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Pressure-tunable large anomalous Hall effect of the ferromagnetic kagome-lattice Weyl semimetal Co3Sn2S2

Physical Review B 2019年第16期100卷 165145-165145页

作者： Xuliang Chen Maoyuan Wang Chuanchuan Gu Shuyang Wang Yonghui Zhou Chao An Ying Zhou Bowen Zhang Chunhua Chen Yifang Yuan Mengyao Qi Lili Zhang Haidong Zhou Jianhui Zhou Yugui Yao Zhaorong Yang Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions High Magnetic Field Laboratory Chinese Academy of Sciences Hefei 230031 China Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE) Beijing Key Laboratory of Nanophotonics and Ultrafine Optoelectronic Systems School of Physics Beijing Institute of Technology Beijing 100081 China Department of Materials Science and Engineering Southern University of Science and Technology Shenzhen 518055 China School of Physical Sciences University of Science and Technology of China Hefei 230026 China Institutes of Physical Science and Information Technology Anhui University Hefei 230601 China Shanghai Institute of Applied Physics Chinese Academy of Sciences Shanghai 201204 China Shanghai Synchrotron Radiation Facility Shanghai Advanced Research Institute Chinese Academy of Sciences Shanghai 201204 China Department of Physics and Astronomy University of Tennessee Knoxville Tennessee 37996-1200 USA Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education) School of Physics and Astronomy Shanghai JiaoTong University Shanghai 200240 China Collaborative Innovation Center of Advanced Microstructures Nanjing 210093 China

We report a systematic high-pressure study of magnetic topological semimetal Co3Sn2S2 through measurements of synchrotron x-ray diffraction (XRD), magnetization, electrical, and Hall transports combined with first-principle theoretical calculations. No evident trace of structural phase transition is detected through synchrotron x-ray diffraction over the measured pressure range of 0.2–50.9 GPa. We find that the ferromagnetism and the anomalous Hall resistivity are monotonically suppressed as increasing pressure and almost vanish around 22 GPa. The anomalous Hall conductivity varies nonmonotonically against pressure at low temperatures, involving competition between original and emergent Weyl nodes. Combined with first-principle calculations, we reveal that the intrinsic mechanism due to the Berry curvature dominates the anomalous Hall effect under high pressure.

关键词： Anomalous Hall effect Pressure effects Transport phenomena Topological materials First-principles calculations X-ray powder diffraction

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Frustrated Magnetism in Mott Insulating (V1−xCrx)2O3

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Physical Review X 2019年第1期9卷 011035-011035页

作者： J. C. Leiner H. O. Jeschke R. Valentí S. Zhang A. T. Savici J. Y. Y. Lin M. B. Stone M. D. Lumsden Jiawang Hong O. Delaire Wei Bao C. L. Broholm Center for Correlated Electron Systems Institute for Basic Science (IBS) Seoul 08826 Korea and Department of Physics and Astronomy Seoul National University Seoul 08826 Korea Neutron Scattering Division Oak Ridge National Laboratory Oak Ridge Tennessee 37831 USA Research Institute for Interdisciplinary Science Okayama University Okayama 700-8530 Japan Institut für Theoretische Physik Goethe-Universität Frankfurt Max-von-Laue-Straße 1 60438 Frankfurt am Main Germany Institute for Quantum Matter and Department of Physics and Astronomy The Johns Hopkins University Baltimore Maryland 21218 USA School of Aerospace Engineering and Institute of Advanced Structure Technology Beijing Institute of Technology Beijing 100081 China Materials Science and Technology Division Oak Ridge National Laboratory Oak Ridge Tennessee 37831 USA Department of Mechanical Engineering and Materials Science and Department of Physics Duke University Durham North Carolina 27708 USA Department of Physics Renmin University of China Beijing 100872 China

V2O3 famously features all four combinations of paramagnetic versus antiferromagnetic and metallic versus insulating states of matter in response to percent-level doping, pressure in the GPa range, and temperature below 300 K. Using time-of-flight neutron spectroscopy combined with density functional theory calculations of magnetic interactions, we have mapped and analyzed the inelastic magnetic neutron scattering cross section over a wide range of energy and momentum transfer in the chromium-stabilized antiferromagnetic and paramagnetic insulating phases. Our results reveal an important magnetic frustration and degeneracy of the paramagnetic insulating phase which is relieved by the rhombohedral-to-monoclinic transition at TN=185 K. This leads to the recognition that magnetic frustration is an inherent property of the paramagnetic phase in (V1−xCrx)2O3 and plays a key role in suppressing the magnetic long-range-ordering temperature and exposing a large phase space for the paramagnetic Mott metal-insulator transition to occur.

关键词： Antiferromagnetism Exchange interaction Frustrated magnetism Magnetoelastic effect Magnons Metal-insulator transition Paramagnetism Spin liquid Honeycomb lattice Mott insulators Single crystal materials Density functional theory First-principles calculations Inelastic neutron scattering

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One-shot quantum state exchange

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Physical Review A 2019年第4期100卷 042306-042306页

作者： Yonghae Lee Hayata Yamasaki Gerardo Adesso Soojoon Lee Department of Mathematics and Research Institute for Basic Sciences Kyung Hee University Seoul 02447 Korea Photon Science Center Graduate School of Engineering The University of Tokyo 7-3-1 Hongo Bunkyo-ku Tokyo 113-8656 Japan School of Mathematical Sciences and Centre for the Mathematics and Theoretical Physics of Quantum Non-Equilibrium Systems University of Nottingham University Park Nottingham NG7 2RD England United Kingdom

quantum state exchange is a quantum communication task in which two users exchange their respective quantum information in the asymptotic setting. In this paper, we consider a one-shot version of the quantum state exchange task, in which the users hold a single copy of the initial state, and they exchange their parts of the initial state by means of entanglement-assisted local operations and classical communication. We first derive lower bounds on the least amount of entanglement required for carrying out this task, and provide conditions on the initial state such that the protocol succeeds with zero entanglement cost. Based on these results, we study how the users deal with their symmetric information in order to reduce the entanglement cost. Moreover, we show that it is possible for the users to gain extra shared entanglement after this task.

关键词： Entanglement entropy Entanglement manipulation quantum communication

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Error measurements for a quantum annealer using the one-dimensional Ising model with twisted boundaries

arXiv

引用

arXiv 2020年

作者： Chancellor, Nicholas Crowley, Philip J.D. Ðurić, Tanja Vinci, Walter Amin, Mohammad H. Green, Andrew G. Warburton, Paul A. Aeppli, Gabriel London Centre For Nanotechnology University College London 19 Gordon Street LondonWC1H 0AH United Kingdom D-Wave Systems Inc. 3033 Beta Avenue BurnabyBCV5G 4M9 Canada Physics Department ETH Zürich CH-8093 Switzerland Institut de Physique EPFL LausanneCH-1015 Switzerland Paul Scherrer Institute VilligenCH-5232 Switzerland Quantum Center Eidgenössische Technische Hochschule Zurich ZurichCH-8093 Switzerland Department of Physics Simon Fraser University BurnabyBCV5A 1S6 Canada Department of Electronic and Electrical Engineering UCL Torrington Place LondonWC1E 7JE United Kingdom

A finite length ferromagnetic chain with opposite spin polarisation imposed at its two ends is one of the simplest frustrated spin models. In the clean classical limit the domain wall inserted on account of the boundary conditions resides with equal probability on any one of the bonds, and the degeneracy is precisely equal to the number of bonds. If quantum mechanics is introduced via a transverse field, the domain wall will behave as a particle in a box, and prefer to be nearer the middle of the chain rather than the ends. A simple characteristic of a real quantum annealer is therefore which of these limits obtains in practice. Here we have used the ferromagnetic chain with antiparallel boundary spins to test a real flux qubit quantum annealer and discover that contrary to both expectations, the domain walls found are non-uniformly distributed on account of effective random longitudinal fields present notwithstanding tuning carried out to zero out such fields when the couplings between qubits are nominally zero. We present a simple derivation of the form of the distribution function for the domain walls, and show also how the effect we have discovered can be used to determine the strength of the effective random fields (noise) characterising the annealer. The noise measured in this fashion is smaller than what is seen during the single qubit tuning process, but nonetheless qualitatively affects the outcome of the simulation performed by the annealer. Copyright © 2020, The Authors. All rights reserved.

关键词： Domain walls

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quantum systems for monte carlo methods and applications to fractional stochastic processes

arXiv

引用

arXiv 2018年

作者： Tudor, Sebastian F. Chatterjee, Rupak Nguyen, Lac Huang, Yuping School of Business Financial Engineering Division Hanlon Financial Systems Center Stevens Institute of Technology HobokenNJ07030 United States Department of Physics Center for Quantum Science and Engineering Hanlon Financial Systems Center Stevens Institute of Technology HobokenNJ07030 United States Department of Physics Center for Quantum Science and Engineering Stevens Institute of Technology HobokenNJ07030 United States

Random numbers are a fundamental and useful resource in science and engineering with important applications in simulation, machine learning and cyber-security. quantum systems can produce true random numbers because of the inherent randomness at the core of quantum mechanics. As a consequence, quantum random number generators are an efficient method to generate random numbers on a large scale. We study in this paper the applications of a viable source of unbiased quantum random numbers (QRNs) whose statistical properties can be arbitrarily programmed without the need for any post-processing and that pass all standard randomness tests of the NIST and Dieharder test suites without any randomness extraction. Our method is based on measuring the arrival time of single photons in shaped temporal modes that are tailored with an electro-optical modulator. The advantages of our QRNs are shown via two applications: simulation of a fractional Brownian motion, which is a non-Markovian process, and option pricing under the fractional SABR model where the stochastic volatility process is assumed to be driven by a fractional Brownian motion. The results indicate that using the same number of random units, our QRNs achieve greater accuracy than those produced by standard pseudo-random number generators. Moreover, we demonstrate the advantages of our method via an increase in computational speed, efficiency, and convergence. Copyright © 2018, The Authors. All rights reserved.

关键词： Monte Carlo methods

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Interfacial Dzyaloshinskii-Moriya Interaction: Effect of 5d Band Filling and Correlation with Spin Mixing Conductance

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Physical Review Letters 2018年第15期120卷 157204-157204页

作者： Xin Ma Guoqiang Yu Chi Tang Xiang Li Congli He Jing Shi Kang L. Wang Xiaoqin Li Department of Physics Center for Complex Quantum Systems The University of Texas at Austin Austin Texas 78712 USA Department of Electrical and Computer Engineering University of California Santa Barbara California 93106 USA Department of Electrical Engineering University of California Los Angeles California 90095 USA Beijing National Laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences Beijing 100190 China Department of Physics and Astronomy University of California Riverside California 92521 USA Department of Physics University of California Los Angeles California 90095 USA

The Dzyaloshinskii-Moriya interaction (DMI) at the heavy metal (HM) and ferromagnetic metal (FM) interface has been recognized as a key ingredient in spintronic applications. Here we investigate the chemical trend of DMI on the 5d band filling (5d3–5d10) of the HM element in HM/FM (FM=CoFeB,Co)/MgO multilayer thin films. DMI is quantitatively evaluated by measuring asymmetric spin wave dispersion using Brillouin light scattering. Sign reversal and 20 times modification of the DMI coefficient D have been measured as the 5d HM element is varied. The chemical trend can be qualitatively understood by considering the 5d and 3d bands alignment at the HM/FM interface and the subsequent orbital hybridization around the Fermi level. Furthermore, a correlation is observed between DMI and effective spin mixing conductance at the HM/FM interfaces. Our results provide new insights into the interfacial DMI for designing future spintronic devices.

关键词： Dzyaloshinskii-Moriya interaction Spin waves Brillouin scattering & spectroscopy

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Microsecond Valley Lifetime of Defect-Bound Excitons in Monolayer WSe2

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Physical Review Letters 2018年第5期121卷 057403-057403页

作者： Galan Moody Kha Tran Xiaobo Lu Travis Autry James M. Fraser Richard P. Mirin Li Yang Xiaoqin Li Kevin L. Silverman National Institute of Standards and Technology Boulder Colorado 80305 USA Department of Physics and Center for Complex Quantum Systems University of Texas at Austin Austin Texas 78712 USA Department of Physics and Institute of Materials Science and Engineering Washington University in St. Louis St. Louis Missouri 63136 USA Department of Physics Engineering Physics and Astronomy Queen’s University Kingston Ontario K7L 3N6 Canada

In atomically thin two-dimensional semiconductors such as transition metal dichalcogenides (TMDs), controlling the density and type of defects promises to be an effective approach for engineering light-matter interactions. We demonstrate that electron-beam irradiation is a simple tool for selectively introducing defect-bound exciton states associated with chalcogen vacancies in TMDs. Our first-principles calculations and time-resolved spectroscopy measurements of monolayer WSe2 reveal that these defect-bound excitons exhibit exceptional optical properties including a recombination lifetime approaching 200 ns and a valley lifetime longer than 1 μs. The ability to engineer the crystal lattice through electron irradiation provides a new approach for tailoring the optical response of TMDs for photonics, quantum optics, and valleytronics applications.

关键词： Excitons Valleytronics Transition metal dichalcogenides

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Hybrid quantum-classical convolutional neural networks

arXiv

引用

arXiv 2019年

作者： Liu, Junhua Lim, Kwan Hui Wood, Kristin L. Huang, Wei Guo, Chu Huang, He-Liang Information Systems Technology and Design Singapore University of Technology and Design 8 Somapah Road 487372 Singapore SUTD-MIT International Design Center Singapore University of Technology and Design 8 Somapah Road 487372 Singapore Engineering Product Develoment Singapore University of Technology and Design 8 Somapah Road 487372 Singapore Guangxi Key Laboratory of Optoelectronic Information Processing Guilin University of Electronic Technology Guilin541004 China Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education Department of Physics Synergetic Innovation Center for Quantum Effects and Applications Hunan Normal University Changsha410081 China Hefei National Laboratory for Physical Sciences at Microscale Department of Modern Physics University of Science and Technology of China Anhui Hefei230026 China Shanghai Branch Cas Ctr. for Excellence and Synergetic Innovation Centre in Quantum Information and Quantum Physics University of Science and Technology of China Anhui Hefei201315 China Henan Key Laboratory of Quantum Information and Cryptography Henan Zhengzhou450000 China

Deep learning has been shown to be able to recognize data patterns better than humans in specific circumstances or contexts. In parallel, quantum computing has demonstrated to be able to output complex wave functions with a few number of gate operations, which could generate distributions that are hard for a classical computer to produce. Here we propose a hybrid quantum-classical convolutional neural network (QCCNN), inspired by convolutional neural networks (CNNs) but adapted to quantum computing to enhance the feature mapping process. QCCNN is friendly to currently noisy intermediate-scale quantum computers, in terms of both number of qubits as well as circuit's depths, while retaining important features of classical CNN, such as nonlinearity and scalability. We also present a framework to automatically compute the gradients of hybrid quantum-classical loss functions which could be directly applied to other hybrid quantum-classical algorithms. We demonstrate the potential of this architecture by applying it to a Tetris dataset, and show that QCCNN can accomplish classification tasks with learning accuracy surpassing that of classical CNN. Copyright © 2019, The Authors. All rights reserved.

关键词： Convolution

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The CALorimetric Electron Telescope (CALET) on the international space station: Results from the first two years on orbit

arXiv

引用

arXiv 2019年

作者： Asaoka, Y. Adriani, O. Akaike, Y. Asano, K. Bagliesi, M.G. Berti, E. Bigongiari, G. Binns, W.R. Bonechi, S. Bongi, M. Bruno, A. Brogi, P. Buckley, J.H. Cannady, N. Castellini, G. Checchia, C. Cherry, M.L. Collazuol, G. Di Felice, V. Ebisawa, K. Fuke, H. Guzik, T.G. Hams, T. Hasebe, N. Hibino, K. Ichimura, M. Ioka, K. Ishizaki, W. Israel, M.H. Kasahara, K. Kataoka, J. Kataoka, R. Katayose, Y. Kato, C. Kawanaka, N. Kawakubo, Y. Kohri, K. Krawczynski, H.S. Krizmanic, J.F. Lomtadze, T. Maestro, P. Marrocchesi, P.S. Messineo, A.M. Mitchell, J.W. Miyake, S. Moiseev, A.A. Mori, K. Mori, M. Mori, N. Motz, H.M. Munakata, K. Murakami, H. Nakahira, S. Nishimura, J. de Nolfo, G.A. Okuno, S. Ormes, J.F. Ozawa, S. Pacini, L. Palma, F. Pal'shin, V. Papini, P. Penacchioni, A.V. Rauch, B.F. Ricciarini, S.B. Sakai, K. Sakamoto, T. Sasaki, M. Shimizu, Y. Shiomi, A. Sparvoli, R. Spillantini, P. Stolzi, F. Sugita, S. Suh, J.E. Sulaj, A. Takahashi, I. Takayanagi, M. Takita, M. Tamura, T. Tateyama, N. Terasawa, T. Tomida, H. Torii, S. Tsunesada, Y. Uchihori, Y. Ueno, S. Vannuccini, E. Wefel, J.P. Yamaoka, K. Yanagita, S. Yoshida, A. Yoshida, K. Waseda Research Institute for Science and Engineering Waseda University Japan JEM Utilization Center Human Spaceflight Technology Directorate Japan Aerospace Exploration Agency Japan Department of Physics University of Florence Italy INFN Sezione di Florence Italy Department of Physics University of Maryland United States Astroparticle Physics Laboratory NASA/GSFC United States Institute for Cosmic Ray Research University of Tokyo Japan Department of Physical Sciences Earth and Environment University of Siena Italy INFN Sezione di Pisa Italy Department of Physics Washington University United States Heliospheric Physics Laboratory NASA GSFC United States Department of Physics and Astronomy Louisiana State University United States Italy Department of Physics and Astronomy University of Padova Italy INFN Sezione di Padova Italy University of Rome "Tor Vergata" Italy INFN Sezione di Rome "Tor Vergata" Italy Institute of Space and Astronautical Science Japan Aerospace Exploration Agency Japan CRESST and Astroparticle Physics Laboratory NASA GSFC United States Kanagawa University Japan Faculty of Science and Technology Graduate School of Science and Technology Hirosaki University Japan Yukawa Institute for Theoretical Physics Kyoto University Japan National Institute of Polar Research Japan Faculty of Engineering Division of Intelligent Systems Engineering Yokohama National University Japan Faculty of Science Shinshu University Japan Hakubi Center Kyoto University Japan Department of Astronomy Graduate School of Science Kyoto University Japan College of Science and Engineering Department of Physics and Mathematics Aoyama Gakuin University Japan High Energy Accelerator Research Organization Japan University of Pisa Italy Department of Electrical and Electronic Systems Engineering National Institute of Technology Ibaraki College Japan Department of Astronomy University of Maryland College ParkMD20742 United States Department of Physical Sciences College o

The CALorimetric Electron Telescope (CALET) is a high-energy astroparticle physics space experiment installed on the International Space Station (ISS), developed and operated by Japan in collaboration with Italy and the United States. The CALET mission goals include the investigation of possible nearby sources of high-energy electrons, of the details of galactic particle acceleration and propagation, and of potential signatures of dark matter. CALET measures the cosmic-ray electron+positron flux up to 20 TeV, gamma-rays up to 10 TeV, and nuclei with Z=1 to 40 up to 1,000 TeV for the more abundant elements during a long-term observation aboard the ISS. Starting science operation in mid-October 2015, CALET performed continuous observation without major interruption with close to 20 million triggered events over 10 GeV per month. Based on the data taken during the first two-years, we present an overview of CALET observations: 1) Electron+positron energy spectrum, 2) Nuclei analysis, 3) Gamma-ray observation including a characterization of on-orbit performance. Results of the electromagnetic counterpart search for LIGO/Virgo gravitational wave events are discussed as well. Copyright © 2019, The Authors. All rights reserved.

关键词： Electrons

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quantum transport properties in single crystals of α−Bi4I4

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Physical Review Materials 2018年第11期2卷 114408-114408页

作者： Dong-Yun Chen Da-Shuai Ma Yongkai Li Z. Z. Du Xiaolu Xiong Yuan He JunXi Duan Junfeng Han Dong Chen Wende Xiao Yugui Yao Beijing Institute of Technology Beijing Key Laboratory of Nanophotonics and Ultrafine Optoelectronic Systems School of Physics Beijing 100081 China Institute for Quantum Science and Engineering and Department of Physics South University of Science and Technology of China Shenzhen 518055 China School of Physics Southeast University Nanjing 211189 China Shenzhen Key Laboratory of Quantum Science and Engineering Shenzhen 518055 China Micronano Center Beijing Institute of Technology Beijing 100081 China College of Physics Qingdao University Qingdao 266071 China

We report the magnetotransport properties of α−Bi4I4 single crystals, which have a crystal structure similar to that of the quasi-one-dimensional topological insulator β−Bi4I4. Prominent Shubnikov–de Hass oscillations and weak antilocalization effect are observed in all measured samples. The angular-dependent magnetoresistance indicates that the behavior of Shubnikov–de Hass oscillations is two-dimensional (2D) in n-type samples, while it is three-dimensional (3D) in p-type samples. First-principles calculations show that the n-type samples have a 2D Fermi surface, while the p-type samples have a 3D Fermi surface. Considering the similar carrier density and mobility, we infer that the transport behaviors in both types of samples come from bulk electron contributions. In addition, a large negative magnetoresistance with a transverse configuration is observed in the n-type sample A1. All the results indicate that α−Bi4I4 is an important material platform for investigation of novel and interesting phenomena. Our work may also provide important references for studying the topological surface transport properties in β−Bi4I4 in the future.

关键词： Magnetotransport quantum transport Weak antilocalization

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