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arXiv 2025年

作者： Celaya, Adrian Fuentes, David Riviere, Beatrice Department of Computational Applied Mathematics and Operations Research Rice University HoustonTX United States Department of Imaging Physics The University of Texas MD Anderson Cancer Center HoustonTX United States

physics-informed neural networks (PINNs) have gained significant attention for solving forward and inverse problems related to partial differential equations (PDEs). While advancements in loss functions and network architectures have improved PINN accuracy, the impact of collocation point sampling on their performance remains underexplored. Fixed sampling methods, such as uniform random sampling and equispaced grids, can fail to capture critical regions with high solution gradients, limiting their effectiveness for complex PDEs. Adaptive methods, inspired by adaptive mesh refinement from traditional numerical methods, address this by dynamically updating collocation points during training but may overlook residual dynamics between updates, potentially losing valuable information. To overcome this limitation, we propose an adaptive collocation point selection strategy utilizing the QR Discrete Empirical Interpolation Method (QR-DEIM), a reduced-order modeling technique for efficiently approximating nonlinear functions. Our results on benchmark PDEs, including the wave, Allen-Cahn, and Burgers’ equations, demonstrate that our QR-DEIM-based approach improves PINN accuracy compared to existing methods, offering a promising direction for adaptive collocation point strategies. © 2025, CC BY.

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Three-dimensional construction of hyperuniform, nonhyperuniform, and antihyperuniform disordered heterogeneous materials and their transport properties via spectral density functions

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Physical Review E 2025年第3期111卷 035310-035310页

作者： Wenlong Shi Yang Jiao Salvatore Torquato Materials Science and Engineering Arizona State University Tempe Arizona 85287 USA Department of Physics Arizona State University Tempe Arizona 85287 USA Department of Chemistry Princeton University Princeton New Jersey 08544 USA Department of Physics Princeton University Princeton New Jersey 08544 USA Princeton Institute of Materials Princeton University Princeton New Jersey 08544 USA Program in Applied and Computational Mathematics Princeton University Princeton New Jersey 08544 USA

Rigorous theories connecting physical properties of a heterogeneous material to its microstructure offer a promising avenue to guide the computational material design and optimization. The spectral density function χ̃V(k), which can be obtained experimentally from scattering data, enables accurate determination of various transport and wave propagation characteristics, including the time-dependent diffusion spreadability S(t) and effective dynamic dielectric constant εe for electromagnetic wave propagation. Moreover, χ̃V(k) determines rigorous upper bounds on the fluid permeability K. Given the importance of χ̃V(k), we present here an efficient Fourier-space based computational framework to construct three-dimensional (3D) statistically isotropic two-phase heterogeneous materials corresponding to targeted spectral density functions. In particular, we employ a variety of analytical functional forms for χ̃V(k) that satisfy all known necessary conditions to construct disordered stealthy hyperuniform, standard hyperuniform, nonhyperuniform, and antihyperuniform two-phase heterogeneous material systems at varying phase volume fractions. We show that by tuning the correlations in the system across length scales via the targeted functions, one can generate a rich spectrum of distinct structures within each of the above classes of materials. Importantly, we present the first realization of antihyperuniform two-phase heterogeneous materials in 3D, which are characterized by autocovariance function χV(r) with a power-law tail, resulting in microstructures that contain clusters of dramatically different sizes and morphologies. We also determine the diffusion spreadability S(t) and estimate the fluid permeability K associated with all of the constructed materials directly from the corresponding spectral densities. Although it is well established that the long-time asymptotic scaling behavior of S(t) only depends on the functional form of χ̃V(k), with the stealthy hyperuniform a

关键词： Spectral density

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Good plasmons in a bad metal

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Science (New York, N.Y.) 2025年第6735期387卷 786-791页

作者： Ruta, Francesco L. Shao, Yinming Acharya, Swagata Mu, Anqi Jo, Na Hyun Ryu, Sae Hee Balatsky, Daria Su, Yifan Pashov, Dimitar Kim, Brian S Y Katsnelson, Mikhail I. Analytis, James G. Rotenberg, Eli Millis, Andrew J. van Schilfgaarde, Mark Basov, D.N. Department of Physics Columbia University New York NY USA Department of Applied Physics and Applied Mathematics Columbia University New York NY USA National Renewable Energy Laboratory Golden CO United States Advanced Light Source E.O. Lawrence Berkeley National Laboratory Berkeley CA United States Department of Physics University of Michigan Ann Arbor MI United States Department of Chemistry University of California Berkeley CA United States Department of Physics University of California Berkeley CA United States Theory and Simulation of Condensed Matter King's College London London United Kingdom Department of Mechanical Engineering Columbia University New York NY USA Institute for Molecules and Materials Radboud University Nijmegen Netherlands CIFAR Quantum Materials Toronto ON Canada Kavli Energy Nanoscience Institute Berkeley CA United States Center for Computational Quantum Physics Flatiron Institute New York NY USA Department of Physics University of Colorado Boulder CO United States

Correlated metals may exhibit unusually high resistivity that increases linearly in temperature, breaking through the Mott-Ioffe-Regel bound, above which coherent quasiparticles are destroyed. The fate of collective charge excitations, or plasmons, in these systems is a subject of debate. Several studies have suggested that plasmons are overdamped, whereas other studies have detected propagating plasmons. In this work, we present direct nano-optical images of low-loss hyperbolic plasmon polaritons (HPPs) in the correlated van der Waals metal MoOCl2. HPPs are plasmon-photon modes that waveguide through extremely anisotropic media and are remarkably long-lived in MoOCl2. Photoemission data presented here reveal a highly anisotropic Fermi surface, reconstructed and made partly incoherent, likely through electronic interactions as explained by many-body theory. HPPs remain long-lived despite this, revealing previously unseen imprints of many-body effects on plasmonic collective modes.

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Atomic determination of the nuclear quadrupole moment Q(209Bi) using the multi-configuration Dirac-Hartree-Fock method

arXiv

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arXiv 2025年

作者： Li, Jiguang Bieron, Jacek Godefroid, Michel Jönsson, Per Institute of Applied Physics and Computational Mathematics Beijing100088 China Instytut Fizyki Teoretycznej Uniwersytet Jagielloński Kraków Poland Université Libre de Bruxelles Brussels1050 Belgium Department of Materials Science and Applied Mathematics Malmö University MalmöS-20506 Sweden

The multiconfiguration Dirac-Hartree-Fock method implemented in the Grasp2018 package was employed to calculate the magnetic dipole hyperfine interaction constants and electric field gradients of levels in the ground configuration of the neutral bismuth atom. Combining the calculated electric field gradient of the ground state with the measured electric quadrupole hyperfine interaction constant, we extracted the nuclear quadrupole moment for the 209Bi isotope, Q(209Bi) = −422(22) mb. This value, together with other results obtained from atomic- and molecular-structure calculations, created the "world average" nuclear quadrupole moment of this isotope, Q(209Bi) = −420(17) mb. © 2025, CC BY.

关键词： Atoms

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Diverging entanglement of critical magnons in easy-axis antiferromagnets

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Physical Review B 2025年第9期111卷 094402-094402页

作者： Jongjun M. Lee Hyun-Woo Lee Myung-Joong Hwang Department of Physics Pohang University of Science and Technology (POSTECH) Pohang 37673 Korea Division of Natural and Applied Sciences Duke Kunshan University Kunshan Jiangsu 215300 China Zu Chongzhi Center for Mathematics and Computational Science Duke Kunshan University Kunshan Jiangsu 215300 China

We study the instability of antiferromagnets with easy-axis anisotropy under a magnetic field, uncovering single or even multiple phase transitions at the boundary between noncollinear and collinear spin orderings. Near the phase boundary, the entanglement between the sublattice magnons diverges due to the interplay among antiferromagnetic exchange interaction, anisotropy, and magnetic field. Furthermore, our study reveals that this magnetic criticality extends to a superradiant phase transition within cavity magnonics systems. The magnon-photon interaction results in diverging cavity photon numbers and squeezing in the ground state at the transition points between spin orderings. This investigation not only elucidates the criticality of multicomponent squeezed magnons in antiferromagnets, but also proposes cavity photon measurements as a viable method for detecting magnetic phase transitions.

关键词： Anisotropy

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Advancing Carriers Mobility in MnSb2Te4 Thermoelectrics via Tailored Textures and Vacancy Modification

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Advanced Energy Materials 2025年第0期

作者： Xu, Xiao Mao, Dasha Liedke, Maciej Oskar Butterling, Maik Cui, Juan Wang, Jinghan Luo, Yiyuan Ge, Zhenhua Hirschmann, Eric Wagner, Andreas He, Jiaqing Nielsch, Kornelius He, Ran Institute for Metallic Materials Leibniz Institute for Solid State and Materials Research Dresden01069 Germany Department of Physics Southern University of Science and Technology Shenzhen518055 China Institute of Radiation Physics Helmholtz-Zentrum Dresden-Rossendorf Dresden01328 Germany Laboratory of Computational Physics Institute of Applied Physics and Computational Mathematics Beijing100088 China Faculty of Materials Science and Engineering Kunming University of Science and Technology Kunming650093 China

Enhancing carrier mobility plays a crucial role in significantly improving thermoelectric performance. However, due to the lack of a systematic strategy, achieving high mobility remains an elusive goal for most compounds. In this study, the hot-forging method is applied to polycrystalline MnSb₂Te₄, achieving a remarkable 300% improvement in carrier mobility. Through electron backscattering diffraction microstructural analysis, it is demonstrated how optimizing textures can accelerate carrier movement in MnSb₂Te₄ bulk materials. Moreover, theoretical calculations, combined with experimental positron annihilation spectroscopy, reveal that Te vacancies help counteract intrinsic cation defects, leading to a simultaneous increase in carrier mobility. As a result, the hot-forged MnSb₂Te₄ specimen, with a diameter of 15 mm, reaches a record-high maximum figure of merit (ZT) value of 1.3 at 773 K and an impressive average ZT of 0.7 between 323 and 773 K. The experimental output efficiency of 4.6%, observed at 773 K on the MnSb₂Te₄-based single-leg module, further confirms that the improved transport properties are due to the enhanced carrier mobility. This comprehensive study offers valuable insights into mobility enhancement in MnSb₂Te₄ and provides a promising direction for exploring similar improvements in other thermoelectric materials. © 2025 The Author(s). Advanced Energy Materials published by Wiley-VCH GmbH.

关键词： Positron annihilation

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THE MANY-BODY GROUND STATE MANIFOLD OF FLAT BAND INTERACTING HAMILTONIAN FOR MAGIC ANGLE TWISTED BILAYER GRAPHENE

arXiv

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arXiv 2025年

作者： Stubbs, Kevin D. Ragone, Michael Macdonald, Allan H. Lin, Lin Department of Mathematics University of California BerkeleyCA94720 United States Department of Physics University of Texas at Austin AustinTX78712 United States Applied Mathematics and Computational Research Division Lawrence Berkeley National Laboratory BerkeleyCA94720 United States

At a magic relative twist angle, magic angle twisted bilayer graphene (MATBG) has an octet of flat bands that can host strong correlation physics when partially filled. A key theoretical discovery in MATBG is the existence of ferromagnetic Slater determinants as exact ground states of the corresponding flat band interacting (FBI) Hamiltonian. The FBI Hamiltonian describes the behavior of electrons that interact with each other in a high-dimensional space, and is constructed from the band structure of the non-interacting Bistritzer–MacDonald model at the chiral limit. A key property of the FBI Hamiltonian for MATBG is that it is frustration free and can be written as a sum of non-commuting terms. In this work, we provide a complete characterization of the ground state manifold of the FBI Hamiltonian, proving that it is precisely the linear span of such ferromagnetic Slater determinants. © 2025, CC BY.

关键词： Ferromagnetism

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Can One Hear the Shape of a Crystal?

arXiv

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arXiv 2025年

作者： Wang, Haina Torquato, Salvatore Department of Chemistry Princeton University PrincetonNJ08544 United States Department of Physics Princeton University PrincetonNJ08544 United States Princeton Materials Institute Princeton University PrincetonNJ08540 United States Program in Applied and Computational Mathematics PrincetonNJ08544 United States

Isospectrality is a general fundamental concept often involving whether various operators can have identical spectra, i.e., the same set of eigenvalues. In the context of the Laplacian operator, the famous question "Can one hear the shape of a drum?" concerns whether different shaped drums can have the same vibrational modes. The isospectrality of a lattice in d-dimensional Euclidean space Rd is a tantamount to whether it is uniquely determined by its theta series, i.e., the radial distribution function g2(r). While much is known about the isospectrality of Bravais lattices across dimensions, little is known about this question of more general crystal (periodic) structures with an n-particle basis (n ≥ 2). Here, we ask, What is nmin(d), the minimum value of n for inequivalent (i.e., unrelated by isometric symmetries) crystals with the same theta function in space dimension d? To answer these questions, we use rigorous methods as well as a precise numerical algorithm that enables us to determine the minimum multi-particle basis of inequivalent isospectral crystals. Our algorithm identifies isospectral 4-, 3- and 2-particle bases in one, two and three spatial dimensions, respectively. For many of these isospectral crystals, we rigorously show that they indeed possess identical g2(r) up to infinite r. Based on our analyses, we conjecture that nmin(d) = 4, 3, 2 for d = 1, 2, 3, respectively. The identification of isospectral crystals enables one to study the degeneracy of the ground-state under the action of isotropic pair potentials. Indeed, using inverse statistical-mechanical techniques, we find an isotropic pair potential whose low-temperature configurations in two dimensions obtained via simulated annealing can lead to both of two isospectral crystal structures with n = 3, the proportion of which can be controlled by the cooling rate. Our findings provide general insights into the structural and ground-state degeneracies of crystal structures as determined by radia

关键词： Eigenvalues and eigenfunctions

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Enhanced accuracy of isotope-shift measurements of Yb+ 369- and 935-nm transitions via sympathetic cooling

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Physical Review A 2025年第3期111卷 033101-033101页

作者： Jize Han Ying Zheng Yanmei Yu Jiguang Li Zhiguo Huang Jingwei Wen Ling Qian Lijun Wang Department of Precision Instrument Tsinghua University Beijing 100084 China China Mobile (Suzhou) Software Technology Company Ltd. Suzhou 215163 China Department of Physics Tsinghua University Beijing 100084 China Beijing National Laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences Beijing 100190 China University of Chinese Academy of Sciences Beijing 100049 China Institute of Applied Physics and Computational Mathematics Beijing 100088 China

We report enhanced accuracy in isotope-shift (IS) measurement using sympathetic cooling, demonstrated with Yb+170,172,174,176 transitions at 369 and 935 nm. Considering only type-A uncertainties, sympathetic cooling achieves 30- and 200-fold improvements in IS measurement accuracy at 369 and 935 nm compared with previous single-ion results. Our measurements remain the most accurate to date including type-B uncertainties. King-plot analysis yields model-independent IS factors for these transitions [F369=−12.3(8) GHz/fm2, K369=−1800(1400) GHz u, F935=30.7(2.0) GHz/fm2, and K935=12900(3000) GHz u] and their ratio [F935F369=−2.498(4)] along with K935−K369F935F369=8410(90) GHz u, representing a 17-fold improvement. More reliable nuclear charge radii for Yb170–174,176 are also determined with an accuracy of 0.01 fm2. This paper complements collinear laser spectroscopy, introduces a robust approach for researching unstable isotopes, and supports applications of sympathetic cooling in trapped-ion quantum computers and quantum frequency standards.

关键词： Quantum computers

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Enhanced thermoelectric properties of two-dimensional Janus ferromagnetic LaBrI with strain-induced valley degeneracy

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Physical Review B 2025年第15期111卷 155433-155433页

作者： Anuja Kumari Raman D. K. Tanu Choudhary Raju K. Biswas Abhinav Nag Santanu K. Maiti Jagdish Kumar Physics and Applied Mathematics Unit Indian Statistical Institute 203 Barrackpore Trunk Road Kolkata- 700 108 India Department of Computational Sciences Central University of Punjab Bathinda-151 401 India Department of Physics M S Ramaiah University of Applied Sciences Bengaluru-560 058 India Department of Physics North Eastern Regional Institute of Science and Technology Nirjuli Arunachal Pradesh-791 109 India Department of Physics GGDSD College Rajpur Palampur-176 061 India

Since the successful synthesis of the MoSSe monolayer, which violated the out-of-plane mirror symmetry of transition metal dichalcogenide monolayers, considerable and systematic research has been conducted on Janus monolayer materials. By systematically analyzing the LaBrI monolayer, we are able to learn more about the novel Janus material by focusing on the halogen family next to group VIA (S, Se, Te). The structural optimizations have been carried out using pseudopotential-based Quantum Espresso code. Computed structural parameters are in good agreement with literature reports. The optimized crystal structures are used for computing the effect of strain on electronic and thermoelectric properties. Dynamical stability predicts that this material can withstand up to 10% of tensile strain. Computed electronic structure reveals material to be indirect wide band-gap ferromagnet with magnetic moment 1 µB. With increase in the biaxial tensile strain the band gap decreases. Furthermore, the computed magnetothermoelectric properties predict high Seebeck coefficient ∼400 µV/K and low thermal conductivity of ∼0.93 W/m K in LaBrI, which results in a high ZT∼1.84 for 4% strain at 800 K. The present study supports the fact that tensile strain on ferromagnetic LaBrI material can further enhance TE properties, making it a promising material for TE applications at higher temperatures.

关键词： Tensile strain

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