Table of contents

19 March 2025, Volume 34 Issue 4 Previous issue   

GENERAL

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New interaction solutions in Mel’nikov equation obtained by modulating the phase shift Mi Chen(陈觅) and Zhen Wang(王振) Chin. Phys. B, 2025, 34 (4):  040201.  DOI: 10.1088/1674-1056/adaccb Abstract ( 28 )   PDF (907KB) ( 9 )   The degradation and nonlinear interactions of a two-breather solution of the Mel’nikov equation are analyzed. By modulating the phase shift and limit method, we prove that in different regions near the non-singular boundaries, there are four kinds of solutions with repulsive interaction or attractive interaction in addition to the two-breather solution. They are the interaction solution between soliton and breather, the two-soliton solution, and the two-breather solution with small amplitude, which all exhibit repulsive interactions; and the two-breather solution with small amplitude, which exhibits attractive interaction. Interestingly, a new breather acts as a messenger to transfer energy during the interaction between two breather solutions with small amplitude.

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Trajectory equations of interaction and evolution behaviors of a novel multi-soliton to a (2+1)-dimensional shallow water wave model Xi-Yu Tan(谭茜宇) and Wei Tan(谭伟) Chin. Phys. B, 2025, 34 (4):  040202.  DOI: 10.1088/1674-1056/ada7da Abstract ( 26 )   PDF (1819KB) ( 2 )   Based on a new bilinear equation, we investigated some new dynamic behaviors of the (2+1)-dimensional shallow water wave model, such as hybridization behavior between different solitons, trajectory equations for lump collisions, and evolution behavior of multi-breathers. Firstly, the $N$-soliton solution of Ito equation is studied, and some high-order breather waves can be obtained from the $N$-soliton solutions through paired-complexification of parameters. Secondly, the high-order lump solutions and the hybrid solutions are obtained by employing the long-wave limit method, and the motion velocity and trajectory equations of high-order lump waves are analyzed. Moreover, based on the trajectory equations of the higher-order lump solutions, we give and prove the trajectory theorem of 1-lump before and after interaction with $n$-soliton. Finally, we obtain some new lump solutions from the multi-solitons by constructing a new test function and using the parameter limit method. Meanwhile, some evolutionary behaviors of the obtained solutions are shown through a large number of three-dimensional graphs with different and appropriate parameters.

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Analysis and image encryption of memristive chaotic system with coexistence bubble Da Qiu(邱达), Bo Zhang(张博), Tingting Zhang(张婷婷), Song Liu(刘嵩), and Peiyu He(何培宇) Chin. Phys. B, 2025, 34 (4):  040203.  DOI: 10.1088/1674-1056/adbee5 Abstract ( 1 )   PDF (25271KB) ( 0 )   In recent years, the phenomenon of multistability has attracted wide attention. In this paper, a memristive chaotic system with extreme multistability is constructed by using a memristor. The dynamic behavior of the system is analyzed by Poincaré mapping, a time series diagram, and a bifurcation diagram. The results show that the new system has several significant characteristics. First, the new system has a constant Lyapunov exponent, transient chaos and one complete Feigenbaum tree. Second, the system has the phenomenon of bifurcation map shifts that depend on the initial conditions. In addition, we find periodic bursting oscillations, chaotic bursting oscillations, and the transition of chaotic bursting oscillations to periodic bursting oscillations. In particular, when the system parameters take different discrete values, the system generates a bubble phenomenon that varies with the initial conditions, and this bubble can be shifted with the initial values, which has rarely been seen in the previous literature. The implementation by field-programmable gate array (FPGA) and analog circuit simulation show close alignment with the MATLAB numerical simulation results, validating the system's realizability. Additionally, the image encryption algorithm integrating DNA-based encoding and chaotic systems further demonstrates its practical applicability.

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Graph distillation with network symmetry Feng Lin(林峰) and Jia-Lin He(何嘉林) Chin. Phys. B, 2025, 34 (4):  040205.  DOI: 10.1088/1674-1056/adbeda Abstract ( 25 )   PDF (631KB) ( 0 )   Graph neural networks (GNNs) have demonstrated excellent performance in graph representation learning. However, as the volume of graph data grows, issues related to cost and efficiency become increasingly prominent. Graph distillation methods address this challenge by extracting a smaller, reduced graph, ensuring that GNNs trained on both the original and reduced graphs show similar performance. Existing methods, however, primarily optimize the feature matrix of the reduced graph and rely on correlation information from GNNs, while neglecting the original graph's structure and redundant nodes. This often results in a loss of critical information within the reduced graph. To overcome this limitation, we propose a graph distillation method guided by network symmetry. Specifically, we identify symmetric nodes with equivalent neighborhood structures and merge them into "super nodes", thereby simplifying the network structure, reducing redundant parameter optimization and enhancing training efficiency. At the same time, instead of relying on the original node features, we employ gradient descent to match optimal features that align with the original features, thus improving downstream task performance. Theoretically, our method guarantees that the reduced graph retains the key information present in the original graph. Extensive experiments demonstrate that our approach achieves significant improvements in graph distillation, exhibiting strong generalization capability and outperforming existing graph reduction methods.

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Uncertainties of the standard quantum teleportation channel Zhihua Zhang(章志华), Zehao Guo(郭泽豪), and Zhipeng Qiu(邱志鹏) Chin. Phys. B, 2025, 34 (4):  040301.  DOI: 10.1088/1674-1056/adb263 Abstract ( 22 )   PDF (378KB) ( 1 )   From the perspective of state-channel interaction, standard quantum teleportation can be viewed as a communication process characterized by both input and output, functioning as a quantum depolarizing channel. To achieve a precise quantification of the quantumness introduced by this channel, we examine its uncertainties, which encompass both state-dependent and state-independent uncertainties. Specifically, for qudit systems, we provide general formulas for these uncertainties. We analyze the uncertainties associated with standard quantum teleportation when induced by isotropic states, Werner states, and X-states, and we elucidate the correlation between these uncertainties and the parameters of the specific mixed states. Our findings demonstrate the validity of quantifying these uncertainties.

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Robust quantum gate optimization with first-order derivatives of ion–phonon and ion–ion couplings in trapped ions Jing-Bo Wang(汪景波) Chin. Phys. B, 2025, 34 (4):  040302.  DOI: 10.1088/1674-1056/adb40e Abstract ( 20 )   PDF (493KB) ( 5 )   Trapped ion hardware has made significant progress recently and is now one of the leading platforms for quantum computing. To construct two-qubit gates in trapped ions, experimental manipulation approaches for ion chains are becoming increasingly prevalent. Given the restricted control technology, how implementing high-fidelity quantum gate operations is crucial. Many works in current pulse design optimization focus on ion-phonon and effective ion-ion couplings while ignoring the first-order derivative terms expansion impacts of these two terms brought on by experiment defects. This paper proposes a novel robust quantum control optimization method in trapped ions. By introducing the first-order derivative terms caused by the error into the optimization cost function, we generate an extremely robust Mølmer-Sørensen gate with infidelity below ${10}^{-3}$ under a drift noise range of $\pm 10$ kHz, the relative robustness achieves a tolerance of ±5%, compared to the 200-kHz frequency spacing between phonon modes, and for time noise drift, the tolerance reached to 2%. Our work reveals the vital role of the first-order derivative terms of coupling in trapped ion pulse control optimization, especially the first-order derivative terms of ion-ion coupling. It provides a robust optimization scheme for realizing more efficient entangled states in trapped ion platforms.

SPECIAL TOPIC — Quantum communication and quantum network

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Asymmetric mode-pairing quantum key distribution with advantage distillation Hai-Tao Wang(汪海涛), Chun Zhou(周淳), Yi-Fei Lu(陆宜飞), Chen-Peng Hao(郝辰鹏), Yan-Mei Zhao(赵燕美), Yan-Yang Zhou(周砚扬), Hong-Wei Li(李宏伟), and Wan-Su Bao(鲍皖苏) Chin. Phys. B, 2025, 34 (4):  040305.  DOI: 10.1088/1674-1056/adbb5c Abstract ( 2 )   PDF (611KB) ( 1 )   Mode-pairing quantum key distribution (MP-QKD) is an excellent scheme that can exceed the repeaterless rate-transmittance bound without complex phase locking. Nevertheless, MP-QKD usually needs to ensure that the communication distances of the two channels are equal. To address the problem, the asymmetric MP-QKD protocol is proposed. In this paper, we enhance the performance of the asymmetric MP-QKD protocol based on the advantage distillation (AD) method without modifying the quantum process. The simulation results show that the AD method can extend the communication distance by about 70 km in the case of asymmetry. And we observe that as the misalignment error increases, the AD method further increases the expandable communication distance. Our work can further enhance the robustness and promote the practical application of the asymmetric MP-QKD.

GENERAL

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University of percolation at dynamic pseudocritical point Qiyuan Shi(石骐源), Shuo Wei(魏硕), Youjin Deng(邓友金), and Ming Li(李明) Chin. Phys. B, 2025, 34 (4):  040501.  DOI: 10.1088/1674-1056/adaccf Abstract ( 29 )   PDF (705KB) ( 2 )   Universality, encompassing critical exponents, scaling functions, and dimensionless quantities, is fundamental to phase transition theory. In finite systems, universal behaviors are also expected to emerge at the pseudocritical point. Focusing on two-dimensional percolation, we show that the size distribution of the largest cluster asymptotically approaches to a Gumbel form in the subcritical phase, a Gaussian form in the supercritical phase, and transitions within the critical finite-size scaling window. Numerical results indicate that, at consistently defined pseudocritical points, this distribution exhibits a universal form across various lattices and percolation models (bond or site), within error bars, yet differs from the distribution at the critical point. The critical polynomial, universally zero for two-dimensional percolation at the critical point, becomes nonzero at pseudocritical points. Nevertheless, numerical evidence suggests that the critical polynomial, along with other dimensionless quantities such as wrapping probabilities and Binder cumulants, assumes fixed values at the pseudocritical point that are independent of the percolation type (bond or site) but vary with lattice structures. These findings imply that while strict universality breaks down at the pseudocritical point, certain extreme-value statistics and dimensionless quantities exhibit quasi-universality, revealing a subtle connection between scaling behaviors at critical and pseudocritical points.

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Study and circuit design of stochastic resonance system based on memristor chaos induction Qi Liang(梁琦), Wen-Xin Yu(于文新), and Qiu-Mei Xiao(肖求美) Chin. Phys. B, 2025, 34 (4):  040502.  DOI: 10.1088/1674-1056/adb268 Abstract ( 1 )   PDF (4643KB) ( 0 )   Memristor chaotic research has become a hotspot in the academic world. However, there is little exploration combining memristor and stochastic resonance, and the correlation research between chaos and stochastic resonance is still in the preliminary stage. In this paper, we focus on the stochastic resonance induced by memristor chaos, which enhances the dynamics of chaotic systems through the introduction of memristor and induces memristor stochastic resonance under certain conditions. First, the memristor chaos model is constructed, and the memristor stochastic resonance model is constructed by adjusting the parameters of the memristor chaos model. Second, the combination of dynamic analysis and experimental verification is used to analyze the memristor stochastic resonance and to investigate the trend of the output signal of the system under different amplitudes of the input signal. Finally, the practicality and reliability of the constructed model are further verified through the design and testing of the analog circuit, which provides strong support for the practical application of the memristor chaos-induced stochastic resonance model.

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Associated network family of the unified piecewise linear chaotic family and their relevance Haoying Niu(牛浩瀛) and Jie Liu(刘杰) Chin. Phys. B, 2025, 34 (4):  040503.  DOI: 10.1088/1674-1056/adb26a Abstract ( 17 )   PDF (6670KB) ( 2 )   Duality analysis of time series and complex networks has been a frontier topic during the last several decades. According to some recent approaches in this direction, the intrinsic dynamics of typical nonlinear systems can be better characterized by considering the related nonlinear time series from the perspective of networks science. In this paper, the associated network family of the unified piecewise-linear (PWL) chaotic family, which can bridge the gap of the PWL chaotic Lorenz system and the PWL chaotic Chen system, was firstly constructed and analyzed. We constructed the associated network family via the original and the modified frequency-degree mapping strategy, as well as the classical visibility graph and horizontal visibility graph strategy, after removing the transient states. Typical related network characteristics, including the network fractal dimension, of the associated network family, are computed with changes of single key parameter $\alpha$. These characteristic vectors of the network are also compared with the largest Lyapunov exponent (LLE) vector of the related original dynamical system. It can be found that, some network characteristics are highly correlated with LLE vector of the original nonlinear system, i.e., there is an internal consistency between the largest Lyapunov exponents, some typical associated network characteristics, and the related network fractal dimension index. Numerical results show that the modified frequency-degree mapping strategy can demonstrate highest correlation, which means it can behave better to capture the intrinsic characteristics of the unified PWL chaotic family.

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A novel approach to visual image encryption: 2D hyperchaos, variable Josephus, and 3D diffusion Yan Hong(洪炎), Xinyan Duan(段心妍), Jingming Su(苏静明), Zhaopan Wang(王昭盼), and Shihui Fang(方士辉) Chin. Phys. B, 2025, 34 (4):  040504.  DOI: 10.1088/1674-1056/adacc7 Abstract ( 0 )   PDF (30722KB) ( 0 )   With the development of the Internet, image encryption technology has become critical for network security. Traditional methods often suffer from issues such as insufficient chaos, low randomness in key generation, and poor encryption efficiency. To enhance performance, this paper proposes a new encryption algorithm designed to optimize parallel processing and adapt to images of varying sizes and colors. The method begins by using SHA-384 to extract the hash value of the plaintext image, which is then processed to determine the chaotic system's initial value and block size. The image is padded and divided into blocks for further processing. A novel two-dimensional infinite collapses hyperchaotic map (2D-ICHM) is employed to generate the intra-block scrambling sequence, while an improved variable Joseph traversal sequence is used for inter-block scrambling. After removing the padding, 3D forward and backward shift diffusions, controlled by the 2D-ICHM sequences, are applied to the scrambled image, producing the ciphertext. Simulation results demonstrate that the proposed algorithm outperforms others in terms of entropy, anti-noise resilience, correlation coefficient, robustness, and encryption efficiency.

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Finite time hybrid synchronization of heterogeneous duplex complex networks via time-varying intermittent control Cheng-Jun Xie(解成俊) and Xiang-Qing Lu(卢向清) Chin. Phys. B, 2025, 34 (4):  040601.  DOI: 10.1088/1674-1056/adacc6 Abstract ( 1 )   PDF (334KB) ( 0 )   This paper study the finite time internal synchronization and the external synchronization (hybrid synchronization) for duplex heterogeneous complex networks by time-varying intermittent control. There few study hybrid synchronization of heterogeneous duplex complex networks. Therefore, we study the finite time hybrid synchronization of heterogeneous duplex networks, which employs the time-varying intermittent control to drive the duplex heterogeneous complex networks to achieve hybrid synchronization in finite time. To be specific, the switch frequency of the controllers can be changed with time by devise Lyapunov function and boundary function, the internal synchronization and external synchronization are achieved simultaneously in finite time. Finally, numerical examples are presented to illustrate the validness of theoretical results.

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Generation of acoustical Bessel-like collimated beams using ring-excited flat plate structure transducers Ming-Liang Han(韩明亮), Ruo-Yu Tang(唐若昱), Ning Ma(马宁), Guang-Bin Zhang(张光斌), and Xiao-Feng Zhang(张小凤) Chin. Phys. B, 2025, 34 (4):  040702.  DOI: 10.1088/1674-1056/adb38c Abstract ( 12 )   PDF (892KB) ( 1 )   This paper proposes a method to generate Bessel-like collimated beams with suppressed side lobes using the flexural vibration modes of a fixed boundary circular plate, which is excited by a longitudinally vibrating transducer in a ring excitation manner. The factors affecting the generation of Bessel-like collimated beams are investigated by theoretical analysis, numerical simulation and experimental methods. The results indicate that Bessel-like wave can be generated by a thin circular plate with fixed boundaries. The third-order mode of the circular plate can be modified to generate a collimated beam with suppressing side lobes when it is excited in a ring excitation manner and the excitation position lies between the first two nodal circles of the plate. As the excitation radius increases, the main lobe width of the resulting Bessel-like collimated beam decreases, the extent of the focusing region increases, and the amplitude of the side lobes initially increases and then decreases. Based on the simulation results, a prototype Bessel-like collimated beam generation system is made and measured experimentally. The experimental results are in good agreement with the numerical results. The Bessel-like collimated beam can be generated by the proposed system, which has potential application in the fields of long-range detection, imaging of highly attenuated materials, and airflow acceleration.

DATA PAPER

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Spectroscopic and transition properties of strontium chloride Dong-Lan Wu(伍冬兰), Bi-Kun Liu(刘必坤), Wen-Tao Zhou(周文涛), Jia-Yun Chen(陈佳运), Zhang-Li Lai(赖章丽), Bo Liu(刘波), and Bing Yan(闫冰) Chin. Phys. B, 2025, 34 (4):  043101.  DOI: 10.1088/1674-1056/adb264 Abstract ( 2 )   PDF (536KB) ( 0 )   The spectroscopic and transition properties of strontium chloride (SrCl) are investigated based on the theoretical approach of ab initio quantum chemistry. The calculation accuracy is improved by introducing Davidson correction, core-valence correlation (CV), the scalar relativistic and spin-orbit coupling (SOC) effects. The results show that the spectroscopic constants of X${}^2{\mathrm{\Sigma }}^{+}$ and A${}^2\mathrm{\Pi }$ states are consistent with the experimental results. The spectroscopic and molecular constants of most highly excited electronic states are reported for the first time. The permanent dipole moment (PDMs) and the spin-orbit (SO) matrix element have a sudden change for the avoidance of crossing. The potential energy curves (PECs) of the 14 $\mathrm{\Lambda }$-S states split into 30 $\mathrm{\Omega }$ states. The splitting energy of A${}^2\mathrm{\Pi }$ is 290.76 cm${}^{-1}$, which has a little difference from the experimental value 295.597 cm${}^{-1}$. Finally, the transition properties are given, including transition dipole moment (TDMs), Franck-Canton factor (FCFs) and radiation lifetime. It is found that the calculated radiation lifetime is in the order of 10 ns. The research will provide a theoretical reference for the feasibility of laser cooling of SrCl molecule. The dataset that supported the findings of this study is available in Science Data Bank, with the link https://www.doi.org/10.57760/sciencedb.j00113.00218.

ATOMIC AND MOLECULAR PHYSICS

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Electron momentum spectroscopy study on trifluorobromomethane: Electronic structure and electron correlation Guangqing Chen(陈广庆), Shanshan Niu(牛珊珊), Yanguo Tang(唐亚国), Yuting Zhang(张雨亭), Zhaohui Liu(刘朝辉), Chunkai Xu(徐春凯), Enliang Wang(王恩亮), Xu Shan(单旭), and Xiangjun Chen(陈向军) Chin. Phys. B, 2025, 34 (4):  043401.  DOI: 10.1088/1674-1056/adb273 Abstract ( 13 )   PDF (755KB) ( 1 )   We present a comprehensive electron momentum spectroscopy study on the electronic structure of trifluorobromomethane. The binding energy spectrum and electron momentum profiles of the entire outer-valence orbitals and the first inner-valence orbital along with several shake-up states were measured by using a high-sensitivity (e, 2e) apparatus at an electron impact energy of 1213 eV. Theoretical calculations employing the density functional theory with B3LYP hybrid functional and the symmetry-adapted cluster configuration-interaction method were performed to interpret the experimental results. Important effects of electron correlations in the initial neutral and final ionic states on the electron momentum profiles have been observed.

ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS

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Nonclassicality of photons in mean-field anisotropic quantum light-matter interacting lattices: Two-photon correlation function and quadrature squeezing Xu-Min Chen(陈许敏), Pei-Yao Chen(陈佩瑶), and Chen Wang(王晨) Chin. Phys. B, 2025, 34 (4):  044201.  DOI: 10.1088/1674-1056/ada9db Abstract ( 26 )   PDF (1055KB) ( 1 )   The generation of nonclassical photons via quantum light–matter interactions is of fundamental importance in quantum optics. Here we investigate steady-state two-photon correlation function and photon squeezing in an open anisotropic Rabi lattice by applying quantum dressed master equation embedded with the mean-field approximation. The expanded antibunching effect of photons due to anisotropic qubit–photon interaction, is strongly suppressed by including inter-site photon tunneling, whereas the giant photon bunching keeps robust with weak inter-site photon tunneling strength. The microscopic processes for photon antibunching and bunching effects are presented based on incoherent transitions between eigenstates. The photon squeezing is also analyzed under the influences of qubit–photon coupling and anisotropic factor. The quadrature squeezing shows persistency by tuning on the inter-site photon tunneling, and becomes dramatically pronounced at the small anisotropic factor. Moreover, the increasing number of qubits significantly enhances quadrature squeezing with strong qubit–photon interaction. We hope such results may provide physical insights into efficient generation and manipulation of nonclassical features of photons in quantum light–matter interacting lattice systems.

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Coherent feedback ground-state cooling of mechanical resonators assisted by a quantum well Qinghong Liao(廖庆洪), Songyun Ouyang(欧阳嵩沄), Shaoping Cheng(程绍平), and Yiping Cheng(程依萍) Chin. Phys. B, 2025, 34 (4):  044202.  DOI: 10.1088/1674-1056/adb266 Abstract ( 1 )   PDF (529KB) ( 0 )   We theoretically investigate a cooling scheme assisted by a quantum well (QW) and coherent feedback within a hybrid optomechanical system. Although the exciton mode in the QW and the mechanical resonator (MR) are initially uncoupled, their interaction via the microcavity field leads to an indirect exciton-mode-mechanical-mode coupling. The coherent feedback loop is applied by feeding back a fraction of the output field of the cavity through a controllable beam splitter to the cavity's input mirror. It is shown that the cooling capability is enhanced by effectively suppressing the Stokes process through coupling with the QW. Furthermore, the effect of the anti-Stokes process is enhanced through the application of the coherent feedback loop. This particular system configuration enables cooling of the mechanical resonator even in the unresolved sideband regime (USR). This study has some important guiding significance in the field of quantum information processing.

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Electromagnetically-induced-absorption-like ground state cooling in a hybrid optomechanical system Yaoyong Dong(董耀勇), Xuejun Zheng(郑学军), Denglong Wang(王登龙), and Peng Zhao(赵鹏) Chin. Phys. B, 2025, 34 (4):  044203.  DOI: 10.1088/1674-1056/adb260 Abstract ( 16 )   PDF (513KB) ( 2 )   We present a scheme for the electromagnetically-induced-absorption (EIA)-like ground state cooling in a hybrid optomechanical system which is combined by two-level quantum systems (qubits) and a high-$Q$ optomechanical cavity. Under the weak qubit-cavity coupling, the system exhibits an EIA-like effect and this effect is caused by quantum destructive interference that is distinct from the conventional EIA effect driven by quantum constructive interference. More importantly, the EIA-like cooling mechanism can significantly enhance the cooling rate of the hybrid system, enabling the final phonon number beyond the classical cooling limit in the strong optomechanical coupling regime. Meanwhile, the cooling effects of the EIA case is better than that of the normalmode splitting case under the same optomechanical coupling strength and qubit dissipation rate.

GENERAL

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Broadband polarization-independent terahertz multifunctional liquid crystal coding metasurface based on topological optimization Yu Chen(陈羽), Wu-Hao Cao(曹吴昊), Jia-Qi Li(李嘉琦), Ming-Zhe Zhang(张明哲), Xin-Yi Du(杜欣怡), Ding-Shan Gao(郜定山), and Pei-Li Li(李培丽) Chin. Phys. B, 2025, 34 (4):  044205.  DOI: 10.1088/1674-1056/adad55 Abstract ( 18 )   PDF (2417KB) ( 1 )   A broadband polarization-independent terahertz multifunctional coding metasurface based on topological optimization using liquid crystal (LC) is proposed. The metasurface can achieve reconfigurability for beam steering and vortex beam generation within a frequency range of 0.68 THz-0.72 THz. Firstly, the metasurface unit is topologically optimized using the non-dominant sequencing genetic algorithms (NSGA-II) multi-objective optimization algorithm. By applying the LC's electrically tunable refractive index properties, the metasurface unit enables polarization-independent 2-bit coding within a frequency range of 0.68 THz-0.72 THz. Then, based on the designed metasurface unit, the array arrangement of the metasurface is reverse-designed to achieve beam steering and vortex beam generation. The results show that, for beam steering, not only can polarization-independent steering of both single- and multi-beam be achieved within the 35${}^{\circ }$ elevation angle range, but also independent control of the target angle of each beam in the multi-beam steering. For vortex beam generation, the metasurfaces can achieve the generation of single- and multi-vortex beams with topological charges $l=\pm 1$, $\pm 2$ within the 35${}^{\circ }$ elevation angle range, and the generation angles of each vortex beam in the multi-vortex beam can be independently controlled. This provides flexibility and diversity in the generation of vortex beams. Therefore, the proposed terahertz LC metasurface can realize flexible control of reconfigurable functions and has certain application prospects in terahertz communication, phased array radar, and vortex radar.

ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS

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Multi-parameter ultrasound imaging for musculoskeletal tissues based on a physics informed generative adversarial network Pengxin Wang(王鹏鑫), Heyu Ma(马贺雨), Tianyu Liu(刘天宇), Chengcheng Liu(刘成成), Dan Li(李旦), and Dean Ta(他得安) Chin. Phys. B, 2025, 34 (4):  044301.  DOI: 10.1088/1674-1056/adb390 Abstract ( 1 )   PDF (4657KB) ( 0 )   Full waveform inversion (FWI) has showed great potential in the detection of musculoskeletal disease. However, FWI is an ill-posed inverse problem and has a high requirement on the initial model during the imaging process. An inaccurate initial model may lead to local minima in the inversion and unexpected imaging results caused by cycle-skipping phenomenon. Deep learning methods have been applied in musculoskeletal imaging, but need a large amount of data for training. Inspired by work related to generative adversarial networks with physical informed constrain, we proposed a method named as bone ultrasound imaging with physics informed generative adversarial network (BUIPIGAN) to achieve unsupervised multi-parameter imaging for musculoskeletal tissues, focusing on speed of sound (SOS) and density. In the in-silico experiments using a ring array transducer, conventional FWI methods and BUIPIGAN were employed for multi-parameter imaging of two musculoskeletal tissue models. The results were evaluated based on visual appearance, structural similarity index measure (SSIM), signal-to-noise ratio (SNR), and relative error (RE). For SOS imaging of the tibia-fibula model, the proposed BUIPIGAN achieved accurate SOS imaging with best performance. The specific quantitative metrics for SOS imaging were SSIM 0.9573, SNR 28.70 dB, and RE 5.78%. For the multi-parameter imaging of the tibia-fibula and human forearm, the BUIPIGAN successfully reconstructed SOS and density distributions with SSIM above 94%, SNR above 21 dB, and RE below 10%. The BUIPIGAN also showed robustness across various noise levels (i.e., 30 dB, 10 dB). The results demonstrated that the proposed BUIPIGAN can achieve high-accuracy SOS and density imaging, proving its potential for applications in musculoskeletal ultrasound imaging.

COMPUTATIONAL PROGRAMS FOR PHYSICS

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A program for modeling the RF wave propagation of ICRF antennas utilizing the finite element method Lei-Yu Zhang(张雷宇), Yi-Xuan Li(李屹轩), Ming-Yue Han(韩明月), and Quan-Zhi Zhang(张权治) Chin. Phys. B, 2025, 34 (4):  045201.  DOI: 10.1088/1674-1056/adaccc Abstract ( 17 )   PDF (568KB) ( 4 )   Controlled nuclear fusion represents a significant solution for future clean energy, with ion cyclotron range of frequency (ICRF) heating emerging as one of the most promising technologies for heating the fusion plasma. This study primarily presents a self-developed 2D ion cyclotron resonance antenna electromagnetic field solver (ICRAEMS) code implemented on the MATLAB platform, which solves the electric field wave equation by using the finite element method, establishing perfectly matched layer (PML) boundary conditions, and post-processing the electromagnetic field data. This code can be utilized to facilitate the design and optimization processes of antennas for ICRF heating technology. Furthermore, this study examines the electric field distribution and power spectrum associated with various antenna phases to investigate how different antenna configurations affect the electromagnetic field propagation and coupling characteristics.

PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES

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Molecular dynamics evaluation of self-diffusion coefficients in two-dimensional dusty plasmas Muhammad Asif Shakoori, Misbah Khan, Haipeng Li(李海鹏), Aamir Shahzad, Maogang He(何茂刚), and Syed Ali Raza Chin. Phys. B, 2025, 34 (4):  045202.  DOI: 10.1088/1674-1056/adacce Abstract ( 4 )   PDF (684KB) ( 0 )   We employ the Green-Kubo (G-K) and Einstein relations to estimate the self-diffusion coefficients (denoted as $D_{\mathrm{G}}$ and $D_{\mathrm{E}}$, respectively) in two-dimensional (2D) strongly coupled dusty plasmas (SC-DPs) via equilibrium molecular dynamics (EMD) simulations. $D_{\mathrm{G}}$ and $D_{\mathrm{E}}$ are computed for a broad domain of screening length ($\kappa$) and coupling parameters ($\Gamma$) along with different system sizes. It is observed that both $D_{\mathrm{G}}$ and $D_{\mathrm{E}}$ decrease linearly with increasing $\Gamma$ in warm liquid states and increase with increasing $\kappa$. In cold liquid states, the Einstein relation accurately predicts $D_{\mathrm{E}}$ in 2D SC-DPs because diffusion motion is close to normal diffusion, but the G-K relation provides overestimations of $D_{\mathrm{G}}$, because VACF indicates anomalous diffusion; thus, $D_{\mathrm{G}}$ is not accurate. Our new simulation outcomes reveal that $D_{\mathrm{G}}$ and $D_{\mathrm{E}}$ remain independent of system sizes. Furthermore, our investigations demonstrate that at higher temperatures, $D_{\mathrm{G}}$ and $D_{\mathrm{E}}$ converge, suggesting diffusion motion close to normal diffusion, while at lower temperatures, these two values diverge. We find reasonable agreement by comparing current and existing numerical, theoretical and experimental data. Moreover, when normalizing diffusion coefficients by the Einstein frequency and testing against the universal temperature scaling law, $D_{\mathrm{G}}$ deviates from theoretical curves at low temperatures and $\kappa$, whereas $D_{\mathrm{E}}$ only disagrees with theory at very small $\kappa$ ($\simeq 0.10$). These findings provide valuable insight into diagnosing dust component parameters within 2D DP systems and contribute to the broader understanding of diffusion processes in DP environments.

SPECIAL TOPIC — Structures and properties of materials under high pressure

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Strain rate effects on pressure-induced amorphous-to-amorphous transformation in fused silica Wenhao Song(宋文豪), Bo Gan(甘波), Dongxiao Liu(刘东晓), Jie Wu(吴杰), Martin T. Dove, and Youjun Zhang(张友君) Chin. Phys. B, 2025, 34 (4):  046101.  DOI: 10.1088/1674-1056/adb38f Abstract ( 28 )   PDF (678KB) ( 12 )   Fused silica (SiO${}_2$ glass), a key amorphous component of Earth's silicate minerals, undergoes coordination and phase transformations under high pressure. Although extensive studies have been conducted, discrepancies between theoretical and experimental studies remain, particularly regarding strain rate effects during compression. Here, we examine strain rate influences on the shock-induced amorphous-amorphous phase transitions in fused silica by measuring its Hugoniot equation of state and longitudinal sound velocity ($C_{\mathrm{L}}$) up to 7 GPa at strain rates of 10${}^6$-10${}^7$ s${}^{-1}$ using a one-stage light-gas gun. A discontinuity in the relationship between shock velocity ($U_{\mathrm{S}}$) and particle velocity ($U_{\mathrm{P}}$) and a significant softening in $C_{\mathrm{L}}$ of fused silica were observed near ~5 GPa under shock loading. Our results indicate that high strain rates restrict Si-O-Si rotation in fused silica, modifying their bonds and increasing silicon coordination. The transition pressure by shock compression is significantly higher than that under static high-pressure conditions (2-3 GPa), which agrees with some recent theoretical predictions with high compression rates, reflecting the greater pressure needed to overcome energy barriers with the strain rate increase. These findings offer insights into strain rate-dependent phase transitions in fused silica and other silicate minerals (e.g., quartz, olivine, and forsterite), bridging gaps between theoretical simulations and experiments.

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Well defined phase boundaries and superconductivity with high Tc in PbSe single crystal Jiawei Hu(胡佳玮), Yanghao Meng(孟养浩), He Zhang(张赫), Wei Zhong(钟韦), Hang Zhai(翟航), Xiaohui Yu(于晓辉), Binbin Yue(岳彬彬), and Fang Hong(洪芳) Chin. Phys. B, 2025, 34 (4):  046102.  DOI: 10.1088/1674-1056/adb272 Abstract ( 27 )   PDF (943KB) ( 69 )   Lead chalcogenides represent a significant class of materials that exhibit intriguing physical phenomena, including remarkable thermoelectric properties and superconductivity. In this study, we present a comprehensive investigation on the superconductivity of PbSe single crystal under high pressure. The signature of superconducting (SC) transition starts to appear at 7.2 K under 16.5 GPa. Upon further compression, the SC temperature ($T_{\mathrm{c}}$) decreases, and it is reduced to 3.5 K at 45.0 GPa. The negative pressure dependent behavior of $T_{\mathrm{c}}$ is consistent with the trend of $T_{\mathrm{c}}$-$P$ relations observed in other lead chalcogenides. The highest $T_{\mathrm{c}}$ is 8.0 K observed at 20.5 GPa during decompression process, which is also the highest record among all other PbSe derivatives, such as doped samples, superlattices, and so on. The phase boundaries of the structural and electronic transitions are well defined by Raman spectroscopy, and then phase diagrams are plotted for both compression and decompression processes. This work corrects the previous claim of positive pressure dependence of $T_{\mathrm{c}}$ in PbSe and provides clear phase diagrams for intrinsic superconductivity in PbSe under pressure.

CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

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Molecular dynamics simulations of collision cascades in polycrystalline tungsten Lixia Liu(刘丽霞), Mingxuan Jiang(蒋明璇), Ning Gao(高宁), Yangchun Chen(陈阳春), Wangyu Hu(胡望宇), and Hiuqiu Deng(邓辉球) Chin. Phys. B, 2025, 34 (4):  046103.  DOI: 10.1088/1674-1056/adb410 Abstract ( 3 )   PDF (1720KB) ( 2 )   Using molecular dynamics methods, simulations of collision cascades in polycrystalline tungsten (W) have been conducted in this study, including different primary-knock-on atom (PKA) directions, grain sizes, and PKA energies between 1 keV and 150 keV. The results indicate that a smaller grain size leads to more defects forming in grain boundary regions during cascade processes. The impact of high-energy PKA may cause a certain degree of distortion of the grain boundaries, which has a higher probability in systems with smaller grain sizes and becomes more pronounced as the PKA energy increases. The direction of PKA can affect the formation and diffusion pathways of defects. When the PKA direction is perpendicular to the grain boundary, defects preferentially form near the grain boundary regions; by contrast, defects are more inclined to form in the interior of the grains. These results are of great significance for comprehending the changes in the performance of polycrystalline W under the high-energy fusion environments and can provide theoretical guidance for further optimization and application of W-based plasma materials.

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Enhancing neural network robustness: Laser fault injection resistance in 55-nm SRAM for space applications Qing Liu(刘清), Haomiao Cheng(程浩淼), Xiang Yao(姚骧), Zhengxuan Zhang(张正选), Zhiyuan Hu(胡志远), and Dawei Bi(毕大炜) Chin. Phys. B, 2025, 34 (4):  046104.  DOI: 10.1088/1674-1056/adacd1 Abstract ( 15 )   PDF (1427KB) ( 2 )   The integration of artificial intelligence (AI) with satellite technology is ushering in a new era of space exploration, with small satellites playing a pivotal role in advancing this field. However, the deployment of machine learning (ML) models in space faces distinct challenges, such as single event upsets (SEUs), which are triggered by space radiation and can corrupt the outputs of neural networks. To defend against this threat, we investigate laser-based fault injection techniques on 55-nm SRAM cells, aiming to explore the impact of SEUs on neural network performance. In this paper, we propose a novel solution in the form of Bin-DNCNN, a binary neural network (BNN)-based model that significantly enhances robustness to radiation-induced faults. We conduct experiments to evaluate the denoising effectiveness of different neural network architectures, comparing their resilience to weight errors before and after fault injections. Our experimental results demonstrate that binary neural networks (BNNs) exhibit superior robustness to weight errors compared to traditional deep neural networks (DNNs), making them a promising candidate for spaceborne AI applications.

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Microstructure and microwave surface resistance of YBCO films deposited under different oxygen pressures Zhi-Bo Sheng(盛智博), Fu-Cong Chen(陈赋聪), Pei-Yu Xiong(熊沛雨), Qi-Ru Yi(易栖如), Jie Yuan(袁洁), Yu Chen(陈雨), Yue-Liang Gu(顾月良), Kui Jin(金魁), Huan-Hua Wang(王焕华), Xiao-Long Li(李晓龙), and Chen Gao(高琛) Chin. Phys. B, 2025, 34 (4):  046105.  DOI: 10.1088/1674-1056/adb261 Abstract ( 29 )   PDF (1261KB) ( 4 )   YBa${}_2$Cu${}_3$O${}_{7-x}$ (YBCO) films with low microwave surface resistance ($R_{\mathrm{S}}$) are essential for high temperature superconducting microwave devices. The oxygen pressure during deposition has been found to influence $R_{\mathrm{S}}$ significantly. In this work, we deposited highly $c$-axis aligned YBCO films on single crystal MgO (001) substrates under different oxygen pressures via pulsed laser ablation. Their detailed microstructure was characterized with three-dimensional reciprocal space mapping (3D-RSM) method and their microwave surface resistance was also measured with resonant cavity perturbation method. We found that the variation of oxygen pressure can affect film microstructure, including grain orientation distribution and the concentration of crystal defects. The microstructure modulation can explain $R_{\mathrm{S}}$ dependence on the oxygen pressure.

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Non-negligible influence of vacancies and interlayer coupling on electronic properties of heavy ion irradiated SnSe2 FETs Shifan Gao(高诗凡), Siyuan Ma(马思远), Shengxia Zhang(张胜霞), Pengliang Zhu(朱彭靓), Jie Liu(刘杰), Lijun Xu(徐丽君), Pengfei Zhai(翟鹏飞), Peipei Hu(胡培培), and Yan Li(李燕) Chin. Phys. B, 2025, 34 (4):  046106.  DOI: 10.1088/1674-1056/adb270 Abstract ( 3 )   PDF (1143KB) ( 0 )   Influences of swift heavy ion (SHI) irradiation induced defects on electronic properties of the bulk SnSe${}_2$ based FETs are explored. Latent tracks and amounts of Se vacancies in the irradiated SnSe${}_2$ were confirmed. Red shift of the A${}_{1\mathrm{g}}$ peak indicates that the resonance frequency of the phonons is reduced due to the defect generation in SnSe${}_2$. The source-drain current $I_{\mathrm{d}\mathrm{s}}$ increased at ion fluence of 1$\times {10}^{10}$ ions$\cdot$cm${}^{-2}$, which was attributeded to the irradiation caused Se vacancies, which hence increases the concentration of conduction electrons. The carrier mobility was about 16.9 cm${}^2\cdot$V${}^{-1}\cdot$s${}^{-1}$ for the devices irradiated at ion fluence of 1$\times {10}^9$ ions$\cdot$cm${}^{-2}$, which benefited from heavy ion irradiation enhanced interlayer coupling. The mechanism of device performance optimization after irradiation is discussed in detail. This work provides evidence that, given the electronic properties of two-dimensional material-based device, vacancies and interlayer coupling effects caused by SHI irradiation should not be ignored.

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Design and preparation of amorphous carbon nanotubes reinforced copper Xiaona Ren(任晓娜), Wentao Wu(吴文涛), Zhipei Chen(陈志培), and Changchun Ge(葛昌纯) Chin. Phys. B, 2025, 34 (4):  046107.  DOI: 10.1088/1674-1056/adb8b7 Abstract ( 21 )   PDF (2485KB) ( 3 )   Carbon nanotubes (CNTs) reinforced copper (CNTs/Cu) is one of the most promising and extensively researched materials for replacing traditional Cu-based materials in high-load and high-current applications, particularly within the aerospace industry. Amorphous carbon nanotubes (aCNTs) are a type of carbon nanotubes characterized by the presence of mesopores distributed across their amorphous sidewalls, facilitating connectivity between the hollow core and the external environment. Therefore, we propose utilizing aCNTs as a reinforcing agent for Cu. The mesoporous structure of aCNTs facilitates the interpenetration of Cu into the aCNTs, thereby maintaining the continuity of the matrix properties. Experimental results demonstrate that Cu effectively penetrates the mesoporous sidewalls of aCNTs. Both pure Cu and aCNTs-reinforced Cu exhibit comparable electrical conductivity, while the hardness of the aCNTs/Cu composite is significantly enhanced. Additionally, both the density and porosity of aCNTs/Cu are lower than those of pure Cu, and the introduction of aCNTs helps to reduce the sintering temperature.

CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

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Effect of copper/tungsten heterophase interface on radiation resistance: Insights from atomistic simulations Wen Chen(陈文), Min Li(李敏), Bao-Qin Fu(付宝勤), Tun Chen(陈暾), Jie-Chao Cui(崔节超), and Qing Hou(侯氢) Chin. Phys. B, 2025, 34 (4):  046108.  DOI: 10.1088/1674-1056/adb40d Abstract ( 3 )   PDF (1712KB) ( 0 )   Nanostructured materials have demonstrated superior radiation-damage tolerance compared to their coarse-grained counterparts, contributing to the extended lifespan of nuclear materials. However, the mechanisms underlying this enhanced irradiation resistance remain unclear. In this study, we present atomistic simulations to investigate the impact of Cu/W heterophase interface on the evolution of irradiation-induced defects. The simulation results reveal that the Cu/W interfaces can act as defect sinks, effectively trapping self-interstitial atoms (SIAs). Furthermore, the interface demonstrates both the interstitial emission and interstitial transfer mechanisms, wherein the trapped W SIAs facilitate the emission of Cu atoms from the interface to the Cu side. These emitted Cu SIAs can promote defect recombination on the Cu side, leading to a reduced defect concentration in the Cu/W nanomultilayers. Consequently, these combined mechanisms contribute to a lower overall concentration of irradiation-induced defect, thereby enhancing the radiation resistance of Cu/W nano-multilayers.

SPECIAL TOPIC — Structures and properties of materials under high pressure

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Pressure-driven crystal structure evolution in RbB2C4 compounds Jinyu Liu(刘金禹), Ailing Liu(刘爱玲), Yujia Wang(王雨佳), Lili Gao(高丽丽), Xiangyi Luo(罗香怡), and Miao Zhang(张淼) Chin. Phys. B, 2025, 34 (4):  046201.  DOI: 10.1088/1674-1056/adb271 Abstract ( 5 )   PDF (1273KB) ( 0 )   As an extreme physical condition, high pressure serves as a potent means to substantially modify the interatomic distances and bonding patterns within condensed matter, thereby enabling the macroscopic manipulation of material properties. We employed the CALYPSO method to predict the stable structures of RbB${}_2$C${}_4$ across the pressure range from 0 GPa to 100 GPa and investigated its physical properties through first-principles calculations. Specially, we found four novel structures, namely, $P$6${}_3$/mcm-, Amm2-, $P$1-, and $I$4/mmm-RbB${}_2$C${}_4$. Under pressure conditions, electronic structure calculations reveal that all of them exhibit metallic characteristics. The calculation results of formation enthalpy show that the $P$6${}_3$/mcm structure can be synthesized within the pressure range of 0-40 GPa. Specially, the Amm2, $P1$, and $I$4/mmm structures can be synthesized above 4 GPa, 6 GPa, 10 GPa, respectively. Moreover, the estimated Vickers hardness value of $I$4/mmm-RbB${}_2$C${}_4$ compound is 47 GPa, suggesting that it is a superhard material. Interestingly, this study uncovers the continuous transformation of the crystal structure of RbB${}_2$C${}_4$ from a layered configuration to folded and tubular forms, ultimately attaining a stabilized cage-like structure under the pressure span of 0-100 GPa. The application of pressure offers a formidable impetus for the advancement and innovation in condensed matter physics, facilitating the exploration of novel states and functions of matter.

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Stoichiometric change and solid decomposition in Ca-S compounds under high pressure Yang Lv(吕阳), Jian-Fu Li(李建福), Zhao-Bin Zhang(张钊彬), Yong Liu(刘勇), Jia-Nan Yuan(袁嘉男), Jia-Ni Lin(林佳妮), and Xiao-Li Wang(王晓丽) Chin. Phys. B, 2025, 34 (4):  046202.  DOI: 10.1088/1674-1056/adb38e Abstract ( 6 )   PDF (2785KB) ( 2 )   As an independent thermodynamic parameter, pressure significantly influences interatomic distances, leading to an increase in material density. In this work, we employ the CALYPSO structure search and density functional theory calculations to explore the structural phase transitions and electronic properties of calcium-sulfur compounds (Ca${}_x$S${}_{1-x}$, where $x=1/4$, 1/3, 1/2, 2/3, 3/4, 4/5) under 0-1200 GPa. The calculated formation enthalpies suggest that Ca${}_x$S${}_{1-x}$ compounds undergo multiple phase transitions and eventually decompose into elemental Ca and S, challenging the traditional view that pressure stabilizes and densifies compounds. The analysis of formation enthalpy indicates that an increase in pressure leads to a rise in internal energy and the $PV$ term, resulting in thermodynamic instability. Bader charge analysis reveals that this phenomenon is attributed to a decrease in charge transfer under high pressure. The activation of Ca-3d orbitals is significantly enhanced under pressure, leading to competition with Ca-4s orbitals and S-3p orbitals. This may cause the formation enthalpy minimum on the convex hull to shift sequentially from CaS to CaS${}_3$, then to Ca${}_3$S and Ca${}_2$S, and finally back to CaS. These findings provide critical insights into the behavior of alkaline-earth metal sulfides under high pressure, with implications for the synthesis and application of novel materials under extreme conditions and for understanding element distribution in planetary interiors.

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Robustness of ferromagnetism in van der Waals magnet Fe3GeTe2 to hydrostatic pressure Yonglin Wang(王涌霖), Xu-Tao Zeng(曾旭涛), Bo Li(李博), Cheng Su(宿程), Takanori Hattori, Xian-Lei Sheng(胜献雷), and Wentao Jin(金文涛) Chin. Phys. B, 2025, 34 (4):  046203.  DOI: 10.1088/1674-1056/adb26f Abstract ( 30 )   PDF (2999KB) ( 5 )   Two-dimensional van der Waals ferromagnet Fe${}_3$GeTe${}_2$ (FGT) holds a great potential for applications in spintronic devices due to its high Curie temperature, easy tunability, and excellent structural stability in air. Theoretical studies have shown that pressure, as an external parameter, significantly affects its ferromagnetic properties. In this study, we have performed comprehensive high-pressure neutron powder diffraction (NPD) experiments on FGT up to 5 GPa to investigate the evolution of its structural and magnetic properties with hydrostatic pressure. The NPD data clearly reveal the robustness of the ferromagnetism in FGT, despite of an apparent suppression by hydrostatic pressure. As the pressure increases from 0 to 5 GPa, the Curie temperature is found to decrease monotonically from 225(5) K to 175(5) K, together with a dramatically suppressed ordered moment of Fe, which is well supported by the first-principles calculations. Although no pressure-driven structural phase transition is observed up to 5 GPa, quantitative analysis on the changes of bond lengths and bond angles indicates a significant modification of the exchange interactions, which accounts for the pressure-induced suppression of the ferromagnetism in FGT.

CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

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Elastic–plastic behavior of nickel-based single crystal superalloys with γ–γ' phases based on molecular dynamics simulations Jing-Zhao Cao(曹景昭), Yun-Guang Zhang(张云光), Zhong-Kui Zhang(张中奎), Jiang-Peng Fan(范江鹏), Qi Dong(董琪), and Ying-Ying Fang(方盈盈) Chin. Phys. B, 2025, 34 (4):  046204.  DOI: 10.1088/1674-1056/adb40f Abstract ( 14 )   PDF (5005KB) ( 7 )   The effects of temperature and Re content on the mechanical properties, dislocation morphology, and deformation mechanism of $\gamma$-${\gamma }^{\prime }$ phases nickel-based single crystal superalloys are investigated by using the molecular dynamics method through the model of $\gamma$-${\gamma }^{\prime }$ phases containing hole defect. The addition of Re makes the dislocation distribution tend towards the $\gamma$ phase. The higher the Re content, the earlier the $\gamma$ phase yields, while the ${\gamma }^{\prime }$ phase yields later. Dislocation bends under the combined action of the applied force and the resistance of the Re atoms to form a bend point. The Re atoms are located at the bend points and strengthen the alloy by fixing the dislocation and preventing it from cutting the ${\gamma }^{\prime }$ phase. Dislocations nucleate first in the $\gamma$ phase, causing the $\gamma$ phase to deform plastically before the ${\gamma }^{\prime }$ phase. As the strain increases, the dislocation length first remains unchanged, then increases rapidly, and finally fluctuates and changes. The dislocation lengths in the $\gamma$ phase are larger than those in the ${\gamma }^{\prime }$ phase at different temperatures. The dislocation length shows a decreasing tendency with the increase of the temperature. Temperature can affect movement of the dislocation, and superalloys have different plastic deformation mechanisms at low, medium and high temperatures.

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Unveiling the role of high-order anharmonicity in thermal expansion: A first-principles perspective Tianxu Zhang(张天旭), Kun Zhou(周琨), Yingjian Li(李英健), Chenhao Yi(易晨浩), Muhammad Faizan, Yuhao Fu(付钰豪), Xinjiang Wang(王新江), and Lijun Zhang(张立军) Chin. Phys. B, 2025, 34 (4):  046301.  DOI: 10.1088/1674-1056/adb94c Abstract ( 33 )   PDF (1744KB) ( 5 )   Thermal expansion is crucial for various industrial processes and is increasingly the focus of research endeavors aimed at improving material performance. However, it is the continuous advancements in first-principles calculations that have enabled researchers to understand the microscopic origins of thermal expansion. In this study, we propose a coefficient of thermal expansion (CTE) calculation scheme based on self-consistent phonon theory, incorporating the fourth-order anharmonicity. We selected four structures (Si, CaZrF${}_6$, SrTiO${}_3$, NaBr) to investigate high-order anharmonicity's impact on their CTEs, based on bonding types. The results indicate that our method goes beyond the second-order quasi-harmonic approximation and the third-order perturbation theory, aligning closely with experimental data. Furthermore, we observed that an increase in the ionicity of the structures leads to a more pronounced influence of high-order anharmonicity on CTE, with this effect primarily manifesting in variations of the Grüneisen parameter. Our research provides a theoretical foundation for accurately predicting and regulating the thermal expansion behavior of materials.

DATA PAPER

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An ab initio dataset of size-dependent effective thermal conductivity for advanced technology transistors Han Xie(谢涵), Ru Jia(贾如), Yonglin Xia(夏涌林), Lei Li(李磊), Yue Hu(胡跃), Jiaxuan Xu(徐家璇), Yufei Sheng(盛宇飞), Yuanyuan Wang(王元元), and Hua Bao(鲍华) Chin. Phys. B, 2025, 34 (4):  046501.  DOI: 10.1088/1674-1056/adbd13 Abstract ( 25 )   PDF (889KB) ( 4 )   As the size of transistors shrinks and power density increases, thermal simulation has become an indispensable part of the device design procedure. However, existing works for advanced technology transistors use simplified empirical models to calculate effective thermal conductivity in the simulations. In this work, we present a dataset of size-dependent effective thermal conductivity with electron and phonon properties extracted from \textit{ab initio} computations. Absolute in-plane and cross-plane thermal conductivity data of eight semiconducting materials (Si, Ge, GaN, AlN, 4H-SiC, GaAs, InAs, BAs) and four metallic materials (Al, W, TiN, Ti) with the characteristic length ranging from 5 nm to 50 nm have been provided. Besides the absolute value, normalized effective thermal conductivity is also given, in case it needs to be used with updated bulk thermal conductivity in the future.

SPECIAL TOPIC — Recent progress on kagome metals and superconductors

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High-throughput discovery of kagome materials in transition metal oxide monolayers Renhong Wang(王人宏), Cong Wang(王聪), Ruixuan Li(李睿宣), Deping Guo(郭的坪) Jiaqi Dai(戴佳琦), Canbo Zong(宗灿波), Weihan Zhang(张伟涵), and Wei Ji(季威) Chin. Phys. B, 2025, 34 (4):  046801.  DOI: 10.1088/1674-1056/adb265 Abstract ( 23 )   PDF (843KB) ( 3 )   Kagome materials are known for hosting exotic quantum states, including quantum spin liquids, charge density waves, and unconventional superconductivity. The search for kagome monolayers is driven by their ability to exhibit neat and well-defined kagome bands near the Fermi level, which are more easily realized in the absence of interlayer interactions. However, this absence also destabilizes the monolayer forms of many bulk kagome materials, posing significant challenges to their discovery. In this work, we propose a strategy to address this challenge by utilizing oxygen vacancies in transition metal oxides within a “1+3” design framework. Through high-throughput computational screening of 349 candidate materials, we identified 12 thermodynamically stable kagome monolayers with diverse electronic and magnetic properties. These materials were classified into three categories based on their lattice geometry, symmetry, band gaps, and magnetic configurations. Detailed analysis of three representative monolayers revealed kagome band features near their Fermi levels, with orbital contributions varying between oxygen 2p and transition metal d states. This study demonstrates the feasibility of the “1+3” strategy, offering a promising approach to uncovering low-dimensional kagome materials and advancing the exploration of their quantum phenomena.

CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES

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Electronic structure of a narrow-gap semiconductor KAg3Te2 Rong Feng(冯荣), Haotian Zheng(郑昊天), Haoran Liu(刘浩然), Binru Zhao(赵彬茹), Xunqing Yin(尹训庆), Zhihua Liu(刘智华), Feng Liu(刘峰), Guohua Wang(王国华), Xiaofeng Xu(许晓峰), Wentao Zhang(张文涛), Weidong Luo(罗卫东), Wei Zhou(周苇), and Dong Qian(钱冬) Chin. Phys. B, 2025, 34 (4):  047102.  DOI: 10.1088/1674-1056/adb680 Abstract ( 2 )   PDF (2431KB) ( 0 )   KAg${}_3$Te${}_2$ with a layered crystal structure has been predicted to be a possible topological insulator. Through electrical transport measurements, we revealed its semiconducting behavior with a narrow band gap of $\sim 0.4$ eV and p-type character. The infrared transmission spectra of single crystals yielded an optical band gap of $\sim 0.3$ eV. Angle-resolved photoemission spectroscopy reveals a bulk energy gap at the Brillouin zone center, with no observable surface state, suggesting that KAg${}_3$Te${}_2$ is a topological trivial narrow-gap semiconductor. The experimentally determined effective mass of the holes in KAg${}_3$Te${}_2$ is very small ($\sim 0.12m_{\mathrm{e}}$). The valence band maximum is quasi-two-dimensional, while the conduction band minimum is fully three-dimensional. Such intriguing dimensional anisotropy can be attributed to the distinct orbital contributions from K, Ag, and Te atoms to the respective bands.

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Gate leakage mechanisms in Al2O3/SiN/AlN/GaN MIS-HEMTs on Si substrates Hui-Lin Li(李惠琳), Jie-Jie Zhu(祝杰杰), Ling-Jie Qin(秦灵洁), Si-Mei Huang(黄思美), Shi-Yang Li(李诗洋), Bo-Xuan Gao(高渤轩), Qing Zhu(朱青), and Xiao-Hua Ma(马晓华) Chin. Phys. B, 2025, 34 (4):  047103.  DOI: 10.1088/1674-1056/adb26d Abstract ( 18 )   PDF (943KB) ( 6 )   This study investigates the gate leakage mechanisms of AlN/GaN metal-insulator-semiconductor high-electron-mobility transistors (MIS-HEMTs) fabricated on silicon substrate with Al${}_2$O${}_3$/SiN as stacked gate dielectrics, analyzing behaviors across high and low temperature conditions. In the high-temperature reverse bias region ($T>275$ K, $V_{\mathrm{G}}<0$ V), Poole-Frenkel emission (PFE) dominates at low electric fields, while trap-assisted tunneling (TAT) is the primary mechanism at medium to high electric fields. The shift from PFE to TAT as the dominant conduction mechanism is due to the increased tunneling effect of electrons as the electric field strength rises. Additionally, TAT is found to be the main gate leakage mechanism under low-temperature reverse bias ($T<275$ K, $V_{\mathrm{G}}<0$ V). At lower temperatures, the reduction in electron energy causes the emission process to rely more on electric field forces. Furthermore, under forward bias conditions at both high and low temperatures ($225\mathrm{K}<T<375\mathrm{K}$, $V_{\mathrm{G}}>0\mathrm{V}$), conduction is primarily dominated by defect-assisted tunneling (DAT).

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Strain-modulated superconductivity of monolayer Tc2B2 Zhengtao Liu(刘正涛), Zihan Zhang(张子涵), Hao Song(宋昊), Tian Cui(崔田) and Defang Duan(段德芳) Chin. Phys. B, 2025, 34 (4):  047104.  DOI: 10.1088/1674-1056/adb94d Abstract ( 25 )   PDF (5735KB) ( 3 )   Two-dimensional (2D) superconductors have attracted significant research interest due to their promising potential applications in optoelectronic and microelectronic devices. Herein, we employ first-principles calculations to predicted a new 2D conventional superconductor, Tc${}_2$B${}_2$, demonstrating its stable structural configuration. Remarkably, under biaxial strain, the superconducting transition temperature ($T_{\mathrm{c}}$) of Tc${}_2$B${}_2$ demonstrates a significant enhancement, achieving 19.5 K under 3{\%} compressive strain and 9.2 K under 11{\%} tensile strain. Our study reveals that strain-induced modifications in Fermi surface topology significantly enhance the Fermi surface nesting effect, which amplifies electron-phonon coupling interactions and consequently elevates $T_{\mathrm{c}}$. Additionally, the presence of the Lifshitz transition results in a more pronounced rise in $T_{\mathrm{c}}$ under compressive strain compared to tensile strain. These insights offer important theoretical guidance for designing 2D superconductors with high-$T_{\mathrm{c}}$ through strain modulation.

TOPICAL REVIEW — Moiré physics in two-dimensional materials

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Quantum anomalous Hall effect in twisted bilayer graphene Wen-Xiao Wang(王文晓), Yi-Wen Liu(刘亦文), and Lin He(何林) Chin. Phys. B, 2025, 34 (4):  047301.  DOI: 10.1088/1674-1056/adb38a Abstract ( 32 )   PDF (1599KB) ( 2 )   Recent advancements in two-dimensional van der Waals moiré materials have unveiled the captivating landscape of moiré physics. In twisted bilayer graphene (TBG) at ‘magic angles’, strong electronic correlations give rise to a diverse array of exotic physical phenomena, including correlated insulating states, superconductivity, magnetism, topological phases, and the quantum anomalous Hall (QAH) effect. Notably, the QAH effect demonstrates substantial promise for applications in electronic and quantum computing devices with low power consumption. This article focuses on the latest developments surrounding the QAH effect in magic-angle TBG. It provides a comprehensive analysis of magnetism and topology — two crucial factors in engineering the QAH effect within magic-angle TBG. Additionally, it offers a detailed overview of the experimental realization of the QAH effect in moiré superlattices. Furthermore, this review highlights the underlying mechanisms driving these exotic phases in moiré materials, contributing to a deeper understanding of strongly interacting quantum systems and facilitating the manipulation of new material properties to achieve novel quantum states.

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Fabrication of two-dimensional van der Waals moiré superlattices Zihao Wan(万子豪), Chao Wang(王超), Hang Zheng(郑航), Wenna Tang(唐文娜), Zihao Fu(付梓豪), Weilin Liu(刘伟林), Zhenjia Zhou(周振佳), Jun Li(李骏), Guowen Yuan(袁国文), and Libo Gao(高力波) Chin. Phys. B, 2025, 34 (4):  047302.  DOI: 10.1088/1674-1056/adb38b Abstract ( 28 )   PDF (6081KB) ( 5 )   Two-dimensional (2D) van der Waals (vdW) moiré superlattices have attracted significant attention due to their novel physical properties and quantum phenomena. The realization of these fascinating properties, however heavily depends on the quality of the measured moiré superlattices, emphasizing the importance of advanced fabrication techniques. This review provides an in-depth discussion of the methods for fabricating moiré superlattices. It begins with a brief overview of the structure, properties, and potential applications of moiré superlattices, followed by a detailed examination of fabrication techniques, focuses on different kinds of transfer techniques and growth methods, particularly chemical vapor deposition (CVD) method. Finally, it addresses current challenges in fabricating high-quality moiré superlattices and discusses potential directions for future advancements in this field. This review will enhance the understanding of moiré superlattice fabrication and contributing to the continued development of 2D twistronics.

SPECIAL TOPIC — Recent progress on kagome metals and superconductors

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Scanning tunneling microscopy study on symmetry breaking of charge density wave in FeGe Jiakang Zhang(张嘉康), Ziyuan Chen(陈子元), Xueliang Wu(吴学良), Mingzhe Li(李明哲), Yuanji Li(李元骥), Ruotong Yin(尹若彤), Jiashuo Gong(巩佳硕), Shiyuan Wang(王适源), Aifeng Wang(王爱峰), Dong-Lai Feng(封东来), and Ya-Jun Yan(闫亚军) Chin. Phys. B, 2025, 34 (4):  047303.  DOI: 10.1088/1674-1056/adb389 Abstract ( 23 )   PDF (4525KB) ( 3 )   The complex symmetry breaking states in $A$V${}_3$Sb${}_5$ family have attracted extreme research attention, but controversy still exists, especially in the question of time reversal symmetry breaking of the charge density wave (CDW). Most recently, a chiral CDW has been suggested in kagome magnet FeGe, but the related study is very rare. Here, we use a scanning tunneling microscope to study the symmetry breaking behavior of both the short- and long-range CDWs in FeGe. Different from previous studies, our study reveals an isotropic long-range CDW without obvious symmetry breaking, while local rotational symmetry breaking appears in the short-range CDW, which may be related to the existence of strong structural disorders. Moreover, the charge distribution of the short-range CDW is inert to the applied external magnetic fields and the detailed spin arrangements of FeGe, inconsistent with the expectation of a chiral CDW associated with chiral flux. Our results rule out the existence of spontaneous chiral and rotational symmetry breaking in the CDW state of FeGe, putting strong constraints on the further understanding of CDW mechanism.

CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES

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Band alignment of heterojunctions formed by PtSe2 with doped GaN Zhuoyang Lv(吕卓阳), Guijuan Zhao(赵桂娟), Wanting Wei(魏婉婷), Xiurui Lv(吕秀睿), and Guipeng Liu(刘贵鹏) Chin. Phys. B, 2025, 34 (4):  047304.  DOI: 10.1088/1674-1056/adb67b Abstract ( 15 )   PDF (5085KB) ( 1 )   In order to investigate the effect of different doping types on the band alignment of heterojunctions, we prepared PtSe${}_2$/n-GaN, PtSe${}_2$/p-GaN, and PtSe${}_2$/u-GaN heterojunctions by wet transfer technique. The valence band offsets (VBO) of the three heterojunctions were measured by x-ray photoelectron spectroscopy (XPS), while the PtSe${}_2$/n-GaN is 3.70$\pm$0.15 eV, PtSe${}_2$/p-GaN is 0.264$\pm$0.15 eV, and PtSe${}_2$/u-GaN is 3.02$\pm$0.15 eV. The conduction band offset (CBO) of the three heterojunctions was calculated from the material bandgap and VBO, while the PtSe${}_2$/n-GaN is 0.61$\pm$0.15 eV, PtSe${}_2$/p-GaN is 2.83$\pm$0.15 eV, and PtSe${}_2$/u-GaN is 0.07$\pm$0.15 eV. This signifies that both PtSe${}_2$/u-GaN and PtSe${}_2$/p-GaN exhibit type-I band alignment, but the PtSe${}_2$/n-GaN heterojunction has type-III band alignment. This signifies that the band engineering of PtSe${}_2$/GaN heterojunction can be achieved by manipulating the concentration and type of doping, which is significantly relevant for the advancement of related devices through the realization of band alignment and the modulation of the material properties of the PtSe${}_2$/GaN heterojunction.

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First principles prediction of the valley Hall effect in ScBrCl monolayer Xiang Yu(于翔), Ping Li(李萍), and Chang-Wen Zhang(张昌文) Chin. Phys. B, 2025, 34 (4):  047305.  DOI: 10.1088/1674-1056/adbacb Abstract ( 19 )   PDF (2131KB) ( 4 )   Two-dimensional (2D) ferrovalley materials with valley-dependent Hall effect have attracted great interest due to their significant applications in spintronics. In this paper, by using first-principles computational simulations, we predict that the ScBrCl monolayer is a 2D ferrovalley material with valley-dependent multiple Hall effects. After calculations, we found that the ScBrCl monolayer has excellent thermodynamic stability and kinetic stability, and has a high magnetic transition temperature. When the magnetization direction is turned from in-plane to out-of-plane, a large valley polarization of 44 meV can be generated. In particular, under 5.1%-5.3% tensile strain conditions, ScBrCl monolayer can achieve quantum anomalous Hall effect, and further prove its existence through non-zero Chern number and non-trivial edge state. Our discovery enriches the research on valley-dependent Hall effect and promotes the potential application of 2D Janus monolayer in valley electronics.

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Phase transition extracted by principal component analysis in the disordered Moore-Read state Na Jiang(江娜), Shuaixin Fu(付帅鑫), Zhengzhi Ma(马正直), and Lian Wang(王莲) Chin. Phys. B, 2025, 34 (4):  047306.  DOI: 10.1088/1674-1056/adb25f Abstract ( 1 )   PDF (399KB) ( 0 )   We study the influence of disorder on the Moore-Read state by principal component analysis (PCA), which is one of the ground state candidates for the 5/2 fractional Hall state. By using PCA, the topological features of the ground state wave functions with different disorder strengths can be distilled. As the disorder strength increases, the Moore-Read state will be destroyed. We explore the phase transition by analyzing the overlaps between the random sample wave functions and the topologically distilled state. The cross-point between the amplitudes of the principal component and its counterpart is the phase transition point. Additionally, the origin of the second component comes from the excited states, which is different from the Laughlin state.

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Regulation of superconductivity in Nb thin films induced by interstitial oxygen atoms Yuchuan Liu(刘钰川), Ming Yang(杨明), Yun Fan(范云), Zulei Xu(徐祖磊), Yu Wu(吴禹), Yixin Liu(刘以鑫), Wei Peng(彭炜), Gang Mu(牟刚), and Zhi-Rong Lin(林志荣) Chin. Phys. B, 2025, 34 (4):  047401.  DOI: 10.1088/1674-1056/adb26c Abstract ( 16 )   PDF (596KB) ( 1 )   The regulation of superconductivity in thin films can provide important information on low-dimensional superconducting properties, and also has important reference values for the application in superconducting devices. Herein, we report the successful regulation of both the superconductivity and normal-state properties of Nb films in a wide range by the controllable introduction of interstitial oxygen atoms. The lattice parameter is enhanced for an extent as large as 4.4%, and the normal-state resistivity ${\rho }_{\mathrm{n}}$ is tuned for more than 15 times. The slope of upper critical field near $T_{\mathrm{c}}$ shows a close correlation with ${\rho }_{\mathrm{n}}$ in a wide range. Importantly, it is found that the suppression of $T_{\mathrm{c}}$ by disorder reveals a linear dependence with ${\rho }_{\mathrm{n}}$ in the region with an unchanged crystalline quality, which can be understood based on the picture of three-dimensional ballistic motion.

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Synergistic SERS effects in organic/MoS2 heterojunctions with cavity structure enabling nanoplastics screening and antibiotic adsorption behavior detection Liqi Ma(马立琪), Abdur Rahim(阿卜杜勒-拉希姆), Baiju Lü(吕白菊), Muhammad Saleem(穆罕默德-萨利姆), Xiaoyu Zhang(张晓雨), Mingyue Li(李明月), Muhammad Zahid(穆罕默德-扎希德), and Mei Liu(刘玫) Chin. Phys. B, 2025, 34 (4):  047402.  DOI: 10.1088/1674-1056/ada888 Abstract ( 10 )   PDF (2394KB) ( 1 )   The detection of nanoplastics (NPs) and their interactions with antibiotics is critical due to their potential environmental and health risks. Traditional detection methods are challenged by the small size and chemical similarity of NPs to microplastics. Current surface-enhanced Raman scattering (SERS) substrates for NP detection are limited by high cost, reliance on single enhancement modes, and insufficient sensitivity and selectivity, especially for NP-antibiotic complexes. In this study, the F/M-AAO substrate, which integrates 2,3,5,6-tetrafluoro-tetracyanoquinodimethane (F${}_4$TCNQ) and molybdenum disulfide (MoS${}_2$) with anodic aluminum oxide (AAO) templates, is used to enhance the detection of NPs and NP-antibiotic complexes. The conical cavity structure of the substrate facilitates the enrichment and direct detection of NPs with diameters smaller than 450 nm. The three-dimensional (3D) F/M-AAO substrate achieved a limit of detection (LOD) of 1.73$\times {10}^6$ ng/L for 100-nm NPs and a minimum detection concentration of 10${}^{-10}$ M for ciprofloxacin adsorbed on NPs (NPs-CIP). It demonstrated remarkable sensitivity and selectivity in the detection of both individual NPs and NP-antibiotic complexes. This work highlights the innovative application of the F/M-AAO substrate in the SERS detection of NPs and NP-antibiotic complexes, providing a low-cost and effective platform for monitoring emerging environmental contaminants.

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Superconductivity in titanium probed by AC magnetic susceptibility to 120 Gpa Jing Song(宋静), Hongyu Liu(刘红玉), Xiancheng Wang(望贤成), and Changqing Jin(靳常青) Chin. Phys. B, 2025, 34 (4):  047403.  DOI: 10.1088/1674-1056/adb26e Abstract ( 35 )   PDF (694KB) ( 3 )   We used a highly sensitive AC magnetic susceptibility technique to probe superconductivity in elemental titanium (Ti) under extreme pressures to 120 GPa in a diamond anvil cell (DAC). The measurements reveal that the critical temperature ($T_{\mathrm{c}}$) of Ti rises monotonically with increasing pressure, reaching 6.1 K at 120 GPa. Our results confirm the bulk nature of the superconductivity in Ti, as evidenced by a robust diamagnetic response in the AC magnetic susceptibility. Our work provides a routine technique to probe Meissner effect of elemental superconductors at megabar pressures.

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Direct observation of ultrafast magnetization dynamics in Co/Ni bit patterned media by time-resolved scanning Kerr microscopy Wei Zhang(张伟), Wei He(何为), Qin-Li Lv(吕琴丽), Jian-Wang Cai(蔡建旺), Xiang-Qun Zhang(张向群), and Zhao-Hua Cheng(成昭华) Chin. Phys. B, 2025, 34 (4):  047501.  DOI: 10.1088/1674-1056/adb67e Abstract ( 3 )   PDF (1509KB) ( 1 )   Bit patterned recording (BPR) has attracted much attention due to its promising potential in achieving high densities in magnetic storage devices. The materials with strong perpendicular magnetic anisotropy (PMA) are always preferred in designing the BPR. Here, the patterned Co/Ni multilayers showing d-d hybridization induced PMA was studied. In particular, we record the ultrafast spin dynamics by means of time-resolved scanning magneto-optical Kerr effect (TRMOKE) microscopy. We are able to acquire the "snapshot" magnetic maps of the sample surface because of both the femtosecond temporal and submicrometer spatial resolution in our TRMOKE microscopy. Furthermore, the spatially inhomogeneous ultrafast demagnetization was observed in experiment, and this has been evidenced by simulations.

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Influence of cooling atmosphere on the structure, magnetization, and dielectric properties of CaBaCo4O7 Gaoshang Gong(龚高尚), Minghao Wang(王明豪), Ruoshui Liu(刘若水), Yang Wu(吴杨), Lichen Wang(王利晨), Yongqiang Wang(王永强), and Baogen Shen(沈保根) Chin. Phys. B, 2025, 34 (4):  047502.  DOI: 10.1088/1674-1056/adbadc Abstract ( 1 )   PDF (756KB) ( 0 )   CaBaCo${}_4$O${}_7$ has been widely studied because of its distinctive structure and magnetic properties. This study examined the influence of different cooling atmospheres on the structure, magnetic properties, and dielectric behavior of CaBaCo${}_4$O${}_7$. Samples were cooled under different atmospheric conditions to assess these influences. Our findings indicate that reduced oxygen content leads to increased lattice distortion. Since oxygen atoms play a crucial role in mediating magnetic exchange, oxygen deficiency disrupts long-range magnetic order and promotes short-range antiferromagnetic interactions. Additionally, the cooling atmosphere significantly impacts grain size, thereby affecting the dielectric constant and dielectric loss. In the argon-cooled CaBaCo${}_4$O${}_7$ (Ar) sample, oxygen deficiency reduced dielectric permittivity and increased dielectric loss.

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High-performance KNN-based piezoelectric ceramics for buzzer application Cheng Xiong(熊城), Bosen Li(李博森), Zhongxin Liao(廖忠新), Yan Qiu(邱䶮), and Daqiang Gao(高大强) Chin. Phys. B, 2025, 34 (4):  047701.  DOI: 10.1088/1674-1056/adb25e Abstract ( 33 )   PDF (1052KB) ( 5 )   Piezoelectric ceramic materials are important components of piezoelectric buzzers, where the parameter of inverse piezoelectric coefficient ($d_{33}^{\ast }$) plays a decisive role in the performance of the buzzer. Here, we report the manufacture and performance of a lead-free ceramic-based (0.96(K${}_{0.5}$Na${}_{0.5}$)(Nb${}_{0.96}$Sb${}_{0.04}$)O${}_3$-0.04(Bi${}_{0.5}$Na${}_{0.5}$)ZrO${}_3$-1 mol{\%} Al${}_2$O${}_3$, abbreviated as KNNS-BNZ-1 mol{\%} Al${}_2$O${}_3$) piezoelectric buzzer and compare it with commercial (PbZr${}_{0.5}$Ti${}_{0.5}$O${}_3$, abbreviated as PZT) ceramics. Briefly, KNN-based ceramics have a typical perovskite structure and piezoelectric properties of $d_{33}=480$ pC/N, $k_{\mathrm{p}}=0.62$ and $d_{33}^{\ast }=830$ pm/V, compared to $d_{33}=500$ pC/N, $k_{\mathrm{p}}=0.6$ and $d_{33}^{\ast }=918$ pm/V of the commercial PZT-4 ceramics. Our results show that the KNNS-BNZ-1 mol{\%} Al${}_2$O${}_3$ ceramics have a similar sound pressure level performance over the testing frequency range to commercial PZT ceramics (which is even better in the 3-4 kHz range). These findings highlight the great application potential of KNN-based piezoelectric ceramics.

INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY

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Anisotropy of average potential energy of passive plate in bacterial suspensions Luhui Ning(宁鲁慧), Ziwei Xiao(肖紫薇), Yuxin Tian(田宇鑫), Hongwei Zhu(朱红伟), Yi Peng(彭毅), Peng Liu(刘鹏), Ning Zheng(郑宁), Mingcheng Yang(杨明成), and Junqing Chen(陈君青) Chin. Phys. B, 2025, 34 (4):  048201.  DOI: 10.1088/1674-1056/adbee6 Abstract ( 19 )   PDF (600KB) ( 1 )   We conduct optical-tweezers experiments to investigate the average potential energies of passive plates harmonically trapped in bacterial suspensions. Our results show that the mean potential energies along both the major and minor axes increase with bacterial concentration but decrease with trap stiffness. Notably, the average potential energy along the major axis consistently exceeds that along the minor axis. This discrepancy from equilibrium systems is primarily attributed to the distinct bacterial flow fields and direct bacterium-plate collisions near the major and minor axes, as evidenced by the higher orientational order around the plate along the major compared to the minor axis, despite identical bacterial densities in these regions. Our findings highlight the critical role of hydrodynamic interactions in determining the potential energy of passive objects immersed in an active bath.

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Multiscale structural complexity analysis of neuronal activity in suprachiasmatic nucleus: Insights from tetrodotoxin-induced disruptions Ping Wang(王萍), Changgui Gu(顾长贵), and Huijie Yang(杨会杰) Chin. Phys. B, 2025, 34 (4):  048701.  DOI: 10.1088/1674-1056/adaccd Abstract ( 13 )   PDF (585KB) ( 1 )   The suprachiasmatic nucleus in the hypothalamus is the master circadian clock in mammals, coordinating physiological processes with the 24-hour day-night cycle. Comprising various cell types, the suprachiasmatic nucleus (SCN) integrates environmental signals to maintain complex and robust circadian rhythms. Understanding the complexity and synchrony within SCN neurons is essential for effective circadian clock function. Synchrony involves coordinated neuronal firing for robust rhythms, while complexity reflects diverse activity patterns and interactions, indicating adaptability. Interestingly, the SCN retains circadian rhythms in vitro, demonstrating intrinsic rhythmicity. This study introduces the multiscale structural complexity method to analyze changes in SCN neuronal activity and complexity at macro and micro levels, based on Bagrov et al.'s approach. By examining structural complexity and local complexities across scales, we aim to understand how tetrodotoxin, a neurotoxin that inhibits action potentials, affects SCN neurons. Our method captures critical scales in neuronal interactions that traditional methods may overlook. Validation with the Goodwin model confirms the reliability of our observations. By integrating experimental data with theoretical models, this study provides new insights into the effects of tetrodotoxin (TTX) on neuronal complexities, contributing to the understanding of circadian rhythms.

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A bionic robotic fish with a dielectric elastomer Chenghong Zhang(张成红) Chin. Phys. B, 2025, 34 (4):  048702.  DOI: 10.1088/1674-1056/adacc9 Abstract ( 5 )   PDF (1366KB) ( 0 )   Dielectric elastomer actuators (DEAs) are promising enabling devices which can be used in a wide range of robots, artificial muscles, and microfluidics. They are characterized by high actuating strain, low cost and noise, and high energy density and efficiency. There are three main challenges for enabling DEs to become actuators: (i) developing suitable and compatible electrode materials; (ii) effectively isolating the actuator electrode from the surrounding fluid; and (iii) creating a rigid frame that usually requires prestraining of the dielectric layer. The use of robotic fish in water is an important application field of biomimetic soft robots. At present, most underwater robotic fish use spiral propulsion, which has several problems, including propulsion efficiency, position controllability and aquatic organism involvement. To provide solutions, the research and development of underwater robotic fish that imitate the fins and body propulsion of fish and the use of soft underwater robotic fish are in full adoption. This project involves the research and development of a bionic soft underwater robot fish with a software driver, which can imitate swimming via the tail fin and body of a fish, especially with respect to stable swimming propulsion, to successfully develop high-performance soft underwater robot fish. In addition, to imitate the unstable swimming movements of fish, such as turning and sharp acceleration and deceleration, robot fish that use DE drivers with good flexibility and high strain have been researched and developed.

REVIEW

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Pedestrian collision and future work in the restricted indoor space: A state-of-the-art review on influencing factors, behaviors, and methods Zhenxiang Tao(陶振翔);, Ying Li(李滢), Xubo Huang(黄绪勃), Yisen Wang(王一森), Rui Yang(杨锐), and Hui Zhang(张辉) Chin. Phys. B, 2025, 34 (4):  048901.  DOI: 10.1088/1674-1056/adacca Abstract ( 21 )   PDF (1144KB) ( 1 )   Emergency evacuation involves rapid transfer of individuals from hazardous areas, where limited time and space can lead to collisions. Although the collision behavior of evacuees has been studied previously, there is a lack of systematic summaries. This study used the CiteSpace visualization software to analyze keywords in the evacuation collision literature. Based on the frequency of keyword occurrence, we determined the research trend; classified the keywords; and analyzed and summarized their influencing factors, behavioral characteristics, and research methods. Clearly, the evacuation environment and emergency guidance directly affect individual behavior and emotions, mainly affecting gait adjustment and decisionmaking processes, which in turn determine evacuation efficiency and collision risk. In the future, emphasis should be placed on post-collision psychological activities, coping strategies, and the application of virtual and mixed reality technologies to observe the interaction between individuals and the environment and to strengthen evacuation research.

COMPUTATIONAL PROGRAMS FOR PHYSICS

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Identifying important nodes of hypergraph: An improved PageRank algorithm Yu-Hao Piao(朴宇豪), Jun-Yi Wang(王俊义), and Ke-Zan Li(李科赞) Chin. Phys. B, 2025, 34 (4):  048902.  DOI: 10.1088/1674-1056/adb269 Abstract ( 14 )   PDF (658KB) ( 0 )   Hypergraphs can accurately capture complex higher-order relationships, but it is challenging to identify their important nodes. In this paper, an improved PageRank (ImPageRank) algorithm is designed to identify important nodes in a directed hypergraph. The algorithm introduces the Jaccard similarity of directed hypergraphs. By comparing the numbers of common neighbors between nodes with the total number of their neighbors, the Jaccard similarity measure takes into account the similarity between nodes that are not directly connected, and can reflect the potential correlation between nodes. An improved susceptible-infected (SI) model in directed hypergraph is proposed, which considers nonlinear propagation mode and more realistic propagation mechanism. In addition, some important node evaluation methods are transferred from undirected hypergraphs and applied to directed hypergraphs. Finally, the ImPageRank algorithm is used to evaluate the performance of the SI model, network robustness and monotonicity. Simulations of real networks demonstrate the excellent performance of the proposed algorithm and provide a powerful framework for identifying important nodes in directed hypergraphs.

CORRIGENDUM

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Corrigendum to “Elastic properties of Cu-6wt% Ag alloy wires for pulsed magnets investigated by ultrasonic techniques” Ziyu Li(李滋雨), Tianyi Gu(顾天逸), Wenqi Wei(魏文琦), Yang Yuan(袁洋), Zhuo Wang(王卓), Kangjian Luo(罗康健), Yupeng Pan(潘宇鹏), Jianfeng Xie(谢剑峰), Shaozhe Zhang(张绍哲), Tao Peng(彭涛), Lin Liu(柳林), Qi Chen(谌祺), Xiaotao Han(韩小涛), Yongkang Luo(罗永康), and Liang Li(李亮) Chin. Phys. B, 2025, 34 (4):  049901.  DOI: 10.1088/1674-1056/adc66a Abstract ( 4 )   PDF (294KB) ( 0 )   Figure 3 in the paper [Chin. Phys. B 34 020701 (2025)] contains an axis labeling error. The revised figure is provided. This modification does not affect the result presented in the paper.