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Quantized anomalous Hall resistivity achieved in molecular beam epitaxy-grown Mn Bi2Te4 thin films

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National science Review 2024年第2期11卷 24-32页

作者： Yunhe Bai Yuanzhao Li Jianli Luan Ruixuan Liu Wenyu Song Yang Chen Peng-Fei Ji Qinghua Zhang Fanqi Meng Bingbing Tong Lin Li Yuying Jiang Zongwei Gao Lin Gu Jinsong Zhang Yayu Wang Qi-Kun Xue Ke He Yang Feng Xiao Feng State Key laboratory of Low Dimensional Quantum physics Department of Physics Tsinghua University Institute of physics Chinese Academy of Sciences School of Materials science and Engineering Tsinghua University Beijing Academy of Quantum Information sciences Frontier science Center for Quantum Information Hefei National laboratory Southern University of science and technology

The intrinsic magnetic topological insulator MnBi2Te4provides a feasible pathway to the high-temperature quantum anomalous Hall（QAH） effect as well as various novel topological quantum phases. Although quantized transport properties have been observed in exfoliated MnBi2Te4thin flakes, it remains a big challenge to achieve molecular beam epitaxy（MBE）-grown MnBi2Te4thin films even close to the quantized regime. In this work, we report the realization of quantized anomalous Hall resistivity in MBE-grown MnBi2Te4thin films with the chemical potential tuned by both controlled in situ oxygen exposure and top gating. We find that elongated post-annealing obviously elevates the temperature to achieve quantization of the Hall resistivity, but also increases the residual longitudinal resistivity, indicating a picture of high-quality QAH puddles weakly coupled by tunnel barriers. These results help to clarify the puzzles in previous experimental studies on MnBi2Te4and to find a way out of the big difficulty in obtaining MnBi2Te4samples showing quantized transport properties.

关键词： intrinsic magnetic topological insulator quantized anomalous Hall resistivity molecular beam epitaxy quantized transport property

Single thiolate replacement of metal nanoclusters

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science China Chemistry 2024年第2期67卷 523-528页

作者： Ambreen Ambreen Yue Zhou Wanmiao Gu Qing You Liang Fang Guoqing Bian Nan Yan Nan Xia Zhikun Wu Key laboratory of Materials physics Anhui Key Laboratory of Nanomaterials and NanotechnologyInstitute of Solid State PhysicsHefei Institutes of Physical Science(HFIPS)Chinese Academy of SciencesHefei230031China University of science and technology of China Hefei230601China Institute of Physical science and Information technology Anhui UniversityHefei230601China

Surface thiolates play important roles in evincing the structures and properties of thiolated metal nanoclusters—one type of recently emerging inorganic-organic hybrids,and thus the thiolate substitution,especially single thiolate substitution,is highly desirable for subtly tailoring the structures and properties of metal ***,such a single-thiolate substituting is challenging,and its influence on the metal-metal and metal-sulfur bonds remains mysterious due to the absence of the singlethiolate-substituted ***,we developed a combined method,concurrently synthesized the single-thiolate-substituted nanocluster and its parent nanocluster,and successfully resolved their structures by single crystal X-ray crystallography,which reveals that the single thiolate substitute has an obvious influence on the metal-metal and metal-sulfur bond lengths although it has no effect on the absorption ***,the metal-metal and metal-sulfur bonds show various thermal extensibility and even the negative thermal expansion phenomena of the Au–S bond were observed in the single-thiolate-substituted *** bond length-related stability was also ***,this study highlights a novel synthesis method and offers novel structural insights and an in-depth structure-property correlation of thiolated metal nanoclusters.

关键词： metal nanoclusters single thiolate replacement thermal expansion stability intercluster interaction

In situ Simulation of Thermal Reality

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Research 2024年第2期2023卷 685-690页

作者： Peng Jin Jinrong Liu Fubao Yang Fabio Marchesoni Jian-Hua Jiang Jiping Huang Department of physics State Key Laboratory of Surface Physicsand Key Laboratory of Micro and Nano Photonic Structures(MOE)Fudan UniversityShanghai 200438China Center for Phononics and Thermal Energy science Shanghai Key Laboratory of Special Artificial Microstructure Materials and TechnologySchool of Physics Science and EngineeringTongji UniversityShanghai 200092China Department of physics University of CamerinoCamerino 62032Italy Suzhou Institute for Advanced Research University of Science and Technology of ChinaSuzhou 215123China

Simulated reality encompasses virtual,augmented,and mixed realities梕ach characterized by different degrees of truthfulness in the visual perception:"all false","coexistence of true and false,"and"difficult distinction between true and false,"*** all these technologies,however,the temperature rendering of virtual objects is still an unsolved ***,the lack of thermal tactile functions substantially reduces the quality of the user's real-experience *** address this challenge,we propose theoretically and realize experimentally a technological platform for the in situ simulation of thermal *** this purpose,we design a thermal metadevice consisting of a reconfigurable array of radiating units,capable of generating the thermal image of any virtual object,and thus rendering it in situ together with its thermal *** is a substantial technological advance,which opens up new possibilities for simulated reality and its applications to human activities.

关键词： false rendering signature

Generation of visible Raman operation laser by a fiber electro-optical modulator feedback loop

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Chinese Optics Letters 2024年第2期22卷 180-185页

作者：李睿睿叶蔚然陈一龙陈树谦亓文昊崔金明黄运锋李传锋郭光灿 CAS Key laboratory of Quantum Information University of Science and Technology of ChinaHefei 230026China CAS Center for Excellence in Quantum Information and Quantum physics University of Science and Technology of ChinaHefei 230026China Hefei National laboratory University of Science and Technology of ChinaHefei 230088China

Phase-coherent multi-tone lasers play a critical role in atomic,molecular,and optical *** them,the Raman opeartion laser for manipulating atomic hyperfine qubits requires gigahertz bandwidth and low phase noise to retain long-term *** operation lasers generated by directly modulated and frequency-multipled infrared lasers are compact and stable but lack feedback control to actively suppress the phase noise,which limits their performance in practical *** this work,we employ a fiber electro-optical modulator driven by a voltage-controlled oscillator(VCO)to modulate a monochromatic laser and employ a second-harmonic generation process to convert it to the visible domain,where the beat note of the Raman operation laser is stabilized by controlling the output frequency of VCO with a digital phase-locked loop(PLL).The low-frequency phase noise is effectively suppressed compared to the scheme without active feedback and it reaches-80 d Bc/Hz@5 k Hz with a 20 k Hz loop ***,this compact and robust scheme effectively reduces the system's complexity and cost,which is promising for extensive application in atomic,molecular,and optical physics.

关键词： phase-coherent laser quantum information trapped ion stimulated Raman transition phase-locked loop

Origin of the near-room temperature resistance transition in lutetium with H2/N2 gas mixture under high pressure

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National science Review 2024年第7期11卷 26-32页

作者： Di Peng Qiaoshi Zeng Fujun Lan Zhenfang Xing Zhidan Zeng Xiaoxing Ke Yang Ding Ho-kwang Mao Key laboratory of Materials physics Institute of Solid State Physics Hefei Institutes of Physical Science(HFIPS)Chinese Academy of Sciences science Island Branch Graduate School of University of Science and Technology of China Center for High Pressure science and technology Advanced Research Shanghai Key laboratory of Material Frontiers Research in Extreme Environments(MFree) Shanghai Advanced Research in Physical Sciences(SHARPS) State Key laboratory of Superhard Materials Institute of PhysicsJilin University College of Materials science&Engineering Beijing University of Technology

The recent report of room-temperature superconductivity at near-ambient pressure in nitrogen-doped lutetium hydride（Lu-H-N） by Dasenbrock-Gammon et al. [Nature 615, 244–250（2023）] has attracted tremendous attention due to its anticipated great impact on technology. However, the results could not be independently reproduced by other groups worldwide in follow-up studies, which elicited intense controversy. Here, we develop a reliable experimental protocol to minimize the extensively concerned extrinsic influences on the sample by starting the reaction from pure lutetium loaded with an H2/N2gas mixture in a diamond anvil cell under different pressures and temperatures and simultaneously monitoring the entire chemical reaction process using in situ four-probe resistance measurements. Therefore, we could repeatedly reproduce the near-room temperature upsurge of electrical resistance at a relatively early stage of the chemical reaction. However, the mechanism is suggested to be a metal-to-semiconductor/insulator transition associated with the structural modulation in the non-stoichiometric Lu-H-N, rather than superconductivity.

关键词： superconductivity high pressure lutetium hydride resistance transition metal-to-semiconductor/insulator transition

Preparation of panda-shaped photonic crystal fibers with and without silver wire

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Chinese Optics Letters 2024年第5期22卷 29-35页

作者：娄俊波杨永辉曲强李曙光 School of Electronic and Information Engineering University of Science and Technology LiaoningAnshan 114051China State Key laboratory of Metastable Materials science&technology and Key laboratory for Microstructural Material physics of Hebei Province School of ScienceYanshan UniversityQinhuangdao 066004China

A method of preparing panda-shaped photonic crystal fibers(PCFs)based on secondary drawing technology is proposed in this *** secondary drawing can not only reduce fiber diameter but also reduce core size by adding a glass ***-filled and non-silver-filled panda PCFs are *** two ends of silver-filled panda PCF are connected with a broadband light source and a spectrometer,respectively,and the surface plasmon resonance phenomenon is *** secondary drawing technology provides a meaningful reference for the preparation of PCF in the future,and the prepared silver-filled panda PCF can be prepared into an optical fiber filter.

关键词： photonic crystal fiber secondary drawing technology air pressure regulation surface plasmon resonance

New results on the dynamics of critical collapse

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Chinese physics C 2024年第6期48卷 204-210页

作者：郭俊起胡宇王盼盼邵成刚 School of physics and technology University of JinanJinan 250022China MOE Key laboratory of Fundamental Physical Quantities Measurement Hubei Key Laboratory of Gravitation and Quantum PhysicsPGMFand School of PhysicsHuazhong University of Science and TechnologyWuhan 430074China

We study the dynamics of the critical collapse of a spherically symmetric scalar *** analytic expressions for the metric functions and matter field in the large-radius region are *** the central region,owing to the bo... 详细信息

关键词： critical collapse spacetime singularities numerical relativity

A novel graph oversampling framework for node classification in class-imbalanced graphs

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science China(Information sciences) 2024年第6期67卷 214-229页

作者： Riting XIA Chunxu ZHANG Yan ZHANG Xueyan LIU Bo YANG Key laboratory of Symbolic computation and Knowledge Engineering of Ministry of Education Jilin University College of Artificial Intelligence Jilin University College of Computer science and technology Jilin University College of Communication Engineering Jilin University

Graph neural network(GNN) is a promising method to analyze graphs. Most existing GNNs adopt the class-balanced assumption, which cannot deal with class-imbalanced graphs well. The oversampling technique is effective in alleviating class-imbalanced problems. However, most graph oversampling methods generate synthetic minority nodes and their edges after applying GNNs. They ignore the problem that the representations of the original and synthetic minority nodes are dominated by majority nodes caused by aggregating neighbor information through GNN before oversampling. In this paper, we propose a novel graph oversampling framework, termed distribution alignment-based oversampling for node classification in classimbalanced graphs(named Graph-DAO). Our framework generates synthetic minority nodes before GNN to avoid the dominance of majority nodes caused by message passing in GNNs. Additionally, we introduce a distribution alignment method based on the sum-product network to learn more information about minority nodes. To our best knowledge, it is the first to use the sum-product network to solve the class-imbalanced problem in node classification. A large number of experiments on four real datasets show that our method achieves the optimal results on the node classification task for class-imbalanced graphs.

关键词： graph neural network class-imbalanced graphs sum-product network oversampling node classification

Surface-sensitive electronic structure of kagome superconductor CsV_(3)Sb_(5)

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Chinese physics B 2024年第10期33卷 35-40页

作者： Zhisheng Zhao Jianghao Yao Rui Xu Yuzhe Wang Sen Liao Zhengtai Liu Dawei Shen Shengtao Cui Zhe Sun Yilin Wang Donglai Feng Juan Jiang School of Emerging technology and Department of physics University of Science and Technology of ChinaHefei 230026China Shanghai Synchrotron Radiation Facility Shanghai Advanced Research InstituteChinese Academy of SciencesShanghai 201210China National Synchrotron Radiation laboratory School of Nuclear science and technology and New Cornerstone Science LaboratoryUniversity of Science and Technology of ChinaHefei 230026China

We systematically study the electronic structure of a kagome superconductor CsV_(3)Sb_(5)at different temperatures coveringboth its charge density wave state and normal state with angle-resolved photoemission *** observe thatthe V-shaped band aroundГshows three different behaviors,referred to as a/a',βandγ,mainly at different *** investigations confirm that these bands are all from the same bulk Sb-p_(z)origin,but they are quite sensitiveto the sample surface conditions mainly modulated by ***,the intriguing temperature dependent electronicbehavior of the band nearГis affected by the sample surface condition,rather than intrinsic electronic behavior originatingfrom the phase *** result systematically reveals the confusing electronic structure behavior of the energy bandsaroundГ,facilitating further exploration of the novel properties in this material.

关键词： kagome ARPES charge density wave surface sensitive