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Hydrogen and deuterium tunneling in niobium

Physical Review B 2025年第2期111卷 L020103-L020103页

作者： Abdulaziz Abogoda W. A. Shelton I. Vekhter J. A. Sauls Hearne Institute for Theoretical Physics Louisiana State University Baton Rouge Louisiana 70803 USA Applied Physics Graduate Program Northwestern University Evanston Illinois 60208 USA Department of Physics and Astronomy Louisiana State University Baton Rouge Louisiana 70803 USA

We use density functional methods to identify the atomic configurations of H and D atoms trapped by O impurities embedded in bulk Nb. The O atoms are located at the octahedral position in the Nb body-centered cubic (BCC) lattice, and H (D) atoms tunnel between two degenerate tetrahedral sites separated by a mirror plane. Using nudged elastic band (NEB) methods, we calculate the double-well potential for O-H and O-D impurities and the wave functions and tunnel splittings for H and D atoms. Our results agree with those obtained from analysis of heat capacity and neutron scattering measurements on Nb with low concentrations of O-H and O-D.

关键词： Atoms

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Anomalous properties of spark plasma sintered boron nitride solids

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Materials Today 2025年 86卷 42-51页

作者： Biswas, Abhijit Serles, Peter Alvarez, Gustavo A. Schimpf, Jesse Hache, Michel Kong, Jonathan Demingos, Pedro Guerra Yuan, Bo Pieshkov, Tymofii S. Li, Chenxi Puthirath, Anand B. Gao, Bin Gray, Tia Zhang, Xiang Murukeshan, Jishnu Vajtai, Robert Dai, Pengcheng Singh, Chandra Veer Howe, Jane Zou, Yu Martin, Lane W. Clancy, James Patrick Tian, Zhiting Filleter, Tobin Ajayan, Pulickel M. Department of Materials Science and Nanoengineering Rice University HoustonTX77005 United States Department of Mechanical & Industrial Engineering University of Toronto 5 King's College Road TorontoM5S 3G8 Canada Sibley School of Mechanical and Aerospace Engineering Cornell University IthacaNY14853 United States Department of Materials Science and Engineering University of California Berkeley94720 United States Department of Materials Science and Engineering University of Toronto 184 College St TorontoM5S 3E4 Canada Department of Physics and Astronomy McMaster University HamiltonL8S 4M1 Canada Applied Physics Graduate Program Smalley-Curl Institute Rice University HoustonTX77005 United States Department of Physics and Astronomy Rice University HoustonTX77005 United States Materials Sciences Division Lawrence Berkeley National Laboratory Berkeley94720 United States

Hexagonal boron nitride (h-BN) is a brittle ceramic with a layered structure, however, recent experiments have suggested that inter-layer structural engineering could be key to new structural and functional properties. Here we report the scalable bulk synthesis of high-density crystalline h-BN solids, by using high-temperature spark plasma sintering (SPS) of h-BN powders, which show high values of mechanical strength, ductility, dielectric constant, thermal conductivity, and exceptional neutron radiation shielding capability. Through exhaustive characterizations we reveal that SPS induces non-basal plane crystallinity, twisting of layers, and facilitates inter-grain fusion with a high degree of in-plane alignment across macroscale dimensions, resulting in near-theoretical density and improved properties. Our findings highlight the importance of material design, via new approaches such as layer twisting and interlayer interconnections, to create novel ceramics with properties that could go beyond their intrinsic limits. © 2025

关键词： Ductility

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Incommensurate broken helix induced by nonstoichiometry in the axion insulator candidate EuIn2As2

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Physical Review B 2025年第8期111卷 L081109-L081109页

作者： Masaki Gen Yukako Fujishiro Kazuki Okigami Satoru Hayami Max T. Birch Kiyohiro Adachi Daisuke Hashizume Takashi Kurumaji Hajime Sagayama RIKEN Center for Emergent Matter Science (CEMS) Wako 351-0198 Japan Institute for Solid State Physics University of Tokyo Kashiwa Chiba 277-8581 Japan RIKEN Cluster for Pioneering Research (CPR) Wako 351-0198 Japan Department of Applied Physics University of Tokyo Tokyo 113-8656 Japan Graduate School of Science Hokkaido University Sapporo 060-0810 Japan Materials Characterization Support Team RIKEN Center for Emergent Matter Science (CEMS) Wako 351-0198 Japan Department of Advanced Materials Science University of Tokyo Kashiwa 277-8561 Japan Division of Physics Mathematics and Astronomy California Institute of Technology Pasadena California 91125 USA Institute of Materials Structure Science High Energy Accelerator Research Organization Tsukuba 305-0801 Japan

Zintl phase EuIn2As2 has garnered growing attention as an axion insulator candidate, triggered by the identification of a commensurate double-Q broken-helix state in previous studies, however, its periodicity and symmetry remain subjects of debate. Here, we perform resonant x-ray scattering experiments on EuIn2As2, revealing an incommensurate nature of the broken-helix state, where both the wave number and the amplitude of the helical modulation exhibit systematic sample dependence. Furthermore, the application of an in-plane magnetic field brings about a fanlike state that appears to preserve the double-Q nature, which might be attributed to multiple-spin interactions in momentum space. We propose that the itinerant character of EuIn2As2, most likely induced by Eu deficiency, gives rise to the helical modulation and impedes the realization of a theoretically predicted axion state with the collinear antiferromagnetic order.

关键词： X ray scattering

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Topological orders with classical Lie group symmetries from coupling electron wires

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Physical Review B 2025年第16期111卷 165140-165140页

作者： Pak Kau Lim Michael Mulligan Jeffrey C. Y. Teo Department of Physics and Astronomy University of California Riverside California 92521 USA Department of Physics University of Virginia Charlottesville Virginia 22904 USA Theoretical Sciences Visiting Program Okinawa Institute of Science and Technology Graduate University Onna 904-0495 Japan

We study the topological order that arises from chiral states with SU(N) or SO(N) edge-state symmetry. This extends our previous study of topological orders that descend from the bosonic E8 quantum Hall state. We use exactly solvable models of coupled electron wires to construct states with SU(m)n, SO(m)n, or Sp(m)n topological order for various levels n. We use our constructions to write down string operators for various non-Abelian anyons. We thereby provide a systematic, model derivation of quantum Hall states, topological superconductors, and spin liquids with emergent non-Abelian quasiparticle excitations, including those of Ising, metaplectic, and Fibonacci type.

关键词： Lie groups

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Degradation of Organic LEDs Characterized with Algebraic Decay Relaxation Function 15

Degradation of Organic LEDs Characterized with Algebraic Dec...

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Advances in Display Technologies XV 2025

作者： Aygen, Can Richards, Michael Yazdaanpanah, Ramin Kulkarni, Sachin Tanriover, Ibrahim Onsager, Claire Lin, BoYen Lee, Jiun-Haw Aydin, Koray Grayson, Matthew A. Department of Electrical & Computer Engineering Northwestern University EvanstonIL United States Department of Opto-Electronic Engineering National Dong Hwa University Hualien Taiwan Graduate Institute of Photonics and Optoelectronics Department of Electrical Engineering National Taiwan University Taipei Taiwan Program in Applied Physics Northwestern University EvanstonIL United States

ISBN: (纸本)9781510685246

Lifetime studies of organic light emitting diodes are necessary to both understand and mitigate causes of degradation. Here, electroluminescence (EL) studies of green organic light-emitting diode (OLED) pixels are measured continuously using three different dc currents over a period of one week, and their slow EL degradation is accurately fit to an analytical expression with only two fit parameters. The slower-than-exponential EL decay is fit to an empirical unified heavy-tail function that can interpolate between power-law algebraic decays (AD) and stretched-exponential decays (SE). Whereas SE and AD are largely indistinguishable down to 50% of the initial luminance, here we report degradation down to 10% of the initial luminance which most closely fits an AD function with remarkable precision over the entire duration of the experiment. All relaxations share the same characteristic exponent β = 0.53 in the power law decay, whereas the characteristic time-scale τ for degradation decreases with a power-law exponent B = 1.9 as the current increases. The high degree of accuracy in the fit allows asymptotic predictions at time scales that are orders of magnitude longer than the duration of the data collection. The voltage across the OLED is simultaneously monitored under constant-current degradation and reveals an early-onset time scale where the voltage reaches a minimum before degradation runoff. © 2025 SPIE.

关键词： Organic light emitting diodes (OLED)

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Nonconvex entanglement monotone determining the characteristic length of entanglement distribution in continuous-variable quantum networks

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Physical Review A 2025年第4期111卷 042429-042429页

作者： Yaqi Zhao Jinchuan Hou Kan He Nicolò Lo Piparo Xiangyi Meng College of Mathematics Taiyuan University of Technology Taiyuan 030024 China Okinawa Institute of Science and Technology Graduate University 1919-1 Tancha Onna-son Okinawa 904-0495 Japan Department of Physics Applied Physics and Astronomy Rensselaer Polytechnic Institute Troy New York 12180 USA

Quantum networks (QNs) promise to enhance the performance of various quantum technologies in the near future by distributing entangled states over long distances. The first step towards this is to develop novel entanglement measures that are both informative and computationally tractable at large scales. While numerous such entanglement measures exist for discrete-variable (DV) systems, a comprehensive exploration for experimentally preferred continuous-variable (CV) systems is lacking. Here, we introduce a class of CV entanglement measures, among which we identify a nonconvex entanglement monotone—the ratio negativity, which possesses a simple, scalable form that determines the exponential decay of optimal entanglement swapping on a chain of pure Gaussian states. This characterization opens avenues for leveraging statistical physics tools to analyze swapping-protocol-based CV QNs.

关键词： Quantum entanglement

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Emulating complex synapses using interlinked proton conductors

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Physical Review applied 2025年第1期23卷 014027-014027页

作者： Lifu Zhang Ji-An Li Yang Hu Jie Jiang Rongjie Lai Marcus K. Benna Jian Shi Department of Materials Science and Engineering Rensselaer Polytechnic Institute Troy New York 12180 USA Neurosciences Graduate Program University of California San Diego La Jolla California 92093 USA Department of Mathematics Purdue University West Lafayette Indiana 47907 USA Department of Neurobiology School of Biological Sciences University of California at San Diego La Jolla California 92093 USA Department of Physics Applied Physics and Astronomy Rensselaer Polytechnic Institute Troy New York 12180 USA

In terms of energy efficiency and computational speed, neuromorphic electronics based on nonvolatile memory devices are expected to be one of most promising hardware candidates for future artificial intelligence (AI). However, catastrophic forgetting, networks rapidly overwriting previously learned weights when learning new tasks, remains a pivotal obstacle in either digital or analog AI chips for unleashing the true power of brainlike computing. To address catastrophic forgetting in the context of online memory storage, a complex synapse model (the Benna-Fusi model) was proposed recently [M. K. Benna and S. Fusi, Nat. Neurosci. 19, 1697 (2016)], the synaptic weight and internal variables of which evolve following diffusion dynamics. In this work, by designing a proton transistor with a series of charge-diffusion-controlled storage components, we have experimentally realized the Benna-Fusi artificial complex synapse. Memory consolidation from coupled storage components is revealed by both numerical simulations and experimental observations. Different memory timescales for the complex synapse are engineered by the diffusion length of charge carriers and the capacity and number of coupled storage components. The advantages of the demonstrated complex synapse for both memory capacity and memory consolidation are revealed by neural network simulations of face-familiarity detection. Our experimental realization of the complex synapse suggests a promising approach to enhance memory capacity and to enable continual learning.

关键词： Nonvolatile storage

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Negative superfluid density and spatial instabilities in driven superconductors

arXiv

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arXiv 2025年

作者： Grankin, Andrey Galitski, Victor Oganesyan, Vadim Joint Quantum Institute Department of Physics University of Maryland College ParkMD20742 United States Physics Program and Initiative for the Theoretical Sciences The Graduate Center CUNY New YorkNY10016 United States Department of Physics and Astronomy College of Staten Island CUNY Staten IslandNY10314 United States

We consider excitation of Higgs modes via the modulation of the BCS coupling within the Migdal-Eliashberg-Keldysh theory of time-dependent superconductivity. Despite the presence of phonons, which break integrability, we observe Higgs amplitude oscillations reminiscent of the integrable case. The dynamics of quasiparticles follows from the effective Bogolyubov-de Gennes equations, which represent a Floquet problem for the Bogolyubov quasiparticles. We find that when the Floquet-Bogolyubov bands overlap, the homogeneous solution formally leads to a negative superfluid density, which is no longer proportional to the amplitude of the order parameter. This result indicates an instability, which we explore using spatially-resolved BdG equations. Spontaneous appearance of spatial inhomogeneities in the order parameter is observed and they first occur when the superfluid density becomes unphysical. We conclude that the homogeneous solution to time-dependent superconductivity is generally unstable and breaks up into a complicated spatial landscape via an avalanche of topological excitations. Copyright © 2025, The Authors. All rights reserved.

关键词： Penetration depth (superconductivity)

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Characterisation of Hβ spectra from EXO 051910+3737.7 X-rays binaries

arXiv

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arXiv 2025年

作者： Nuchvanichakul, Pornisara Irawati, Puji Rittipruk, Pakakaew Gandhi, Poshak Knigge, Christian Charles, Phil Wannawichian, Suwicha M.S. Program in Applied Physics Department of Physics and Materials Science Faculty of Science Chiang Mai University Chiang Mai50200 Thailand Department of Physics and Astronomy University of Southampton Southampton United Kingdom National Astronomical Research Institute of Thailand Chiang Mai50180 Thailand Department of Physics and Materials Science Faculty of Science Chiang Mai University Chiang Mai50200 Thailand

We investigate the spectral characteristics of the Be/X-ray binary system, EXO 051910+3737.7, in which Be/X-ray systems are the largest sub-class of high-mass X-ray binaries. Spectroscopic observations are taken by the Thai National Telescope (TNT) with a Medium-RESolution spectrograph (MRES) instrument for seven nights spanning from 2020 to 2021. Our primary focus is directed towards the analysis of two Balmer lines, namely Hα and Hβ, given that Be stars typically exhibit emission features in at least one of these hydrogen Balmer lines during certain phases. Our observations reveal split Balmer emission lines throughout the entire duration of our monitoring. Double Gaussian profiles were employed for line fitting to characterize these lines. The presence of double peaks in the Balmer lines indicates the presence of asymmetries within the circumstellar disc. We then analyze V/R variations and the changes in Hβ spectra. Our analysis of V/R variation which Violet (V) and Red (R) peak intensity components, revealed rapid fluctuations occurring within a single day, although determining the precise periodicity was constrained by instrumental limitations and the duration of observability. Furthermore, employing observed the wavelength differences (∆λ) in conjunction with typical Be star parameters allowed us to estimate the radius (rβ) of the Hβ emitting envelope. The average value was calculated to be 2.585r∗, with a standard deviation of 0.050r∗ © 2025, CC BY-NC-ND.

关键词： Stars

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Interference and Measurement: Obtaining information from the QAOA MaxCut state

arXiv

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arXiv 2025年

作者： Agarwal, Pranjal Ali, Nada Hillery, Mark Department of Physics and Astronomy Hunter College The City University of New York 695 Park Avenue New YorkNY10065 United States Physics Program Graduate Center The City University of New York 365 Fifth Avenue New YorkNY10016 United States

In using the QAOA algorithm for the MaxCut problem one encodes the number of edges connecting the sets resulting from a partition of the vertices of a graph into phases of amplitudes of a quantum state (QAOA state). One wants to use the quantum state to find partitions with large numbers of edges connecting them. In the QAOA algorithm this is done by using a mixing operation and parameter optimization. Here we want to see what can be done if we only use simple aspects of quantum mechanics, interference and measurement, to extract information from the QAOA state. The idea is to use constructive interference to enhance the amplitudes corresponding to partitions with a large number of edges between the sets. We examine examples, but analytically and numerically. We also show how the results of sequences of measurements can be used to gain information about the landscape of solutions. Copyright © 2025, The Authors. All rights reserved.

关键词： Graph algorithms

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