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arXiv 2019年

作者： Poncé, Samuel Jena, Debdeep Giustino, Feliciano Department of Materials University of Oxford Parks Road OxfordOX1 3PH United Kingdom School of Electrical and Computer Engineering Cornell University IthacaNY14853 United States Department of Material Science and Engineering Cornell University IthacaNY14853 United States

A fundamental obstacle toward the realization of GaN p-channel transistors is its low hole mobility. Here we investigate the intrinsic phonon-limited mobility of electrons and holes in wurtzite GaN using the ab initio Boltzmann transport formalism, including all electron-phonon scattering processes and many-body quasiparticle band structures. We predict that the hole mobility can be increased by reversing the sign of the crystal-field splitting, in such a way as to lift the split-off hole states above the light and heavy holes. We find that a 2% biaxial tensile strain can increase the hole mobility by 230%, up to a theoretical Hall mobility of 120 cm2/Vs at room temperature and 620 cm2/Vs at 100 K. Copyright © 2019, The Authors. All rights reserved.

关键词： Gallium nitride

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Coordinate Dual Averaging for Decentralized Online Optimization with Nonseparable Global Objectives

Coordinate Dual Averaging for Decentralized Online Optimizat...

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作者： Lee, Soomin Nedic, Angelia Raginsky, Maxim Department of Mechanical Engineering and Materials Science Duke University DurhamNC27708 United States Department of Industrial and Enterprise Systems Engineering University of Illinois at Urbana-Champaign UrbanaIL61801 United States Department of Electrical and Computer Engineering University of Illinois at Urbana-Champaign UrbanaIL61801 United States

We consider a decentralized online convex optimization problem in a network of agents, where each agent controls only a coordinate (or a part) of the global decision vector. For such a problem, we propose two decentralized variants (ODA-C and ODA-PS) of Nesterov's primal-dual algorithm with dual averaging. In ODA-C, to mitigate the disagreements on the primal-vector updates, the agents implement a generalization of the local information-exchange dynamics recently proposed by Li and Marden [1] over a static undirected graph. In ODA-PS, the agents implement the broadcast-based push-sum dynamics [2] over a time-varying sequence of uniformly connected digraphs. We show that the regret bounds in both cases have sublinear growth of O(T), with the time horizon T, when the stepsize is of the form 1t and the objective functions are Lipschitz-continuous convex functions with Lipschitz gradients. We also implement the proposed algorithms on a sensor network to complement our theoretical analysis. © 2014 IEEE.

关键词： Convex optimization

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Simultaneous Optical and electrical Spin-Torque Magnetometry with Phase-Sensitive Detection of Spin Precession

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Physical Review Applied 2019年第3期11卷 034047-034047页

作者： Yi Li Hilal Saglam Zhizhi Zhang Rao Bidthanapally Yuzan Xiong John E. Pearson Valentine Novosad Hongwei Qu Gopalan Srinivasan Axel Hoffmann Wei Zhang Department of Physics Oakland University Rochester Michigan 48309 USA Materials Science Division Argonne National Laboratory Argonne Illinois 60439 USA Department of Physics Illinois Institute of Technology Chicago Illinois 60616 USA School of Optical and Electronic Information Huazhong University of Science and Technology Wuhan 430074 China Department of Electrical and Computer Engineering Oakland University Rochester Michigan 48309 USA

Spin-based coherent information processing and encoding utilize the precession phase of spins in magnetic materials. However, the detection and manipulation of spin precession phases remain a major challenge for advanced spintronic functionalities. By using simultaneous electrical and optical detection, we demonstrate the direct measurement of the spin precession phase of a permalloy device driven by the spin-orbit torques from adjacent heavy metals. The spin Hall angle of the heavy metals can be independently determined from concurrent electrical and optical signals. The phase-sensitive optical detection also allows spatially-resolved measurements of local spin-torque parameters and ferromagnetic resonance with comprehensive amplitude and phase information. Our study offers a route toward future advanced characterizations of spin-torque oscillators, magnonic circuits, and tunneling junctions, where measuring the current-induced spin dynamics of individual nanomagnets is required.

关键词： Magnetization dynamics Spin torque Spin waves Spintronics Magnetic multilayers electrical techniques Magneto-optical Kerr effect Optically detected magnetic resonance

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Frontispiece: Peptoid-Directed Formation of Five-Fold Twinned Au Nanostars through Particle Attachment and Facet Stabilization

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Angewandte Chemie International Edition 2022年第14期61卷

作者： Dr. Biao Jin Dr. Feng Yan Dr. Xin Qi Dr. Bin Cai Dr. Jinhui Tao Dr. Xiaofeng Fu Dr. Susheng Tan Dr. Peijun Zhang Dr. Jim Pfaendtner Nada Y. Naser Dr. François Baneyx Dr. Xin Zhang Dr. James J. DeYoreo Dr. Chun-Long Chen Physical Sciences Division Pacific Northwest National Laboratory 902 Battelle Boulevard Richland WA 99352 USA School of Chemistry & Chemical Engineering Linyi University The Middle Part of Shuangling Road Linyi Shandong Province 276005 China Department of Chemical Engineering University of Washington 1410 NE Campus Parkway Seattle WA 98195 USA Present address: School of Chemistry and Chemical Engineering Shandong University Shanda Nan Road 27 Jinan (China) Department of Biological Science Florida State University 600 W College Ave Tallahassee FL 32306 USA Department of Electrical and Computer Engineering & Petersen Institute of Nanoscience and Engineering (PINSE) University of Pittsburgh 4200 Fifth Ave Pittsburgh PA 15260 USA Division of Structural Biology Wellcome Trust Centre for Human Genetics University of Oxford Roosevelt Drive Wellington Square Oxford OX3 7BN UK Diamond Light Source Harwell Science and Innovation Campus Didcot OX11 0DE UK Department of Materials Science and Engineering University of Washington 1410 NE Campus Parkway Seattle WA 98195 USA

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Experimental observation of high intrinsic thermal conductivity of AlN

arXiv

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arXiv 2019年

作者： Cheng, Zhe Koh, Yee Rui Mamun, Abdullah Shi, Jingjing Bai, Tingyu Huynh, Kenny Yates, Luke Liu, Zeyu Li, Ruiyang Lee, Eungkyu Liao, Michael Wang, Yekan Yu, Hsuan Ming Kushimoto, Maki Luo, Tengfei Goorsky, Mark S. Hopkins, Patrick E. Amano, Hiroshi Khan, Asif Graham, Samuel George W. Woodruff School of Mechanical Engineering Georgia Institute of Technology AtlantaGA30332 United States Department of Mechanical and Aerospace Engineering University of Virginia CharlottesvilleVA22904 United States Department of Electrical Engineering University of South Carolina ColumbiaSC29208 United States Materials Science and Engineering University of California Los Angeles Los AngelesCA91355 United States Department of Aerospace and Mechanical Engineering University of Notre Dame Notre DameIN46556 United States Department of Electrical Engineering and Computer Science Nagoya University Furo-cho Chikusa-ku Nagoya464-8603 Japan Institute of Materials and Systems for Sustainability Nagoya University Furo-cho Chikusa-ku Nagoya464-8601 Japan Department of Materials Science and Engineering University of Virginia CharlottesvilleVA22904 United States Department of Physics University of Virginia CharlottesvilleVA22904 United States School of Materials Science and Engineering Georgia Institute of Technology AtlantaGA30332 United States

AlN is an ultra-wide bandgap semiconductor which has been developed for applications including power electronics and optoelectronics. Thermal management of these applications is the key for stable device performance and allowing for long lifetimes. AlN, with its potentially high thermal conductivity, can play an important role serving as a dielectric layer, growth substrate, and heat spreader to improve device performance. However, the intrinsic high thermal conductivity of bulk AlN predicted by theoretical calculations has not been experimentally observed because of the difficulty in producing materials with low vacancy and impurity levels, and other associated defect complexes in AlN which can decrease the thermal conductivity. This work reports the growth of thick (>15 μm) AlN layers by metal-organic chemical vapor deposition with an air-pocketed AlN layer and the first experimental observation of intrinsic thermal conductivity from 130 K to 480 K that matches density-function-theory calculations for single crystal AlN, producing some of the highest values ever measured. Detailed material characterizations confirm the high quality of these AlN samples with one or two orders of magnitude lower impurity concentrations than seen in commercially available bulk AlN. Measurements of these commercially available bulk AlN substrates from 80 K to 480 K demonstrated a lower thermal conductivity, as expected. A theoretical thermal model is built to interpret the measured temperature dependent thermal conductivity. Our work demonstrates that it is possible to obtain theoretically high values of thermal conductivity in AlN and such films may impact the thermal management and reliability of future electronic and optoelectronics devices. Copyright © 2019, The Authors. All rights reserved.

关键词： Aluminum nitride

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Reproducible brain-wide association studies require thousands of individuals (Mar, 10.1038/s41586-022-04492-9, 2022)

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NATURE 2022年第7911期605卷 E11-E11页

作者： Marek, Scott Tervo-Clemmens, Brenden Calabro, Finnegan J. Montez, David F. Kay, Benjamin P. Hatoum, Alexander S. Donohue, Meghan Rose Foran, William Miller, Ryland L. Hendrickson, Timothy J. Malone, Stephen M. Kandala, Sridhar Feczko, Eric Miranda-Dominguez, Oscar Graham, Alice M. Earl, Eric A. Perrone, Anders J. Cordova, Michaela Doyle, Olivia Moore, Lucille A. Conan, Gregory M. Uriarte, Johnny Snider, Kathy Lynch, Benjamin J. Wilgenbusch, James C. Pengo, Thomas Tam, Angela Chen, Jianzhong Newbold, Dillan J. Zheng, Annie Seider, Nicole A. Van, Andrew N. Metoki, Athanasia Chauvin, Roselyne J. Laumann, Timothy O. Greene, Deanna J. Petersen, Steven E. Garavan, Hugh Thompson, Wesley K. Nichols, Thomas E. Yeo, B. T. Thomas Barch, Deanna M. Luna, Beatriz Fair, Damien A. Dosenbach, Nico U. F. Department of Psychiatry Washington University School of Medicine St Louis MO USA Department of Neurology Washington University School of Medicine St Louis MO USA Department of Psychological and Brain Sciences Washington University in St Louis St Louis MO USA Department of Psychiatry Massachusetts General Hospital Harvard Medical School Boston MA USA Department of Psychology University of Pittsburgh Pittsburgh PA USA Department of Psychiatry University of Pittsburgh Pittsburgh PA USA Department of Bioengineering University of Pittsburgh Pittsburgh PA USA Department of Biomedical Engineering Washington University in St Louis St Louis MO USA Department of Radiology Washington University School of Medicine St Louis MO USA Department of Neurological Surgery Washington University School of Medicine St Louis MO USA Program in Occupational Therapy Washington University School of Medicine St Louis MO USA Department of Pediatrics Washington University School of Medicine St Louis MO USA University of Minnesota Informatics Institute University of Minnesota Minneapolis MN USA Department of Psychology University of Minnesota Minneapolis MN USA Masonic Institute for the Developing Brain University of Minnesota Medical School Minneapolis MN USA Department of Pediatrics University of Minnesota Medical School Minneapolis MN USA Department of Psychiatry Oregon Health and Science University Portland OR USA Minnesota Supercomputing Institute University of Minnesota Minneapolis MN USA Institute of Child Development University of Minnesota Medical School Minneapolis MN USA Department of Electrical and Computer Engineering National University of Singapore Singapore Singapore Centre for Sleep and Cognition National University of Singapore Singapore Singapore Centre for Translational MR Research National University of Singapore Singapore Singapore N.1 Institute for Health Institute for Digital Medicine National University of Singapore Singapore Sing

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All-optical reconfigurable chiral meta-molecules

arXiv

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arXiv 2019年

作者： Lin, Linhan Lepeshov, Sergey Krasnok, Alex Jiang, Taizhi Peng, Xiaolei Korgel, Brian A. Alu, Andrea Zheng, Yuebing Department of Mechanical Engineering University of Texas at Austin AustinTX78712 United States Materials Science & Engineering Program Texas Materials Institute University of Texas at Austin AustinTX78712 United States ITMO University St. Petersburg197101 Russia Department of Electrical and Computer Engineering University of Texas at Austin AustinTX78712 United States Mc Ketta Department of Chemical Engineering University of Texas at Austin AustinTX78712 United States Photonics Initiative Advanced Science Research Center City University of New York New YorkNY10031 United States Physics Program Graduate Center City University of New York NY10016 United States Department of Electrical Engineering City College of The City University New YorkNY10031 United States

Chirality is a ubiquitous phenomenon in the natural world. Many biomolecules without inversion symmetry such as amino acids and sugars are chiral molecules. Measuring and controlling molecular chirality at a high precision down to the atomic scale are highly desired in physics, chemistry, biology, and medicine, however, have remained challenging. Herein, we achieve all-optical reconfigurable chiral meta-molecules experimentally using metallic and dielectric colloidal particles as artificial atoms or building blocks to serve at least two purposes. One is that the on-demand meta-molecules with strongly enhanced optical chirality are well-suited as substrates for surface-enhanced chiroptical spectroscopy of chiral molecules and as active components in optofluidic and nanophotonic devices. The other is that the bottom-up-assembled colloidal meta-molecules provide microscopic models to better understand the origin of chirality in the actual atomic and molecular systems. Copyright © 2019, The Authors. All rights reserved.

关键词： Atoms

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Frontispiz: Peptoid-Directed Formation of Five-Fold Twinned Au Nanostars through Particle Attachment and Facet Stabilization

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Angewandte Chemie 2022年第14期134卷

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Peptoid-Directed Formation of Five-Fold Twinned Au Nanostars through Particle Attachment and Facet Stabilization

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Angewandte Chemie 2022年第14期134卷

While bio-inspired synthesis offers great potential for controlling nucleation and growth of inorganic particles, precisely tuning biomolecule–particle interactions is a long-standing challenge. Herein, we used variations in peptoid sequence to manipulate peptoid–Au interactions, leading to the synthesis of concave five-fold twinned, five-pointed Au nanostars via a process of repeated particle attachment and facet stabilization. Ex situ and liquid-phase TEM observations show that a balance between particle attachment biased to occur near the star points, preferential growth along the [100] direction, and stabilization of (111) facets is critical to forming star-shaped particles. Molecular simulations predict that interaction strengths between peptoids and distinct Au facets differ significantly and thus can alter attachment kinetics and surface energies to form the stars. This work provides new insights into how sequence-defined ligands affect particle growth to regulate crystal morphology.

关键词： Facet Stabilization Five-Fold Twinned Au Star Particle Attachment Sequence-Defined Peptoids

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Guided mode resonances in flexible 2D THz photonic crystals

arXiv

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arXiv 2020年

作者： Kyaw, C. Yahiaoui, R. Chase, Z.A. Tran, V. Baydin, A. Tay, F. Kono, J. Manjappa, M. Singh, R. Abeysinghe, D.C. Urbas, A.M. Searles, T.A. Department of Physics and Astronomy Howard University WashingtonDC20059 United States Department of Electrical and Computer Engineering Rice University HoustonTX70005 United States Department of Physics and Astronomy Rice University HoustonTX70005 United States Department of Materials Science and Nanoengineering Rice University HoustonTX70005 United States Division of Physics and Applied Physics School of Physical and Mathematical Sciences Nanyang Technological University 21 Nanyang Link Singapore637371 Singapore Air Force Research Laboratory Materials and Manufacturing Directorate Wright-Patterson Air Force BaseOH45433 United States

In terahertz (THz) photonics, there is an ongoing effort to develop thin, compact devices such as dielectric photonic crystal (PhC) slabs with desirable light matter interactions. However, previous works in THz PhC slabs are limited to rigid substrates with thicknesses ∼ 100s of micrometers. Dielectric PhC slabs have been shown to possess in-plane modes that are excited by external radiation to produce sharp guided mode resonances with minimal absorption for applications in sensors, optics and lasers. Here, we confirm the existence of guided resonances in a membrane-type THz PhC slab with subwavelength (λ0/6 - λ0/12) thicknesses of flexible dielectric polyimide films. The transmittance of the guided resonances was measured for different structural parameters of the unit cell. Furthermore, we exploited the flexibility of the samples to modulate the linewidth of the guided modes down to 1.5 GHz for bend angle of θ ≥ 5◦;confirmed experimentally by the suppression of these modes. The mechanical flexibility of the device allows for an additional degree of freedom in system design for optical components for high-speed communications, soft wearable photonics and implantable medical devices. Copyright © 2020, The Authors. All rights reserved.

关键词： Photonic crystals

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