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Coexistence of Dirac and Weyl points in non-centrosymmetric semimetal NbIrTe_(4)

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Chinese Physics B 2024年第4期33卷 146-151页

作者：刘清馨付阳丁鹏飞马欢郭朋杰雷和畅王善才 Department of Physics Key Laboratory of Quantum State Construction and ManipulationRenmin University of ChinaBeijing 100872China Beijing Key laboratory of Opto-Electronic Functional Materials&micro-nano devices Renmin University of ChinaBeijing 100872China

Using angle-resolved photoemission spectroscopy and density functional theory calculations methods,we investigate the electronic structures and topological properties of ternary tellurides NbIrTe_(4),a candidate for type-II Weyl *** demonstrate the presence of several Fermi arcs connecting their corresponding Weyl points on both termination surfaces of the topological *** analysis reveals the existence of Dirac points,in addition to Weyl points,giving both theoretical and experimental evidences of the coexistence of Dirac and Weyl points in a single *** findings not only confirm NbIrTe_(4) as a unique topological semimetal but also open avenues for exploring novel electronic devices based on its coexisting Dirac and Weyl fermions.

关键词： Fermi arc Weyl point Dirac point angle-resolved photoemission spectroscopy

Semiclassical approach to spin dynamics of a ferromagnetic S = 1 chain

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Chinese Physics B 2024年第6期33卷 95-100页

作者：李承晨崔祎于伟强俞榕 Department of Physics and Beijing Key laboratory of Opto-electronic Functional Materials and micro-nano devices Renmin University of ChinaBeijing 100872China Key laboratory of quantum State Construction and Manipulation(Ministry of Education) Renmin University of ChinaBeijing 100872China

Motivated by recent experimental progress on the quasi-one-dimensional quantum magnet Ni Nb2O6, we study the spin dynamics of an S = 1 ferromagnetic Heisenberg chain with single-ion anisotropy by using a semiclassical molecular dynamics approach. This system undergoes a quantum phase transition from a ferromagnetic to a paramagnetic state under a transverse magnetic field, and the magnetic response reflecting this transition is well described by our semiclassical *** show that at low temperature the transverse component of the dynamical structure factor depicts clearly the magnon dispersion, and the longitudinal component exhibits two continua associated with single-and two-magnon excitations,respectively. These spin excitation spectra show interesting temperature dependence as effects of magnon interactions. Our findings shed light on the experimental detection of spin excitations in a large class of quasi-one-dimensional magnets.

关键词： one-dimensional ferromagnetism spin dynamics magnon excitation molecular dynamics

Relationship between disorder,magnetism and band topology in Mn(Sb_(1-x)Bi_(x))_(2)Te_(4) single crystals

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Chinese Physics B 2024年第6期33卷 102-107页

作者：席明雷和畅 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

We investigate the evolution of magnetic properties as well as the content and distribution of Mn for Mn(Sb_(1-x)Bi_(x))_(2)Te_(4) single crystals grown by large-temperature-gradient chemical vapor transport *** is found that the ferromagnetic MnSb_(2)Te_(4) changes to antiferromagnetism with Bi doping when x≥*** analysis implies that the occupations of Mn ions at Sb/Bi site Mn_(Sb/Bi) and Mn site Mn_(Mn) have a strong influence on the magnetic ground states of these *** the decrease of Mn_(Mn) increase of Mn_(Sb/Bi),the system will favor the ferromagnetic ground *** addition,the rapid decrease of T_(C/N) with increasing Bi content when x ≤0.25 and the insensitivity of T_(N) to x when x> 0.25 suggest that the main magnetic interaction may change from the Ruderman-Kittel-Kasuya-Yosida type at low Bi doping region to the van-Vleck type in high Bi doped samples.

关键词： magnetic topological insulator magnetic properties antisite defects chemical vapor transport

Experimentally Ruling Out Joint Reality Based on Locality with Device-Independent Steering

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Chinese Physics Letters 2024年第1期41卷 1-5页

作者： Shuaining Zhang Xiang Zhang Zhiyue Zheng Wei Zhang Beijing Academy of quantum Information Sciences Beijing 100193China Department of Physics and Beijing Key laboratory of Opto-electronic Functional Materials and micro-nano devices Renmin University of ChinaBeijing 100872China Key laboratory of quantum State Construction and Manipulation(Ministry of Education) Renmin University of ChinaBeijing 100872China

As an essential concept to understand the world,whether the real values(or physical realities)of observables are suitable to physical systems beyond the classic has been debated for many *** standard nogo results based on Bell inequalities have ruled out the joint reality of incompatible quantum observables,the possibility of giving simple yet strong arguments to rule out joint reality in any physical system(not necessarily quantum)with weaker assumptions and less observables has been explored and proposed ***,we perform a device-independent experiment on a two-qubit superconducting system to show that the joint reality of two observables is incompatible with locality under the weaker assumption of the reality of observables in a single space-time region(or single qubit).Our results clearly show the violation of certain inequalities derived from both linear and nonlinear *** addition,we study the robustness of the linear and nonlinear criterion against the effect of systematic *** demonstration opens up the possibility of delineating classical and non-classical boundaries with simpler nontrivial quantum system.

关键词： observable quantum system

Progress on the antiferromagnetic topological insulator MnBi2Te4

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National Science Review 2024年第2期11卷 33-49页

作者： Shuai Li Tianyu Liu Chang Liu Yayu Wang Hai-Zhou Lu X.C.Xie Department of Physics Harbin Institute of Technology Shenzhen Institute for quantum Science and Engineering and Department of Physics Southern University of Science and Technology(SUSTech) quantum Science Center of Guangdong-Hong Kong-Macao Greater Bay Area(Guangdong) Shenzhen Key laboratory of quantum Science and Engineering International quantum Academy Beijing Academy of quantum Information Sciences Beijing Key laboratory of Optoelectronic Functional Materials&micro-nano devices Department of Physics Renmin University of China State Key laboratory of Low Dimensional quantum Physics Department of PhysicsTsinghua University Frontier Science Center for quantum Information Hefei National laboratory International Center for quantum Materials School of Physics Peking University Institute for nanoelectronic devices and quantum Computing Fudan University

Topological materials, which feature robust surface and/or edge states, have now been a research focus in condensed maTher physics. They represent a new class of materials exhibiting nontrivial topological phases,and provide a platform for exploring exotic transport phenomena, such as the quantum anomalous Hall effect and the quantum spin Hall effect. Recently, magnetic topological materials have attracted considerable interests due to the possibility to study the interplay between topological and magnetic *** particular, the quantum anomalous Hall and axion insulator phases can be realized in topological insulators with magnetic order. MnBi2Te4, as the first intrinsic antiferromagnetic topological insulator discovered, allows the examination of existing theoretical predictions; it has been extensively studied, and many new discoveries have been made. Here we review the progress made on MnBi2Te4from both experimental and theoretical aspects. The bulk crystal and magnetic structures are surveyed first, followed by a review of theoretical calculations and experimental probes on the band structure and surface states, and a discussion of various exotic phases that can be realized in MnBi2Te4. The properties of MnBi2Te4thin films and the corresponding transport studies are then reviewed, with an emphasis on the edge state transport. Possible future research directions in this field are also discussed.

关键词： MnBi2Te4 magnetic topological insulator antiferromagnetic quantum anomalous Hall effect axion insulator

Structure and superconducting properties of Ru_(1-x)Mo_(x)(x=0.1-0.9)alloys

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Chinese Physics B 2024年第4期33卷 173-179页

作者：付阳龚春生涂志俊田尚杰王守国雷和畅 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 Renmin University of ChinaBeijing 100872China Anhui Key laboratory of Magnetic Functional Materials and devices School of Materials Science and EngineeringAnhui UniversityHefei 230601China

We report the detailed crystal structures and physical properties of Ru_(1-x)Mo_(x)alloys in the solid solution range of x=*** characterizations indicate that the crystal structure changes from the hcp-Mg-type,toβ-CrFe-type,and then *** measurements of physical properties show that the Ru_(1-x)Mo_(x)samples with x≥0.2are superconductors and the superconducting transition temperature T_c as a function of Mo content exhibits a dome-like behavior.

关键词： superconductivity alloy crystal structures Ru_(1-x)Mo_(x)

Optimal parameter space for stabilizing the ferroelectric phase of Hf_(0.5)Zr_(0.5)O_(2) thin films under strain and electric fields

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Chinese Physics B 2024年第7期33卷 509-517页

作者：王侣锦王聪周霖蔚周谐宇潘宇浩吴幸季威 Beijing Key laboratory of Optoelectronic Functional Materials&micro-nano devices Department of PhysicsRenmin University of ChinaBeijing 100872China Key laboratory of quantum State Construction and Manipulation(Ministry of Education) Renmin University of ChinaBeijing 100872China In Situ devices Center School of Integrated CircuitsEast China Normal UniversityShanghai 200241China

Hafnia-based ferroelectric materials, like Hf_(0.5)Zr_(0.5)O_(2)(HZO), have received tremendous attention owing to their potentials for building ultra-thin ferroelectric devices. The orthorhombic(O)-phase of HZO is ferroelectric but metastable in its bulk form under ambient conditions, which poses a considerable challenge to maintaining the operation performance of HZO-based ferroelectric devices. Here, we theoretically addressed this issue that provides parameter spaces for stabilizing the O-phase of HZO thin-films under various conditions. Three mechanisms were found to be capable of lowering the relative energy of the O-phase, namely, more significant surface-bulk portion of(111) surfaces, compressive c-axis strain,and positive electric fields. Considering these mechanisms, we plotted two ternary phase diagrams for HZO thin-films where the strain was applied along the in-plane uniaxial and biaxial, respectively. These diagrams indicate the O-phase could be stabilized by solely shrinking the film-thickness below 12.26 nm, ascribed to its lower surface energies. All these results shed considerable light on designing more robust and higher-performance ferroelectric devices.

关键词： Hf_(0.5)Zr_(0.5)O_(2) orthorhombic phase ferroelectric films phase stability thickness-dependent ternary phase diagrams

Diffractive neural networks with improved expressive power for gray-scale image classification

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Photonics Research 2024年第6期12卷 1159-1166页

作者： MINJIA ZHENG WENZHE LIU LEI SHI JIAN ZI State Key laboratory of Surface Physics Key Laboratory of Micro-and Nano-Photonic Structures(Ministry of Education)and Department of PhysicsFudan UniversityShanghai 200433China Institute for nanoelectronic devices and quantum Computing Fudan UniversityShanghai 200433China Collaborative Innovation Center of Advanced microstructures Nanjing UniversityNanjing 210093China Shanghai Research Center for quantum Sciences Shanghai 210315China

In order to harness diffractive neural networks(DNNs)for tasks that better align with real-world computer vision requirements,the incorporation of gray scale is ***,DNNs are not powerful enough to accomplish gray-scale image processing tasks due to limitations in their expressive *** our work,we elucidate the relationship between the improvement in the expressive power of DNNs and the increase in the number of phase modulation layers,as well as the optimization of the Fresnel number,which can describe the diffraction *** demonstrate this point,we numerically trained a double-layer DNN,addressing the prerequisites for intensitybased gray-scale image ***,we experimentally constructed this double-layer DNN based on digital micromirror devices and spatial light modulators,achieving eight-level intensity-based gray-scale image classification for the MNIST and Fashion-MNIST data *** optical system achieved the maximum accuracies of 95.10%and 80.61%,respectively.

关键词： process mirror limitations

Mobility edges and localization characteristics in one-dimensional quasiperiodic quantum walk

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Chinese Physics B 2024年第6期33卷 156-160页

作者：崔鑫辉王慧敏李志坚 Institute of Theoretical Physics State Key Laboratory of Quantum Optics and Quantum DevicesShanxi UniversityTaiyuan 030006China

We construct a one-dimensional quasiperiodic quantum walk to investigate the localization–delocalization *** inverse participation ratio and Lyapunov exponent are employed as two indexes to determine the mobility edge, a critical energy to distinguish the energy regions of extended and localized states. The analytical solution of mobility edge is obtained by the Lyapunov exponents in global theory, and the consistency of the two indexes is confirmed. We further study the dynamic characteristics of the quantum walk and show that the probabilities are localized to some specific lattice sites with time evolution. This phenomenon is explained by the effective potential of the Hamiltonian which corresponds to the phase in the coin operator of the quantum walk.

关键词： quantum walk mobility edges quasiperiodicity