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Crossed Nonlinear Dynamical Hall Effect in Twisted Bilayers

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arXiv 2023年

作者： Chen, Cong Zhai, Dawei Xiao, Cong Yao, Wang New Cornerstone Science Laboratory Department of Physics University of Hong Kong Hong Kong HKU-UCAS Joint Institute of Theoretical and Computational Physics at Hong Kong Hong Kong Institute of Applied Physics and Materials Engineering University of Macau Taipa China

We propose a novel nonlinear dynamical Hall effect characteristic of layered materials with chiral symmetry, which is driven by the joint action of in-plane and time variation of out-of-plane ac fields jH ∼ E⊥ × E. A new band geometric quantity – interlayer Berry connection polarizability, which probes a mixed quantum metric characteristic of layer hybridized electrons by twisted interlayer coupling, underlies this effect. When the two orthogonal fields have common frequency, their phase difference controls the on/off, direction and magnitude of the rectified Hall current. We show sizable effects in twisted homobilayer transition metal dichalcogenides and twisted bilayer graphene over broad range of twist angles. Our work opens the door to discovering mixed quantum metric responses unique to van der Waals stacking and concomitant applications under the nonlinear spotlight. Copyright © 2023, The Authors. All rights reserved.

关键词： Transition metals

Dynamic mode decomposition of nonequilibrium electron-phonon dynamics: accelerating the first-principles real-time Boltzmann equation

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arXiv 2023年

作者： Maliyov, Ivan Yin, Jia Yao, Jia Yang, Chao Bernardi, Marco Department of Applied Physics and Materials Science California Institute of Technology PasadenaCA91125 United States Applied Mathematics and Computational Research Division Lawrence Berkeley National Laboratory BerkeleyCA94720 United States Department of Physics California Institute of Technology PasadenaCA91125 United States

Nonequilibrium dynamics governed by electron-phonon (e-ph) interactions plays a key role in electronic devices and spectroscopies and is central to understanding electronic excitations in materials. The real-time Boltzmann transport equation (rt-BTE) with collision processes computed from first principles can describe the coupled dynamics of electrons and atomic vibrations (phonons). Yet, a bottleneck of these simulations is the calculation of e-ph scattering integrals on dense momentum grids at each time step. Here we show a data-driven approach based on dynamic mode decomposition (DMD) that can accelerate the time propagation of the rt-BTE and identify dominant electronic processes. We apply this approach to two case studies, high-field charge transport and ultrafast excited electron relaxation. In both cases, simulating only a short time window of ∼10% of the dynamics suffices to predict the dynamics from initial excitation to steady state using DMD extrapolation. Analysis of the momentum-space modes extracted from DMD sheds light on the microscopic mechanisms governing electron relaxation to steady state or equilibrium. The combination of accuracy and efficiency makes our DMD-based method a valuable tool for investigating ultrafast dynamics in a wide range of materials. Copyright © 2023, The Authors. All rights reserved.

关键词： Dynamic mode decomposition

Self-generated magnetic field in three-dimensional ablative Rayleigh-Taylor instability

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arXiv 2024年

作者： Zhang, Dehua Jiang, Xian Tao, Tao Li, Jun Yan, Rui Sun, De-Jun Zheng, Jian Department of Modern Mechanics University of Science and Technology of China Hefei230026 China Department of Plasma Physics and Fusion Engineering University of Science and Technology of China Anhui Hefei230026 China Institute of Applied Physics and Computational Mathematics Beijing100094 China IFSA Collaborative Innovation Center Shanghai Jiao Tong University Shanghai200240 China

The self-generated magnetic field in three-dimensional (3D) single-mode ablative Rayleigh-Taylor instabilities (ARTI) relevant to the acceleration phase of a direct-drive inertial confinement fusion (ICF) implosion is investigated. It is found that stronger magnetic fields up to a few thousands of T can be generated by 3D ARTI than by its two-dimensional (2D) counterpart. The Nernst effects significantly alter the magnetic fields convection and amplify the magnetic fields. The scaling law for the magnetic flux obtained in the 2D simulations performs reasonably well in the 3D cases. While the magnetic field significantly accelerates the bubble growth in the short-wavelength 2D modes through modifying the heat fluxes, the magnetic field mostly accelerates the spike growth but has little influence on the bubble growth in 3D ARTI. Copyright © 2024, The Authors. All rights reserved.

关键词： Acceleration

The Phonon Quasiparticle Approach for Anharmonic Properties of Solids 32

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The Phonon Quasiparticle Approach for Anharmonic Properties ...

32nd IUPAP Conference in computational physics, CCP 2021

作者： Zhang, Zhen Zhang, Dong-Bo Sun, Tao Wentzcovitch, Renata M. Department of Applied Physics and Applied Mathematics Columbia University New YorkNY10027 United States College of Nuclear Science and Technology Beijing Normal University Beijing100875 China Beijing Computational Science Research Center Beijing100193 China Key Laboratory of Computational Geodynamics Chinese Academy of Sciences Beijing100049 China Department of Earth and Environmental Sciences Columbia University New YorkNY10027 United States Lamont-Doherty Earth Observatory Columbia University PalisadesNY10964 United States

Knowledge of lattice anharmonicity is essential to elucidate distinctive thermal properties in crystalline solids. Yet, accurate ab initio investigations of lattice anharmonicity encounter difficulties owing to the cumbersome computations. Here we introduce the phonon quasiparticle approach and review its application to various materials. This method efficiently and reliably addresses lattice anharmonicity by combining ab initio molecular dynamics and lattice dynamics calculations. Thus, in principle, it accounts for full anharmonic effects and overcomes finite-size effects typical of ab initio molecular dynamics. The validity and effectiveness of the current approach are demonstrated in the computation of thermodynamic and heat transport properties of weakly and strongly anharmonic systems. © Published under licence by IOP Publishing Ltd.

关键词： Calculations

Trident-shaped Dual Band Monopole Antenna with Defected Ground Plane for 5G Applications

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Trident-shaped Dual Band Monopole Antenna with Defected Grou...

2022 IEEE Wireless Antenna and Microwave Symposium, WAMS 2022

作者： Sharma, Preeti Tiwari, Rakesh N. Singh, Prabhakar Kumar, Pradeep School of Basic and Applied Sciences Galgotias University Physics Division Greater Noida India Greater Noida Institute of Technology Department of Applied Science Greater Noida India School of Computational and Integrative Sciences Jawaharlal Nehru University New Delhi India Electronic and Computer Engineering University of KwaZulu-Natal Discipline of Electrical Durban South Africa

ISBN: (数字)9781665458467

ISBN: (纸本)9781665458467

This work explores a compact dual band trident-shaped monopole antenna for 5G applications. The designed antenna has dimension 32 × 25 × 1.524 mm3. The structure of the antenna consists of symmetric trident-shaped patch with arrow shaped strip in the center. The L-shaped slots are used to modify the defected ground plane and to obtain the dual band characteristics. The proposed design demonstrates the measured impedance bandwidths in the range 3.27-3.88 GHz (lower band) and 4.85-5.23 GHz (upper band), respectively. The radiation efficiency for both the operating bands are above 76%, the realized average gains are 1.28 dBi and 1.7 dBi across both the operating bands, respectively. The radiation patterns of the monopole antenna are acceptable for 5G applications. The proposed design is modeled and simulated using CST microwave studio. The simulated results agreeing well with the fabricated antenna. © 2022 IEEE.

关键词： Monopole antennas

Ideal hourglass-type charge-three Weyl fermions in spinless systems

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Physical Review B 2024年第7期109卷 075160-075160页

作者： Xiaoliang Xiao Yuanjun Jin Da-Shuai Ma Weixiang Kong Jing Fan Rui Wang Xiaozhi Wu Institute for Structure and Function & Department of Physics Chongqing University Chongqing 400044 People's Republic of China Division of Physics and Applied Physics School of Physical and Mathematical Sciences Nanyang Technological University Singapore 637371 Singapore Center of Quantum Materials and Devices Chongqing University Chongqing 400044 People's Republic of China Center for Computational Science and Engineering Southern University of Science and Technology Shenzhen 518055 People's Republic of China Chongqing Key Laboratory for Strongly Coupled Physics Chongqing 400044 People's Republic of China

Hourglass-type Weyl fermions with the maximally topological charge of |C|=3, namely hourglass-type charge-three Weyl fermions (CTWFs), have seldom been reported due to the nonnegligible spin-orbit coupling effect and Pauli exclusion principles. Here, based on symmetry arguments and the low-energy effective k·p model, we confirm that two chiral space groups (SGs), i.e., SG P63 (No. 173) and SG P6322 (No. 182), can host ideal hourglass-type CTWFs in spinless systems. Moreover, we take Li2CO4 as a concrete example to show the ideal hourglass-type CTWFs, which possess ultralong sextuple- and triple-helicoid Fermi arcs, making them easier to be detected by experiments. Our work not only offers an avenue to search for ideal hourglass-type CTWFs but also provides a promising platform for experiments to verify this kind of unconventional quasiparticles with the ultralong sextuple- and triple-helicoid surface arcs.

关键词： Electronic structure Fermions First-principles calculations Symmetry protected topological states 3-dimensional systems Crystal structures Weyl semimetal High-throughput calculations Symmetries in condensed matter Wannier function methods k dot p method

Discovering dense hydrogen solid at 1200K with deep variational free energy approach

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arXiv 2025年

作者： Dong, Xinyang Xie, Hao Chen, Yixiao Liang, Wenshuo Zhang, Linfeng Wang, Lei Wang, Han Beijing National Laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences Beijing100190 China AI for Science Institute Beijing100080 China Department of Astrophysics University of Zürich Winterthurerstrasse 190 Zürich8057 Switzerland Princeton University PrincetonNJ08544 United States DP Technology Beijing100080 China Laboratory of Computational Physics Institute of Applied Physics and Computational Mathematics Fenghao East Road 2 Beijing100094 China

We perform deep variational free energy calculations to investigate the dense hydrogen system at 1200 K and high pressures. In this computational framework, neural networks are used to model the free energy through the proton Boltzmann distribution and the electron wavefunction. By directly minimizing the free energy, our results reveal the emergence of a crystalline order associated with the center of mass of hydrogen molecules at approximately 180 GPa. This transition from atomic liquid to a molecular solid is marked by discontinuities in both the pressure and thermal entropy. Additionally, we discuss the broader implications and limitations of these findings in the context of recent studies of dense hydrogen under similar conditions. Copyright © 2025, The Authors. All rights reserved.

关键词： Molecules

Orbital polarization, charge transfer, and fluorescence in reduced-valence nickelates

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Physical Review B 2023年第16期107卷 165124-165124页

作者： M. R. Norman A. S. Botana J. Karp A. Hampel H. LaBollita A. J. Millis G. Fabbris Y. Shen M. P. M. Dean Materials Science Division Argonne National Laboratory Lemont Illinois 60439 USA Department of Physics Arizona State University Tempe Arizona 85287 USA Department of Applied Physics and Applied Math Columbia University New York New York 10027 USA Center for Computational Quantum Physics Flatiron Institute 162 5th Avenue New York New York 10010 USA Department of Physics Columbia University New York New York 10027 USA Advanced Photon Source Argonne National Laboratory Lemont Illinois 60439 USA Condensed Matter Physics and Materials Science Department Brookhaven National Laboratory Upton New York 11973 USA

This paper presents a simple formalism for calculating x-ray absorption (XAS) and resonant inelastic x-ray scattering (RIXS) that has as input orbital-resolved density of states from a single-particle or many-body ab initio calculation and is designed to capture itinerant like features. We use this formalism to calculate both the XAS and RIXS with input from density functional theory (DFT) and DFT+DMFT for the recently studied reduced valence nickelates R4Ni3O8 and RNiO2 (R=rare earth), and these results are then contrasted with those for the cuprate CaCuO2 and the unreduced nickelate R4Ni3O10. In contrast to the unreduced R4Ni3O10, the reduced valence nickelates as well as the cuprate show strong orbital polarization due to the dominance of x2−y2 orbitals for the unoccupied 3d states. We also reproduce two key aspects of a recent RIXS experiment for R4Ni3O8: (i) a charge-transfer feature between 3d and oxygen 2p states whose energy we find to decrease as one goes from RNiO2 to R4Ni3O8 to the cuprate, and (ii) an energy-dependent polarization reversal of the fluorescence line that arises from hybridization of the unoccupied 3z2−r2 states with R 5d states. We end with some implications of our results for the nature of the 3d electrons in reduced valence nickelates.

关键词： Strongly correlated systems Electronic structure Resonant inelastic x-ray scattering

Overcoming the pulse-width limitation of third-order optical nonlinearity for above bandgap excitation in nanoparticles

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Physical Review Materials 2025年第5期9卷 055201-055201页

作者： Ankit Sharma Mansi Pathak Ravi Kumar Trivedi Abhishek Das Rituraj Sharma Deepali Sharma Brahmananda Chakraborty Ravi Shankar Singh C. S. Rout K. V. Adarsh Department of Physics Indian Institute of Science Education and Research Bhopal 462066 India Centre for Nano and Materials Science Jain University Ramanagaram Bangalore 562112 India Department of Physics Karpagam Academy of Higher Education Coimbatore 641021 Tamil Nadu India Centre for Computational Physics Karpagam Academy of Higher Education Coimbatore 641021 Tamil Nadu India Centre for Scientific and Applied Research IPS Academy Indore 452012 India High Pressure & Synchroton Radiation Physics Division Bhabha Atomic Research Centre Trombay Mumbai 400085 India

The instantaneous nonlinear optical (NLO) responses of materials are typically limited to subbandgap excitation involving virtual states. However, achieving fast responses for above-bandgap excitation is extremely challenging because of the involvement of real states and associated electron-phonon (e-ph) scattering processes. Here, we investigate the NLO response of NiSe2 nanoparticles (NPs) using femtosecond (120 fs) and nanosecond (7 ns) laser pulses. Our experiments, supported by first-principles calculations, reveal that NiSe2 exhibits reverse saturable absorption (RSA) for femtosecond excitation, enabled by near-instantaneous intraband thermalization within the pulse duration. In contrast, CoSe2 NPs display saturable absorption, likely due to incomplete thermalization. Notably, when the laser interaction time is extended to nanoseconds, RSA emerges in both materials, which concurs with our model. Strikingly, NiSe2 NPs exhibit an unprecedented enhancement in the NLO response for nanosecond excitation, exceeding four orders of magnitude compared to femtosecond excitation, highlighting the role of prolonged excited-state dynamics. Our results provide a frontier in ultrafast optoelectronic device applications for above-bandgap excitations.

关键词： Nanoparticles