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Band structures of strained kagome lattices

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Chinese physics B 2024年第2期33卷 456-463页

作者：徐露婷杨帆 Center for Joint Quantum Studies and department of physics School of ScienceTianjin UniversityTianjin 300354China tianjin key laboratory of low dimensional materials physics and preparing technology Department of PhysicsTianjin UniversityTianjin 300354China

materials with kagome lattices have attracted significant research attention due to their nontrivial features in energy *** theoretically investigate the evolution of electronic band structures of kagome lattices in response to uniaxial strain using both a tight-binding model and an antidot model based on a periodic muffin-tin *** is found that the Dirac points move with applied ***,the flat band of unstrained kagome lattices is found to develop into a highly anisotropic shape under a stretching strain along y direction,forming a partially flat band with a region dispersionless along ky direction while dispersive along kx *** results shed light on the possibility of engineering the electronic band structures of kagome materials by mechanical strain.

关键词： kagome lattice strain band structure engineering

D-band center coordination modulated enzyme-like activity in Fe-Cu dual-metal single-atom nanozymes

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Nano Research 2024年第7期17卷 5872-5883页

作者： Ling Liu Shaofang Zhang Guo Li Yadong Zhe Jiamin Liu Xinxu Zhang Jiahao Wei Xin Sun Yonghui Li Xiao-Dong Zhang tianjin key laboratory of Brain Science and Neural Engineering Academy of Medical Engineering and Translational MedicineTianjin UniversityTianjin 300072China department of physics and tianjin key laboratory of low dimensional materials physics and preparing technology School of SciencesTianjin UniversityTianjin 300350China

After explorations in a diversity of single-atom nanozymes(SAzymes),developing dual-centered SAzymes becomes a promising approach for superior catalytic *** confusing mechanisms including atomic coordination,spatial configuration,and metal–metal atom interaction hinder the development and design of ***,a dual-centered Fe-Cu-N_(x)SAzyme exhibits excellent peroxidase(POD)-and catalase(CAT)-like activities with d-band center(ε_(d))coordination of Fe and Cu in multiple reaction stages,which plays a critical role in the adsorption of H_(2)O_(2)molecule and H_(2)O and O_(2)***,the dband center coordination,which can be represented byε_(d)(Fe)–ε_(d)(Cu)shifts,leads to the competition between one-side and bilateral adsorption,which determines the favorable reaction path with lower energy *** on experimental statistics,simulated formation energies,and reaction barriers,3 configurations,Fe-Cu-N6-I,Fe-Cu-N_(8)-II,and Fe-Cu-N_(8)-III,are modeled and ***,configuration-dependent catalytic selectivity and the competition between one-side and bilateral adsorption can be unveiled by d-band center coordination paradigm *** simulations suggest that the unsymmetrical charge distribution over the three Fe-Cu configurations could tune the adsorption strength compared with the counterparts FeN_(4)and CuN_(4).The present work provides a potential route for optimizing enzyme-like catalysis by designing the dual-or even triple-metal SAzymes,which demonstrates the large space to modulate the metal atomic configuration and interaction.

关键词： single-atom catalysis Fe-Cu dual-metal d-band center coordination enzyme mimicking competitive adsorption mechanisms

On-chip terahertz orbital angular momentum demultiplexer

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Photonics Research 2024年第5期12卷 1044-1054页

作者： XIAOHAN JIANG WANYING LIU QUAN XU YUANHAO LANG YIKAI FU FAN HUANG HAITAO DAI YANFENG LI XUEQIAN ZHANG JIANQIANG GU JIAGUANG HAN WEILI ZHANG Center for Terahertz Waves College of Precision Instrument and Optoelectronics Engineeringand Key Laboratory of Optoelectronics Information and Technology(Ministry of Education)Tianjin UniversityTianjin 300072China tianjin key laboratory of low dimensional materials physics and preparing technology School of ScienceTianjin UniversityTianjin 300072China Guangxi key laboratory of Optoelectronic Information Processing School of Optoelectronic EngineeringGuilin University of Electronic TechnologyGuilin 541004China School of Electrical and Computer Engineering Oklahoma State UniversityStillwaterOklahoma 74078USA

The terahertz regime is widely recognized as a fundamental domain with significant potential to address the demands of next-generation wireless *** parallel,mode division multiplexing based on orbital angular momentum(OAM)shows promise in enhancing bandwidth utilization,thereby expanding the overall communication channel *** this study,we present both theoretical and experimental demonstrations of an on-chip terahertz OAM *** device effectively couples and steers seven incident terahertz vortex beams into distinct high-quality focusing surface plasmonic beams,and the focusing directions can be arbitrarily *** proposed design strategy integrates space-to-chip mode conversion,OAM recognition,and on-chip routing in a compact space with subwavelength thickness,exhibiting versatility and superior performance.

关键词： demultiplexer momentum angular

Significantly enhanced superconductivity in monolayer FeSe films on SrTiO3（001） via metallic δ-doping

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National Science Review 2024年第3期11卷 119-127页

作者： Xiaotong Jiao Wenfeng Dong Mingxia Shi Heng Wang Cui Ding Zhongxu Wei Guanming Gong Yanan Li Yuanzhao Li Binjie Zuo Jian Wang Ding Zhang Minghu Pan Lili Wang Qi-Kun Xue State key laboratory of low-dimensional Quantum physics Department of Physics Tsinghua University School of physics&Information technology Shaanxi Normal University Beijing Academy of Quantum Information Sciences department of physics Southern University of Science and Technology International Center for Quantum materials School of Physics Peking University department of physics The Pennsylvania State University Collaborative Innovation Center of Quantum Matter Hefei National laboratory

Superconductivity transition temperature（Tc） marks the inception of a macroscopic quantum phase-coherent paired state in fermionic systems. For 2D superconductivity, the paired electrons condense into a coherent superfluid state at Tc, which is usually lower than the pairing temperature, between which intrinsic physics including Berezinskii–Kosterlitz–Thouless transition and pseudogap state are hotly debated. In the case of monolayer FeSe superconducting films on SrTiO3（001）, although the pairing temperature（Tp） is revealed to be 65–83 K by using spectroscopy characterization, the measured zero-resistance temperature（Tc0） is limited to 20 K. Here, we report significantly enhanced superconductivity in monolayer FeSe films by δ-doping of Eu or Al on SrTiO3（001） surface, in which Tc0is enhanced by 12 K with a narrowed transition width ΔTc～8 K, compared with non-doped samples. Using scanning tunneling microscopy/spectroscopy measurements, we demonstrate lowered work function of the δ-doped SrTiO3（001） surface and enlarged superconducting gaps in the monolayer FeSe with improved morphology/electronic homogeneity. Our work provides a practical route to enhance 2D superconductivity by using interface engineering.

关键词： monolayer FeSe interface superconductivity δ-doping zero-resistance temperature superconductivity transition temperature

Enhanced measurement precision with continuous interrogation during dynamical decoupling

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Chinese physics B 2024年第3期33卷 88-94页

作者：张军杜鹏敬雷徐鹏尤力张文献 key laboratory of Artificial Micro- and Nano-structures of Ministry of Education and School of Physics and TechnologyWuhan UniversityWuhan 430072China State key laboratory of low-dimensional Quantum physics Department of PhysicsTsinghua UniversityBeijing 100084China Wuhan Institute of Quantum technology Wuhan 430206China

Dynamical decoupling(DD)is normally ineffective when applied to DC *** its straightforward implementation,DD nulls out DC signal as well while suppressing *** work proposes a phase relay method that is capable of continuously interrogating the DC signal over many DD *** illustrate its efficacy when applied to the measurement of a weak DC magnetic field with an atomic spinor Bose-Einstein *** approaching standard quantum limit or Heisenberg limit are potentially realizable for a coherent spin state or a squeezed spin state of 10000 atoms,respectively,while ambient laboratory level noise is suppressed by *** work offers a practical approach to mitigate the limitations of DD to DC measurement and would find other applications for resorting coherence in quantum sensing and quantum information processing research.

关键词： quantum sensing continuous interrogation quantum magnetometer dynamical decoupling Heisenberg limit

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

ARPES investigation of the electronic structure and its evolution in magnetic topological insulator MnBi2+2nTe4+3n family

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National Science Review 2024年第2期11卷 81-93页

作者： Runzhe Xu Lixuan Xu Zhongkai Liu Lexian Yang Yulin Chen State key laboratory of low dimensional Quantum physics Department of PhysicsTsinghua University School of Physical Science and technology Shanghai Tech University and CAS-Shanghai Science Research Center Shanghai Tech laboratory for Topological physics Frontier Science Center for Quantum Information Collaborative Innovation Center of Quantum Matter department of physics Clarendon LaboratoryUniversity of Oxford

In the past 5 years,there has been significant research interest in the intrinsic magnetic topological insulator family compounds MnBi2+2nTe4+3n（where n=0,1,2…）.In particular,exfoliated thin films of MnBi2Te4have led to numerous experimental breakthroughs,such as the quantum anomalous Hall effect,axion insulator phase and high-Chern number quantum Hall effect without Landau ***,despite extensive efforts,the energy gap of the topological surface states due to exchange magnetic coupling,which is a key feature of the characteristic band structure of the system,remains experimentally *** electronic structure measured by using angle-resolved photoemission （ARPES） shows significant deviation from ab initio prediction and scanning tunneling spectroscopy measurements,making it challenging to understand the transport results based on the electronic *** paper reviews the measurements of the band structure of MnBi2+2nTe4+3nmagnetic topological insulators using ARPES,focusing on the evolution of their electronic structures with temperature,surface and bulk doping and film *** aim of the review is to construct a unified picture of the electronic structure of MnBi2+2nTe4+3ncompounds and explore possible control of their topological properties.

关键词： magnetic topological insulator MnBi2Te4 electronic structure angle-resolved photoemission spectroscopy

Parameter estimation in n-dimensional massless scalar field

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Chinese physics B 2024年第3期33卷 231-237页

作者：杨颖荆继良 Hunan Provincial key laboratory of Intelligent Sensors and Advanced Sensor materials School of Physics and ElectronicsHunan University of Science and TechnologyXiangtan 411201China department of physics Key Laboratory of Low Dimensional Quantum Structures and Quantum Control of Ministry of Educationand Synergetic Innovation Center for Quantum Effects and ApplicationsHunan Normal UniversityChangsha 410081Chin

Quantum Fisher information(QFI)associated with local metrology has been used to parameter estimation in open quantum *** this work,we calculated the QFI for a moving Unruh-DeWitt detector coupled with massless scalar fields in n-dimensional spacetime,and analyzed the behavior of QFI with various parameters,such as the dimension of spacetime,evolution time,and Unruh *** discovered that the QFI of state parameter decreases monotonically from 1 to 0 over ***,we noted that the QFI for small evolution times is several orders of magnitude higher than the QFI for long evolution *** also found that the value of QFI decreases at first and then stabilizes as the Unruh temperature *** was observed that the QFI depends on initial state parameterθ,and Fθis the maximum forθ=0 orθ=π,Fφis the maximum forθ=π/*** also obtain that the maximum value of QFI for state parameters varies for different spacetime dimensions with the same evolution time.

关键词： quantum Fisher information parameter estimation open quantum systems

Two-dimensional Conductive Metal-Organic Framework Reinforced Spinterface in Organic Spin Valves

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CCS Chemistry 2024年第1期6卷 208-217页

作者： Xiaoyu Song Chao Jin Hongliang Chen Shuaishuai Ding Zhongyi Liu Yang Li Xiaoli Yan Wenbo Mi Long Chen Wenping Hu department of Chemistry Tianjin Key Laboratory of Molecular Optoelectronic ScienceTianjin UniversityTianjin 300072 School of Chemistry and Chemical Engineering Yantai UniverisityYantaiShandong 264005 tianjin key laboratory of low dimensional materials physics and Processing technology School of ScienceTianjin UniversityTianjin 300072 State key laboratory of Supramolecular Structure and materials College of ChemistryJilin UniversityChangchunJilin 130012

Interface engineering in device fabrication is a significant but complicated *** great successes have been achieved by conventional physical in situ or ex situ methods,it still suffers from complicated *** this work,we present a facile method for fabricating phthalocyanine(Pc)-based two-dimensional conductive metal–organic framework(MOF)*** on PcM-Cu(M=Ni,Cu,H_(2))MOF films,spin valves with a vertical configuration of La_(0.67)Sr_(0.33)MnO_(3)/PcM-Cu MOFs/Co were constructed successfully,and exhibited notably high negative magnetoresistance(MR)up to -22% at 50 *** penetrated Co atoms coordinated with the dehydrogenated hydroxy groups in the MOFs resulting in an antiferromagnetic layer of the PcM-Cu-Co hybrid ***,a significant exchange bias effect was demonstrated at the PcM-Cu MOF/Co interface,beneficial for the MR ***,our present study provides new insights into developing high-performance organic spin valves via de novo molecular design.

关键词： two-dimensional conductive metal-organic framework two-dimensional polymer phthalocyanine spintronics organic spin valve