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Light-Tunable Ferromagnetism in Atomically Thin Fe3GeTe2 Driven by Femtosecond Laser Pulse

Physical Review Letters 2020年第26期125卷 267205-267205页

作者： Bo Liu Shanshan Liu Long Yang Zhendong Chen Enze Zhang Zihan Li Jing Wu Xuezhong Ruan Faxian Xiu Wenqing Liu Liang He Rong Zhang Yongbing Xu National Laboratory of Solid State Microstructures and Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials School of Electronic Science and Engineering Nanjing University Nanjing 210093 People’s Republic of China State Key Laboratory of Surface Physics and Department of Physics Fudan University Shanghai 200433 People’s Republic of China York-Nanjing Joint Center in Spintronics Department of Electronic Engineering and Department of Physics The University of York York YO10 5DD United Kingdom Institute for Nanoelectronic Devices and Quantum Computing Fudan University Shanghai 200433 People’s Republic of China Department of Electronic Engineering Royal Holloway University of London Egham Surrey TW20 0EX United Kingdom

The recent discovery of intrinsic ferromagnetism in two-dimensional (2D) van der Waals (vdW) crystals has opened up a new arena for spintronics, raising an opportunity of achieving tunable intrinsic 2D vdW magnetism. Here, we show that the magnetization and the magnetic anisotropy energy (MAE) of few-layered Fe3GeTe2 (FGT) is strongly modulated by a femtosecond laser pulse. Upon increasing the femtosecond laser excitation intensity, the saturation magnetization increases in an approximately linear way and the coercivity determined by the MAE decreases monotonically, showing unambiguously the effect of the laser pulse on magnetic ordering. This effect observed at room temperature reveals the emergence of light-driven room-temperature (300 K) ferromagnetism in 2D vdW FGT, as its intrinsic Curie temperature TC is ∼200 K. The light-tunable ferromagnetism is attributed to the changes in the electronic structure due to the optical doping effect. Our findings pave a novel way to optically tune 2D vdW magnetism and enhance the TC up to room temperature, promoting spintronic applications at or above room temperature.

关键词： Ferromagnetism Light-induced magnetic effects Magnetic anisotropy Optical generation of spin carriers

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Cooperative bi-path metric for few-shot learning

arXiv

引用

arXiv 2020年

作者： Wang, Zeyuan Zhao, Yifan Li, Jia Tian, Yonghong State Key Laboratory of Virtual Reality Technology and Systems SCSE Beihang University Beijing100191 China School of Electronics Engineering and Computer Science Peking University Beijing100871 China Beijing Advanced Innovation Center for Big Data and Brain Computing Beihang University Beijing100191 China Peng Cheng Laboratory Shenzhen518066 China

Given base classes with sufficient labeled samples, the target of few-shot classification is to recognize unlabeled samples of novel classes with only a few labeled samples. Most existing methods only pay attention to the relationship between labeled and unlabeled samples of novel classes, which do not make full use of information within base classes. In this paper, we make two contributions to investigate the few-shot classification problem. First, we report a simple and effective baseline trained on base classes in the way of traditional supervised learning, which can achieve comparable results to the state of the art. Second, based on the baseline, we propose a cooperative bi-path metric for classification, which leverages the correlations between base classes and novel classes to further improve the accuracy. Experiments on two widely used benchmarks show that our method is a simple and effective framework, and a new state of the art is established in the few-shot classification field. Copyright © 2020, The Authors. All rights reserved.

关键词： Image classification

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Enhanced phase estimation with coherently boosted two-mode squeezed beams and its application to optical gyroscopes

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Physical Review A 2020年第2期102卷 022614-022614页

作者： Xiao-Qi Xiao Elisha S. Matekole Jiankang Zhao Guihua Zeng Jonathan P. Dowling Hwang Lee Department of Communication Engineering Shanghai Dianji University Shanghai 200240 China Hearne Institute for Theoretical Physics and Department of Physics and Astronomy Louisiana State University Baton Rouge Louisiana 70803 USA State Key Laboratory of Advanced Optical Communication Systems and Networks Institute of Sensing and Navigation Department of Electronic Engineering Shanghai Jiaotong University Shanghai 200030 China National Institute of Information and Communications Technology Tokyo 184-8795 Japan NYU-ECNU Institute of Physics at NYU Shanghai Shanghai 200062 China CAS-Alibaba Quantum Computing Laboratory USTC Shanghai 201315 China

Quantum techniques, developed in recent decades, provide new approaches to achieving high-precision measurements beyond the classical bounds. In this paper, we theoretically demonstrate a metrology method for improving the sensitivity of the interferometric optical gyroscope, robust against the loss, by using coherent-light stimulated two-mode squeezed beams as the light source. The detection protocol is based on a simple intensity measurement, and the quantum noise is far below the shot-noise limit. The enhancement factors for different coherent light fields are analyzed in detail. Additionally, the influence of loss during the propagation in the optical path is studied, and the conditions for achieving sub-shot-noise measurement sensitivity are obtained. We also find that the phase sensitivity of the proposed gyroscope scheme becomes closer to the quantum Cramér-Rao bound with increasing of the photon number of the coherent beams.

关键词： Quantum metrology

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Simulation of Passenger Evacuation of High-speed Train Cars 9

Simulation of Passenger Evacuation of High-speed Train Cars

引用

9th International Conference on Fire Science and Fire Protection engineering, ICFSFPE 2019

作者： Huang, Shenshi Wei, Ruichao Shi, Kai Hu, Jinxing Lu, Shouxiang Lian, Liping Institute of Advanced Computing and Digital Engineering Shenzhen Institute of Advanced Technology Chinese Academy of Science Shenzhen China Smart City Research Institute of China Electronics Technology Group Corporation Shenzhen China State Key Laboratory of Fire Science University of Science and Technology of China Hefei China School of Urban Planning and Design Peking University Shenzhen China

ISBN: (纸本)9781728153223

This study is to evaluate the passenger evacuation of the high-speed train. Geometry was built up based on current Chinese train type CRH380B, and scenarios were designed according to the current emergency response plans. Simulation runs were performed by Pathfinder and uncertainty of evacuation time was obtained. It is observed that the passenger flow rates in train coaches are generally stable. Passenger transfer time and evacuation time are approximately proportional to passenger attendance rate. However, in some complicated scenarios, it is found that the process of passenger transfer affects the evacuation results a lot. Reasonable passenger transfer scale can maximize the effectiveness of emergency plans. This study provides an evaluation method on the topic of train car evacuation, and future work can be carried out to optimize the design of emergency response. © 2019 IEEE.

关键词： Railroad cars

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Nonreciprocal transport in a bilayer of MnBi2Te4 and Pt

arXiv

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arXiv 2022年

作者： Ye, Chen Xie, Xiangnan Lv, Wenxing Huang, Ke Yang, Allen Jian Jiang, Sicong Liu, Xue Zhu, Dapeng Qiu, Xuepeng Tong, Mingyu Zhou, Tong Hsu, Chuang-Han Chang, Guoqing Lin, Hsin Li, Peisen Yang, Kesong Wang, Zhenyu Jiang, Tian Wang, Xiao Renshaw Division of Physics and Applied Physics School of Physical and Mathematical Sciences Nanyang Technological University 21 Nanyang Link 637371 Singapore State Key Laboratory of High Performance Computing College of Computer Science and Technology National University of Defense Technology Changsha410073 China Physics Laboratory Industrial Training Center Shenzhen Polytechnic Guangdong Shenzhen518055 China Department of NanoEngineering Program of Chemical Engineering University of California La Jolla San DiegoCA92093-0448 United States Program of Materials Science and Engineering University of California La Jolla San DiegoCA92093-0418 United States Institutes of Physical Science and Information Technology Anhui University Hefei230601 China Fert Beijing Institute MIIT Key Laboratory of Spintronics School of Integrated Circuit Science and Engineering Beihang University Beijing100191 China Beihang-Goertek Joint Microelectronics Institute Qingdao Research Institute Beihang University Qingdao266000 China Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology School of Physics Science and Engineering Tongji University Shanghai200092 China College of Advanced Interdisciplinary Studies National University of Defense Technology Changsha410073 China Insitute of Physics Academia Sinica Taipei115229 Taiwan College of Intelligence Science and Technology National University of Defense Technology Changsha410073 China National Innovation Institute of Defense Technology Academy of Military Sciences PLA China Beijing100010 China Beijing Academy of Quantum Information Sciences Beijing100084 China Beijing Institute for Advanced Study National University of Defense Technology Changsha410073 China School of Electrical and Electronic Engineering Nanyang Technological University 50 Nanyang Ave 639798 Singapore

MnBi2Te4 (MBT) is the first intrinsic magnetic topological insulator with the interaction of spin-momentum locked surface electrons and intrinsic magnetism, and it exhibits novel magnetic and topological phenomena. Recent studies suggested that the interaction of electrons and magnetism can be affected by the Mn-doped Bi2Te3 phase at the surface due to inevitable structural defects. Here we report an observation of nonreciprocal transport, i.e. current-direction-dependent resistance, in a bilayer composed of antiferromagnetic MBT and nonmagnetic Pt. The emergence of the nonreciprocal response below the Néel temperature confirms a correlation between nonreciprocity and intrinsic magnetism in the surface state of MBT. The angular dependence of the nonreciprocal transport indicates that nonreciprocal response originates from the asymmetry scattering of electrons at the surface of MBT mediated by magnon. Our work provides an insight into nonreciprocity arising from the correlation between magnetism and Dirac surface electrons in intrinsic magnetic topological insulators. © 2022, CC BY.

关键词： Magnetism

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Self-embedding Image Watermarking based on Combined Decision Using Pre-offset and Post-offset Blocks

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Computers, Materials & Continua 2018年第11期57卷 243-260页

作者： Daofu Gong Yan Chen Haoyu Lu Zhenyu Li Yibing Han Zhengzhou Science and Technology Institute Zhengzhou450001China State Key Laboratory of Mathematical Engineering and Advanced Computing Zhengzhou450001China Department of Computer Science University of YorkYork YO105GHUK

To detect and recover random tampering areas,a combined-decision-based self-embedding watermarking scheme is proposed *** this scheme,the image is first partitioned into 2×2 size ***,the high 5 bits of a block’s average value is embedded into its offset *** tampering type of block is detected by comparing the watermarks of its pre-offset and post-offset *** theoretical analysis and experiments demonstrate that the proposed scheme not only has a lower ratio of false detection but also better performance with regard to avoiding random tampering.

关键词： Fragile watermarking self-embedding offset block tamper recovery random tampering

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An Image Steganography Algorithm Based on Quantization Index Modulation Resisting Scaling Attacks and Statistical Detection

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Computers, Materials & Continua 2018年第7期56卷 151-167页

作者： Yue Zhang Dengpan Ye Junjun Gan Zhenyu Li Qingfeng Cheng State Key Laboratory of Mathematical Engineering and Advanced Computing Zhengzhou 450001China Computer School of Wuhan University Wuhan 430072China Department of Computer Science University of YorkYork YO105GHUK

In view of the fact that the current adaptive steganography algorithms are difficult to resist scaling attacks and that a method resisting scaling attack is only for the nearest neighbor interpolation method,this paper proposes an image steganography algorithm based on quantization index modulation resisting both scaling attacks and statistical *** the spatial image,this paper uses the watermarking algorithm based on quantization index modulation to extract the embedded *** construct the embedding distortion function of the new embedded domain based on S-UNIWARD steganography,and use the minimum distortion coding to realize the embedding of the secret ***,according to the embedding modification amplitude of secret messages in the new embedded domain,the quantization index modulation algorithm is applied to realize the final embedding of secret messages in the original embedded *** experimental results show that the algorithm proposed is robust to the three common interpolation attacks including the nearest neighbor interpolation,the bilinear interpolation and the bicubic *** the average correct extraction rate of embedded messages increases from 50%to over 93% after 0.5 times-fold scaling attack using the bicubic interpolation method,compared with the classical steganography algorithm *** the algorithm proposed has higher detection resistance than the original watermarking algorithm based on quantization index modulation.

关键词： Image steganography anti-scaling attack anti-statistical detection quantization index modulation

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The effects of different travel modes and travel destinations on COVID-19 transmission in global cities

引用

Science Bulletin 2022年第6期67卷 588-592,M0003页

作者： Rui Zhu Luc Anselin Michael Batty Mei-Po Kwan Min Chen Wei Luo Tao Cheng Che Kang Lim Paolo Santi Cheng Cheng Qiushi Gu Man Sing Wong Kai Zhang Guonian Lü Carlo Ratti Department of Land Surveying and Geo-Informatics the Hong Kong Polytechnic UniversityHong KongChina Key Laboratory of Virtual Geographic Environment(Ministry of Education) Nanjing Normal UniversityNanjing 210023China Senseable City Laboratory Future Urban Mobility IRGSingapore-MIT Alliance for Research and TechnologySingapore 138602Singapore Center for Spatial Data Science Division of the Social SciencesUniversity of ChicagoChicago IL 60637USA School of Geography Science Nanjing Normal UniversityNanjing 210023China Centre for Advanced Spatial Analysis Faculty of the Built EnvironmentUniversity College LondonLondon WC1E 6BTUK Department of Geography and Resource Management the Chinese University of Hong KongHong KongChina Institute of Space and Earth Information Science the Chinese University of Hong KongHong KongChina Department of Human Geography and Spatial Planning Utrecht UniversityUtrecht 3584 CSNetherlands State Key Laboratory Cultivation Base of Geographical Environment Evolution Nanjing 210023China Department of Geography National University of SingaporeSingapore 117570Singapore SpaceTimeLab Department of CivilEnvironmental and Geomatic EngineeringUniversity College LondonLondon WC1E 6BTUK Department of Clinical Translational Research Singapore General HospitalSingapore 169856Singapore Division of Clinical Immunology and Transfusion Medicine Department of Laboratory MedicineKarolinska InstitutetStockholm 17177Sweden Senseable City Laboratory Department of Urban Studies and PlanningMassachusetts Institute of TechnologyCambridgeMA 02139USA Istituto di Informatica e Telematica del CNR Pisa 56124Italy Department of System Science Institute of High Performance Computing Agency for ScienceTechnology and ResearchSingapore 138632Singapore Department of Tourism Studies School of HumanitiesSoutheast UniversityNanjing 210096China

The international community has made significant efforts to flatten the COVID-19 curve,including predicting transmission[1,2],executing unprecedented global lockdowns and social distancing[3,4],promoting the wearing of facemasks and social distancing measures[5],and isolating confirmed cases and contacts[6].Because of the adverse consequences of these lockdown measures[7],many cities have reopened so they can rebuild their ***,as mobility has gradually returned towards normal,imported cases from unknown sources have disrupted the recovery situation,and cities are continually at high risk of new waves of infection[8,9]since airborne transmission is the dominant transmission route[10].

关键词：多变量时间序列疫情传播出行方式谷歌公司交通出行病毒传播出行行为大城市

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Long-range propagation of magnon polaritons in a canted antiferromagnet

引用

Physical Review Applied 2025年第6期23卷 L061002-L061002页

作者： Hanchen Wang Jinlong Wang Kanglin Yu Lutong Sheng Yongjian Zhou Rundong Yuan Chensong Hua Weichao Yu Junfeng Hu Jilei Chen Cheng Song Jean-Philippe Ansermet Mehrdad Elyasi Gerrit E.W. Bauer Haiming Yu Fert Beijing Institute MIIT Key Laboratory of Spintronics School of Integrated Circuit Science and Engineering Beihang University Beijing 100191 China International Quantum Academy Shenzhen 518048 China Department of Materials ETH Zurich Zurich 8093 Switzerland Key Laboratory of Advanced Materials (MOE) School of Materials Science and Engineering Tsinghua University Beijing 100084 China Cavendish Laboratory Department of Physics University of Cambridge Cambridge CB3 0HE United Kingdom Institute for Nanoelectronic Devices and Quantum Computing State Key Laboratory of Surface Physics Fudan University Shanghai 200433 China Zhangjiang Fudan International Innovation Center Fudan University Shanghai 201210 China Shenzhen Institute for Quantum Science and Engineering Southern University of Science and Technology Shenzhen 518055 China Institute of Physics École Polytechnique Fédérale de Lausanne (EPFL) 1015 Lausanne Switzerland WPI Advanced Institute for Materials Research Tohoku University Sendai 980-8577 Japan Kavli Institute for Theoretical Sciences University of the Chinese Academy of Sciences Beijing 100190 China Institute for Materials Research Tohoku University Sendai 980-8577 Japan

We report strong coupling between magnons and cavity photons in a single-crystalline slab of α-Fe2O3 (hematite) with canted antiferromagnetic order at room temperature. The hybridized magnon polaritons propagate over many millimeters due to their high group velocities, as experimentally characterized using time-of-flight spectroscopy. The conventional dipolar and spin-orbit-interaction-induced chirality can explain an observed nonreciprocity. Our findings highlight the potential of antiferromagnetic magnon polaritons for on-chip spin-based information technologies.

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Delay-distance correlation study for IP geolocation

arXiv

引用

arXiv 2019年

作者： Ding, Shichang Luo, Xiangyang Ye, Dengpan Liu, Fenlin State Key Laboratory of Mathematical Engineering and Advanced Computing Zhengzhou Henan450001 China School of Computer Wuhan University Wuhan Hubei430072 China

Although many classical IP geolocation algorithms are suitable to rich-connected networks, their performances are seriously affected in poor-connected networks with weak delay-distance correlation. This paper tries to improve the performances of classical IP geolocation algorithms by finding rich-connected sub-networks inside poor-connected networks. First, a new delay-distance correlation model (RTD-Corr model) is proposed. It builds the relationship between delay-distance correlation and actual network factors such as the tortuosity of the network path, the ratio of propagation delay and the direct geographical distance. Second, based on the RTD-Corr model and actual network characteristics, this paper discusses about how to find rich-connected networks inside China Internet which is a typical actual poor-connected network. Then we find rich-connected sub-networks of China Internet through a large-scale network measurement which covers three major ISPs and thirty provinces. At last, based on the founded rich-connected sub-networks, we modify two classical IP geolocation algorithms and the experiments in China Internet show that their accuracy is significantly increased. Copyright © 2019, The Authors. All rights reserved.

关键词： Network security

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