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Tunable two-dimensional group-III metal alloys

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arXiv 2021年

作者： Rajabpour, Siavash Vera, Alexander He, Wen Katz, Benjamin N. Koch, Roland J. Lassaunière, Margaux Chen, Xuegang Li, Cequn Nisi, Katharina El-Sherif, Hesham Wetherington, Maxwell T. Dong, Chengye Bostwick, Aaron Jozwiak, Chris van Duin, Adri C.T. Bassim, Nabil Zhu, Jun Wang, Gwo-Ching Wurstbauer, Ursula Rotenberg, Eli Crespi, Vincent Quek, Su Ying Robinson, Joshua A. Department of Chemical Engineering The Pennsylvania State University University ParkPA United States Center for 2-Dimensional and Layered Materials The Pennsylvania State University University ParkPA United States Department of Materials Science and Engineering The Pennsylvania State University University ParkPA United States Department of Materials Science and Engineering National University of Singapore 9 Engineering Drive Singapore Singapore Centre for Advanced 2D Materials National University of Singapore 6 Science Drive 2 Singapore Singapore Department of Physics The Pennsylvania State University University ParkPA United States Advanced Light Source Lawrence Berkeley National Laboratory BerkeleyCA United States Institute of Physics University of Münster Münster Germany Center for Soft Nanoscience University of Münster Münster Germany Department of Physics Applied Physics and Astronomy Rensselaer Polytechnic Institute TroyNY United States Physics Department Technical University of Munich Garching Germany Department of Materials Science and Engineering McMaster University HamiltonON Canada Materials Research Institute The Pennsylvania State University University ParkPA United States 2-Dimensional Crystal Consortium The Pennsylvania State University University ParkPA United States Department of Mechanical Engineering The Pennsylvania State University University ParkPA United States Department of Chemistry The Pennsylvania State University University ParkPA United States Department of Engineering Science and Mechanics The Pennsylvania State University University ParkPA United States Canadian Centre for Electron Microscopy HamiltonON Canada Department of Physics National University of Singapore Singapore Singapore NUS Graduate School Integrative Sciences and Engineering Programme National University of Singapore 117456 Singapore

Chemically stable quantum-confined 2D metals are of interest in next-generation nanoscale quantum devices. Bottom-up design and synthesis of such metals could enable the creation of materials with tailored, on-demand, electronic and optical properties for applications that utilize tunable plasmonic coupling, optical non-linearity, epsilon-near-zero behavior, or wavelength-specific light trapping. In this work, we demonstrate that the electronic, superconducting and optical properties of air-stable two-dimensional metals can be controllably tuned by the formation of alloys. Environmentally robust large-area two-dimensional InxGa1-x alloys are synthesized by Confinement Heteroepitaxy (CHet). Near-complete solid solubility is achieved with no evidence of phase segregation, and the composition is tunable over the full range of x by changing the relative elemental composition of the precursor. The optical and electronic properties directly correlate with alloy composition, wherein the dielectric function, band structure, superconductivity, and charge transfer from the metal to graphene are all controlled by the indium/gallium ratio in the 2D metal layer. © 2021, CC BY.

关键词： Metals

Origin of Friction in Superlubric Graphite Contacts

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Physical Review Letters 2020年第12期125卷 126102-126102页

作者： Cangyu Qu Kunqi Wang Jin Wang Yujie Gongyang Robert W. Carpick Michael Urbakh Quanshui Zheng Institute of Superlubricity Technology Research Institute of Tsinghua University in Shenzhen Shenzhen 518057 China Center for Nano and Micro Mechanics Tsinghua University Beijing 100084 China Department of Engineering Mechanics Tsinghua University Beijing 100084 China State Key Laboratory of Tribology & Department of Mechanical Engineering Tsinghua University Beijing 100084 China Mechanical Engineering and Applied Mechanics Department University of Pennsylvania Philadelphia Pennsylvania 19147 USA Department of Physical Chemistry School of Chemistry The Raymond and Beverly Sackler Faculty of Exact Sciences and The Sackler Center for Computational Molecular and Materials Science Tel Aviv University Tel Aviv 69978 Israel

More than thirty years ago, it was theoretically predicted that friction for incommensurate contacts between atomically smooth, infinite, crystalline materials (e.g., graphite, MoS2) is vanishing in the low speed limit, and this corresponding state was called structural superlubricity (SSL). However, experimental validation of this prediction has met challenges, since real contacts always have a finite size, and the overall friction arises not only from the atoms located within the contact area, but also from those at the contact edges which can contribute a finite amount of friction even when the incommensurate area does not. Here, we report, using a novel method, the decoupling of these contributions for the first time. The results obtained from nanoscale to microscale incommensurate contacts of graphite under ambient conditions verify that the average frictional contribution of an inner atom is no more than 10−4 that of an atom at the edge. Correspondingly, the total friction force is dominated by friction between the contact edges for contacts up to 10 μm in lateral size. We discuss the physical mechanisms of friction observed in SSL contacts, and provide guidelines for the rational design of large-scale SSL contacts.

关键词： Friction Solid-solid interfaces

Bismuth-doped fiber pulse source with versatile states

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Chinese Optics Letters 2025年第7期23卷 071401-071401页

作者： Xiaoxiao Wen Minjie Pan Mengting Guo Tian Qiao Chiyi Wei Meng Zhou Chunlei Yu Xiaoming Wei Zhongmin Yang Kenneth K. Y. Wong Department of Electrical and Electronic Engineering University of Hong Kong Hong Kong 999077 China School of Physics and Optoelectronics State Key Laboratory of Luminescent Materials and Devices Guangdong Engineering Technology Research and Development Center of Special Optical Fiber Materials and Devices Guangdong Provincial Key Laboratory of Fiber Laser Materials and Applied Techniques South China University of Technology Guangzhou 510640 China Key Laboratory of Materials for High Power Laser Shanghai Institute of Optics and Fine Mechanics Chinese Academy of Sciences Shanghai 201800 China Advanced Biomedical Instrumentation Centre Hong Kong Science Park Hong Kong 999077 China

We demonstrate a versatile bismuth-doped fiber pulse source that is seeded by a mode-locked fiber laser operating in different regimes with different net dispersions in the same cavity, including the square-wave noise-like pulse regime with anomalous net dispersion at 1331 nm and the multi-pulse soliton regime with normal net dispersion at 1320 nm. The versatile pulse evolutions and the multi-pulse dynamics in these two regimes are investigated under different pump powers or polarization states. The seed pulses are then amplified by a bismuth-doped fiber amplifier, which boosts the pulse energy to 21 nJ with a slope efficiency of 21.3% without power saturation and is anticipated to be useful for practical applications.

关键词： Fiber Bragg gratings High power lasers Mode-locked fiber lasers Optical coherence tomography Raman fiber lasers Semiconductor saturable absorber mirrors

A sharp interface Lagrangian-Eulerian method for flexible-body fluid-structure interaction

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arXiv 2022年

作者： Kolahdouz, Ebrahim M. Wells, David R. Rossi, Simone Aycock, Kenneth I. Craven, Brent A. Griffith, Boyce E. Center for Computational Biology Flatiron Institute Simons Foundation New YorkNY United States Department of Mathematics University of North Carolina Chapel HillNC United States Division of Applied Mechanics Office of Science and Engineering Laboratories Center for Devices and Radiological Health United States Food and Drug Administration Silver SpringMD United States Departments of Mathematics and Biomedical Engineering University of North Carolina Chapel HillNC United States Carolina Center for Interdisciplinary Applied Mathematics University of North Carolina Chapel HillNC United States Computational Medicine Program University of North Carolina Chapel HillNC United States McAllister Heart Institute University of North Carolina Chapel HillNC United States

This paper introduces a sharp-interface approach to simulating fluid-structure interaction (FSI) involving flexible bodies described by general nonlinear material models and across a broad range of mass density ratios. This new flexible-body immersed Lagrangian-Eulerian (ILE) scheme extends our prior work on integrating partitioned and immersed approaches to rigid-body FSI. Our numerical approach incorporates the geometrical and domain solution flexibility of the immersed boundary (IB) method with an accuracy comparable to body-fitted approaches that sharply resolve flows and stresses up to the fluid-structure interface. Unlike many IB methods, our ILE formulation uses distinct momentum equations for the fluid and solid subregions with a Dirichlet-Neumann coupling strategy that connects fluid and solid subproblems through simple interface conditions. As in earlier work, we use approximate Lagrange multiplier forces to treat the kinematic interface conditions along the fluid-structure interface. This penalty approach simplifies the linear solvers needed by our formulation by introducing two representations of the fluid-structure interface, one that moves with the fluid and another that moves with the structure, that are connected by stiff springs. This approach also enables the use of multi-rate time stepping, which allows us to use different time step sizes for the fluid and structure subproblems. Our fluid solver relies on an immersed interface method (IIM) for discrete surfaces to impose stress jump conditions along complex interfaces while enabling the use of fast structured-grid solvers for the incompressible Navier-Stokes equations. The dynamics of the volumetric structural mesh are determined using a standard finite element approach to large-deformation nonlinear elasticity via a nearly incompressible solid mechanics formulation. This formulation also readily accommodates compressible structures with a constant total volume, and it can handle fully compressibl

关键词： Fluid structure interaction

Topology of three-dimensional Dirac semimetals and generalized quantum spin Hall systems without gapless edge modes

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arXiv 2020年

作者： Tyner, Alexander C. Sur, Shouvik Puggioni, Danilo Rondinelli, James M. Goswami, Pallab Graduate Program in Applied Physics Northwestern University EvanstonIL60208 United States Department of Physics and Astronomy Northwestern University EvanstonIL60208 United States Department of Materials Science and Engineering Northwestern University IL60208 United States Northwestern Argonne Institute for Science and Engineering EvanstonIL60208 United States

Usually the quantum spin Hall states are expected to possess gapless, helical edge modes. Are there clean, non-interacting, quantum spin Hall states without gapless, edge modes? We show the generic, n-fold-symmetric, momentum planes of three-dimensional, stable Dirac semi-metals, which are orthogonal to the direction of nodal separation are examples of such generalized quantum spin Hall systems. We demonstrate that the planes lying between two Dirac points and the celebrated Bernevig-Zhang-Hughes model support identical quantized, non-Abelian Berry flux of magnitude 2π. Consequently, both systems exhibit spin-charge separation in response to electromagnetic, π-flux vortex. The Dirac points are identified as the unit-strength, monopoles of SO(5) Berry connections, describing topological quantum phase transitions between generalized, quantum spin Hall and trivial insulators. Our work identifies precise bulk invariant and quantized response of Dirac semimetals and shows that many two-dimensional higher-order topological insulators can be understood as generalized quantum spin Hall systems, possessing gapped edge states. Copyright © 2020, The Authors. All rights reserved.

关键词： Fruits

Phase equilibrium of water with hexagonal and cubic ice using the SCAN functional

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arXiv 2021年

作者： Piaggi, Pablo Miguel Panagiotopoulos, Athanassios Z. Debenedetti, Pablo G. Car, Roberto Department of Chemistry Princeton University PrincetonNJ08544 United States Department of Chemical and Biological Engineering Princeton University PrincetonNJ08544 United States Princeton Institute for the Science and Technology of Materials Princeton University PrincetonNJ08544 United States Department of Physics Princeton University PrincetonNJ08544 United States Program in Applied and Computational Mathematics Princeton University PrincetonNJ08544 United States

Machine learning models are rapidly becoming widely used to simulate complex physicochemical phenomena with ab initio accuracy. Here, we use one such model as well as direct density functional theory (DFT) calculations to investigate the phase equilibrium of water, hexagonal ice (Ih), and cubic ice (Ic), with an eye towards studying ice nucleation. The machine learning model is based on deep neural networks and has been trained on DFT data obtained using the SCAN exchange and correlation functional. We use this model to drive enhanced sampling simulations aimed at calculating a number of complex properties that are out of reach of DFT-driven simulations and then employ an appropriate reweighting procedure to compute the corresponding properties for the SCAN functional. This approach allows us to calculate the melting temperature of both ice polymorphs, the driving force for nucleation, the heat of fusion, the densities at the melting temperature, the relative stability of ice Ih and Ic, and other properties. We find a correct qualitative prediction of all properties of interest. In some cases, quantitative agreement with experiment is better than for state-of-the-art semiempirical potentials for water. Our results also show that SCAN correctly predicts that ice Ih is more stable than ice Ic. Copyright © 2021, The Authors. All rights reserved.

关键词： Ice

Chemical Electron Tomography at Lower Dose and Higher Resolution

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Microscopy and Microanalysis 2024年第SUPPLEMENT_1期30卷

作者： Hovden, Robert Schwartz, Jonathan Sung, Suk Hyun Di, Zichao Wendy Jiang, Yi Manassa, Jason Pietryga, Jacob Qian, Yiwen Cho, Min Gee Rowell, Jonathan L Zheng, Huihuo Robinson, Richard D Gu, Junsi Kirilin, Alexey Rozeveld, Steve Ercius, Peter Scott, Mary Department of Materials Science and Engineering University of Michigan Ann Arbor MI Applied Physics Program University of Michigan Ann Arbor MI Chan Zuckerberg Initiative Redwood City CA Rowland Institute at Harvard Cambridge MA. Mathematics and Computer Science Division Argonne National Laboratory Lemont IL Advanced Photon Source Facility Argonne National Laboratory Lemont IL Department of Materials Science and Engineering U.C. Berkeley Berkeley CA National Center for Electron Microscopy Molecular Foundry Berkeley CA Department of Chemistry and Chemical Biology Cornell University Ithaca NY Argonne Leadership Computing Facility Argonne National Laboratory Lemont IL Dow Chemical Co. Terneuzen Netherlands Dow Chemical Co. Midland MI

Outer diameter and Surface Quality of Micro Metal Tubes in Hollow Sinking

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Procedia Manufacturing 2020年 47卷 217-223页

作者： Takuma Kishimoto Hayate Sakaguchi Saki Suematsu Kenichi Tashima Satoshi Kajino Shiori Gondo Shinsuke Suzuki Waseda University Graduate School of Fundamental Science and Engineering Department of Applied Mechanics 3-4-1 Okubo Shinjuku Tokyo 169-8555 Japan Factory-Automation Electronics Inc. 1-6-14 Higashi-nakajima Higashi-yodogawa Osaka Osaka 533-0033 Japan National Institute of Advanced Industrial Science and Technology (AIST) Material Processing Group Advanced Manufacturing Research Institute Department of Electronics and Manufacturing Tsukuba East 1-2-1 Namiki Tsukuba Ibaraki 305-8564 Waseda University Faculty of Science and Engineering Department of Applied Mechanics and Aerospace Engineering 3-4-1 Okubo Shinjuku Tokyo 169-8555 Japan Kagami Memorial Research Institute of Materials Science and Technology Waseda University 2-8-26 Nishi-waseda Shinjuku Tokyo 169-0051 Japan

To clarify deformation behavior of tubes in hollow sinking, the outer diameter and surface quality of the final drawn tubes were evaluated. Copper tubes were drawn for one pass under various drawing conditions (e.g., die reduction, drawing speed ratio, and die half angle) without an inner tool. The result of the experiment indicates the deformation behavior of tubes during hollow sinking. The outer diameter of the drawn tube on the die entrance became less than that of the starting material. Free surface roughening seems to develop on the outer surface of the drawn tube on the die entrance side due to the outer diameter reduction. Therefore, the height deviation in the outer uneven surface of the drawn tube on the die entrance became greater than that of the starting material. The height deviation on the die exit side was less than that on the die entrance side because of the tube deformations subjected by the die. The outer diameter decreased from the die approach end as either the drawing speed ratio or the die half angle increased. The height deviation in the outer uneven surface of the drawn tube on the die exit side became larger as the outer diameter decreased from the die approach end due to free surface roughening.

关键词： Tube forming Hollow sinking Micro forming Dimension control

Alternation of Magnetic Anisotropy Accompanied by Metal-Insulator Transition in Strained Ultrathin Manganite Heterostructures

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Physical Review applied 2021年第6期15卷 064019-064019页

作者： Masaki Kobayashi Le Duc Anh Masahiro Suzuki Shingo Kaneta-Takada Yukiharu Takeda Shin-ichi Fujimori Goro Shibata Arata Tanaka Masaaki Tanaka Shinobu Ohya Atsushi Fujimori Department of Electrical Engineering and Information Systems The University of Tokyo 7-3-1 Hongo Bunkyo-ku Tokyo 113-8656 Japan Center for Spintronics Research Network The University of Tokyo 7-3-1 Hongo Bunkyo-ku Tokyo 113-8656 Japan Institute of Engineering Innovation Graduate School of Engineering The University of Tokyo 7-3-1 Hongo Bunkyo-ku Tokyo 113-8656 Japan PRESTO JST 4-1-8 Honcho Kawaguchi Saitama 332-0012 Japan Department of Physics The University of Tokyo 7-3-1 Hongo Bunkyo-ku Tokyo 113-0033 Japan Materials Sciences Research Center Japan Atomic Energy Agency Sayo-gun Hyogo 679-5148 Japan Department of Applied Physics Tokyo University of Science Katsushika Tokyo 125-8585 Japan Quantum Matter Program Graduate School of Advanced Science and Engineering Hiroshima University Higashi-Hiroshima 739-8530 Japan Department of Applied Physics Waseda University Okubo Shinjuku Tokyo 169-8555 Japan

A fundamental understanding of the interfacial magnetic properties in ferromagnetic heterostructures is essential for utilizing ferromagnetic materials for spintronic device applications. Here, we investigate the interfacial magnetic and electronic structures of epitaxial single-crystalline LaAlO3(LAO)/La0.6Sr0.4MnO3(LSMO)/Nb:SrTiO3(Nb:STO) heterostructures with varying LSMO layer thicknesses, in which the magnetic anisotropy strongly changes with the LSMO thickness due to the delicate balance between strains originating from both the Nb:STO and LAO layers, using x-ray magnetic circular dichroism and photoemission spectroscopy. We successfully detect the clear change of the magnetic behavior of the Mn ions concomitant with the thickness-dependent metal-insulator transition. Our results suggest that the double-exchange interaction induces ferromagnetism in the metallic LSMO film under tensile strain caused by the STO substrate, while the superexchange interaction determines the magnetic behavior in the insulating LSMO film under compressive strain originating from the top LAO layer. The change in strain, depending on LSMO layer thickness, is confirmed by scanning transmission electron microscopy. Based on those findings, the formation of a magnetic dead layer near the LAO/LSMO interface is attributed to competition between the superexchange interaction via Mn 3d3z2−r2 orbitals under compressive strain and the double-exchange interaction via the 3dx2−y2 orbitals. These findings provide key aspects of ferromagnetic oxide heterostructures for the development of spintronic device applications.

关键词： Electronic structure Ferromagnetism Magnetic anisotropy Metal-insulator transition Spintronics Transition metal oxides Photoemission spectroscopy X-ray magnetic circular dichroism