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Suppressed Fluctuations as the Origin of the Static Magnetic Order in Strained Sr2RuO4

Physical Review Letters 2023年第2期130卷 026702-026702页

作者： Bongjae Kim Sergii Khmelevskyi Cesare Franchini I. I. Mazin Department of Physics Kunsan National University Gunsan 54150 Korea Center for Computational Materials Science Institute for Applied Physics Vienna University of Technology Wiedner Hauptstrasse 8-10 1040 Vienna Austria University of Vienna Faculty of Physics and Center for Computational Materials Science Vienna A-1090 Austria Dipartimento di Fisica e Astronomia Università di Bologna 40127 Bologna Italy Department of Physics and Astronomy George Mason University Fairfax Virginia 22030 USA Quantum Science and Engineering Center George Mason University Fairfax Virginia 22030 USA

Combining first-principles density-functional calculations and Moriya’s self-consistent renormalization theory, we explain the recently reported counterintuitive appearance of an ordered magnetic state in uniaxially strained Sr2RuO4 beyond the Lifshitz transition. We show that strain weakens the quantum spin fluctuations, which destroy the static order, more strongly than the tendency to magnetism. A different rate of decrease of the spin fluctuations vs magnetic stabilization energy promotes the onset of a static magnetic order beyond a critical strain.

关键词： Magnetic order Superconductivity First-principles calculations

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Quantum correction to the anomalous Hall effect in PtMnGe thin films

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Physical Review B 2023年第22期107卷 224409-224409页

作者： K. K. Meng J. K. Chen Y. Wu X. G. Xu T. Kikkawa L. P. Sun D. Z. Hou Q. Li N. N. Zhang Z. G. Fu T. Zhu Y. Jiang E. Saitoh School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China Department of Applied Physics The University of Tokyo Tokyo 113-8656 Japan School of Science Beijing University of Civil Engineering and Architecture Beijing 100044 China Hefei National Research Center for Physical Sciences at the Microscale University of Science and Technology of China Hefei 230026 China Institute of Applied Physics and Computational Mathematics Beijing 100094 China The Institute of Physics Chinese Academy of Sciences Beijing 100190 China

The role of quantum correction such as weak localization in anomalous Hall effects (AHEs) is an important issue. In this work, we have investigated the robust quantum correction to the AHE in magnetic PtMnGe (PMG) thin films of high crystalline quality. The PMG films have not shown long-range magnetic order. The observed temperature and magnetic field dependence of the sheet conductivities in the ultrathin PMG films are explained based on the perturbation theory, where the interplay of spin-dependent scattering and the spin Zeeman splitting effect are taken into consideration. It is found that, as long as the magnetic scattering time is comparable to the spin-orbit scattering time, the conductivity correction due to the Cooperons between antiparallel spins that involves spin-flip scattering can be negligible in the two dimensions. Therefore, even when the spin-dependent scattering exists, the quantum correction to the transport behavior is robust in the two-dimensional PMG system. Our work makes a significant step toward clarifying the role of quantum correction in the AHE of the magnetic materials.

关键词： Anomalous Hall effect Quantum interference effects Weak localization Ultrathin films Neutron reflectometry X-ray magnetic circular dichroism X-ray magnetic linear dichroism

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Unified Gas-Kinetic Wave-Particle Methods VI:Disperse Dilute Gas-Particle Multiphase Flow

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Communications in computational physics 2022年第3期31卷 669-706页

作者： Xiaojian Yang Chang Liu Xing Ji Wei Shyy Kun Xu Department of Mechanical and Aerospace Engineering Hong Kong University of Science and TechnologyClear Water BayKowloonHong KongChina Institute of Applied Physics and Computational Mathematics BeijingChina Department of Mathematics Hong Kong University of Science and TechnologyClear Water BayKowloonHong KongChina Guangdong-Hong Kong-Macao Joint Laboratory for Data-Driven Fluid Mechanics and Engineering Applications Hong Kong University of Science and TechnologyHong KongChina Shenzhen Research Institute Hong Kong University of Science and TechnologyShenzhenChina

A coupled gas-kinetic scheme(GKS)and unified gas-kinetic wave-particle(UGKWP)method for the disperse dilute gas-particle multiphaseflow is *** the two-phaseflow,the gas phase is always in the hydrodynamic regime and is fol-lowed by GKS for the Navier-Stokes *** particle phase is solved by UGKWP in all regimes from particle trajectory crossing to the hydrodynamic wave interac-tion with the variation of particle’s Knudsen *** the intensive particle colli-sion regime,the UGKWP gives a hydrodynamic wave representation for the particle phase and the GKS-UGKWP for the two-phaseflow reduces to the two-fluid Eulerian-Eulerian(EE)*** the rarefied regime,the UGKWP tracks individual particle and the GKS-UGKWP goes back to the Eulerian-Lagrangian(EL)*** the tran-sition regime for the solid particle,the GKS-UGKWP takes an optimal choice for the wave and particle decomposition for the solid particle phase and connects the EE and EL methods *** GKS-UGKWP method will be tested in allflow regimes with a large variation of Knudsen number for the solid particle transport and Stokes number for the two-phase *** is confirmed that GKS-UGKWP is an efficient and accurate multiscale method for the gas-particle two-phaseflow.

关键词： Unified gas-kinetic wave-particle method gas-kinetic scheme disperse gas-particle two-phaseflow.

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Thermoelastic properties of bridgmanite using deep-potential molecular dynamics

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Physical Review B 2024年第9期109卷 094101-094101页

作者： Tianqi Wan Chenxing Luo Yang Sun Renata M. Wentzcovitch Department of Applied Physics and Applied Mathematics Columbia University New York New York 10027 USA Department of Physics Xiamen University Xiamen 361005 China Department of Physics Iowa State University Ames Iowa 50011 USA Department of Earth and Environmental Sciences Columbia University New York New York 10027 USA Lamont–Doherty Earth Observatory Columbia University Palisades New York 10964 USA Data Science Institute Columbia University New York New York 10027 USA Center for Computational Quantum Physics Flatiron Institute New York New York 10010 USA

The high-pressure Pbnm-perovskite polymorph of MgSiO3, i.e., bridgmanite (Bm), plays a crucial role in the Earth's lower mantle. It is likely responsible for ∼75 vol. % of this region and its properties dominate the properties of this region, especially its elastic properties that are challenging to measure at ambient conditions. This study combines deep-learning potential (DP) with density-functional theory (DFT) to investigate the structural and elastic properties of Bm under lower-mantle conditions. To simulate this system, we developed a series of potentials capable of faithfully reproducing DFT calculations using different functionals, i.e., local density approximation (LDA), Perdew-Burke-Ernzerhof parametrization (PBE), revised PBE for solids (PBEsol), and strongly constrained and appropriately normed (SCAN) meta–generalized-gradient approximation functionals. Our predictions with DP-SCAN exhibit a remarkable agreement with experimental measurements of high-temperature equations of states and elastic properties and highlight its superior performance, closely followed by DP-LDA in accurately predicting. This hybrid computational approach offers a solution to the accuracy-efficiency dilemma in obtaining precise elastic properties at high pressure and temperature conditions for minerals like Bm, opening a way to study the Earth material's thermodynamic properties and related phenomena.

关键词： Elasticity Pressure effects Minerals Deep learning First-principles calculations Molecular dynamics

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Specialising neural network potentials for accurate properties and application to the mechanical response of titanium

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npj computational Materials 2021年第1期7卷 1908-1918页

作者： Tongqi Wen Rui Wang Lingyu Zhu Linfeng Zhang Han Wang David J.Srolovitz Zhaoxuan Wu Department of Materials Science and Engineering City University of Hong KongKowloonHong KongSARChina Hong Kong Institute for Advanced Study City University of Hong KongKowloonHong KongSARChina Beijing Institute of Big Data Research BeijingChina Laboratory of Computational Physics Institute of Applied Physics and Computational MathematicsBeijingChina Department of Mechanical Engineering The University of Hong KongHong KongSARChina International Digital Economy Academy(IDEA) ShenzhenChina

Large scale atomistic simulations provide direct access to important materials phenomena not easily accessible to experiments or quantum mechanics-based calculation *** and efficient interatomic potentials are the key enabler,but their development remains a challenge for complex materials and/or complex *** learning potentials,such as the Deep Potential(DP)approach,provide robust means to produce general purpose interatomic ***,we provide a methodology for specialising machine learning potentials for high fidelity simulations of complex phenomena,where general potentials do not *** an example,we specialise a general purpose DP method to describe the mechanical response of two allotropes of titanium(in addition to other defect,thermodynamic and structural properties).The resulting DP correctly captures the structures,energies,elastic constants andγ-lines of Ti in both the HCP and BCC structures,as well as properties such as dislocation core structures,vacancy formation energies,phase transition temperatures,and thermal *** DP thus enables direct atomistic modelling of plastic and fracture behaviour of *** approach to specialising DP interatomic potential,DPspecX,for accurate reproduction of properties of interest“X”,is general and extensible to other systems and properties.

关键词： titanium enable neural

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Neoclassical toroidal viscous torque due to 3D magnetic perturbations in EU-DEMO 49

Neoclassical toroidal viscous torque due to 3D magnetic pert...

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49th EPS Conference on Plasma physics, EPS 2023

作者： Buchholz, R. Albert, C.G. Kasilov, S.V. Kernbichler, W. Lainer, P. Pigatto, L. Fusion@ÖAW Institut für Theoretische Physik - Computational Physics Technische Universität Graz Petersgasse 16 Graz8010 Austria Institute of Plasma Physics National Science Center "Kharkov Institute of Physics and Technology" Kharkiv61108 Ukraine Department of Applied Physics and Plasma Physics V. N. Karazin Kharkiv National University Kharkiv61022 Ukraine Consorzio RFX CNR ENEA INFN Università di Padova Acciaierie Venete SpA C.so Stati Uniti 4 Padova35127 Italy

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Transition energies and oscillator strengths for the intrashell and intershell transitions of the C-like ions in a thermodynamic equilibrium plasma environment

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Physical Review E 2022年第1期105卷 015206-015206页

作者： Chensheng Wu Yong Wu Jun Yan T. N. Chang Xiang Gao Institute for Applied Physics and Computational Mathematics Beijing 100088 China Beijing Computational Science Research Center Beijing 100193 China Department of Physics University of Southern California Los Angeles California 90089-0484 USA Institute for Theoretical Physics Vienna University of Technology A-1040 Vienna Austria

We present a theoretical study of the transition energies ω and the oscillator strengths gf for the C-like ions (with Z from 14–36) subject to plasma environment for atomic transitions, which meet the spatial and temporal criteria of the Debye-Hückel (DH) approximation. Two strong dipole-allowed transitions, viz., the intrashell transition 2s2p33D1→2s22p23P0, and the intershell transition 2s22p3d3D1→2s22p23P0 are investigated in detail. We found that both ω and gf increase for the intrashell transition under the Debye-Hückel screening potential VDH in terms of the Debye length D, which is linked to the ratio between the plasma density Ne and its temperature kT. In contrast, both ω and gf decrease for the intershell transition. Our theoretically estimated data have led to a general scaling feature for the change in ω of both intershell and intrashell transitions for ions with different nuclear charge Z. A similar general feature for the change in gf is also found for the intrashell transition. However, due to the change of the electron correlations between electrons in different shells with respect to the relativistic spin-orbit interaction as Z varies, the variation of gf subject to the surrounding plasma is more complicated for the intershell transition. The results presented in this work may facilitate the plasma diagnostic to determine the plasma temperature and density for the astrophysical objects and the controlled fusion facilities.

关键词： Atomic & molecular processes in external fields Atomic & molecular structure Plasma-particle interactions

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Quantum second-order optimization algorithm for general polynomials

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science China(physics,Mechanics & Astronomy) 2021年第10期64卷 54-63页

作者： Pan Gao Keren Li Shijie Wei Gui-Lu Long State Key Laboratory of Low-Dimensional Quantum Physics and Department of Physics Tsinghua UniversityBeijing 100084China Shenzhen JL Computational Science and Applied Research Institute Shenzhen 518109China Beijing Academy of Quantum Information Sciences Beijing 100193China Beijing National Research Center for Information Science and Technology and School of Information Tsinghua UniversityBeijing 100084China Frontier Science Center for Quantum Information Beijing 100084China

Quantum optimization algorithms can outperform their classical counterpart and are key in modern technology. The second-order optimization algorithm(the Newton algorithm) is a critical optimization method, speeding up the convergence by employing the second-order derivative of loss functions in addition to their first derivative. Here, we propose a new quantum second-order optimization algorithm for general polynomials with a computational complexity of O(poly(log d)). We use this algorithm to solve the nonlinear equation and learning parameter problems in factorization machines. Numerical simulations show that our new algorithm is faster than its classical counterpart and the first-order quantum gradient descent algorithm. While existing quantum Newton optimization algorithms apply only to homogeneous polynomials, our new algorithm can be used in the case of general polynomials, which are more widely present in real applications.

关键词： quantum computation quantum algorithm optimization

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Coherent enhancement of a frequency comb modulated by a terahertz laser field in high-order harmonic generation

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Physical Review A 2023年第4期108卷 043101-043101页

作者： Yuan-Yuan Wu Chang-Tong Liang Bao-Guang Zhao Peng-Cheng Li Research Center for Advanced Optics and Photoelectronics Department of Physics College of Science Shantou University Shantou Guangdong 515063 China Key Laboratory of Intelligent Manufacturing Technology of MOE Shantou University Shantou Guangdong 515063 China Institute of Applied Physics and Computational Mathematics Beijing 100088 China

We present the coherent enhancement of the frequency comb via high-order harmonic generation (HHG) in a train of infrared laser pulses combined with terahertz (THz) laser fields. The HHG spectra are obtained by solving the three-dimensional time-dependent Schrödinger equation by means of the time-dependent generalized pseudospectral method. We find that the structure of the frequency comb via HHG becomes much smoother and more regular, and the yield of the comb is increased by nearly two orders of magnitude. By analyzing the phase coherence of HHG spectra, we demonstrate that the THz laser fields are responsible for the optimization of the structure and yield of the frequency comb since the constructive phase coherence of the HHG spectra is modulated by the THz field. The physical origin of the constructive phase coherence is thanks to the uniform ionization efficiency induced by the THz laser field for each laser pulse, which greatly improves the synchronization of the harmonic emission. Our finding provides a promising method for the enhancement of the frequency comb via HHG.

关键词： Atomic & molecular processes in external fields High-order harmonic generation Light-matter interaction Ultrafast phenomena

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Cross sections for valence-shell excitations of H2O in the 9.85–12.15-eV energy-loss range studied by high-energy inelastic electron scattering

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Physical Review A 2022年第3期105卷 032801-032801页

作者： Wei-Qing Xu Yi-Geng Peng Jian-Hui Zhu Xiao-Jiao Du Yuan-Chen Xu Li-Han Wang Bo Li Hao-Ran Zhang Bei-Yuan Zhang Zi-Ru Ma Shu-Xing Wang Yong Wu Jian-Guo Wang Lin-Fan Zhu Center for Transformative Science ShanghaiTech University Shanghai 201210 China Department of Applied Physics Nanjing University of Science and Technology Nanjing 210094 China Institute of Applied Physics and Computational Mathematics Beijing 100088 China Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics University of Science and Technology of China Hefei Anhui 230026 China HEDPS Center for Applied Physics and Technology and College of Engineering Peking University Beijing 100871 China

The recent measurement of the generalized oscillator strengths (GOSs) for ÃB11 and B̃A11 of H2O exhibits the apparent deviations from the first Born approximation calculations in the large squared momentum transfer region [W. Q. Xu et al., Phys. Rev. A 103, 032808 (2021)]. Here a simplified theoretical model was proposed to calculate the GOSs of the two excitations at large momentum transfer within the second Born approximation. The accord of the experimental GOSs and the theoretical ones is improved, but the differences still exist. In addition, the GOSs and the integral cross sections for the higher excitations of H2O in 9.85–12.15 eV are presented, which could be used to complete the database of electron-impact excitation cross sections of H2O and be beneficial for modeling interaction processes between electrons and H2O in the earth's atmosphere, plasmas, radiation physics, biology, etc.

关键词： Electron & positron scattering Electronic excitation & ionization Electronic structure of atoms & molecules Molecular spectra Molecules Configuration interaction High-resolution electron energy loss spectroscopy

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