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Revisit of the anisotropic vortex states of 2H-NbSe_(2) towards the zero-field limit

Chinese physics B 2024年第6期33卷 80-86页

作者：张凡侯兴元姜宇轩张宗源涂玉兵朱相德陈根富单磊 Beijing National laboratory for condensed matter physics Institute of PhysicsChinese Academy of SciencesBeijing 100190China School of Physical Sciences University of Chinese Academy of SciencesBeijing 100190China Center of Free Electron Laser and High Magnetic Field Anhui UniversityHefei 230601China Information Materials and Intelligent Sensing laboratory of anhui Province Institutes of Physical Science and Information TechnologyAnhui UniversityHefei 230601China key laboratory of Structure and Functional Regulation of Hybrid Materials in anhui University Ministry of EducationHefei 230601China School of physics and Materials Science Anhui UniversityHefei 230601China anhui key laboratory of condensed matter physics at extreme conditions High Magnetic Field LaboratoryHFIPSAnhuiChinese Academy of Sciencesand University of Science and Technology of ChinaHefei 230031China Hefei National laboratory Hefei 230088China

We revisited the vortex states of 2H-NbSe_(2) towards zero fields by a low-temperature scanning tunneling microscope.Fine structures of the anisotropic vortex states were distinguished, one is a spatially non-splitting zero bias peak, and the other is an in-gap conductance anomaly resembling evolved crossing features around the center of the three nearest vortices.Both of them distribute solely along the next nearest neighboring direction of the vortex lattice and become unresolved in much higher magnetic fields, implying an important role played by the vortex–vortex interactions. To clarify these issues,we have studied the intrinsic vortex states of the isolated trapped vortex in zero fields at 0.45 K. It is concluded that the anisotropic zero bias peak is attributed to the superconducting gap anisotropy, and the spatially evolved crossing features are related to the vortex–vortex interaction. The vortex core size under the zero-field limit is determined. These results provide a paradigm for studying the inherent vortex states of type-II superconductors especially based on an isolated vortex.

关键词： vortex states zero-bias conductance peak scanning tunneling microscopy

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Absence of metallicity and bias-dependent resistivity in low-carrier-density EuCd_(2)As_(2)

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Science China(physics,Mechanics & Astronomy) 2024年第4期67卷 119-125页

作者： Yuxiang Wang Jianwen Ma Jian Yuan Wenbin Wu Yong Zhang Yicheng Mou Jiaming Gu Peihong Cheng Wu Shi Xiang Yuan Jinglei Zhang Yanfeng Guo Cheng Zhang State key laboratory of Surface physics and Institute for Nanoelectronic Devices and Quantum Computing Fudan UniversityShanghai 200433China School of Physical Science and Technology ShanghaiTech UniversityShanghai 201210China State key laboratory of Precision Spectroscopy East China Normal UniversityShanghai 200241China anhui Province key laboratory of condensed matter physics at extreme conditions High Magnetic Field Laboratory of the Chinese Academy of SciencesHefei 230031China School of physics and Electronic Science East China Normal UniversityShanghai 200241China Zhangjiang Fudan International Innovation Center Fudan UniversityShanghai 201210China ShanghaiTech laboratory for Topological physics Shanghai 201210China

EuCd_(2)As_(2)was theoretically predicted to be a minimal model of Weyl semimetals with a single pair of Weyl points in the ferromagnet state.However,the heavily p-doped Eu Cd_(2)As_(2)crystals in previous experiments prevent direct identification of the semimetal hypothesis.Here,we present a comprehensive magneto-transport study of high-quality Eu Cd_(2)As_(2)crystals with ultralow bulk carrier density(10^(13)cm^(-3)).In contrast to the general expectation of a Weyl semimetal phase,Eu Cd_(2)As_(2)shows insulating behavior in both antiferromagnetic and ferromagnetic states as well as surface-dominated conduction from band bending.Moreover,the application of a dc bias current can dramatically modulate the resistance by over one order of magnitude,and induce a periodic resistance oscillation due to the geometric resonance.Such nonlinear transport results from the high nonequilibrium state induced by an electrical field near the band edge.Our results suggest an insulating phase in Eu Cd_(2)As_(2)and put a strong constraint on the underlying mechanism of anomalous transport properties in this system.

关键词： magnetic Weyl semimetal quantum transport Hall effect nonlinear resistivity

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Low-energy spin dynamics in a Kitaev material Na_(3)Ni_(2)BiO_(6) investigated by nuclear magnetic resonance

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Chinese physics B 2024年第6期33卷 518-524页

作者：史昕雨崔祎上官艳艳徐霄宇吴占龙胡泽李硕杜柯帆陈颖马龙刘正鑫温锦生张金珊于伟强 Mathematics and physics Department North China Electric Power UniversityBeijing 102206China Department of physics and Beijing key laboratory of Opto-electronic Functional Materials&Micro-nano Devices Renmin University of ChinaBeijing 100872China key laboratory of Quantum State Construction and Manipulation(Ministry of Education) Renmin University of ChinaBeijing 100872China National laboratory of Solid State Microstructures and Department of physics Nanjing UniversityNanjing 210093China anhui Province key laboratory of condensed matter physics at extreme conditions High Magnetic Field LaboratoryChinese Academy of SciencesHefei 230031China Innovative Center for Advanced Microstructures Nanjing UniversityNanjing 210093China

We perform ^(23)Na nuclear magnetic resonance(NMR) and magnetization measurements on an S=1,quasi-2D honeycomb lattice antiferromagnet Na_(3)Ni_(2)BiO_(6).A large positive Curie-Weiss constant of 22.9 K is observed.The NMR spectra at low fields are consistent with a zigzag magnetic order,indicating a large easy-axis anisotropy.With the field applied along the c*axis,the NMR spectra confirm the existence of a 1/3-magnetization plateau phase between 5.1 T and 7.1 T.The transition from the zigzag order to the 1/3-magnetization plateau phase is also found to be a first-order type.A monotonic decrease of the spin gap is revealed in the 1/3-magnetization plateau phase,which reaches zero at a quantum critical field H_(C)≈8.35 T before entering the fully polarized phase.These data suggest the existence of exchange frustration in the system along with strong ferromagnetic interactions,hosting the possibility for Kitaev physics.Besides,well below the ordered phase,the 1/T_(1) at high fields shows either a level off or an enhancement upon cooling below 3 K,which suggests the existence of low-energy fluctuations.

关键词： one–third magnetization plateau phase nuclear magnetic resonance honeycomb-lattice antiferromagnet Kitaev interaction

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Unveiling a novel metal-to-metal transition in LuH_(2):Critically challenging superconductivity claims in lutetium hydrides

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matter and Radiation at extremes 2024年第3期9卷 65-73页

作者： Dong Wang Ningning Wang Caoshun Zhang Chunsheng Xia Weicheng Guo Xia Yin Kejun Bu Takeshi Nakagawa Jianbo Zhang Federico Gorelli Philip Dalladay-Simpson Thomas Meier Xujie Lü Liling Sun Jinguang Cheng Qiaoshi Zeng Yang Ding Ho-kwang Mao Center for High-Pressure Science and Technology Advanced Research Beijing 100094China Beijing National laboratory for condensed matter physics and Institute of physics Chinese Academy of SciencesBeijing 100190China Shanghai key laboratory of Material Frontiers Research in extreme Environments(MFree) Shanghai Advanced Research in Physical Sciences(SHARPS)Shanghai 201203China

Following the recent report by Dasenbrock-Gammon et al.[Nature 615,244–250(2023)]of near-ambient superconductivity in nitrogendoped lutetium trihydride(LuH_(3-δ)N_(ε)),significant debate has emerged surrounding the composition and interpretation of the observed sharp resistance drop.Here,we meticulously revisit these claims through comprehensive characterization and investigations.We definitively identify the reported material as lutetium dihydride(LuH_(2)),resolving the ambiguity surrounding its composition.Under similar conditions(270–295 K and 1–2 GPa),we replicate the reported sharp decrease in electrical resistance with a 30%success rate,aligning with the observations by Dasenbrock-Gammon et al.However,our extensive investigations reveal this phenomenon to be a novel pressure-induced metal-to-metal transition intrinsic to LuH_(2),distinct from superconductivity.Intriguingly,nitrogen doping exerts minimal impact on this transition.Our work not only elucidates the fundamental properties of LuH_(2)andLuH_(3),but also critically challenges the notion of superconductivity in these lutetium hydride systems.These findings pave the way for future research on lutetium hydride systems,while emphasizing the crucial importance of rigorous verification in claims of ambient-temperature superconductivity.

关键词： resistance hydride superconductivity

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Two-dimensional Sb net generated nontrivial topological states in SmAgSb_2 probed by quantum oscillations

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Chinese physics B 2024年第7期33卷 51-58页

作者：袁健石贤彪杜红李田郗传英王霞夏威王保田钟瑞丹郭艳峰 School of Physical Science and Technology ShanghaiTech UniversityShanghai 201210China Institute of High Energy physics Chinese Academy of SciencesBeijing 100049China Tsung-Dao Lee Institute Shanghai Jiao Tong UniversityShanghai 200240China Xingzhi College Zhejiang Normal UniversityJinhua 321100China anhui Province key laboratory of condensed matter physics at extreme conditions High Magnetic Field Laboratory of the Chinese Academy of SciencesHefei 230031China ShanghaiTech laboratory for Topological physics ShanghaiTech UniversityShanghai 201210China

The REAgSb_2(RE = rare earth and Y) family has drawn considerable research interest because the two-dimensional Sb net in their crystal structures hosts topological fermions and hence rich topological properties. We report herein the magnetization and magnetotransport measurements of SmAgSb_2 single crystal, which unveil very large magnetoresistance and high carrier mobility up to 6.2 × 10~3% and 5.58 × 10~3cm~2·V~(-1)·s~(-1), respectively. The analysis of both Shubnikov–de Haas and de Haas–van Alphen quantum oscillations indicates nontrivial Berry phases in the paramagnetic state while trivial Berry curvature in the antiferromagnetic state, indicating a topological phase transition induced by the antiferromagnetic order. It is also supported by the first-principles calculations. The results not only provide a new interesting topological material but also offer valuable insights into the correlation between magnetism and nontrivial topological states.

关键词： large magnetoresistance quantum oscillations topological phase transition

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Diagnosis of indirectly driven double shell targets with point-projection hard x-ray radiography

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matter and Radiation at extremes 2024年第2期9卷 50-62页

作者： Chao Tian Minghai Yu Lianqiang Shan Fengjuan Wu Bi Bi Qiangqiang Zhang Yuchi Wu Tiankui Zhang Feng Zhang Dongxiao Liu Weiwu Wang Zongqiang Yuan Siqian Yang Lei Yang Zhigang Deng Jian Teng Weimin Zhou Zongqing Zhao Yuqiu Gu Baohan Zhang Science and Technology on Plasma physics laboratory Laser Fusion Research CenterChina Academy of Engineering PhysicsMianyang 621900People’s Republic of China Joint laboratory for extreme conditions matter Properties Southwest University of Science and TechnologyMianyang 621010People’s Republic of China IFSA Collaborative Innovation Center Shanghai Jiao Tong UniversityShanghai 200240People’s Republic of China

We present an application of short-pulse laser-generated hard x rays for the diagnosis of indirectly driven double shell targets. Coneinserted double shell targets were imploded through an indirect drive approach on the upgraded SG-II laser facility. Then, based on thepoint-projection hard x-ray radiography technique, time-resolved radiography of the double shell targets, including that of their near-peakcompression, were obtained. The backlighter source was created by the interactions of a high-intensity short pulsed laser with a metalmicrowire target. Images of the target near peak compression were obtained with an Au microwire. In addition, radiation hydrodynamicsimulations were performed, and the target evolution obtained agrees well with the experimental results. Using the radiographic images, arealdensities of the targets were evaluated.

关键词： double projection point

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FPGA and computer-vision-based atom tracking technology for scanning probe microscopy

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Chinese physics B 2024年第5期33卷 76-85页

作者：俞风度刘利王肃珂张新彪雷乐黄远志马瑞松郇庆 Beijing National laboratory for condensed matter physics Institute of PhysicsChinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China ACME (Beijing) Technology Co. Ltd.Beijing 101407China key laboratory for Vacuum physics University of Chinese Academy of SciencesBeijing 100190China

Atom tracking technology enhanced with innovative algorithms has been implemented in this study,utilizing a comprehensive suite of controllers and software independently developed domestically.Leveraging an on-board field-programmable gate array(FPGA)with a core frequency of 100 MHz,our system facilitates reading and writing operations across 16 channels,performing discrete incremental proportional-integral-derivative(PID)calculations within 3.4 microseconds.Building upon this foundation,gradient and extremum algorithms are further integrated,incorporating circular and spiral scanning modes with a horizontal movement accuracy of 0.38 pm.This integration enhances the real-time performance and significantly increases the accuracy of atom tracking.Atom tracking achieves an equivalent precision of at least 142 pm on a highly oriented pyrolytic graphite(HOPG)surface under room temperature atmospheric conditions.Through applying computer vision and image processing algorithms,atom tracking can be used when scanning a large area.The techniques primarily consist of two algorithms:the region of interest(ROI)-based feature matching algorithm,which achieves 97.92%accuracy,and the feature description-based matching algorithm,with an impressive 99.99%accuracy.Both implementation approaches have been tested for scanner drift measurements,and these technologies are scalable and applicable in various domains of scanning probe microscopy with broad application prospects in the field of nanoengineering.

关键词： atom tracking FPGA computer vision drift measurement

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Spin‑controlled topological phase transition in non‑Euclidean space

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Frontiers of Optoelectronics 2024年第1期17卷 67-76页

作者： Zhuochen Du Jinze Gao Qiuchen Yan Cuicui Lu Xiaoyong Hu Qihuang Gong State key laboratory for Mesoscopic physics and Department of physics Collaborative Innovation Center of Quantum Matter and Frontiers Science Center for Nano‑OptoelectronicsBeijing Academy of Quantum Information SciencesPeking UniversityBeijing 100871China key laboratory of Advanced Optoelectronic Quantum Architecture and Measurements of Ministry of Education Beijing Key Laboratory of Nanophotonics and Ultrafine Optoelectronic SystemsSchool of PhysicsBeijing Institute of TechnologyBeijing 100081China Peking University Yangtze Delta Institute of Optoelectronics Nantong 226010China Collaborative Innovation Center of extreme Optics Shanxi UniversityTaiyuan 030006China Hefei National laboratory Hefei 230088China

Modulation of topological phase transition has been pursued by researchers in both condensed matter and optics research fields,and has been realized in Euclidean systems,such as topological photonic crystals,topological metamaterials,and coupled resonator arrays.However,the spin-controlled topological phase transition in non-Euclidean space has not yet been explored.Here,we propose a non-Euclidean configuration based on Mobius rings,and we demonstrate the spin-controlled transition between the topological edge state and the bulk state.The Mobius ring,which is designed to have an 8πperiod,has a square cross section at the twist beginning and the length/width evolves adiabatically along the loop,accompanied by conversion from transverse electric to transverse magnetic modes resulting from the spin-locked effect.The 8πperiod Mobius rings are used to construct Su–Schrieffer–Heeger configuration,and the configuration can support the topological edge states excited by circularly polarized light,and meanwhile a transition from the topological edge state to the bulk state can be realized by controlling circular polarization.In addition,the spin-controlled topological phase transition in non-Euclidean space is feasible for both Hermitian and non-Hermitian cases in 2D systems.This work provides a new degree of polarization to control topological photonic states based on the spin of Mobius rings and opens a way to tune the topological phase in non-Euclidean space.

关键词： Topological phase transition Non-Euclidean space Möbius ring Spin-locked effect

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Unveiling strain-enhanced moiréexciton localization in twisted van der Waals homostructures

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Nano Research 2024年第4期17卷 3245-3252页

作者： Henry Rui He Haihong Zheng Biao Wu Shaofei Li Junnan Ding Zongwen Liu Jian-Tao Wang Anlian Pan Yanping Liu Institute of Quantum physics School of PhysicsCentral South UniversityChangsha 410083China State key laboratory of Precision Manufacturing for extreme Service Performance Central South UniversityChangsha 410083China School of Chemical and Biomolecular Engineering The University of SydneyNSW 2006Australia Beijing National laboratory for condensed matter physics Institute of PhysicsChinese Academy of SciencesBeijing 100190China College of Materials Science and Engineering Hunan UniversityChangsha 410082China State key laboratory of High-Performance Complex Manufacturing Central South UniversityChangsha 410083China Shenzhen Research Institute of Central South University Shenzhen 51800China

Moirésuperlattices,arising from the controlled twisting of van der Waals homostructures at specific angles,have emerged as a promising platform for quantum emission applications.Concurrently,the manipulation of strain provides a versatile strategy to finely adjust electronic band structures,enhance exciton luminescence efficiency,and establish a robust foundation for two-dimensional quantum light sources.However,the intricate interplay between strain and moirépotential remains partially unexplored.Here,we introduce a meticulously designed fusion of strain engineering and the twisted 2L-WSe_(2)/2L-WSe_(2) homobilayers,resulting in the precise localization of moiréexcitons.Employing low-temperature photoluminescence spectroscopy,we unveil the emergence of highly localized moiré-enhanced emission,characterized by the presence of multiple distinct emission lines.Furthermore,our investigation demonstrates the effective regulation of moirépotential depths through strain engineering,with the potential depths of strained and unstrained regions differing by 91%.By combining both experimental and theoretical approaches,our study elucidates the complex relationship between strain and moirépotential,thereby opening avenues for generating strain-induced moiréexciton single-photon sources.

关键词： moirésuperlattices strain engineering moiréexcitons moirépotential

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Electronic transport evolution across the successive structural transitions in Ni_(50-x)Fe_xTi_(50) shape memory alloys

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Chinese physics B 2024年第7期33卷 529-536页

作者：何萍杨金颖任秋飒王彬彬吴光恒刘恩克 Beijing National laboratory for condensed matter physics Institute of PhysicsChinese Academy of SciencesBeijing 100190China School of Physical Sciences University of Chinese Academy of SciencesBeijing 100049China School of Materials Science and Engineering University of Science and Technology of BeijingBeijing 100083China

TiNi-based shape memory alloys have been extensively investigated due to their significant applications,but a comprehensive understanding of the evolution of electronic structure and electrical transport in a system with martensitic transformations(MT) is still lacking.In this work,we focused on the electronic transport behavior of three phases in Ni_(50-x)Fe_xTi_(50)across the MT.A phase diagram of Ni_(50-x)Fe_xTi_(50) was established based on x-ray diffraction,calorimetric,magnetic,and electrical measurements.To reveal the driving force of MT,phonon softening was revealed using first-principles calculations.Notably,the transverse and longitudinal transport behavior changed significantly across the phase transition,which can be attributed to the reconstruction of electronic structures.This work promotes the understanding of phase transitions and demonstrates the sensitivity of electron transport to phase transition.

关键词： martensitic transformation electronic behavior transport properties first-principles calculations

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