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Doping-Induced Charge Density Wave and Ferromagnetism in the Van der Waals Semiconductor CrSBr

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arXiv 2024年

作者： Feuer, Margalit L. Thinel, Morgan Huang, Xiong Cui, Zhi-Hao Shao, Yinming Kundu, Asish K. Chica, Daniel G. Han, Myung-Geun Pokratath, Rohan Telford, Evan J. Cox, Jordan York, Emma Okuno, Saya Huang, Chun-Ying Bukula, Owethu Nashabeh, Luca M. Qiu, Siyuan Nuckolls, Colin P. Dean, Cory R. Billinge, Simon J.L. Zhu, Xiaoyang Zhu, Yimei Basov, Dmitri N. Millis, Andrew J. Reichman, David R. Pasupathy, Abhay N. Roy, Xavier Ziebel, Michael E. Columbia University Department of Chemistry New YorkNY United States Columbia University Department of Physics New YorkNY United States Pennsylvania State University Department of Physics University ParkPA United States Brookhaven National Laboratory Condensed Matter Physics and Materials Science Department UptonNY United States Brookhaven National Laboratory National Synchrotron Light Source II UptonNY United States University of Basel Department of Chemistry Basel Switzerland Columbia University Department of Mechanical Engineering New YorkNY United States Columbia University Department of Applied Physics and Applied Mathematics New YorkNY United States Flatiron Institute Center for Computational Quantum Physics New YorkNY United States

In materials with one-dimensional electronic bands, electron-electron interactions can produce intriguing quantum phenomena, including spin-charge separation and charge density waves (CDW). Most of these systems, however, are non-magnetic, motivating a search for anisotropic materials where the coupling of charge and spin may affect emergent quantum states. Here, electron doping the van der Waals magnetic semiconductor CrSBr induces an electronically driven quasi-1D CDW, which survives above room temperature. Lithium intercalation also increases the magnetic ordering temperature to 200 K and changes its interlayer magnetic coupling from antiferromagnetic to ferromagnetic. The spin-polarized nature of the anisotropic bands that give rise to this CDW enforces an intrinsic coupling of charge and spin. The coexistence and interplay of ferromagnetism and charge modulation in this exfoliatable material provides a promising platform for studying tunable quantum phenomena across a range of temperatures and thicknesses. Copyright © 2024, The Authors. All rights reserved.

关键词： Van der Waals forces

Metallization of colloidal crystals

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arXiv 2021年

作者： Ehlen, Ali Lopez-Rios, Hector de la Cruz, Monica Olvera Applied Physics Program Northwestern University Department of Materials Science and Engineering Northwestern University

Colloidal crystals formed by size-asymmetric binary particles co-assemble into a wide variety of colloidal compounds with lattices akin to ionic crystals. Recently, a transition from a compound phase with a sublattice of small particles to a metal-like phase in which the small particles are delocalized has been predicted computationally and observed experimentally. In this colloidal metallic phase, the small particles roam the crystal maintaining the integrity of the lattice of large particles, as electrons do in metals. A similar transition also occurs in superionic crystals, termed sublattice melting. Here, we use energetic principles and a generalized molecular dynamics (MD) model of a binary system of functionalized nanoparticles (NPs) to analyze the transition to sublattice delocalization in different co-assembled crystal phases as a function of temperature (T), number of grafted chains on the small particles, and number ratio between the small and large particles ns:nl. We find that ns:nl is the primary determinant of crystal type due to energetic interactions and interstitial site filling, while the number of grafted chains per small particle determines the stability of these crystals. We observe first-order sublattice delocalization transitions as T increases, in which the host lattice transforms from low- to high-symmetry crystal structures, including A20 → BCT → BCC, Ad → BCT → BCC, and BCC → BCC/FCC → FCC transitions and lattices. Analogous sublattice transitions driven primarily by lattice vibrations have been seen in some atomic materials exhibiting an insulator-metal transition also referred to as metallization. We also find minima in the lattice vibrations and diffusion coefficient of small particles as a function of ns:nl, indicating enhanced stability of certain crystal structures for ns:nl values that form compounds. © 2021, CC BY.

关键词： Molecular dynamics

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

Velocity-gauge Real-time Time-dependent Density Functional Tight-binding for Large-scale Condensed Matter Systems

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arXiv 2023年

作者： Xu, Qiang Del Ben, Mauro Okyay, Mahmut Sait Choi, Min Ibrahim, Khaled Z. Wong, Bryan M. Materials Science & Engineering Program Department of Chemistry Department of Physics & Astronomy University of California-Riverside RiversideCA92521 United States Applied Mathematics & Computational Research Division Lawrence Berkeley National Laboratory BerkeleyCA94720 United States

We present a new velocity-gauge real-time, time-dependent density functional tight-binding (VG-rtTDDFTB) implementation in the open-source DFTB+ software package (https://***) for probing electronic excitations in large, condensed matter systems. Our VG-rtTDDFTB approach enables real-time electron dynamics simulations of large, periodic, condensed matter systems containing thousands of atoms with a favorable computational scaling as a function of system size. We provide computational details and benchmark calculations to demonstrate its accuracy and computational parallelizability on a variety of large material systems. As a representative example, we calculate laser-induced electron dynamics in a 512-atom amorphous silicon supercell to highlight the large periodic systems that can be examined with our implementation. Taken together, our VG-rtTDDFTB approach enables new electron dynamics simulations of complex systems that require large periodic supercells, such as crystal defects, complex surfaces, nanowires, and amorphous materials. Copyright © 2023, The Authors. All rights reserved.

关键词： Gages

Structural, Electronic and Optical Properties of Batio3-Cofe2o4 Nanocomposites for Optoelectronic Devices

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SSRN

SSRN 2023年

作者： Rehman, Ata ur Iqbal, Asad Muhammad Channa, Ali Imran Awan, Saifullah Ullah Khan, Muhammad Tahir Department of Physics Faculty of Engineering and Applied Sciences Riphah International University I-14 Islamabad44000 Pakistan Department of Basic Sciences and Humanities College of Electrical and Mechanical Engineering National University of Sciences and Technology Islamabad Pakistan Department of Materials Science and Engineering Hongik University Seoul04066 Korea Republic of Institute of Fundamental and Frontier Sciences University of Electronic Science and Technology of China Chengdu610054 China Department of Electrical Engineering College of Electrical and Mechanical Engineering National University of Sciences and Technology Islamabad Pakistan

Structural, electronic and optical properties of BaTiO3 (BTO), CoFe2O4 (CFO) and their nanocomposites are presented. The XRD spectra of composites exhibited the superposed peak patterns of individual compounds with a consistent shift from BTO to CFO phase with the increase in CFO proportion. The XPS analysis revealed a lower concentration of Oxygen vacancies in the composite samples as compared to that in pure CFO. This finding is also confirmed by the consistent transformation of Co from +2 state in CFO to +3 state in the composite samples. The UV-Vis spectroscopy revealed that optical absorption of BTO is limited to the UV regime, however, CFO exhibited the absorption in visible and infrared (IR) region. However, after the formation of BTO-CFO composite, the optical absorption was broadened from UV to IR regions. The magnitude of absorption was further enhanced by increasing the CFO content in the composites. © 2023, The Authors. All rights reserved.

关键词： Ultraviolet visible spectroscopy

Temporal refraction and reflection in modulated mechanical metabeams: theory and physical observation

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arXiv 2025年

作者： Wang, Shaoyun Shao, Nan Chen, Hui Chen, Jiaji Qian, Honghua Wu, Qian Duan, Huiling Alù, Andrea Huang, Guoliang Department of Mechanical and Aerospace Engineering University of Missouri ColumbiaMO65211 United States Center for Mechanics Plus Under Extreme Environments School of Mechanical Engineering and Mechanics Ningbo University Ningbo315211 China Photonics Initiative Advanced Science Research Center City University of New York New YorkNY United States Physics Program Graduate Center City University of New York New YorkNY United States Department of Mechanics and Engineering Science College of Engineering Peking University Beijing100871 China

Wave reflection and refraction at a time interface follow different conservation laws compared to conventional scattering at a spatial interface. This study presents the experimental demonstration of refraction and reflection of flexural waves across a temporal boundary in a continuum-based mechanical metabeam, and unveils opportunities that emerge by tailoring temporal scattering phenomena for phononic applications. We observe these phenomena in an elastic beam attached to an array of piezoelectric patches that can vary in time the effective elastic properties of the beam. Frequency conversion and phase conjugation are observed upon a single temporal interface. These results are consistent with the temporal Snell’s law and Fresnel equations for temporal interfaces. Further, we illustrate the manipulation of amplitude and frequency spectra of flexural wave temporal refraction and reflection through multi-stepped temporal interfaces. Finally, by implementing a smooth time variation of wave impedance, we numerically and experimentally demonstrate the capabilities of the temporal metabeam to realize waveform morphing and information coding. Our findings lay the foundation for developing time-mechanical metamaterials and time-phononic crystals, offering new avenues for advanced phonon manipulation in both wave amplitude and frequency. © 2025, CC BY.

关键词： Phonons

Silicon–metal and silicon–silicon ultrafast laser welding with domesticated filaments 17

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Silicon–metal and silicon–silicon ultrafast laser welding ...

Laser-based Micro- and Nanoprocessing XVII 2023

作者： Chambonneau, Maxime Li, Qingfeng Blothe, Markus Fedorov, Vladimir Yu. Tzortzakis, Stelios Nolte, Stefan Friedrich Schiller University Jena Institute of Applied Physics Abbe Center of Photonics Albert-Einstein-Straße 15 Jena07745 Germany Science Program Texas A&M University at Qatar P.O. Box 23874 Doha Qatar P.O. Box 1527 HeraklionGR-71110 Greece Materials Science and Technology Department University of Crete Heraklion71003 Greece Fraunhofer Institute for Applied Optics and Precision Engineering Albert-Einstein-Straße 7 Jena07745 Germany

ISBN: (纸本)9781510659230

We demonstrate for the first time ultrafast laser welding in the silicon–metal and silicon–silicon configurations, with focused infrared picosecond pulses. This achievement relies on accurate characterizations of filamentation in silicon with nonlinear propagation imaging. In the silicon–metal configuration, precompensating for the nonlinear focal shift prior to the welding yields bonding strengths > 1 MPa. By combining this filament relocation technique with metallic nanolayer deposition at the interface to exalt the energy deposition, similar bonding strength values are obtained in the silicon–silicon configuration. © 2023 SPIE.

关键词： Silicon

The Equation of Motion for Taut-Line Buzzers

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arXiv 2024年

作者： Gerra, Alexander J. Jones, Courtney C. Dillavou, Sam Hanlan, Jesse M. Radzio, Julia Arratia, Paulo E. Durian, Douglas J. Department of Physics and Astronomy University of Pennsylvania PhiladelphiaPA19104 United States Moravian University BethlehemPA18018 United States University of Maryland - Baltimore County BaltimoreMD21250 United States Department of Mechanical Engineering and Applied Mechanics University of Pennsylvania PhiladelphiaPA19104 United States

Equations of motion are developed for the oscillatory rotation of a disk suspended between twisted strings kept under tension by a hanging mass, to which additional forces may be applied. In the absence of forcing, damped harmonic oscillations are observed to decay with an exponential time envelope for two different string types. This is consistent with damping caused by string viscosity, rather than air turbulence, and may be quantified in terms of a quality factor. To test the proposed equation of motion and model for viscous damping within the string, we measure both the natural oscillation frequency and the quality factor for widely varied values of string length, string radius, disk moment of inertia, and hanging mass. The data are found to scale in good accord with predictions. A variation where rotational kinetic energy is converted back and forth to spring potential energy is also discussed. Copyright © 2024, The Authors. All rights reserved.

关键词： Equations of motion

Carrier confinement and alloy disorder exacerbate Auger-Meitner recombination in AlGaN ultraviolet light-emitting diodes

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arXiv 2024年

作者： Pant, Nick Bushick, Kyle McAllister, Andrew Lee, Woncheol Van de Walle, Chris G. Kioupakis, Emmanouil Applied Physics Program University of Michigan Ann ArborMI48109 United States Department of Materials Science & Engineering University of Michigan Ann ArborMI48109 United States Department of Electrical Engineering & Computer Science University of Michigan Ann ArborMI48109 United States Materials Department University of California Santa BarbaraCA93106 United States

The quantum efficiency of AlGaN ultraviolet light-emitting diodes (LEDs) declines (droops) at increasing operating powers due to Auger-Meitner recombination (AMR). Using first-principles density-functional theory, we show that indirect AMR mediated by electron-phonon coupling and alloy disorder can induce bulk C coefficients as large as ∼10-31 cm6/s. Furthermore, we find that the confinement of carriers by polarization fields within quantum wells severely relaxes crystal-momentum conservation, which exacerbates the rate of AMR over radiative recombination by an order of magnitude relative to the bulk. This results in a striking decrease in quantum efficiency at high power. Suppressing polarization fields and jointly increasing the well width would greatly mitigate AMR and efficiency droop. Copyright © 2024, The Authors. All rights reserved.

关键词： Aluminum gallium nitride