. Results. The results obtained with the proposed approach show significant improvements in the resolved density and radial velocity profiles, and far more realistic values of the plasma β at the boundary and inside the computat

关键词： Magnetohydrodynamics