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    Types and Properties of Copper-Oxide Superconductors with Critical Temperatures Above 110 K

    TONG Shu-yun, CAI Chuan-bing
    Progress in Physics    2023, 43 (3): 68-83.   DOI: 10.13725/j.cnki.pip.2023.03.002
    Abstract981)      PDF (4571KB)(694)      

    Oxide superconductor is one of the most important forms of unconventional superconductors, in which the transition temperatures of thallium series, mercury series and copper-carbon series superconductors can reach 110 K or above. High superconducting transition temperature and irreversible magnetic field in liquid nitrogen temperature region have attracted much attention. Obviously, the high superconducting critical temperature increases the choice of cooling medium for superconducting applications. Economical and practical coolants are expected to expand the application fields of these high superconducting transition temperature (T) superconductors and increase the feasibility of long-term operation. In this paper, the development and superconducting properties of 110 K superconducting materials including thallium, mercury and copper-carbon superconductors are introduced and summarized, and the factors affecting the superconducting transition temperature are analyzed theoretically to qualitatively explain the reasons for the high T of high temperature superconductors. Special attention is paid to the analysis of the differences of their irreversible fields, and the possible new applications of these high critical temperature superconductors are prospected.

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    Historic Origin of Quantum Entanglement in Particle Physics
    SHI Yu
    Progress in Physics    2023, 43 (3): 57-67.   DOI: 10.13725/j.cnki.pip.2023.03.001
    Abstract695)      PDF (1284KB)(833)      

    The historic origin of quantum entanglement in particle physics is studied systematically and in depth. In 1957, Bohm and Aharonov noted that the 1950 Wu-Shaknov experiment had realized the discrete version of the Einstein-Podolsky-Rosen correlation. Indeed this experiment was definitely the first experimental realization of spatially separated quantum entanglement in history. Such an experiment had been proposed by Wheeler, as a test of quantum electrodynamics, but his calculation was erroneous. The correct theoretical calculations were made by Ward and Pryce and also by Snyder, Pasternack and Hornbostel. The entangled state of the photons also satisfies the selection rule of C. N. Yang in 1949. After the publication of Bell inequality in 1964, discussions on whether Wu-Shaknov experiment can be exploited in testing the inequality inspired the progress of this field, and a new experiment was done by Wu’s group. In 1957, Lee, Oehme and Yang established the quantum mechanical formulation of the kaons, and discovered that neutral kaon is a two-state system. The following year,Goldhaber, Lee and Yang wrote down entangled states of a pair of kaons for the first time, in which each kaon is allowed to be charged or neutral, as the entanglement in internal degrees of high energy particles beyond photons written down for the first time. In 1960, as an unpublished work, Lee and Yang discussed an entangled state of a pair of neutral kaons. Such entangled kaons widely exist in meson factories later on. Several physicist are also introduced, especially Ward.

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    Second-Order Nonlinear Optics in Transition Metal Dichalcogenides
    WU Hui , QIN Chun-bo , ZHANG Chun-feng ,
    Progress in Physics    2023, 43 (3): 84-95.   DOI: 10.13725/j.cnki.pip.2023.03.003
    Abstract468)      PDF (5051KB)(609)      

    Second-order nonlinear optics is a crucial technique for light frequency conversion with broad applications in scientific research and technological advancements. Monolayer transition metal dichalcogenides exhibit extraordinarily high second-order nonlinear susceptibilities, indicating their significant potential for efficient nonlinear optical response. Maintain the giant nonlinear coefficient of monolayer, expand material thickness and frequency response region, and improve nonlinear response is an important challenge. This paper presents an overview of the regulation of second-order nonlinear optical effects based on monolayer transition metal dichalcogenides. We discuss the frequency dependence of monolayer transition metal dichalcogenides, as well as multi-layer stacking of different symmetric phases. Additionally, we summarize the potential applications of their nonlinear optical effects. 

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    Environmental Stability of 2D Transition Metal Dichalcogenides
    ZHOU Zhen-jia , XU Jie , GAO Li-bo
    Progress in Physics    2023, 43 (4): 97-116.   DOI: 10.13725/j.cnki.pip.2023.04.001
    Abstract370)      PDF (837KB)(659)      

    Two-dimensional (2D) transition metal dichalcogenides (TMDCs) with a unique unity of favorable electronic and mechanical properties have been developed for fundamental studies and applications in electronics, spintronics, optoelectronics, energy harvesting and catalysis. However, as they are unstable under harsh conditions, and prone to degradation in the ambient environment, most TMDCs applications are limited. In this review, we analyze the recent advances in the research of environmental stability in TMDCs, covering the latest growth methods, the fundamental mechanisms for stability and kinds of routes to protect 2D TMDCs materials from aging and deterioration. By analyzing key factors that affect TMDCs stability from the growth process, we present a short review of optimizing growth methods for improving the stability of TMDCs. Finally, by providing insights into existing factors, this review is expected to guide the growth of stable TMDCs, which could lead to a new potential approach to growing advanced materials and designing more unexplored heterostructures. 

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    Research Progress on Single-Mode Regulation Methods for Whispering Gallery Mode Microcavities
    LIU Shuo, WANG Yu-chen, WANG Xiu-hua, HOU Rui
    Progress in Physics    2023, 43 (4): 117-130.   DOI: 10.13725/j.cnki.pip.2023.04.002
    Abstract319)      PDF (483KB)(642)      

    Whispering gallery mode (WGM) microcavities have attracted wide attention due to their small mode volume, ultra-high Q value, and low threshold. However, in rotationally symmetric WGM microcavities, multiple longitudinal mode laser radiation can be generated, and the directionality of the radiation is poor, which limits its practical applications. Finding effective methods to achieve single-mode radiation of WGM lasers is a key issue for microcavity lasers to move toward practical applications. This review focuses on several methods of single-mode modulation of WGM lasing in recent years, including reducing cavity size, adding mode selection structure, based on the vernier effect, parity-time symmetry breaking, deformed microcavity, etc. This review aims to provide a reference for researchers in related fields and deepen their understanding of the physical mechanism of single-mode modulation of WGM lasing.

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    Low-Frequency Raman Detection of Antiferromagnetic Spin Waves in Cr 2O 3
    Dong Biao , CUI Jun , TIAN Yuan-zhe , WU Di , ZHANG Qi
    Progress in Physics    2023, 43 (5): 142-150.   DOI: 10.13725/j.cnki.pip.2023.05.002
    Abstract275)      PDF (4272KB)(321)      

    The antiferromagnetic (AFM) spin waves are promising for being utilized in highspeed and energy-efficient information processing. However, the excitation and detection of terahertz spin waves in AFM systems is challenging. Here, we demonstrate low-frequency Raman spectroscopy as a powerful tool for spin-wave detection in AFM systems. We present a systematic study of AFM magnons in Cr2O3, a prototypical uniaxial antiferromagnet, via Raman measurements down to 2.3 cm−1 (69 GHz). We resolved the magnon Zeeman splitting and the spin-flop transition. We further determined the sign of angular momentum of the magnon branches via polarization-resolved Raman processes. We also obtained the anisotropy energy, the g-factor, and the spin-flop field of Cr2O3 as a function of temperatures and magnetic fields. A spin-wave renormalization theory accounts for all experimental observations. 

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    Self-trapped Excitons in Metal Halide Perovskites 
    ZHANG Qin-kai , WANG Yu-xiao , ZHANG Chun-feng
    Progress in Physics    2023, 43 (6): 161-177.   DOI: 10.13725/j.cnki.pip.2023.06.001
    Abstract250)      PDF (9908KB)(269)      

    In polar crystals, excited electron-hole pairs can be captured by the deformation potential field created by lattice distortion upon photoexcitation, due to strong electron-phonon interactions, thereby forming self-trapped excitons. Metal halide perovskites are semiconductors that display efficient self-trapped exciton luminescence in various systems due to their ionic crystal nature with strong electron-phonon interactions and a deformable lattice. Consequently, they are considered ideal for creating high-quality white light sources. However, the understanding of the self-trapped exciton luminescence mechanism in metal halide perovskites is still relatively scarce and lags far behind the development of devices. To this end, this paper summarizes the recent research progress on the formation conditions, formation mechanism and related excited state dynamics of self-trapped excitons in metal halide perovskites semiconductors from the perspective of the fundamental physics of self-trapped excitons, and gives an outlook on the future research based on the self-trapped exciton mechanism in this system, so as to provide a clearer physical image for the study of self-trapped excitons in this system

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    Vortex state in a nematic triplet superconductor
    YANG Miao-miao, XIANG Ke, WANG Da, WANG Qiang-hua
    Progress in Physics    2023, 43 (5): 131-141.   DOI: 10.13725/j.cnki.pip.2023.05.001
    Abstract240)      PDF (452KB)(239)      

    The discovery of nematic triplet superconductivity in doped topological insulators CuxBi2Se3 triggers interest in the identification of the d-vector of the triplet, which is related to the antinodal direction of the gap function and determines whether the superconductor is topological. We perform self-consistent analysis of the vortex state properties in a nematic spin-triplet px-wave superconductor. We first derive a Ginzburg-Landau theory to determine the shape of the vortex and vortex lattice. We find the spatial profile of the isolated vortex is elongated along the antinodal direction, and the vortex lattice is a distorted triangular lattice elongated along x, becoming square in the specific case of a small circular Fermi surface. Finally, we calculate the local density of states self-consistently for an isolated vortex and the vortex lattice using the microscopic Bogoliubov-de Gennes equation. We find that the profile of the local density of states at low in-gap energies is always elongated along the antinodal direction. Our findings are valuable for the experimental detection of the antinodal direction of the gap function in nematic triplet superconductors, and subsequently the identification of the topological character of the superconducting state as in CuxBi2Se3.

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    Perovskite Solar Cells Stability Factors And Encapsulaiton For Performance Enhancement
    DAI Jiaqi, ZHANG Dong, WU Xiaoshan
    Progress in Physics    2024, 44 (1): 19-48.   DOI: 10.13725/j.cnki.pip.2024.01.003
    Abstract238)      PDF (5083KB)(171)      

    Perovskite solar cells, which are considered the third generation of new concept solar cells, are known for their high photoelectric conversion efficiency, low cost, and flexible processing advantages, and have been rapidly development in recent years. its photoelectric conversion efficiency is gradually comparable to that of silicon cells and has been close to the level required for industrial applications. However, the main problem with the industrial application of perovskite solar cells is their stability. Researchers need to solve the biggest problem of how to maintain high efficiency for a long time in perovskite solar cells. Encapsulation is currently being widely studied as a solution to the external stability issue of perovskite solar cells. A good encapsulation can not only solve the stability problem of the device but also ensure the safety of the device and extend the service life. The stability of perovskite solar cells and the conditions for testing it are briefly described in this paper. In the end, the various encapsulation structures, techniques, and materials for perovskite solar cells are explained. The continuous advancement of encapsulation research will lead researchers to optimize and solve existing problems, leading to the eventual industrialization of perovskite solar cells on a large scale. 

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    Attractor Dynamics in Spatial Cognition
    WANG Zi-qun , WANG Tao , LIU Feng
    Progress in Physics    2023, 43 (6): 188-201.   DOI: 10.13725/j.cnki.pip.2023.06.003
    Abstract192)      PDF (3411KB)(170)      

    The mammalian navigation system comprises various kinds of neurons responsible for position perception and spatial path planning, involving the integration of multiple information sources. As a unified brain theory capable of providing explanations for complex cognitive functions like memory and decision-making, the theory of attractor dynamics can elucidate the firing dynamics of neurons and path integration in the navigation system. This review describes recent advances in attractor dynamics in spatial cognition. First, it provides a brief overview of computational neuroscience and the general theory of attractor dynamics. Subsequently, focusing on the continuous attractor dynamics, it delves into the dynamical characteristics and functional significance of head direction cells and grid cells. Finally, an extension and prospects of the attractor theory for spatial cognition are presented.

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    Potential Impurity Effect in Twisted Bilayer Graphene
    LIU Ze-zhong , WANG Da
    Progress in Physics    2023, 43 (5): 151-160.   DOI: 10.13725/j.cnki.pip.2023.05.003
    Abstract154)      PDF (5362KB)(278)      

    Flat band has attracted more and more interest in recent years, motivated by its discovery in twisted bilayer graphene (TBG). In this work, we report our study of the impurity effect on this flat band system, which is an important issue for real materials. Employing the Lanczos recursive method, we solve the local density of states (LDOS) around a potential impurity. We find for large impurity size, a series of bound states are formed inside the impurity, and the flat band peak in LDOS is suppressed near the impurity boundary and shifted by the impurity potential deep inside the impurity. As the impurity size becomes smaller, the effect on the flat band becomes weaker, as anticipated from the large scale of the underlying Wannier function. This property distinguishes with the usual flat band systems with small localized Wannier orbitals, and indicates the flat band in TBG is more stable against small-size impurities. 

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    Research Processes on Theoretical Simulation for the X-ray Spectrum in Photoionization Experiment on High Power Laser Facility
    HAN Bo
    Progress in Physics    2023, 43 (6): 178-187.   DOI: 10.13725/j.cnki.pip.2023.06.002
    Abstract121)      PDF (5840KB)(61)      

    Photoionized plasma is an important form of plasma in the universe, which is produced by some high-energy celestial bodies emitting strong radiation fields to irradiate the surrounding thin plasma. With the development of high energy density physics, the photoionized plasma can be produced in laboratory. In 2009, Fujioka et al. used the GEKKO-XII laser facility to produce photoionzed Si plasma, and observed X-ray spectrum similar to that in astrophysical environment. This paper reviews the main theoretical simulation results for the experimental X-ray spectrum since this photoionization experiment, and proposes the future research direction on the photoionized plasma. This review aims to provide a reference for researchers in related fields and deepen their understanding of the physical mechanism of photoionized plasma

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    Phase Transition in Black Phosphorus Induced by Thermal Driven Diffusion of Metal
    CAO Tianjun , SHAN Junjie , WANG Gang, LIN Junhao, LIANG Shijun, MIAO Feng
    Progress in Physics    2024, 44 (1): 1-8.   DOI: 10.13725/j.cnki.pip.2024.01.001
    Abstract117)      PDF (6736KB)(77)      

    Two-dimensional (2D) materials are atomically flat and can be stacked into van der Waals heterostructures, as well as contain abundant physical phenomena and excellent electrical properties. The study of phase transition behavior of 2D materials has been the frontier of condensed matter physics and materials science. In our study, the stage-controlled phase transition induced by thermal-driven metal diffusion in black phosphorus (BP) is realized for the first time. Through thermal annealing treatment of the BP-In interface, the phase transition phenomenon from BP pure phase to BP/InP mixed phase and then to InP pure phase is observed. Combined with the characterization techniques of transmission electron microscopy and Raman spectroscopy, the mechanism responsible for phase transition is deeply analyzed, revealing that the thermal-driven metal diffusion behavior in BP-In is the main inducement of phase transition. The two key threshold temperatures (initiation of phase transition and transformation of pure phase) during the stepwise phase transition are obtained by manipulating the two degrees of freedom (temperature and time) which affect the energy supply in the thermal driving, where are 300 and 350 °C , respectively. This study provides more possibilities for expanding the applications of BP-based electronic and optoelectronic devices. 

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    Progress in Thin-Layer Quantization
    WANG Yonglong, DU Long
    Progress in Physics    2024, 44 (1): 9-18.   DOI: 10.13725/j.cnki.pip.2024.01.002
    Abstract88)      PDF (4146KB)(96)      

    With the rapid development of microtechnology, the low-dimensional materials are fabricated with nontrivial topological structures, and then the action of geometric properties on the effective dynamics receives increasing attention. It is an effective theory that the quantum mechanics of low-dimensional curved systems can be given by using the thin-layer quantization approach, in which the geometric potential and the geometric momentum have been demonstrated experimentally. In the present paper, the thin-layer quantization formalism is first recalled, its fundamental calculation framework is first clarified, and the geometric quantum effects result from the diffeomorphism transformation and the rotation transformation connecting the local frames of different points. The results are helpful to understand the gravitational gauge and emerging gauge, and to image the geometries implied in the artificial gauge. In the particular quantum systems, the novel physical phenomena are briefly recalled that are induced by geometry, such as resonation tunneling, quantum block, quantum Hall effect, quantum Hall viscosity, quantum spin Hall effect, effective monopole magnetic field and so on. The results will shed light from a different angle on the relationships between the geometry and the novel physical phenomenon.

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