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[K2PbI][Ga7Se12]: A New Lead-Containing Nonlinear Optical Material with Moderate Second-Harmonic Generation Response and Large Birefringence

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Crystal Growth and Design 2025年第11期25卷 4057-4063页

作者： Shi, Jinlong Li, Chunxiao Gong, Pifu Yao, Jiyong Beijing Center for Crystal Research and Development Technical Institute of Physics and Chemistry Chinese Academy of Sciences Beijing100190 China Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of Sciences Beijing100049 China Functional Crystals Lab Technical Institute of Physics and Chemistry Chinese Academy of Sciences Beijing100190 China School of Future Technology University of Chinese Academy of Sciences Beijing100049 China University of Chinese Academy of Sciences Beijing100049 China

Nonlinear optical (NLO) materials play an important role in modern laser science and technology fields. Developing new NLO materials with comprehensive performance is highly difficult because of the mutual coupling of basic parameters (nonlinear susceptibility and laser damage threshold). Here, through combining Pb2+ ions with lone-pair electrons and GaSe4 tetrahedra and introducing alkali metal atoms or halogen atoms, a new lead-containing nonlinear optical material, namely, [K2PbI][Ga7Se12], was synthesized. It crystallizes in the orthogonal space group Imm2 (No. 44) featuring a three-dimensional framework comprising highly oriented Ga7Se16 clusters and charge-balanced K+, Pb2+, and I- ions. The band gap of the title compound is measured to be 2.0 eV. Powder second-harmonic generation (SHG) measurement suggests that the title compound displays moderate SHG intensity (0.5 × AgGaS2) in the particle size range of 25-50 μm. Theoretical calculations show that [K2PbI][Ga7Se12] exhibits a large birefringence (0.12 at 1064 nm) and a significant nonlinear coefficient (d24 = 29.14 pm/V). © 2025 American Chemical Society.

关键词： Gallium phosphide

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First-principles investigation of the structure, stability, and magnetic properties of the Heusler alloy Fe2MnSn

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Physical Review B 2023年第5期108卷 054431-054431页

作者： Junaid Jami Rohit Pathak N. Venkataramani K. G. Suresh Amrita Bhattacharya AbCMS Lab Department of Metallurgical Engineering and Materials Science Indian Institute of Technology Bombay Mumbai Maharashtra 400076 India Department of Metallurgical Engineering and Materials Science Indian Institute of Technology Bombay Mumbai Maharashtra 400076 India Department of Physics Indian Institute of Technology Bombay Mumbai Maharashtra 400076 India

Considering the vast compositional space of Heusler alloys, first-principles-based calculations are ideally suitable for predicting the ground state structure and tailoring the magnetic properties of these alloys. We perform density-functional-theory-based calculations for step-by-step identification of the most stable phase of Fe2MnSn, taking into account all the different structural phases exhibited for this alloy (viz., cubic L21, cubic XA, tetragonal L21, tetragonal XA, and hexagonal D019), followed by the calculations of magnetic properties. We identify the magnetic ground state of each phase and then the most stable structural phase by taking into account electronic and geometric relaxation, spin polarization, and vibrational free energy contributions. The ferromagnetic configuration of all the phases is found to be energetically the most favorable magnetic state, while the ferromagnetic hexagonal phase is identified to be the stable structural phase of Fe2MnSn, with a sizable magnetization of 6.45µB/f.u. Furthermore, the exchange interactions in the hexagonal phase are calculated using the Liechtenstein approach, and this phase shows a high Curie temperature of 729 K attributed to the strong Fe-Fe exchange coupling. The stable hexagonal phase reveals an in-plane magnetic anisotropy of −1.24 MJ/m3. The large magnetization and high Curie temperature of this phase can make this material suitable for desired magnetic applications. Computational investigations such as this one, in addition to being a cost effective pathway, may provide many valuable insights for the experimental realization and application of a given alloy.

关键词： Electronic structure Magnetic order Ferromagnets Heusler alloy Density functional calculations

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Arbitrary nonequilibrium steady-state construction with a levitated nanoparticle

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Physical Review Research 2023年第3期5卷 033101-033101页

作者： Yu Zheng Lyu-Hang Liu Xiang-Dong Chen Guang-Can Guo Fang-Wen Sun CAS Key Lab of Quantum Information University of Science and Technology of China Hefei 230026 China CAS Center for Excellence in Quantum Information and Quantum Physics University of Science and Technology of China Hefei 230026 China

Nonequilibrium thermodynamics provides a general framework for understanding nonequilibrium processes, particularly in small systems that are typically far from equilibrium and dominated by fluctuations. However, the experimental investigation of nonequilibrium thermodynamics remains challenging due to the lack of approaches to precisely manipulate nonequilibrium states and dynamics. Here, by shaping the effective potential of energy, we propose a general method to construct a nonequilibrium steady state (NESS) with arbitrary energy distribution. Using a well-designed energy-dependent feedback damping, the dynamics of an optically levitated nanoparticle in vacuum is manipulated and driven into a NESS with the desired energy distribution. Based on this approach, a phonon laser state is constructed with an ultra-narrow linewidth of 6.40µHz. Such an arbitrary NESS construction method provides an approach to manipulating the dynamics processes of micromechanical systems and paves the way for the systematic study of nonequilibrium dynamics in interdisciplinary research fields.

关键词： Optomechanics Micromechanical & nanomechanical oscillators Nonequilibrium systems Optical tweezers

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Solution-processed,flexible and broadband photodetector based on CsPbBr_(3)/PbSe quantum dot heterostructures

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Journal of Materials science & technology 2021年第9期68卷 216-226页

作者： Jinming Hu Shengyi Yang Zhenheng Zhang Hailong Li Chandrasekar Perumal Veeramalai Muhammad Sulaman Muhammad Imran Saleem Yi Tang Yurong Jiang Libin Tang Bingsuo Zou Beijing Key Laboratory of Nanophotonics and Ultrafine Optoelectronic Systems School of PhysicsBeijing Institute of TechnologyBeijing100081China Key Laboratory of Advanced Optoelectronic Quantum Design and Measurement.Ministry of Education Beijing Institute of Technology.Beijing100081China Kunming Institute of Physics Kunming650223China Beijing Key Laboratory for Precision Optoelectronic Measurement Instrument and Technology School of Optics and PhotonicsBeijing Institute of TechnologyBeijing100081China MOE Key Lab of New Processing Technology for Nonferrous Metals and Materials and Guangxi Key Lab of Processing for Nonferrous Metals and Featured Materials School of Physical Science and TechnologyGuangxi UniversityNanning530004China

Due to their promising applications in foldable displays,optical communication equipment and environmental monitoring systems,flexible and broadband optoelectronic devices have gained extensive attention in recent ***,a flexible and broadband photodetector based on CsPbBr_(3)/PbSe quantum dot(QD) heterostructures is firstly *** integrated QD heterostructures possess consecutive detection range from ultraviolet(UV) to long-wave length infrared(LW-IR) regions with efficient light absorption and chemical stability,in comparison with the pristine PbSe *** material characterizations reveal the improved exciton dissociation,carrier transport and carrier lifetime of the QD *** photodetector Ag/CsPbBr_(3)/PbSe/Ag demonstrate a high responsivity of 7.17 A/W with a specific detectivity of 8.97 × 10^(12) Jones under 25 μW/cm^(2) 365 nm illumination at 5 ***,it could maintain 91.2 %(or 94.9 %) of its initial performance even after bending for thousands of times(or exposing in ambient air for 4 weeks).More importantly,its re s ponse time is shortened more than three orders of magnitude as that of pristine PbSe QDs-based ***,it provides a feasible and promising method for the next-generation high-performance broadband photodetectors via constructing heterostructures of various QDs.

关键词： Quantum dots Broadband detection Flexible photodetectors Fast photoresponse speed Heterostructures

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钠离子电池——碳中和世界的储能技术

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Engineering 2023年第2期21卷 36-38页

作者：吴凯 Xinwei Dou 张欣欣欧阳楚英 Contemporary Amperex Technology Limited(CATL) Ningde 352100China Fujian Science&Technology Innovation Laboratory for Energy Devices(21C Lab) Ningde 352100China Department of Physics Jiangxi Normal UniversityNanchang 330022China

Wandering on the shore of the Sandu Bay,looking at the blue ocean and the green mountains,a question comes to mind:How can we meet humans’energy demand while minimizing its effect on the environment?In other words,ho... 详细信息

关键词：钠离子电池储能技术碳中和

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Gate-tuned antiferromagnetic MnBi4Te7: A candidate for high-temperature high-Chern-number insulator at zero magnetic field

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Physical Review B 2025年第11期111卷 115420-115420页

作者： Hengning Wang Ding Li Yan Feng Tao Qin Yingze Jia Hongwei Zhang Chuandi Pan Yan Wang Wei Ning Anhui Key Laboratory of Low-Energy Quantum Materials and Devices High Magnetic Field Laboratory HFIPS Chinese Academy of Sciences Hefei Anhui 230031 China University of Science and Technology of China Hefei 230026 China Department of Materials Science & Engineering Hefei National Research Center for Physical Sciences at the Microscale CAS Key Lab of Materials for Energy Conversion Anhui Laboratory of Advanced Photon Science and Technology University of Science and Technology of China Hefei China School of Physics and Optoelectronics Engineering Anhui University Hefei Anhui Province 230601 People's Republic of China Information Materials and Intelligent Sensing Laboratory of Anhui Province Anhui Key Laboratory of Magnetic Functional Materials and Devices Institutes of Physical Science and Information Technology Anhui University Hefei 230601 China Department of Physics Shaanxi University of Science and Technology Xi'an 710021 China

The quantum anomalous Hall insulator is characterized by a quantized Hall resistance plateau of h/(Ce2) with C being the Chern number. Previously, high-Chern-number insulators with C≥2 that intrinsically suppress the energy dissipation in quantized electrical transport have been realized in few-layer MnBi2Te4 nanoflakes under moderate magnetic fields or in Cr-doped topological insulators at extremely low temperatures. It has nevertheless proven elusive to achieve a high-temperature high-Chern-number insulator at zero magnetic field. Here, we demonstrate that the magnetic state in MnBi4Te7 nanoflakes can be consecutively tuned from an antiferromagnetic (AFM) state to an AFM-ferromagnetic (FM) coexistence state, and finally to a robust ferromagnetic (FM) state with large coercivities at temperatures up to 3 K via a protonic gate. This AFM-FM phase transition is well captured by density functional theory simulations that the FM state develops in MnBi4Te7 under hole doping. Notably, we find that the Chern number of FM MnBi4Te7 can be largely tuned not merely by the Zeeman field but also by the sample thickness. Our work demonstrates that gate-tuned MnBi4Te7 nanoflakes hold high potentials for realizing a high-temperature high-Chern-number insulator at zero magnetic field and promising applications in the field of low-energy electronics.

关键词： Ferromagnetism

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Quantum Many-body Scar Models in One Dimensional Spin Chains

arXiv

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arXiv 2024年

作者： Wang, Jia-Wei Zhou, Xiang-Fa Guo, Guang-Can Zhou, Zheng-Wei CAS Key Lab of Quantum Information University of Science and Technology of China Hefei230026 China Synergetic Innovation Center of Quantum Information and Quantum Physics University of Science and Technology of China Hefei230026 China Hefei National Laboratory University of Science and Technology of China Hefei230088 China

The phenomenon of quantum many-body scars has received widespread attention both in theoretical and experimental physics in recent years due to its unique physical properties. In this paper, based on the su(2) algebraic relations, we propose a general method for constructing scar models by combining simple modules. This allows us to investigate many-body scar phenomena in high-spin systems. We numerically verify the thermalization and non-integrability of this model and demonstrate the dynamical properties of the scar states. We also provide a theoretical analysis of the properties of these scar states. For spin-1 case, we find that our 1D chain model reduces to the famous PXP model[C. J. Turner et al. Phys. Rev. B 98, 155134(2018)] under special parameter condition. In addition, due to the continuous tunability of the parameters, our model also enables us to investigate the transitions of QMBS from non-integrable to integrable system. © 2024, CC BY.

关键词： Spin dynamics

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Growth of Mesoscale Ordered Two-Dimensional Hydrogen-Bond Organic Framework with the Observation of Flat Band

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Physical Review Letters 2023年第3期130卷 036203-036203页

作者： Minghu Pan Xin Zhang Yinong Zhou Pengdong Wang Qi Bian Hang Liu Xingyue Wang Xiaoyin Li Aixi Chen Xiaoxu Lei Shaojian Li Zhengwang Cheng Zhibin Shao Haoxuan Ding Jianzhi Gao Fangsen Li Feng Liu School of Physics and Information Technology Shaanxi Normal University Xi’an 710119 China School of Physics Huazhong University of Science and Technology Wuhan 430074 China School of Physics Northwest University Xi’an 710069 China Department of Materials Science and Engineering University of Utah Salt Lake City Utah 84112 USA Vacuum Interconnected Nanotech Workstation Suzhou Institute of Nano-Tech and Nano-Bionics Chinese Academy of Sciences (CAS) Suzhou 215123 China School of Science and Hubei Engineering Technology Research Center of Energy Photoelectric Device and System Hubei University of Technology Wuhan 430068 China School of Physics and Astronomy University of Birmingham Birmingham B15 2TT United Kingdom

Flat bands (FBs), presenting a strongly interacting quantum system, have drawn increasing interest recently. However, experimental growth and synthesis of FB materials have been challenging and have remained elusive for the ideal form of monolayer materials where the FB arises from destructive quantum interference as predicted in 2D lattice models. Here, we report surface growth of a self-assembled monolayer of 2D hydrogen-bond (H-bond) organic frameworks (HOFs) of 1,3,5-tris(4-hydroxyphenyl)benzene (THPB) on Au(111) substrate and the observation of FB. High-resolution scanning tunneling microscopy or spectroscopy shows mesoscale, highly ordered, and uniform THPB HOF domains, while angle-resolved photoemission spectroscopy highlights a FB over the whole Brillouin zone. Density-functional-theory calculations and analyses reveal that the observed topological FB arises from a hidden electronic breathing-kagome lattice without atomically breathing bonds. Our findings demonstrate that self-assembly of HOFs provides a viable approach for synthesis of 2D organic topological materials, paving the way to explore many-body quantum states of topological FBs.

关键词： Growth 2-dimensional systems Angle-resolved photoemission spectroscopy Density functional calculations Scanning tunneling microscopy

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Towards an understanding of stepwise inference in transformers: a synthetic graph navigation model 24

Towards an understanding of stepwise inference in transforme...

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Proceedings of the 41st International Conference on Machine Learning

作者： Mikail Khona Maya Okawa Jan Hula Rahul Ramesh Kento Nishi Robert Dick Ekdeep Singh Lubana Hidenori Tanaka Massachusetts Institute of Technology and NTT Physics and Informatics Lab NTT Physics and Informatics Lab Czech Technical University in Prague and the University of Ostrava University of Pennsylvania and NTT Physics and Informatics Lab Center for Brain Science Harvard University and NTT Physics and Informatics Lab University of Michigan Center for Brain Science Harvard University and University of Michigan NTT Physics and Informatics Lab and Center for Brain Science Harvard University

Stepwise inference protocols, such as scratchpads and chain-of-thought, help language models solve complex problems by decomposing them into a sequence of simpler subproblems. To unravel the underlying mechanisms of stepwise inference we propose to study autoregressive Transformer models on a synthetic task that embodies the multistep nature of problems where stepwise inference is generally most useful. Specifically, we define a graph navigation problem wherein a model is tasked with traversing a path from a start to a goal node on the graph. We find we can empirically reproduce and analyze several phenomena observed at scale: (i) the stepwise inference reasoning gap, the cause of which we find in the structure of the training data; (ii) a diversity-accuracy trade-off in model generations as sampling temperature varies; (iii) a simplicity bias in the model's output; and (iv) compositional generalization and a primacy bias with in-context exemplars. Overall, our work introduces a grounded, synthetic framework for studying stepwise inference and offers mechanistic hypotheses that can lay the foundation for a deeper understanding of this phenomenon.

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Superconductivity in ThMo_2Si_2C with Mo_2C square net

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science China(physics,Mechanics & Astronomy) 2021年第7期64卷 120-125页

作者： ZiChen Liu BaiZhuo Li YuSen Xiao QingChen Duan YanWei Cui YuXue Mei Qian Tao ShuLi Wei ShuGang Tan Qiang Jing Qing Lu YuPing Sun YunYan Liu ShengGui Fu Hao Jiang Zhi Ren ZhuAn Xu Cao Wang GuangHan Cao School of Physics and Optoelectronic Engineering Shandong University of TechnologyZibo255000China Department of Physics Zhejiang Province Key Laboratory of Quantum Technology and DevicesInterdisciplinary Center for Quantum Informationand State Key Lab of Silicon MaterialsZhejiang UniversityHangzhou310027China School of Science Westlake UniversityHangzhou310064China School of Physics and Optoelectronics Xiangtan UniversityXiangtan411105China

We report the superconductivity of a new quaternary compound ThMo_(2)Si_(2)C, synthesized with the arc-melting technique. The compound crystallizes in a tetragonal CeCr_(2)Si_(2)C-type structure with cell parameters of a = 4.2296A and c = 5.3571 A. An interlayer Si–Si covalent bonding is suggested by the atomic distance. The electrical resistivity and magnetic susceptibility measurements indicate a Pauli-paramagnetic metal with dominant electron-electron scattering in the normal-state. Bulk superconductivity at 2.2 K is demonstrated with a dimensionless specific-heat jump of △C/γnT = 0.98. The superconducting parameters of the critical magnetic fields, coherence length, penetration depth, and superconducting energy gap are given.

关键词： superconductivity quaternary compound physical properties

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