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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
    Abstract535)      PDF (5083KB)(421)      

    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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    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
    Abstract488)      PDF (837KB)(777)      

    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
    Abstract423)      PDF (483KB)(860)      

    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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    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
    Abstract404)      PDF (9908KB)(459)      

    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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    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
    Abstract368)      PDF (4272KB)(415)      

    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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    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
    Abstract305)      PDF (3411KB)(327)      

    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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    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
    Abstract304)      PDF (452KB)(329)      

    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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    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
    Abstract256)      PDF (6736KB)(211)      

    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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    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
    Abstract225)      PDF (5362KB)(317)      

    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
    Abstract202)      PDF (5840KB)(128)      

    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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    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
    Abstract190)      PDF (4146KB)(197)      

    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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    Research Progress on the Regulation of Metal-Site Bismuth Doping in Halide Perovskites
    HUANG Xiao-rui, SUN Yue, HE Sheng-rong, XING Jun
    Progress in Physics    2024, 44 (2): 73-95.   DOI: 10.13725/j.cnki.pip.2024.02.002
    Abstract160)      PDF (8816KB)(252)      
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    Progress in First-Principles Methods for Simulation of Warm Dense Matter
    ZHANG Hang, CHEN Mo-han
    Progress in Physics    2024, 44 (2): 49-72.   DOI: 10.13725/j.cnki.pip.2024.02.001
    Abstract157)      PDF (2466KB)(170)      
    Warm Dense Matter (WDM) represents a transitional state of matter situated between condensed matter and plasma, emerging as a cutting-edge research direction within the realms of planetary physics, laboratory astrophysics, and inertial confinement fusion in the field of high-energy density physics. WDM is characterized by significant quantum effects, partial ionization, strong coupling, electron degeneracy, and thermal effects, necessitating a description based on fundamental quantum mechanical theories. In recent years, simulations and calculations based on quantum mechanics’ first principles have rapidly advanced, increasingly becoming an effective tool for a deeper understanding of WDM properties. On one hand, applying First Principles widely used in condensed matter physics and materials science to WDM poses considerable challenges, especially under extreme conditions such as broad temperature ranges and high pressures, which require continuous improvements to existing first-principle algorithms and software. On the other hand, the rapid development of machine learning-based molecular dynamics methods offers new tools for simulating WDM. In this review, we initially revisit traditional first principles applicable to WDM simulations, including Kohn-Sham Density Functional Theory and Orbital-free Density Functional Theory. Subsequently, we introduce newly developed methods and software, such as Extended First Principles Molecular Dynamics and Stochastic Density Functional Theory, the latter of which has been implemented in the domestically developed open-source density functional theory software, Atomic-orbital Based Ab-initio Computation at UStc (ABACUS). These innovative approaches significantly boost the computational scale and efficiency of WDM studies, thereby elevating the precision of structural, dynamical, and transport coefficient calculations related to WDM
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    Profiling of the Local Distribution of Hot-Carrier-Induced Defects in Nanoscale CMOS Devices
    MA Li-juan, TAO Yong-chun
    Progress in Physics    2024, 44 (2): 97-101.   DOI: 10.13725/j.cnki.pip.2024.02.003
    Abstract110)      PDF (436KB)(49)      
    A surface potential technique is proposed to characterize the local distribution of hot-carrier-induced interface states and oxide charge in nanoscale CMOS devices. These defects are produced by the hot carrier injection stress in the Si/SiO2 interface and the gate oxide layer. With the increase of the stress time, the interface state and oxide charge will cause the drift of the device parameters such as the threshold voltage. Based on the DIBL effect, the threshold voltage offset at the peak of the surface potential is selected to characterize the number of HCI induced interface state and oxide charge at the corresponding position of the channel.The distribution of threshold voltage offset with source/drain voltage before and after HCI stress was measured. The local distribution of interface state and oxide charge numbers along the channel are obtained by surface potential model. In this paper, the distributions of interface state and oxide charge induced by HCI stress in 32 nm CMOS devices are accurately characterized, and the mechanism of HCI generation is analyzed. 
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    Recent Progress on the Effect of the Electronic Structure on Electrocatalytic Performance of Single Atom Catalysts
    HE Yue-xuan, WANG Tong-hui, WEN Zi, JIANG Qing
    Progress in Physics    2024, 44 (3): 136-156.   DOI: 10.13725/j.cnki.pip.2024.03.004
    Abstract91)      PDF (2081KB)(63)      

    Single atom catalysts (SACs) are promising candidates for various catalytic systems due to their unique electronic structures and the highest atom utilization. Modulating the electronic structure of SACs catalysts is the key to its further development, can optimize the adsorption and bonding energies of the catalysts by regulating the electronic properties, and thus improves the catalytic activity and stability. Herein, we provide a comprehensive understanding of SACs in catalysis through their electronic structures and their associated knowledges. Various electronic properties have been discussed, such as energy band structure, orbital hybridization and associated spin states, etc. Electrocatalysis as a technology for reducing carbon emissions and utilizing renewable energy sources which can address growing pollution problems, is receiving increasing attention, making the design of high-performance catalysts critical. From this review, we discusse how the electronic structure of SACs affects their electrochemical catalytic performance and explore its relationship with activity and stability of SACs. The understanding of the fundamentals of electronic structures in catalytic processes can provide rational guidance for the design of catalysts in various catalytic reactions in the future

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    Wave Velocity Measurement and Modulation of Surface Acoustic Waves in Piezoelectric Materials 
    WANG Ren-fei, LIU Xiao, WU Meng-meng, LIN Xi, LIU Yang
    Progress in Physics    2024, 44 (3): 103-111.   DOI: 10.13725/j.cnki.pip.2024.03.001
    Abstract85)      PDF (4278KB)(47)      

    In addition to the well-known conventional acoustic wave propagation mode in three-dimensional solids, there exists the surface acoustic wave propagation mode where energy is only concentrated near the two-dimensional interface. In this work, utilizing the piezoelectric and inverse piezoelectric effects from GaAs substrates, we achieve the conversion between radiofrequency electromagnetic waves and surface acoustic waves with planar interdigital transducers, and successfully measure the surface acoustic wave velocity on a sample with a dimension of only 4 mm using superheterodyne-scheme lock-in technique, yielding a result of (2.9±0.1) km/s. We also fabricate a uniaxial stress cell with piezoelectric ceramics, capable of applying uniaxial strains up to approximately 10−4 to the sample, and observe the influence of strain on the surface acoustic wave velocity. We measure the surface acoustic wave velocity of the important semiconductor GaAs under stress, demonstrating the capability of this velocity measurement technique to probe the internal mechanical properties of solids in situ. The wave velocity measurements based on planar interdigital transducers overcome the macroscopic size requirements of traditional time-of-flight and standing wave methods. The superheterodyne-scheme lock-in technique established in this article has replaced the commercial vector network analyzers for measuring surface acoustic wave velocity, enabling possible future applications with low power input and high phase stability. As the measurement setup can also be used for experimental teaching related to solid-state physics, this work provides detailed parameters and fabrication processes for surface acoustic wave devices and homemade stress cell.

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    Theoretical Insights into the Triplet-Pair State of Singlet Fissio
    TONG Lei, ZHANG Chun-feng
    Progress in Physics    2024, 44 (3): 112-122.   DOI: 10.13725/j.cnki.pip.2024.03.002
    Abstract75)      PDF (1708KB)(75)      

    Singlet fission is a photophysical process in organic materials where a photoexcited singlet exciton splits into two triplet excitons. This process has gained a lot of interest in the past decade for enhancing the efficiency of photovoltaic conversion. Precious work identified a crucial intermediate state in singlet fission, and the construction of the wave function for this correlated triplet-pair state poses a significant challenge. This article serves as a comprehensive introduction to theoretical models designed for constructing the wave function of the correlated triplet-pair. Subsequently, we delve into an exploration of the intricate effects of vibrational, orbital, and spin interactions on the formation and dissociation of the intermediate state. Finally, we conclude with a succinct summary of the challenges anticipated to shape the landscape of future theoretical research in this field.

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    Progress on High-Pressure Structure and Properties of Phosphorus and Phosphide
    HUANG Ye-hua, GUO Zhen-yuan, LI Jun-kai, YANG Xin, GOU Hui-yang
    Progress in Physics    2024, 44 (3): 123-135.   DOI: 10.13725/j.cnki.pip.2024.03.003
    Abstract63)      PDF (6131KB)(59)      

    Phosphorus,a group V non-metallic element, exhibits a unique electronic structure along with excellent optical, electrical and mechanical properties, and has a wide range of application prospects. Recent studies have demonstrated that phosphorus and phosphides are easily affected and regulated by external fields and have rich physical and chemical properties under high pressure. In addition, the unique structure and electronic properties of phosphorus and phosphides give them many physical properties that differ from those of traditional materials. Therefore, the use of high pressure to induce structural transformation and superconducting transformation in phosphorus and phosphides has become the focus of high-pressure research. In this paper, the structural, electrical, and optical responses of black phosphorus, germanium phosphide, and arsenic phosphide under high-pressure conditions are reviewed and discussed. Furthermore, we also explore the structure-activity relationships between the structures and physical properties and forecast the future research directions of phosphides under high pressure.

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