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Chirality-selective transparency induced by lattice resonance in bilayer metasurfaces

Photonics Research 2021年第4期9卷 484-493页

作者： Shuxia Zhao Lei Shao Jianfang Wang Hai-Qing Lin Wei Zhang Institute of Applied Physics and Computational Mathematics Beijing 100088China Beijing Computational Science Research Center Beijing 100193China Department of Physics The Chinese University of Hong KongShatinHong Kong SARChina

Chiral optical responses of bilayer metasurfaces made of twisted metallic nanorods are investigated in detail with focus on the collective effect due to lattice resonance(LR).Using an analytical approach based on the coupled dipole method(supported by full wave simulation),we find optical chirality is dramatically increased by the coupling between localized surface plasmon resonances and *** collective effect results in significant chiral signal even for metasurfaces made of achiral unit *** interlayer coupling generally destroys the Wood’s anomaly and the associated *** making use of Pancharatnam–Berry(PB)phase and propagation phase,one can modulate the optical activity effectively and achieve chirality-selective transparency induced by LR in a designed structure with a g-factor of absorption as high as 1.99(close to the upper limit of 2).Our studies not only reveal a new mechanism of modulating chiral optical response by combination effects from PB phase,propagation phase,and LR,but also give a quantitative relationship between the geometry configuration and chiral optical properties,thus providing helpful guidance for device design.

关键词： transparency chiral lattice

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Evidence for Magnetic Fractional Excitations in a Kitaev Quantum-Spin-Liquid Candidate α-RuCl_(3)

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Chinese physics Letters 2022年第2期39卷 72-77页

作者： Kejing Ran Jinghui Wang Song Bao Zhengwei Cai Yanyan Shangguan Zhen Ma Wei Wang Zhao-Yang Dong P.Cermak A.Schneidewind Siqin Meng Zhilun Lu Shun-Li Yu Jian-Xin Li Jinsheng Wen School of Physical Science and Technology and ShanghaiTech Laboratory for Topological PhysicsShanghaiTech UniversityShanghai 200031China National Laboratory of Solid State Microstructures and Department of Physics Nanjing UniversityNanjing 210093China Institute for Advanced Materials Hubei Normal UniversityHuangshi 435002China School of Science Nanjing University of Posts and TelecommunicationsNanjing 210023China Department of Applied Physics Nanjing University of Science and TechnologyNanjing 210094China Julich Centre for Neutron Science(JCNS)at Heinz Maier-Leibnitz Zentrum(MLZ) Forschungszentrum Jülich GmbHLichtenbergstr.185748 GarchingGermany Charles University Faculty of Mathematics and PhysicsDepartment of Condensed Matter PhysicsKe Karlovu 512116PrahaCzech Republic Helmholtz-Zentrum Berlin fur Materialien und Energie GmbH Hahn-Meitner-Platz 1D-14109BerlinGermany China Institute of Atomic Energy(CIAE) Beijing 102413China The Henry Royce Institute and Department of Materials Science and Engineering The University of SheffieldSir Robert Hadfield BuildingSheffieldS13JDUnited Kingdom Collaborative Innovation Center of Advanced Microstructures Nanjing UniversityNanjing 210093China

It is known that α-RuCl_(3) has been studied extensively because of its proximity to the Kitaev quantum-spin-liquid(QSL)phase and the possibility of approaching it by tuning the competing *** we present the first polarized inelastic neutron scattering study on α-RuCl_(3) single crystals to explore the scattering continuum around the Γ point at the Brillouin zone center,which was hypothesized to be resulting from the Kitaev QSL state but without concrete *** polarization analyses,we find that,while the spin-wave excitations around the Γ point vanish above the transition temperature T_(N),the pure magnetic continuous excitations around the Γ point are robust against ***,by calculating the dynamical spin-spin correlation function using the cluster perturbation theory,we derive magnetic dispersion spectra based on the K-Γ model,which involves with a ferromagnetic Kitaev interaction of −7.2 meV and an off-diagonal interaction of 5.6 *** find this model can reproduce not only the spin-wave excitation spectra around the Γ point,but also the non-spin-wave continuous magnetic excitations around the Γ *** results provide evidence for the existence of fractional excitations around the Γ point originating from the Kitaev QSL state,and further support the validity of the K-Γ model as the effective minimal spin model to describe α-RuCl_(3).

关键词： temperature excitation diagonal

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A self-induced mechanism of large-scale helical structures in compressible turbulent flows

arXiv

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arXiv 2024年

作者： Yan, Zheng Wang, Jianchun Wang, Lifeng Lei, Zhu Wu, Junfeng Duan, Junyi Tong, Fulin Li, Xinliang Yu, Changping Institute of Applied Physics and Computational Mathematics Beijing100094 China Department of Mechanics and Aerospace Engineering Southern University of Science and Technology Guangdong Shenzhen518055 China Center for Applied Physics and Technology HEDPS Peking University Beijing100871 China LHD Institute of Mechanics Chinese Academy of Sciences Beijing100190 China School of Engineering Science University of Chinese Academy of Sciences Beijing100049 China State Key Laboratory of Aerodynamics China Aerodynamics Research and Development Center Mianyang621000 China

A novel self-sustaining mechanism is proposed for large-scale helical structures in compressible turbulent flows. The existence of two channels of subgrid-scale and viscosity terms for large-scale helicity evolution is confirmed for the first time, through selecting a physical definition of the large-scale helicity in compressible turbulence. Under the influence of the fluid element expansion, it is found that the helicity is generated at small scales via the second-channel viscosity, and the inverse cross-scale helicity transfers at inertial scales through the second-channel helicity flux. Together, they form a self-induced mechanism, which provides a physical insight into the long-period characteristic of large-scale helical structures in the evolution of compressible flow systems. © 2024, CC0.

关键词： Turbulent flow

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Macroscopic Auxiliary Asymptotic Preserving Neural Networks for the Linear Radiative Transfer Equations

SSRN

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SSRN 2023年

作者： Li, Hongyan Jiang, Song Sun, Wenjun Xu, Liwei Zhou, Guanyu School of Mathematical Sciences University of Electronic Science and Technology of China Sichuan Chengdu611731 China Institute of Applied Physics and Computational Mathematics Beijing100094 China Institute of Fundamental and Frontier Sciences University of Electronic Science and Technology of China Sichuan Chengdu611731 China

We develop a Macroscopic Auxiliary Asymptotic-Preserving Neural Network (MA-APNN) method to solve the time-dependent linear radiative transfer equations (LRTEs), which have a multi-scale nature and high dimensionality. To achieve this, we utilize the physics-Informed Neural Networks (PINNs) framework and design a new adaptive exponentially weighted Asymptotic-Preserving (AP) loss function, which incorporates the macroscopic auxiliary equation that is derived from the original transfer equation directly and explicitly contains the information of the diffusion limit equation. Thus, as the scale parameter tends to zero, the loss function gradually transitions from the transport state to the diffusion limit state. In addition, the initial data, boundary conditions, and conservation laws serve as the regularization terms for the loss. We present several numerical examples to demonstrate the effectiveness of MA-APNNs. © 2023, The Authors. All rights reserved.

关键词： Radiative transfer

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Cosmological cutting rules for Bogoliubov initial states

arXiv

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arXiv 2024年

作者： Ghosh, Diptimoy Pajer, Enrico Ullah, Farman Indian Institute of Science Education and Research Pune Dr. Homi Bhabha Road Pune411008 India Department of Applied Mathematics and Theoretical Physics University of Cambridge Wilberforce Road CambridgeCB3 0WA United Kingdom

The field theoretic wavefunction in cosmological spacetimes has received much attention as a fundamental object underlying the generation of primordial perturbations in our universe. Assuming an initial Bunch-Davies state, unitary time evolution implies an infinite set of cutting rules for the wavefunction to all orders in perturbation theory, collectively known as the cosmological optical theorem. In this work, we generalise these results to the case of Bogoliubov initial states, accounting for both parity-even and parity-odd interactions. We confirm our findings in a few explicit examples, assuming IR-finite interactions. In these examples, we preserve scale invariance by adiabatically turning on interactions in the infinite past rather than imposing a Bogoliubov state at some finite initial time. Finally, we give a prescription for computing Bogoliubov wavefunction coefficients from the corresponding Bunch-Davies coefficients for both n-point contact and four-point exchange diagrams. © 2024, CC BY.

关键词： Point contacts

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The estimation of parameters of generalized cosmic Chaplygin gas and viscous modified Chaplygin gas and Accretions around Black Hole in the background of Einstein-Aether gravity

arXiv

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arXiv 2024年

作者： Mukherjee, Puja Debnath, Ujjal Chaudhary, Himanshu Mustafa, G. Department of Mathematics Indian Institute of Engineering Science and Technology Shibpur Howrah711 103 India Department of Applied Mathematics Delhi Technological University Delhi110042 India Sagara Odisha Sambalpur768224 India Department of Mathematics Shyamlal College University of Delhi Delhi110032 India Department of Physics Zhejiang Normal University Jinhua321004 China

In this paper, we have investigated the phenomenon of accelerated cosmic expansion in the late universe and the mass accretion process of a 4-dimensional Einstein-Aether black hole. Starting with the basics of Einstein-Aether gravity theory, we have first considered the field equations and two eminent models of Chaplygin gas, viz. generalized cosmic Chaplygin gas model and viscous modified Chaplygin gas model. Then, we obtained the energy density and Hubble parameters equations for these models in terms of some dimensionless density parameters and some unknown parameters. After finding the required parameters, we proceeded with the mass accretion process. For both models, we obtained the equation of mass in terms of the redshift function and represented the change of mass of the black hole graphically with redshift. At the same time, we have made a graphical comparison between the above-mentioned models and the ΛCDM model of the universe. Eventually, we have concluded that the mass of a 4-dimensional black hole will increase along the universe’s evolution in the backdrop of Einstein-Aether gravity. Copyright © 2024, The Authors. All rights reserved.

关键词： Gravitation

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Cosmological tests of dark energy model in FRW universe

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The European Physical Journal C 2023年第10期83卷 1-18页

作者： Chaudhary, Himanshu Bouali, Amine Molla, Niyaz Uddin Debnath, Ujjal Mustafa, G. Department of Applied Mathematics Delhi Technological University Delhi India Pacif Institute of Cosmology and Selfology (PICS) Sagara Sambalpur India Department of Mathematics Shyamlal College University of Delhi Delhi India Laboratory of Physics of Matter and Radiation Mohammed I University Oujda Morocco Department of Mathematics Indian Institute of Engineering Science and Technology Howrah India Department of Physics Zhejiang Normal University Jinhua People’s Republic of China New Uzbekistan University Tashkent Uzbekistan

The paper is devoted to study the observational signatures of $$f(R,G,\mathcal {T})$$ gravity in FRW universe. In this research article, we present a new cosmological model formulated within the $$f(R,G,\mathcal {T})$$ framework. To constrain the model parameters, we employ the Markov Chain Monte Carlo (MCMC) technique, which enables us to explore the parameter space effectively, and used the 36 points of cosmic chronometers and 1701 points from Pantheon Plus data. We compare our proposed $$f(R,G,\mathcal {T})$$ model with the widely accepted $$\Lambda $$ CDM model, considering different cosmological parameters, including deceleration, snap, and jerk. By evaluating these parameters, we gain valuable insights into the dynamics and evolution of the universe within the context of our new model. Moreover, various diagnostic tests have been conducted, such as Statefinder and Om diagnostic, to further investigate the behavior and consistency of our $$f(R,G,\mathcal {T})$$ model. These tests offer deeper insights into the properties of our model and its compatibility with observational data. We subject our model to statistical analysis using Information Criteria, which serves as a rigorous quantitative assessment of the model’s goodness of fit to the data. This analysis aids in determining the level of agreement between our $$f(R,G,\mathcal {T})$$ model and the observational data, thus establishing the viability and reliability of our proposed cosmological framework. Our findings highlight the potential of the $$f(R,G,\mathcal {T})$$ framework in understanding the fundamental aspects of the universe’s evolution and dynamics. The comparative analysis with $$\Lambda $$ CDM, as well as the comprehensive diagnostic tests performed, demonstrate the efficacy and validity of our model in explaining the observed cosmological phenomena. These results contribute to the ongoing pursuit of accurate and comprehensive models that can provide a deeper understanding of the nature of our u

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A Numerical Study of Two-Phase Flows in Complex Domain with a Generalized Navier Slip and Penetration Boundary Condition on Permeable Boundaries

SSRN

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SSRN 2023年

作者： Luo, Li Zhang, Qian Wang, Xiao-Ping Department of Mathematics University of Macau China Department of Materials Science and Engineering Northwestern University United States School of Science and Engineering The Chinese University of Hong Kong Guangdong Shenzhen518172 China Shenzhen International Center for Industrial and Applied Mathematics Shenzhen Research Institute of Big Data Guangdong 518172 China

A phase-field model consisting of the Cahn-Hilliard and Navier-Stokes equations with a generalized Navier slip and penetration boundary condition is proposed to simulate the behavior of two-phase flows through permeable surfaces. The proposed boundary condition is a generalization of the generalized Navier boundary condition to penetrable boundaries, enabling the simulation of significant scientific problems such as gas penetration through polymer films and oil filtration through porous materials. To address the challenges imposed by the new boundary condition to conventional numerical schemes, we develop a new numerical algorithm by using a finite element method that naturally incorporates the boundary condition into the weak formulation. The algorithm solves a semi-implicit system for the Cahn-Hilliard equation and a fully implicit system for the Navier-Stokes equations. Complex geometries required in the applications are handled by using body-conforming unstructured meshes. Furthermore, an adaptive mesh refinement strategy based on a gradient-jump error indicator is devised to accelerate the simulation process while obtaining a reliable solution on an optimally refined mesh. Extensive numerical experiments, including two practical applications, are conducted to validate the effectiveness and efficiency of the proposed approach. The first application involves bubble penetration through a polymer film, encompassing processes such as bouncing, spreading, pinning, slipping, and penetrating. The numerical results show qualitative agreement with experimental results. In the second application, we examine the robustness of the algorithm by testing different physical parameters with high contrast for the displacement and infiltration of two-phase flows in a complex pore structure. © 2023, The Authors. All rights reserved.

关键词： Finite element method

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Effective actions for domain wall dynamics

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Physical Review D 2025年第5期111卷 056007-056007页

作者： Jose J. Blanco-Pillado Alberto García Martín-Caro Daniel Jiménez-Aguilar Jose M. Queiruga IKERBASQUE Basque Foundation for Science 48011 Bilbao Spain EHU Quantum Center University of the Basque Country UPV/EHU 48080 Bilbao Spain Department of Physics University of the Basque Country UPV/EHU 48080 Bilbao Spain Institute of Cosmology Department of Physics and Astronomy Tufts University Medford Massachusetts 02155 USA Department of Applied Mathematics University of Salamanca Casas del Parque 237008 - Salamanca Spain Institute of Fundamental Physics and Mathematics University of Salamanca Plaza de la Merced 1 37008 - Salamanca Spain

We introduce a systematic method to derive the effective action for domain walls directly from the scalar field theory that gives rise to their solitonic solutions. The effective action for the Goldstone mode, which characterizes the soliton’s position, is shown to consist of the Nambu-Goto action supplemented by higher-order curvature invariants associated to its worldvolume metric. Our approach constrains the corrections to a finite set of Galileon terms, specifying both their functional forms and the procedure to compute their coefficients. We do a collection of tests across various models in 2+1 and 3+1 dimensions that confirm the validity of this framework. Additionally, the method is extended to include bound scalar fields living on the world sheet, along with their couplings to the Goldstone mode. These interactions reveal a universal nonminimal coupling of these scalar fields to the Ricci scalar on the world sheet. A significant consequence of this coupling is the emergence of a parametric instability, driven by interactions between the bound states and the Goldstone mode.

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Interacting models for twisted bilayer graphene: A quantum chemistry approach

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Physical Review B 2023年第23期107卷 235123-235123页

作者： Fabian M. Faulstich Kevin D. Stubbs Qinyi Zhu Tomohiro Soejima Rohit Dilip Huanchen Zhai Raehyun Kim Michael P. Zaletel Garnet Kin-Lic Chan Lin Lin Department of Mathematics University of California Berkeley California 94720 USA Department of Physics University of California Berkeley California 94720 USA Division of Engineering and Applied Science California Institute of Technology Pasadena California 91125 United States Division of Chemistry and Chemical Engineering California Institute of Technology Pasadena California 91125 USA Materials Science Division Lawrence Berkeley National Laboratory Berkeley California 94720 USA Applied Mathematics and Computational Research Division Lawrence Berkeley National Laboratory Berkeley California 94720 USA

The nature of correlated states in twisted bilayer graphene (TBG) at the magic angle has received intense attention in recent years. We present a numerical study of an interacting Bistritzer-MacDonald (IBM) model of TBG using a suite of methods in quantum chemistry, including Hartree-Fock, coupled cluster singles, doubles (CCSD), and perturbative triples [CCSD(T)], as well as a quantum chemistry formulation of the density matrix renormalization group method (DMRG). Our treatment of TBG is agnostic to gauge choices, and hence we present a new gauge-invariant formulation to detect the spontaneous symmetry breaking in interacting models. To benchmark our approach, we focus on a simplified spinless, valleyless IBM model. At integer filling (ν=0), all numerical methods agree in terms of energy and C2zT symmetry breaking. Additionally, as part of our benchmarking, we explore the impact of different schemes for removing “double-counting” in the IBM model. Our results at integer filling suggest that cross validation of different IBM models may be needed for future studies of the TBG system. After benchmarking our approach at integer filling, we perform the first systematic study of the IBM model near integer filling (for |ν|<0.2). In this regime, we find that the ground state can be in a metallic and C2zT symmetry breaking phase. The ground state appears to have low entropy, and therefore can be relatively well approximated by a single Slater determinant. Furthermore, we observe many low entropy states with energies very close to the ground-state energy in the near integer filling regime.

关键词： Electronic structure First-principles calculations Bilayer graphene Twisted bilayer graphene Approximation methods for many-body systems Electron-correlation calculations Many-body techniques Mean field theory Quantum chemistry methods Second quantization Symmetries

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