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Correlation versus dissipation in a non-Hermitian Anderson impurity model

Physical Review B 2025年第12期111卷 125157-125157页

作者： Kazuki Yamamoto Masaya Nakagawa Norio Kawakami Department of Physics Tokyo Institute of Technology Meguro Tokyo 152-8551 Japan Department of Physics University of Tokyo Hongo Tokyo 113-0033 Japan Fundamental Quantum Science Program TRIP Headquarters RIKEN Wako 351-0198 Japan Department of Physics Ritsumeikan University Kusatsu Shiga 525-8577 Japan Department of Materials Engineering Science Osaka University Toyonaka Osaka 560-8531 Japan

We analyze the competition between strong correlations and dissipation in quantum impurity systems from the Kondo regime to the valence fluctuation regime by developing a slave-boson theory for a non-Hermitian Anderson impurity model with one-body loss. Notably, in the non-Hermitian Kondo regime, strong correlations qualitatively change the nature of dissipation through renormalization effects, where the effective one-body loss is suppressed and emergent many-body dissipation characterized by the complex-valued hybridization is generated. We unveil the mechanism of a dissipative quantum phase transition of the Kondo state on the basis of this renormalization effect, which counterintuitively enhances the lifetime of the impurity against loss. We also find a crossover from the non-Hermitian Kondo regime to the valence fluctuation regime dominated by one-body dissipation. Our results can be tested in a wide variety of setups such as quantum dots coupled to electronic leads and quantum point contacts in ultracold Fermi gases.

关键词： Bosons

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Impact of In flux on self-assembled InGaN/GaN superlattice grown on GaN template by plasma-assisted molecular beam epitaxy

Impact of In flux on self-assembled InGaN/GaN superlattice g...

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2022 Compound Semiconductor Week, CSW 2022

作者： Khan, Kamruzzaman Sun, Kai Wurm, Christian Ahmadi, Elaheh University of Michigan Department of Materials Science and Engineering Ann ArborMI United States University of California Department of Electrical and Computer Engineering Santa BarbaraCA United States University of Michigan Department of Electrical Engineering and Computer Science Ann ArborMI United States University of Michigan Applied Physics Program Ann ArborMI United States

ISBN: (数字)9781665453400

ISBN: (纸本)9781665453400

We have previously reported spontanous formation of InGaN/GaN superlattice structure on nominal InGaN films grown by plasma-assisted molecular beam epitaxy (PAMBE). In this work, we report on the impact of In flux on the formation and periodicity of self-assembled InxGa1-xN/InyGa1-yN superlattice structure (SASL). We show that the thickness and In composition in the InGaN layer varies by changing the In flux. These films were stucturally characterized by X-ray diffraction and simulated by globalfit software to get the thickness and In composition. The superlattice structures were confimred by scanning transmission electron microscopy and the thickness of InGaN layer and In composition were determined by energy dispersive X-ray spectroscopy. This work can provide a method for using the SASL with better control for their optoelectronics application. © 2022 IEEE.

关键词： III-V semiconductors

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Large magnetic anisotropy and magnetostriction in thin films of CoV2O4

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Physical Review materials 2023年第1期7卷 014408-014408页

作者： Sangsoo Kim Christie J. Thompson Yan Xin Christianne Beekman National High Magnetic Field Laboratory Florida State University Tallahassee Florida 32310 USA Department of Physics Florida State University Tallahassee Florida 32306 USA Materials Science and Engineering Program Florida State University Tallahassee Florida 32310 USA

Spinel cobalt vanadate CoV2O4 has been grown on (001) SrTiO3 substrates. Using torque magnetometry experiments, we find that the previously observed temperature-induced anisotropy change, where the easy axis changes from the out-of-plane [001] direction to a biaxial anisotropy with planar <100> easy axes, occurs in a gradual second-order structural phase transition. This paper characterizes this transition and the magnetic anisotropies in the (001), (100), and (1¯10) rotation planes, and explores their field dependence up to 30 T. Below 80 K, hysteretic features appear around the hard axes, i.e., the out-of-plane direction in (1¯10) and (010) rotations and the planar <110> directions in (001) rotations. This is due to a Zeeman energy that originates from the lag of the magnetization with respect to the applied magnetic field as the sample is rotated. The appearance of the hysteresis, which persists up to very high fields, shows that the anisotropy at low temperature is rather strong. Additionally, field-dependent distortions to the symmetry of the torque response in increasing applied fields shows that magnetostriction plays a large role in determining the direction and magnitude of the anisotropy.

关键词： Magnetic anisotropy Magnetic phase transitions Structural properties

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Cyclic ferroelectric switching and quantized charge transport in CuInP2S6

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Physical Review B 2023年第18期108卷 L180101-L180101页

作者： Daniel Seleznev Sobhit Singh John Bonini Karin M. Rabe David Vanderbilt Department of Physics and Astronomy Center for Materials Theory Rutgers University Piscataway New Jersey 08854 USA Department of Mechanical Engineering University of Rochester Rochester New York 14627 USA Materials Science Program University of Rochester Rochester New York 14627 USA Center for Computational Quantum Physics Flatiron Institute 162 5th Avenue New York New York 10010 USA

The van der Waals layered ferroelectric CuInP2S6 has been found to exhibit a variety of intriguing properties arising from the fact that the Cu ions are unusually mobile in this system. While the polarization switching mechanism is usually understood to arise from Cu ion motion within the monolayers, a second switching path involving Cu motion across the van der Waals gaps has been suggested. In this work, we perform zero-temperature first-principles calculations on such switching paths, focusing on two types that preserve the periodicity of the primitive unit cell: “cooperative” paths preserving the system's glide mirror symmetry, and “sequential” paths in which the two Cu ions in the unit cell move independently of each other. We find that CuInP2S6 features a rich and varied energy landscape, and that sequential paths are clearly favored energetically both for cross-gap and through-layer paths. Importantly, these segments can be assembled to comprise a globally insulating cycle with the out-of-plane polarization evolving by a quantum as the Cu ions shift to neighboring layers. In this sense, we argue that CuInP2S6 embodies the physics of a quantized adiabatic charge pump.

关键词： Electric polarization Electronic structure Ferroelectricity Phonons Structural phase transition

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Recent Advancements in Nanophotonics for Optofluidics

arXiv

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arXiv 2024年

作者： Yang, Sen Hong, Chuchuan Zhu, Guodong Anyika, Theodore Hong, Ikjun Ndukaife, Justus C. Institute of Physics Chinese Academy of Sciences Beijing National Laboratory for Condensed Matter Physics Beijing100190 China Department of Chemistry Department of Materials Science and Engineering Northwestern University EvanstonIL60208 United States Department of Electrical and Computer Engineering Vanderbilt University NashvilleTN37235 United States Department of Mechanical Engineering Vanderbilt University NashvilleTN37235 United States Interdisciplinary Materials Science Program Vanderbilt University NashvilleTN37240 United States

Optofluidics is dedicated to achieving integrated control of particle and fluid motion, particularly on the micrometer scale, by utilizing light to direct fluid flow and particle motion. The field has seen significant growth recently, driven by the concerted efforts of researchers across various scientific disciplines, notably for its successful applications in biomedical science. In this review, we explore a range of optofluidic architectures developed over the past decade, with a primary focus on mechanisms for precise control of micro and nanoscale biological objects and their applications in sensing. Regarding nanoparticle manipulation, we delve into mechanisms based on optical nanotweezers using nanolocalized light fields and light-based hybrid effects with dramatically improved performance and capabilities. In the context of sensing, we emphasize those works that used optofluidics to aggregate molecules or particles to promote sensing and detection. Additionally, we highlight emerging research directions, encompassing both fundamental principles and practical applications in the field. Copyright © 2024, The Authors. All rights reserved.

关键词： Flow of fluids

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Electron Cloaking in MoS2 for High-Performance Optoelectronics

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Nano letters 2025年第23期25卷 2025 May 28页

作者： Yu-Xiang Chen Jian-Jhang Lee Ding-Rui Chen You-Chen Lin Hao-Ting Chin Xiu-Yu Huang Sheng-Kuei Chiu Chu-Chi Ting Mario Hofmann Ya-Ping Hsieh Institute of Atomic and Molecular Sciences Academia Sinica Taipei 10617 Taiwan. International Graduate Program of Molecular Science and Technology National Taiwan University Taipei 10617 Taiwan. Molecular Science and Technology Program Taiwan International Graduate Program Academia Sinica Taipei 10617 Taiwan. Department of Electronic Engineering Chung Yuan Christian University Taoyuan 320 Taiwan. Department of Physics National Taiwan University Taipei 10617 Taiwan. Nano Science and Technology Program Taiwan International Graduate Program Academia Sinica Taipei 10617 Taiwan. Department of Materials Science and Engineering Feng Chia University Taichung 407 Taiwan. Department of Materials Science National University of Tainan Tainan 70005 Taiwan. Graduate Institute of Opto-Mechatronics Department of Mechanical Engineering National Chung Cheng University Chia-Yi 62102 Taiwan.

Defects in two-dimensional (2D) materials represent both challenges and opportunities to their optoelectronic performance. While defects limit the carrier mobility in transistors through increased charge scattering, they also enhance 2D material functionality in sensors. Electron cloaking, a process that reduces Coulomb scattering via localized electron-defect interactions, has recently been shown to mitigate the performance degradation of bulk semiconductors in the presence of defects. We demonstrate the realization of electron cloaking in 2D materials through the metal decoration of defects. Sulfur vacancies were introduced in MoS and selectively decorated with aluminum using atomic layer deposition. Theoretical and experimental characterization demonstrate the suppression of electronic scattering through localized interactions. Optoelectronic measurements reveal a significant improvement in carrier mobility and lifetime, highlighting the effectiveness of the cloaking mechanism. Our findings open a route independently to maximize performance and functionality of optoelectronic devices, which is illustrated by the realization photosensors with unprecedented sensitivity and speed.

关键词： 2D material Coulomb scattering MoS2 defect-limited mobility electron cloaking electron−defect interaction vacancies

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Field-induced spin polarization in the lightly Cr-substituted layered antiferromagnet NiPS3

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Physical Review B 2024年第18期109卷 184405-184405页

作者： Rabindra Basnet Dinesh Upreti Taksh Patel Santosh Karki Chhetri Gokul Acharya Md Rafique Un Nabi M. M. Sharma Josh Sakon Mansour Mortazavi Jin Hu Department of Chemistry and Physics University of Arkansas at Pine Bluff Pine Bluff Arkansas 71603 USA Department of Physics University of Arkansas Fayetteville Arkansas 72701 USA Fayetteville High School Fayetteville Arkansas 72701 USA MonArk NSF Quantum Foundry University of Arkansas Fayetteville Arkansas 72701 USA Department of Chemistry and Biochemistry University of Arkansas Fayetteville Arkansas 72701 USA Materials Science and Engineering Program Institute for Nanoscience and Engineering University of Arkansas Fayetteville Arkansas 72701 USA

Tuning magnetic properties in layered magnets is an important route to realize novel phenomenon related to two-dimensional (2D) magnetism. Recently, tuning antiferromagnetic (AFM) properties through substitution and intercalation techniques has been widely studied in MPX3 compounds. Interesting phenomena, such as diverse AFM structures and even the signatures of ferrimagnetism, have been reported. However, long-range ferromagnetic (FM) ordering has remained elusive. In this work, we explored the magnetic properties of the Cr-substituted NiPS3. We found that Cr substitution is extremely efficient in controlling spin orientation in NiPS3. Our study reveals a field-induced spin polarization in lightly (9%) Cr-substituted NiPS3, which is likely attributed to the attenuation of AFM interactions and magnetic anisotropy due to Cr doping. Our work provides a possible strategy to achieve FM phase in AFM MPX3, which could be useful for investigating 2D magnetism as well as potential device applications.

关键词： Antiferromagnetism Magnetic anisotropy Magnetic order Magnetic phase transitions 2-dimensional systems Antiferromagnets Van der Waals systems Ion implantation Magnetization measurements

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Topological Rigidity and Non-Abelian defect junctions in chiral nematic systems with effective biaxial symmetry

arXiv

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arXiv 2024年

作者： Wu, Jin-Sheng Valenzuela, Roberto Abril Bowick, Mark J. Smalyukh, Ivan I. Department of Physics and Chemical Physics Program University of Colorado Boulder United States Department of Physics University of California Santa Barbara United States Kavli Institute for Theoretical Physics University of California Santa Barbara United States French American Center for Theoretical Science CNRS KITP Santa Barbara United States International Institute for Sustainability with Knotted Chiral Meta Matter Japan Department of Electrical Computer and Energy Engineering Materials Science and Engineering Program and Soft Materials Research Center University of Colorado Boulder United States Renewable and Sustainable Energy Institute National Renewable Energy Laboratory University of Colorado Boulder United States

We study topologically stable defect structures in systems where the defect line classification in three dimensions and associated algebra of interactions (the fundamental group) are governed by the non-Abelian 8-element group, the quaternions Q8. The non-Abelian character of the defect algebra leads to a topological rigidity of bound defect pairs, and trivalent junctions which are the building blocks of multi-junction trivalent networks. We realize such structures laboratory chiral nematics and analyze their behavior analytically, along with numerical modeling © 2024, CC BY.

关键词： Rigidity

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Discovery of Ni Activated Sintering of MoNbTaW Predicted by a Computed Grain Boundary Diagram

SSRN

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SSRN 2023年

作者： Shivakumar, Sashank Song, Keqi Wang, Chunyang Lei, Tianjiao Xin, Huolin L. Rupert, Timothy J. Luo, Jian Department of Nano and Chemical Engineering Program of Materials Science and Engineering University of California San Diego La Jolla CA92093 United States Department of Physics and Astronomy University of California IrvineCA92697 United States Department of Materials Science and Engineering Department of Mechanical and Aerospace Engineering University of California IrvineCA92697 United States

Activated sintering of refractory metals represents a classical phenomenon in powder metallurgy. This study discovers that Ni addition can enhance sintering of MoNbTaW both above and below the bulk solidus composition at 1800 °C, thereby demonstrating the first example of activated sintering of a high-entropy alloy. To probe the underlying mechanism, experiments reveal complete grain boundary (GB) wetting above the bulk solidus composition, which logically infers the stabilization of a liquid-like interfacial phase (GB complexion) in a prewetting region below the bulk solidus composition. Furthermore, bulk CALPHAD (calculation of phase diagram) methods have been extended to model GBs in Ni-doped MoNbTaW to compute a GB "phase" diagram to forecast high-temperature GB disordering in the prewetting region and rationalize the observed Ni activated sintering of MoNbTaW. Only weak GB segregation of Ni is found in furnace-cooled specimens, which suggests GB "drying" during cooling, consistent with the observed nanoscale precipitates along GBs. © 2023, The Authors. All rights reserved.

关键词： Grain boundaries

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Development of Flexible Sendust Composite Sheets with Enhanced Magnetic Permeability for Microwave Absorbers and Antennas

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IEEE Transactions on Magnetics 2025年

作者： Whalen, Matthew P. Plouff, David T. Shevchenko, Nicholas B. Mirotznik, Mark Xiao, John Q. University of Delaware Quantum Science and Engineering Program NewarkDE19716 United States University of Delaware Department of Physics and Astronomy NewarkDE19716 United States University of Delaware Center for Composite Materials NewarkDE19716 United States University of Delaware Department of Electrical and Computer Engineering NewarkDE19716 United States

The demand for high-frequency soft magnetic composites with elevated permeability and flexibility is growing for applications in microwave absorbers and magnetodielectric antennas. However, balancing high permeability with mechanical flexibility remains challenging. This study presents flexible Sendust (FeSiAl) composite sheets, fabricated with a hot-pressing technique that aligns flakes within an acrylic rubber and epoxy resin matrix. The alignment significantly enhances relative permeability at high frequencies, achieving single-layer film properties of μr' = 14.8 and μr"= 20.4 at 1 GHz, alongside high saturation magnetization (118 eμg) and high hesitivity (44.7 kΩ m-1), outperforming commonly used materials such as NiZn ferrite. Our method supports customizable thickness without sacrificing permeability, establishing a versatile platform for advanced conformal microwave absorber and antenna applications. © 2025 IEEE.

关键词： Saturation magnetization

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