Table of contents

24 March 2026, Volume 35 Issue 4 Previous issue   

GENERAL

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Measurement of the equivalent complex permittivity of electromagnetic structural materials without prior thickness Xiang-Bao Zhu(朱香宝), Yun-Peng Zhang(张云鹏), Pin-Hong Xie(谢品鸿), Yi-Hang Tu(涂一航), Jia-Wei Long(龙嘉威), Xue Niu(牛雪), Chong Gao(高冲), Cheng-Yong Yu(余承勇), Yong Gao(高勇), and En Li(李恩) Chin. Phys. B, 2026, 35 (4):  040101.  DOI: 10.1088/1674-1056/ae0434 Abstract ( 26 )   PDF (1133KB) ( 5 )   Electromagnetic structural materials exhibit significant sensitivity to the polarization state and incidence angle of electromagnetic waves. The equivalent complex permittivity is the core parameter that describes the dielectric properties of electromagnetic structural materials. Therefore, accurate characterization of their equivalent complex permittivity is essential for establishing electromagnetic models and guiding the design of functional devices. This paper proposes a broadband inversion method based solely on reflection measurements at different incident polarizations and incident angles. By establishing a set of adaptive equations for multi-reflection measurement states under oblique incidence, the proposed method directly resolves the equivalent complex permittivity without requiring prior knowledge of the sample thickness and iterative phase unwrapping, and obtains broadband measurement results in a single measurement. The simulation and experimental results show that this method has good testing consistency and accuracy. This study provides a high-precision, low-cost and efficient testing solution for dielectric property evaluation of electromagnetic structural materials. It can simplify the complex modeling design of electromagnetic structural materials into an equivalent single-layer material design, providing a reference value for rapid analysis of the scattering characteristics of complex structures.

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Integrable decompositions and superposed nonlinear solutions of (2+1)-dimensional Caudrey-Dodd-Gibbon-Kotera-Sawada equation Yan Li(李岩), Ruoxia Yao(姚若侠), and Senyue Lou(楼森岳) Chin. Phys. B, 2026, 35 (4):  040201.  DOI: 10.1088/1674-1056/ae0435 Abstract ( 20 )   PDF (826KB) ( 4 )   The phenomenon of shallow water waves in nature attracts the attention of scholars and plays an important role in fields such as marine ecology, tidal waves, solitary waves, and offshore engineering. To better understand the phenomenon of shallow water waves, we investigate the $(2+1)$-dimensional Caudrey-Dodd-Gibbon-Kotera-Sawada (2D-CDGKS) equation from the perspective of integrable decomposition. By utilizing the Lax pairs and formal variable separation (FVS) method, the 2D-CDGKS equation can be decomposed into the Sharma-Tasso-Olver (STO) equation, the integrable Svinolupov-Sokolov (SS) equation, and the Sawada-Kotera (SK) equation. We construct some novel exact solutions by linear superposing the integrable decomposition relations. Additionally, the superposition of two-soliton solution with three-soliton solution, two-soliton solution propagating on periodic cnoidal background waves, and soliton-cnoidal wave interaction solutions with interesting dynamics, are explored. Our results have important significance for understanding of the physical events consolidate the complex system under consideration and offering vital insights into the intricate dynamics of its behavior. Furthermore, the present work will enrich the investigation of nonlinear dynamics in high-dimensional nonlinear system, and provide theoretical support for the related experimental phenomena.

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Modified PINN approach integrating conservation laws for efficient multi-stage training of coupled nonlinear systems Jie Deng(邓婕) and Lijia Han(韩励佳) Chin. Phys. B, 2026, 35 (4):  040202.  DOI: 10.1088/1674-1056/ae030b Abstract ( 8 )   PDF (2621KB) ( 5 )   We propose an innovative conservation multi-stage algorithm (CM) based on physics-informed neural networks (PINNs) to investigate the dynamics of vector solitons governed by Zakharov equation. By ingeniously integrating conservation laws into the multi-stage training algorithm, we enhanced the method's constraint and physical consistency in solving nonlinear systems. Numerical simulations of the Zakharov and nonlinear Schrödinger (NLS) equations demonstrated that our method showed obvious improvements in approximation accuracy, convergence speed, and training efficiency, compared to traditional PINN methods. Moreover, when the parameter representing the speed of sound is sufficiently large, our method efficiently simulates the approximation from the Zakharov equation to the NLS equation. The approximative simulation not only confirms the conservation multi-stage algorithm's applicability in various physical environments but also highlights its potential in controlling sound wave propagation characteristics to simulate NLS equation behavior.

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Enhancing spiral microrobot dynamics in ratchet potentials: The role of Gaussian colored noise Xinpeng Shi(史鑫鹏) and Kheder Suleiman Chin. Phys. B, 2026, 35 (4):  040203.  DOI: 10.1088/1674-1056/ae0c00 Abstract ( 27 )   PDF (1115KB) ( 5 )   Random disturbances in microfluidic environments often cause pronounced trajectory deviations in microrobots, posing challenges for robust control. However, most existing models either neglect these disturbances or idealize them as Gaussian white noise, limiting their applicability. To address this, we investigate the influence of Gaussian colored noise (GCN) on the dynamics of a spiral microrobot navigating a ratchet potential. A stochastic dynamic model grounded in resistive force theory is proposed, and the system's response is analyzed using the steady-state probability density function. We systematically examine how variations in ratchet potential, fluid viscosity, and noise intensity affect the microrobot's average velocity and mean first passage time. Moreover, we explore how geometric design impacts propulsion efficiency under stochastic excitation. Results reveal that GCN can significantly enhance propulsion efficiency and promote directional transport, with these effects strongly dependent on the noise correlation time. These findings not only enrich the theoretical framework of noise-induced microrobot dynamics but also provide practical guidance for optimizing design and environmental parameters.

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Quantum dephasing dynamics in the presence of asymmetric random telegraph noise Yanyan Feng(冯言言), Jing Ren(任静), Xiangji Cai(蔡祥吉), and Yonggang Peng(彭勇刚) Chin. Phys. B, 2026, 35 (4):  040204.  DOI: 10.1088/1674-1056/ae0398 Abstract ( 11 )   PDF (1583KB) ( 1 )   Random telegraph noise (RTN) has been widely used to describe the environmental effects on open quantum systems. In most cases, it is assumed that the environmental noise described by RTN has symmetric properties. However, in some important physical processes, the asymmetric characteristics of environmental noise play a crucial role in the dynamical evolution of the quantum systems. We theoretically study the dephasing dynamics of a two-level quantum system induced by RTN with asymmetric properties. Within the framework of the stochastic Liouville equation, we derive the exact expression of the decoherence function quantifying the coherence evolution of the quantum system. It is shown that, in contrast to the case of the symmetric RTN, the asymmetric RTN can induce a frequency shift and may lead to non-Markovian behavior in the decoherence dynamics of the quantum system. Furthermore, by adjusting the average transition rate, the transition rate difference, and the transition amplitude difference of the environmental noise, the decoherence dynamics of the quantum system can be effectively modulated.

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New binary quantum stabilizer codes from classical quasi-cyclic codes of index two Zhen-Hui Zhang(张镇辉), Zhuo Li(李卓), and Li-Juan Xing(邢莉娟) Chin. Phys. B, 2026, 35 (4):  040303.  DOI: 10.1088/1674-1056/ae067b Abstract ( 20 )   PDF (297KB) ( 0 )   We study the algebraic structures of a generalized class of quasi-cyclic codes of index two, and prove that any quasi-cyclic code of index two can be transformed into our proposed quasi-cyclic codes. We determine the generator forms of the proposed quasi-cyclic codes and their Hermitian dual codes. We establish the necessary and sufficient conditions for Hermitian self-orthogonality and dual-containing property to construct quantum stabilizer codes via the Hermitian construction method. As an application, 10 record-breaking quantum stabilizer codes are constructed.

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Quantum designated verifier signature scheme based on Lagrange interpolation Xu-Feng Li(李旭峰), Dong-Huan Jiang(姜东焕), Yu-Guang Yang(杨宇光), and Guang-Bao Xu(徐光宝) Chin. Phys. B, 2026, 35 (4):  040304.  DOI: 10.1088/1674-1056/ae0679 Abstract ( 19 )   PDF (371KB) ( 0 )   Quantum designated verifier signature (QDVS) schemes can be applied in many scenarios, such as e-voting and electronic bidding. In this paper, we propose a novel QDVS scheme based on Lagrange interpolation. By avoiding the preparation of entangled states and the operation of comparing quantum states, our scheme effectively reduces the complexity of the signature scheme. In the process of identity authentication our scheme assigns a unique identity identifier to the signer Alice and the verifier Bob to ensure non-repudiation of the signature. Security analysis shows that the scheme can effectively resist common threats such as forgery attacks and interception attacks. In addition, the qubit efficiency of our scheme reaches 100%. Compared with existing QDVS schemes, the proposed scheme shows significant advantages in terms of resource consumption, computational complexity and practical application feasibility.

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Schemes of IPsec integrated with quantum key distribution Chun-Hui Zhang(张春辉), Wen-Xuan Zhang(张文轩), Xing-Yu Zhou(周星宇), Yuan Cao(曹原), Jun Wang(汪军), Jian Li(李剑), and Qin Wang(王琴) Chin. Phys. B, 2026, 35 (4):  040305.  DOI: 10.1088/1674-1056/ae3301 Abstract ( 7 )   PDF (1710KB) ( 2 )   With the rapid advancement of quantum computing, traditional security protocols based on classical encryption algorithms are increasingly vulnerable to potential quantum attacks. The current IPsec protocol, which relies on classical cryptographic methods, is insufficient to withstand such threats, thereby compromising the security of long-term data transmission. To address this issue, we propose integrating quantum key distribution (QKD) into the internet protocol security (IPsec) protocol, thereby enhancing its resilience against quantum computing attacks. Here, two schemes that merge QKD-generated keys with classical cryptographic keys are designed to enhance both security and stability. Furthermore, we conduct a comprehensive evaluation of the performance of various QKD protocols implemented with the scheme, along with an assessment of its overall efficacy across a topological network configuration. This approach not only ensures secure data transmission in the era of quantum computing but also highlights the potential application value of integrating QKD with IPsec, providing valuable insights for the design and implementation of future quantum-secure communication systems.

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Analysis of urban atmospheric influence on free-space quantum key distribution Hai-Long Zhang(张海龙), Xing-Ran Chen(陈星燃), and Tan Li(李坦) Chin. Phys. B, 2026, 35 (4):  040306.  DOI: 10.1088/1674-1056/ae0bfc Abstract ( 20 )   PDF (523KB) ( 4 )   Quantum key distribution (QKD) has been widely deployed in practical applications after decades of development. However, the QKD system is easily affected by the external environment, especially free-space QKD. In this text, we examine two scenarios of free-space QKD in urban environments: satellite to ground and intercity. For satellite to ground QKD, the effects of stray light are analyzed. For intercity link, we discuss the influence of sea salt particles in coastal cities, and insoluble and soot particles in inland cities. Our findings indicate that using a telescope with a smaller field of view (FOV) and larger aperture diameters in satellite-to-ground QKD can effectively reduce errors induced by stray light. However, the diameter cannot be increased infinitely, when exceeding 0.8 m, the number of stray photons entering receiver rises rapidly and the quantum bits error rate (QBER) shows no significant reduction. For intercity QKD, the strength of extinction varies with relative humidity and aerosol particle radius, consequently altering channel transmittance. We investigate the impact of sea salt, insoluble particles, and soot on the key rate, finding that under the number density $N=10^6$ m$^{-3}$, sea salt exhibits the strongest impacts on key rate, especially when radius exceed 2.5 μm. The impacts of insoluble particles are weaker and soot is the weakest, which can be ignored until $N$ reaches $10^9$ m$^{-3}$. For larger particle density, we can get higher key rate and further transmission distances in a soot-dominated environment. Our work could provide a valuable reference for the practical implementation of QKD in urban atmospheres.

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Asymmetric model of the dynamic quantum Cournot duopoly game with asymmetric information and heterogeneous players Huaxi Chen(陈华鑫) and Wensheng Jia(贾文生) Chin. Phys. B, 2026, 35 (4):  040307.  DOI: 10.1088/1674-1056/ae00af Abstract ( 12 )   PDF (829KB) ( 1 )   Building on the existing symmetric quantization model of the dynamic Cournot duopoly game (CDG) with asymmetric information, we extend it to an asymmetric quantization model and study the stability of the quantum Bayesian Nash equilibrium (QBNE) under heterogeneous expectations. We analyze the influence of various parameters on the stability of QBNE, with a particular focus on the impact of the parameter $\alpha$ on system stability. The results show that when $\alpha < 1$, under the same parameters, the quantum strategy of the asymmetric quantization model is more favorable for stabilizing the market. However, when $\alpha>1$, the quantum strategy of the symmetric quantization model is more conducive to stabilizing the market.

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Hierarchical QAOA circuit design framework for distributed quantum computing Ting-Yu Luo(骆挺宇), and Yu-Xin Deng(邓玉欣) Chin. Phys. B, 2026, 35 (4):  040309.  DOI: 10.1088/1674-1056/ae00ae Abstract ( 8 )   PDF (14099KB) ( 0 )   The quantum approximate optimization algorithm (QAOA) is a promising approach for solving combinatorial optimization problems on real quantum devices. As QAOA scales to tackle larger problem instances, the limited qubit capacity of single-chip systems becomes a critical bottleneck. To overcome this limitation, distributed quantum computing (DQC) provides a scalable solution. However, when QAOA circuits are executed in such systems, their performance is significantly hindered by the high cost of remote communication. Motivated by this challenge, we propose $HiQ$-$DF$, a QAOA circuit design framework tailored for DQC systems. By employing a hierarchical optimization strategy, $HiQ$-$DF$ enables comprehensive multi-objective optimization during circuit construction. Experimental results on QAOA circuits solving MaxCut instances show that our framework significantly outperforms baseline methods, achieving an average reduction of $26.12%$ in EPR pair usage (up to $36.85%$), $26.44%$ in circuit latency (up to $35.27%$), and $39.63%$ in circuit depth (up to $49.3%$).

SPECIAL TOPIC — Quantum communication and quantum network

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Measurement-device-independent quantum key distribution with entanglement-assisted linear Bell state measurement Cheng Zhang(张诚), Cheng Liu(刘成), Jiawei Ying(应佳伟), Shipu Gu(顾世浦), Lan Zhou(周澜), Yin Ma(马寅), Kang Gao(高亢), Hai Wei(魏海), Kai Wen(文凯), and Yubo Sheng(盛宇波) Chin. Phys. B, 2026, 35 (4):  040310.  DOI: 10.1088/1674-1056/ae3605 Abstract ( 18 )   PDF (681KB) ( 5 )   Measurement-device-independent quantum key distribution (MDI QKD) provides inherent immunity against attacks targeting practical measurement devices. Existing MDI QKD protocols all rely on Bell-state measurements (BSM) to establish correlations between the users. However, the success probability of linear-optics BSM is limited to 50%, which severely restricts the achievable key rate of MDI QKD. We propose a high-capacity MDI QKD protocol with entanglement-assisted linear-optical BSM. This protocol has three advantages. First, compared with the original MDI QKD, at least a 25% increase in the key rate can be achieved. Second, simulation results show that this protocol can effectively increase the maximum photon transmission distance of MDI QKD from 262 km to 272 km. Third, this protocol is feasible in a fully linear-optical system under current experimental conditions. Our protocol provides a potential approach for improving the performance of future quantum communication networks.

GENERAL

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Entanglement enhancement in a modulated optomechanical system via squeezed vacuum field Huan-Huan Cheng(程欢欢), Chen-Rui Yang(杨晨锐), Gao-Feng Jiao(焦高锋), Cheng-Hua Bai(白成华), and Shao-Xiong Wu(武少雄) Chin. Phys. B, 2026, 35 (4):  040311.  DOI: 10.1088/1674-1056/ae2d37 Abstract ( 3 )   PDF (1068KB) ( 0 )   We present a double-cavity optomechanical system with a mechanical oscillator, which is jointly driven by an amplitude-modulated laser field and a weak squeezed vacuum field, aiming to explore quantum entanglement effects under the unresolved-sideband regime. Within our proposed scheme, it is possible not only to surpass the limit of maximum steady-state entanglement ln2 for bipartite entanglement, achieving strong entanglement, but also to significantly enhance tripartite entanglement and improve the system's robustness against thermal noise. Meanwhile, the introduction of the squeezed vacuum field plays a crucial role in entanglement control, enabling not only a several-fold enhancement of entanglement but also continuous and precise manipulation of its strength within specific ranges. The suggested method demonstrates exceptional flexibility and adaptability under a wide range of operating conditions, offering a new pathway for theoretical and experimental investigations of strong bipartite entanglement and tripartite entanglement.

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Structural optimization of magnetic flux concentrator based on particle swarm optimization algorithm Yu-Xiao Wang(王雨潇), Shi-Yu Guan(管世钰), Yi Zhang(张燚), Qi-Yuan Jiang(江奇渊), Bing-Feng Sun(孙兵锋), and Zhong-Qi Tan(谭中奇) Chin. Phys. B, 2026, 35 (4):  040701.  DOI: 10.1088/1674-1056/ae0b38 Abstract ( 14 )   PDF (522KB) ( 2 )   This study introduces a structural optimization method for magnetic flux concentrators (MFCs) utilizing the particle swarm optimization (PSO) algorithm, addressing inefficiencies and challenges in achieving optimal structures with traditional methods. By integrating the PSO algorithm with COMSOL Multiphysics simulation software, a co-simulation framework is developed to optimize the parameters of a conical MFC. Compared with traditional methods, this approach enhances optimization results by twofold, achieving a magnetic field amplification factor of up to 200 within the defined parameter range. Additionally, an evaluation criterion for concentrator optimization is proposed, offering novel insights for designing concentrators across various scenarios.

TOPICAL REVIEW — Ultrafast physics in atomic, molecular and optical systems

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Measuring the Coulomb time shift in high-order harmonic generation Shengjun Yue(岳生俊), Siqi Song(宋思琦), Ruofeng Zhong(钟若峰), Jiangkun Li(李江坤), Haiyuan Yu(于海元), and Hongchuan Du(杜洪川) Chin. Phys. B, 2026, 35 (4):  043201.  DOI: 10.1088/1674-1056/ae1951 Abstract ( 22 )   PDF (2301KB) ( 3 )   High-order harmonic generation (HHG), a key nonlinear phenomenon in strong-field physics, enables ultrafast detection on the attosecond timescale. Quantifying ionization/recombination times is essential for trajectory-resolved high-harmonic spectroscopy and for benchmarking its temporal resolution. In this review, we summarize our recent studies [Phys. Rev. A 105 L041103 (2022), Phys. Rev. A 106 023117 (2022), Phys. Rev. A 107 063102 (2023), Phys. Rev. A 111 039902 (2025)] on the role of electron-core interactions in HHG. Employing the classical trajectory model, analytical R-matrix theory, and numerical solutions of time-dependent Schrödinger equations for helium, we reveal how Coulomb attraction induces subtle shifts in ionization and recombination times. Such effects emerge as observable signatures under orthogonally polarized bichromatic fields at high probe frequencies. Because of the direct experimental relevance of these findings, this review seeks to stimulate further experimental efforts to control and resolve electron dynamics in HHG. In the future, it will be of great interest to (i) refine retrieval methods by incorporating Coulomb corrections beyond the static-field approximation, and (ii) advance two-color detection techniques with the capability to reconstruct complete quantum trajectories in HHG.

SPECIAL TOPIC — Ultrafast physics in atomic, molecular and optical systems

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Comparing distinct dissociation pathways of C2H22+ under laser and electron impact Xiangjie Chen(陈祥杰), Jianting Lei(雷建廷), Chenyu Tao(陶琛玉), Shuncheng Yan(闫顺成), Yongzhe Ma(马永哲), Fenghao Sun(孙烽豪), Qincao Liu(刘情操), and Shaofeng Zhang(张少锋) Chin. Phys. B, 2026, 35 (4):  043202.  DOI: 10.1088/1674-1056/ae311d Abstract ( 21 )   PDF (1135KB) ( 4 )   We report a comparative study of the dissociation dynamics of ethyne (C$_{2}$H$_{2}$) molecules and clusters under a strong laser field ($9\times 10^{13}$ W/cm$^{2}$) and 1 keV electron impact. Using coincidence momentum imaging, we identify several two-body dissociation channels of C$_{2}$H$_{2}^{2+}$, including C$_{2}$H$^{+} + {\rm H}^{+}$, CH$_{2}^{+} + {\rm C}^{+}$, symmetric breakup into CH$^{+}$ + CH$^{+}$, as well as dimer dissociation channels such as C$_{2}$H$_{2}^{+} + {\rm C}_{2}$H$_{2}^{+}$ and C$_{2}$H$_{2}^{2+} + {\rm C}_{2}$H$_{2}^{+}$. By analyzing the kinetic energy release (KER) and branching ratios of the dominant fragmentation pathways, we demonstrate that double ionization under a strong laser field preferentially leads to dissociation on the singlet ground-state surface ($^{1}\Delta_{\rm g}$), whereas electron impact favors the triplet ground state ($^{3}\Sigma_{\rm g}^{-}$). This contrast is attributed to different ionization mechanisms: electron impact follows a propensity rule favoring the lower-energy triplet, while strong-field ionization aligned with the $\pi$ orbitals promotes singlet formation due to the Pauli exclusion principle. Our findings provide clear evidence of excitation-condition-dependent dissociation pathways in acetylene dications.

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Molecular orbital effect in above-threshold ionization of vinyl bromide induced by strong laser fields Qi Chen(陈淇), Yang Liu(刘洋), Wei Yang(杨威), Di Liu(刘迪), Hang Lv(吕航), Bing Yan(闫冰), and Haifeng Xu(徐海峰) Chin. Phys. B, 2026, 35 (4):  043303.  DOI: 10.1088/1674-1056/ae4465 Abstract ( 5 )   PDF (661KB) ( 2 )   Ionization is a fundamental process that may induce a variety of highly nonlinear physical phenomena in strong femtosecond laser fields. Compared to that of atoms, strong-field ionization (SFI) of polyatomic molecules is far from being understood because of their diverse geometric and orbital structures. In this study, we experimentally investigate SFI of the vinyl bromide ($\mathrm{C_2 H_3 Br}$) molecule in near ultraviolet and near-infrared strong laser fields employing the electron velocity map imaging (VMI) method. The distinct above-threshold ionization (ATI) structure of the molecule is clearly observed in both strong laser fields. The electron kinetic energy as well as the angular distributions is derived from the electron VMI measurements, and their dependence on the laser intensity is investigated and discussed. Analysis reveals that owing to the small energy difference between the low-lying electronic orbitals of the $\mathrm{C_2 H_3 Br}$ molecule, multiple orbital effect plays a pivotal role in the SFI of the molecule. The present study adds our knowledge on SFI and ATI of the $\mathrm{C_2 H_3 Br}$ molecule, and sheds some light on the interaction of polyatomic molecules with ultrafast strong laser fields.

ATOMIC AND MOLECULAR PHYSICS

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Effects of spin-destruction and spin-exchange collisions on alkali-metal relaxation and magnetometric response Feng Tang(汤丰), Jianjun Li(李建军), and Nan Zhao(赵楠) Chin. Phys. B, 2026, 35 (4):  043401.  DOI: 10.1088/1674-1056/ae37f7 Abstract ( 1 )   PDF (734KB) ( 0 )   Spin-exchange (SE) and spin-destruction (SD) collisions play a central role in determining the coherence properties of alkali-metal vapors and the performance of alkali-metal magnetometers in external magnetic fields. In this work, we investigate how these collisions influence spin relaxation dynamics and magnetometric response using a generalized Bloch equation that fully accounts for the coupled evolution of spin polarizations in different hyperfine manifolds. Our results show that in the low-field regime, both SE and SD collisions contribute to the suppression of transverse spin relaxation and the slowdown of spin precession, whereas longitudinal relaxation depends weakly on the SE rate and is predominantly governed by SD interactions. Building on the established relationship between spin relaxation rates and magnetometric response, we further analyze how SE and SD collisions affect the performance of two representative magnetometer architectures: the spin-exchange relaxation-free (SERF) magnetometer and the magnetic-resonance Mx-type magnetometer. The SERF magnetometer's response is found to be primarily determined by the SD rate, with only minor dependence on the nuclear spin quantum number. In contrast, the magnetic-resonance Mx-type magnetometer's sensitivity is significantly affected by both the magnetic field strength and the SE rate. While the resonance linewidth decreases with reduced magnetic field, the associated measurement accuracy deteriorates markedly. Consequently, reliable magnetic field reconstruction is only achievable in the high-field regime, where the Larmor frequency greatly exceeds the SE rate.

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Charge transfer processes in low-energy Na+-Na collisions Cheng-Cheng Jiang(蒋承呈), Xiao-Xia Wang(王小霞), Kun Wang(王堃), Yi-Zhi Qu(屈一至), Jian-Guo Wang(王建国), Xia Li(李侠), Li Ma(马丽), and Robert J. Buenker Chin. Phys. B, 2026, 35 (4):  043402.  DOI: 10.1088/1674-1056/ae15f0 Abstract ( 2 )   PDF (807KB) ( 0 )   A comprehensive theoretical study of resonant and non-resonant charge transfer processes in the homonuclear Na$^+$ $+$ Na(3s) collision system is provided. The electronic structure of the quasi-molecular system is calculated using the multireference single- and double-excitation configuration interaction (MRD-CI) method under both one-electron (OEM) and thirteen-electron (TEM) models. The radial and rotational coupling matrix elements are obtained with careful inclusion of electron translation factors (ETFs). Based on these data, fully quantum-mechanical scattering calculations were performed using the fully quantum-mechanical molecular orbital close-coupling (QMOCC) method to derive state-selective and total cross sections for electron capture over a broad energy range (0.2-5600 eV/amu). The calculated resonant charge-transfer cross sections show excellent agreement with available theoretical and experimental results. Non-resonant processes, which involve electron capture into excited states of Na$^+$, are found to become increasingly important above several keV/amu. This work provides the first theoretical predictions for non-resonant state-selective cross sections in this system, offering a valuable reference for future experimental and theoretical studies in atomic collision physics.

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

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Dissipative soliton operation in a mode-locked laser based on thulium-doped fiber Wen-Yan Zhang(张文艳), Lei Zheng(郑磊), Tian Zhang(张添), Nan-Nan Liu(刘楠楠), Li-Jie Geng(耿利杰), Kun Yang(杨坤), and Li Zhan(詹黎) Chin. Phys. B, 2026, 35 (4):  044201.  DOI: 10.1088/1674-1056/ae063c Abstract ( 8 )   PDF (996KB) ( 0 )   We report a dissipative soliton laser utilizing thulium-doped fiber as the saturable absorber. By adjusting the polarization controller and pump power, a stable fundamental dissipative pulse has been successfully achieved, featuring a center wavelength of 1565.88 nm, a 3-dB bandwidth of 1.20 nm, a repetition frequency of 36.9 MHz, and a signal-to-noise ratio of 64 dB. Combined the gradual increase of the pump power with the intracavity polarization optimization, the spectral morphology evolves into a parabolic shape, $\Pi$-shape, and M-shape. Moreover, through increasing the gain, multiple dissipative pulses include dissipative soliton pairs and triples are manifested because of the peak power clamping effect. The repetition frequencies are 73.8 MHz and 110.7 MHz, respectively, with signal-to-noise ratios both more than 60 dB, indicating that the constructed dissipative soliton laser has excellent stability. This study not only enhances the understanding of the nonlinear dynamic process of dissipative soliton generation, but also offers a novel approach for designing ultrafast lasers characterized by high stability and an all-fiber structure.

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Mode and orbital angular momentum controlling of nonlocal solitons by anisotropic diffraction Junying Zhu(朱俊英), Qing Wang(王清), and Jianning Wei(魏健宁) Chin. Phys. B, 2026, 35 (4):  044202.  DOI: 10.1088/1674-1056/ae0163 Abstract ( 9 )   PDF (1738KB) ( 0 )   This study presents a novel approach to control the mode transform between Laguerre-Gaussian solitons and Hermite-Gaussian solitons by designing anisotropic diffraction in nonlocal medium. The anisotropic diffraction can introduce differential phase shifts and amplitude modulations to the optical field, and then leading to the transform of the soliton mode from one to another, while the accompanying orbital angular momentum exhibits a periodic variation. When the anisotropic diffraction is designed to become isotropic at the desired distance, various mode solitons with different rotation speeds and directions can be generated, which implies that the mode transform process and the change law of orbital angular momentum can be controlled. This finding establishes a versatile platform for nonlinear mode transform, offering new possibilities for applications in optical signal processing, topological photonics, optical micro-manipulation, and so on.

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Bistable Goos-Hänchen shift owing to leaky-mode excitation in a slab waveguide with Kerr nonlinear medium Yuan-Ping Cai(蔡园平), Li Jiang(姜丽), and Ren-Gang Wan(万仁刚) Chin. Phys. B, 2026, 35 (4):  044203.  DOI: 10.1088/1674-1056/ae00b3 Abstract ( 21 )   PDF (481KB) ( 9 )   We investigate the nonlinear Goos—Hänchen shift of a light beam reflected from a prism-coupled leaky waveguide containing a Kerr medium. As the incident power varies, the system can switch between two states, total internal reflection and frustrated total reflection, owing to the inherent positive feedback arising from the intensity-dependent guiding mode resonance. The reflectance exhibits optical bistability; meanwhile, the lateral shift of the reflected beam also shows hysteresis behavior. It is found that the transition between the two stable states is related to the excitation of a leaky mode in the waveguide, which results from the modulation of the electric field in the nonlinear substrate. We also analyze the effects of system parameters on the bistable Goos—Hänchen shift. The thresholds as well as the width of the hysteresis curve are sensitive to the thicknesses of the gap layer and the guiding layer, which determine the resonance angle. The bistable lateral displacement in the slab waveguide may have potential applications in optical switching, beam steering, etc.

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Role of trajectory symmetry in solid high-order harmonic generation Shuang Wang(王爽), Yu Zhao(赵宇), Hui-Rong Wang(王慧荣), Yun-He Xing(邢云鹤), Xiao-Xin Huo(霍晓鑫), and Jun Zhang(张军) Chin. Phys. B, 2026, 35 (4):  044204.  DOI: 10.1088/1674-1056/ae04da Abstract ( 13 )   PDF (992KB) ( 3 )   High-order harmonic generation (HHG) from a ZnO crystal has been investigated theoretically using a two-band model driven by a few-cycle laser pulse. We observe that harmonics in the cut-off region exhibit periodic frequency shifts with changes in the carrier envelope phase (CEP) of the laser field. When the CEP of the laser pulse is an integer multiple of $\pi$, the cut-off region is dominated by even-order harmonics rather than odd-order harmonics. To illustrate the physical mechanism behind the even-order harmonics, we track the trajectories of electrons and holes between two successive half-cycles by performing time-frequency analysis and applying the recollision model. The results show that the maximum electron displacement is symmetric between successive half-cycles for odd-order harmonics. In contrast, the half-cycle symmetry of the maximum displacement is broken in the case of even-order harmonics.

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Supersymmetry-driven segmented tapered laser for stabilized single transverse and longitudinal mode engineering Yiwen Lou(楼亦文), Tian Lan(兰天), Jun Qi(齐军), Jinlong Zhao(赵金龙), Ying Li(李颖), Baiyi Qin(覃柏颐), Yuying Liu(刘豫颖), Xuesheng Liu(刘学胜), and Zhiyong Wang (王智勇) Chin. Phys. B, 2026, 35 (4):  044207.  DOI: 10.1088/1674-1056/ae29f9 Abstract ( 6 )   PDF (955KB) ( 1 )   Tapered lasers are extensively employed in high power single-mode lasing, yet still suffering from the potential formation of higher-order transverse modes in the tapered region, which severely degrades the laser beam quality. Herein, we propose a novel supersymmetric segmented tapered laser to achieve stable fundamental transverse mode operation. Our design features a three-segmented tapered waveguide along the light propagation direction, with sub-waveguides of varying widths flanking each main waveguide segment. The main waveguides measure 8 μm, 12 μm, and 16 μm in width. Specifically, the 8 μm main waveguide has a corresponding subsidiary waveguide of 2.67 μm; the 12 μm main waveguide has two subsidiary waveguides measuring 4.82 μm and 6.63 μm; and the 16 μm main waveguide has two subsidiary waveguides measuring 7.13 μm and 3.68 μm. Using the coupled-mode theory, we systematically analyzed the coupling coefficients under different inter-waveguide spacings, leading to an optimized spacing of 1.2 μm through comprehensive theoretical simulations and fabrication compatibility constraints. Furthermore, phase-shifted gratings were integrated between tapered waveguide segments to enable precise longitudinal mode selection. This synergistic design could successfully realize robust single-mode operation, offering a scalable framework for on-chip integrated high-power, high-beam-quality tapered lasers.

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Simultaneous frequency stabilization of two 1550-nm lasers at single-photon level Bo Yu(于波), Zhenqiang Yin(银振强), Weijie Ding(丁伟杰), Hui Yang(杨慧), and Weixin Liu(刘伟新) Chin. Phys. B, 2026, 35 (4):  044208.  DOI: 10.1088/1674-1056/ade072 Abstract ( 8 )   PDF (2880KB) ( 3 )   The twin-field quantum key distribution (TF-QKD) requires that two lasers hundreds of kilometers apart must have the same frequency to achieve the high single-photon interference visibility. This means that both lasers need to be stabilized to the same frequency reference. A simple and robust system is presented for simultaneously stabilizing two 1550-nm lasers at the single-photon level. By utilizing the single-photon multi-frequency modulation technology, both the fiber laser and distributed feedback (DFB) laser are stabilized to the $\pi $-phase shifted fiber Bragg grating at the same time. The frequency fluctuations of fiber laser and DFB laser are bounded within 1.39 MHz and 1.53 MHz over 2000 s, respectively. These two frequency-stabilized 1550-nm lasers could be used for TF-QKD.

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A high-gain optical injection amplification system for coherent fiber links Ru Yuan(袁茹), Xiang Zhang(张翔), Qian Zhou(周茜), Qi Zang(臧琦), Bo-Lin Zhang(张林波), Yi-Ting Liu(刘依婷), Dan Wang(王丹), Jie Liu(刘杰), Yu-Can Zhang(张钰灿), Yu-Fang Lei(雷语芳), Tao Liu(刘涛), Rui-Fang Dong(董瑞芳), and Shou-Gang Zhang(张首刚) Chin. Phys. B, 2026, 35 (4):  044209.  DOI: 10.1088/1674-1056/ae111a Abstract ( 3 )   PDF (1539KB) ( 0 )   We design a high-gain optical amplification system based on optical injection locking (OIL) technology, which has an all-fiber structure and is ideally suited for fiber-based optical frequency transfer system. The paper investigates the relationship between amplification gain and frequency detuning under different injection linewidths, showing that smaller injection linewidths result in higher gains for the same frequency detuning. Preliminary experiments show that with a 5 Hz injection linewidth and sufficiently small frequency detuning, an amplification gain exceeding 60 dB can be achieved. In contrast to previous approaches, we introduce an out-of-loop optical path with an acousto-optic modulator to counteract the additional phase noise introduced by the asymmetric optical paths, achieving a higher-performance optical injection amplification system. After effective phase noise suppression, the noise floor of 1m coherent fiber link constructed based on the optical amplification system achieves a fractional frequency instability floor of $1.6\times 10^{-20}$ at an integration time of 10000 s. Based on this high-performance system, a long-distance coherent transmission experiment over a 200 km spooled fiber link was demonstrated, which showed a fractional frequency instability of $3.4\times 10^{-15}$ at 1 s, scaling down to $3.4\times 10^{-20}$ at 10000 s in terms of modified Allan deviation (Mod-ADEV). This work presents a high-gain optical amplification method for transferring ultra-stable optical frequency standards, reducing the number of repeaters and amplifiers in optical frequency transfer, and simplifying the system complexity.

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Generation of squeezed states of magnons and photons based on the Kerr effect in cavity-magnon hybrid system Cheng-Hua Bai(白成华) and Suying Bai(白素英) Chin. Phys. B, 2026, 35 (4):  044210.  DOI: 10.1088/1674-1056/ae4b2d Abstract ( 3 )   PDF (3312KB) ( 0 )   Based on the magnon Kerr effect, we show how to generate quantum squeezed states of magnons and photons in the cavity-magnon hybrid system. We find that the squeezing of magnons can be successfully induced by the magnon nonlinearity and the larger two-magnon effect strength will be beneficial to achieving the stronger squeezing of magnon. Resorting to the beam-splitter interaction between the magnons and photons, we further show that the squeezing of photons can be also effectively achieved. By properly choosing the system parameters, we demonstrate that the desired direction of the generated squeezing both for magnons and photons can be flexibly switched between orthogonal directions. Our scheme provides an alternative manipulation method to explore the quantum phenomena with nonlinear effects and also has significant potential applications in quantum precision measurement.

PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES

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Frequency chirp-induced enhancement of electron–positron pair production in polarized laser fields Obulkasim Olugh(吾布力卡斯木·吾鲁克) Chin. Phys. B, 2026, 35 (4):  045202.  DOI: 10.1088/1674-1056/ae0a3c Abstract ( 18 )   PDF (6884KB) ( 3 )   We investigate electron-positron pair production in frequency-chirped, polarized laser fields using the Dirac-Heisenberg-Wigner formalism. A key theoretical finding is the polarization-dependent critical chirp threshold $b_{\rm c}(\delta)$, which marks the transition between tunneling-dominated and multiphoton pair production regimes: $b_{\rm c}$ doubles as polarization evolves from linear ($\delta=0$, $b_{\rm c}(0)=0.02 {\rm m}^2$) to circular ($\delta=1$, $b_{\rm c}(1)=0.04 {\rm m}^2$). Above this threshold, chirp induces spectral compression with the momentum distribution width scaling as $\Delta q \propto b^{-1/2}$, concentrating pairs into a smaller phase-space volume and enhancing production yields by up to three orders of magnitude, following the universal scaling law $n \propto (b\tau)^{3/2}$. Notably, non-monotonic polarization dependence is observed at intermediate chirp values, where linear polarization temporarily surpasses circular in yield before convergence at large $b$. These results establish chirp as a precise control parameter for optimizing EP pair production in nonperturbative quantum electrodynamics, advancing the theoretical framework for understanding quantum vacuum dynamics and providing a foundation for structured pulse engineering in strong-field quantum electrodynamics.

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Interpretable logistic regression for predicting 1/1 kink-driven regular complete sawtooth phenomenon in EAST tokamak plasmas Haipeng Quan(全海鹏), Liqing Xu(徐立清), Chaowei Mai(麦晁玮), Yan Chao(晁燕), Yuhang Wang(王宇航), and EAST Team Chin. Phys. B, 2026, 35 (4):  045203.  DOI: 10.1088/1674-1056/ae37f5 Abstract ( 7 )   PDF (859KB) ( 0 )   Sawtooth phenomena are a central topic in tokamak fusion research; nevertheless, different sawtooth classes differ markedly in underlying physics, statistical abundance and diagnostic definition. This paper focuses exclusively on regular complete sawtooth — ideal, 1/1 internal-kink-driven events with full magnetic reconnection — which are the most frequent, unambiguously identifiable and theoretically best characterized (hereafter, all references to "sawtooth" denote this specific class). Compound crashes, partial-reconnection events and fast-ion-induced giant sawtooth are deliberately excluded because of their limited data volume and still-contested classification criteria, the inclusion of which would introduce intolerable label noise and theoretical ambiguity. To this aim, we propose a machine-learning-based temporal binary-classification framework that converts multi-diagnostic, high-resolution signals into precise labels distinguishing "oscillation" from "quiet" windows for this specific category, thereby supplying critical timing information for active control. A large-scale database covering 124 discharges and hundreds of millions of samples was constructed, and three representative algorithms — logistic regression, decision tree and random forest — were trained and compared. Among them, logistic regression achieved the best and most robust performance, reaching 95 % accuracy on an independent test set and significantly outperforming the other models. Furthermore, shapley additive explanations (SHAP) was innovatively employed to quantify the contribution magnitude and direction of key physical features to the onset of regular 1/1 sawtooth, substantially enhancing model interpretability and physical fidelity. The study provides an efficient and robust predictor for the active intervals of ordinary 1/1 sawtooth; the uncovered correlations between physical drivers and sawtooth behavior lay a solid foundation for deepening the understanding of regular sawtooth evolution and for optimizing control strategies, thereby holding significant promise for improving the operational stability of fusion plasmas.

CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

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Entropic force of a fluctuating semiflexible polymer exerted on a nanoparticle Shi-Qiang Li(李世强), Yu-Shan Zheng(郑玉山), Xiao-Jing Wan(万晓静), and Kai Li(李凯) Chin. Phys. B, 2026, 35 (4):  046101.  DOI: 10.1088/1674-1056/ae2d31 Abstract ( 1 )   PDF (829KB) ( 0 )   This study theoretically investigates the force exerted on a nanoparticle (NP) by a clamped semiflexible chain in solution. The force exerted by the semiflexible chain on the NP is related to the chain's conformational entropy, known as the entropic force. Under the weakly bending approximation, we derive an analytical formula for the entropic force using perturbation theory. This force can be divided into two components: parallel ($f_{\rho }$) and perpendicular ($f_{z} $, lifting the NP) to the initial vector at the clamped end. These two components are correlated with the local slope of the NP's cross-section, with the component $f_{z} $ additionally linked to the local curvature. We compare the magnitude of force $f_{z} $ with the Euler buckling threshold $f_{\rm c} $. The study reveals that as the chain becomes more compressed, $f_{z} $ initially peaks at a value exceeding the mechanical limit and subsequently decreases to a steady-state value lower than $f_{\rm c} $. This behavior significantly differs from the entropic force derived under flat wall confinement. In three dimensions, $f_{z} $ always stays below the Euler buckling threshold and in two dimensions it is larger than $f_{\rm c} $ for most of the parameter space.

SPECIAL TOPIC — Artificial intelligence and smart materials innovation: From fundamentals to applications

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Unveiling stable and efficient antiperovskite semiconductors via high-throughput computation and interpretable machine learning Hao Qu(瞿浩), Tao Hu(胡涛), Mingjun Li(李明军), Jiangyu Yang(杨江渝), Yunyi Zhou(周云逸), Shichang Li(李世长), Dengfeng Li(李登峰), Gang Tang(唐刚), and Chunbao Feng(冯春宝) Chin. Phys. B, 2026, 35 (4):  046102.  DOI: 10.1088/1674-1056/ae24e7 Abstract ( 0 )   PDF (6524KB) ( 0 )   Nitride antiperovskites have recently been theoretically identified as promising optoelectronic materials, yet their chemical space remains largely unexplored. Here, we employ a high-throughput first-principles screening workflow to systematically investigate the X$_3$BA antiperovskite family. Six candidates that exhibit both structural and dynamical stability together with desirable bandgaps are identified. Electronic-structure calculations reveal that the alkaline-earth-based compounds (e.g., Ca$_3$AsSb, Sr$_3$AsSb, Ba$_3$AsSb) not only possess suitable direct bandgaps and strong optical absorption, but also exhibit favorable ambipolar carrier mobilities and low exciton binding energies ($< 45$ meV). Notably, Sr$_3$AsSb and Ba$_3$AsSb are predicted to achieve theoretical maximum power-conversion efficiencies of 28.1% and 29.4%, respectively. Finally, an interpretable machine-learning model demonstrates that the electronegativity of the A-site anion is the single most influential descriptor governing bandgap trends across the chemical space. This work establishes a data-driven design heuristic and provides a predictive framework for the accelerated discovery of efficient and stable antiperovskite-based optoelectronic materials.

CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

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Dynamic mechanical response of polystyrene at high strain rates under uniaxial strain ramp loading Xuping Zhang(张旭平), Fuli Tan(谭福利), Binqiang Luo(罗斌强), Guiji Wang(王桂吉), Jianheng Zhao(赵剑衡), and Chengwei Sun(孙承纬) Chin. Phys. B, 2026, 35 (4):  046201.  DOI: 10.1088/1674-1056/ae0637 Abstract ( 15 )   PDF (699KB) ( 2 )   Determination of the yield strength of polymers under dynamic loading has proven to be extremely difficult. Until now, few strength data have been obtained for polymers at strain rates above 10$^{5}$ s$^{-1}$. Based on the electromagnetically driven quasi-isentropic loading technique, the yield strength of polystyrene under high pressure and high strain rate is measured experimentally using a pressure comparison method. In the experiment, a polystyrene window method is used to measure the in-situ particle velocity directly, which reduces the experimental error and obtains reliable high-pressure Lagrangian sound velocity and a quasi-isentropic compression line. The yield stress of polystyrene under quasi-isentropic compression is measured continuously at pressure up to 4 GPa and a strain rate of 10$^{6}$ s$^{-1}$. Combined with strength data under quasi-static and intermediate strain rate loading, the strain rate effect of the yield of polystyrene is analyzed. It is found that the yield strength of polystyrene shows strain rate effects, but the "up-turn" phenomenon is not observed. Additionally, the yield stress of polystyrene from 10$^{-3}$ s$^{-1}$ to 10$^{6}$ s$^{-1}$ strain rate can be fitted using the Eyring model, which provides a reference for the study of the physical properties of polymer materials under high strain rate loading.

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Be–B thin film growth: A deep potential and molecular dynamics study Xilei Wang(王熙蕾) and Hong Zhang(张红) Chin. Phys. B, 2026, 35 (4):  046801.  DOI: 10.1088/1674-1056/ae0309 Abstract ( 19 )   PDF (2318KB) ( 3 )   Beryllium-boron (BeB) thin films are important target materials in inertial confinement fusion (ICF) experiments. In this work, molecular dynamics simulations combined with deep learning methods were employed to investigate the deposition behavior and structural evolution of BeB films. The effects of incident angle, incident energy and substrate temperature on the film growth process were systematically studied. A deep learning approach was used to develop interaction potentials based on Be and B elements and the known BeB crystalline phases, enabling an accurate description of cluster growth during deposition. The simulation results indicate that appropriate control of the incident parameters and substrate temperature can significantly improve the surface quality of the films. These findings may offer preliminary insights into the optimization of experimental conditions for the fabrication of high-quality BeB thin films.

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Optical modulation and fabrication of two-dimensional VO2(M)-AgSiO2 shell/core composite photonic crystal structures Jiong Wu(吴炯), Zhangyang Zhou(周章洋), Li Zhu(朱黎), Liushun Wang(王六顺), Ming Du(杜明), Hongjun Wu(吴红君), Qingwei Wang(王情伟), Dahua Ren(任达华), Teng Zhang(张腾), Yongdan Zhu(朱永丹), and Jinqiao Yi(易金桥) Chin. Phys. B, 2026, 35 (4):  046802.  DOI: 10.1088/1674-1056/ae1569 Abstract ( 4 )   PDF (1147KB) ( 0 )   The high phase transition temperature, low solar modulation efficiency, and unfavorable brown-yellow color have limited the practical application of VO$_{2}$-based smart windows. By embedding a hexagonal close-packed monolayer array of SiO$_{2}$ into the monoclinic VO$_{2}$(M)-Ag composite film using an electron-beam evaporation system, a two-dimensional VO$_{2}$(M)-AgSiO$_{2}$ shell/core photonic crystal composite material was formed. Due to the increased contact area between Ag and VO$_{2}$(M) within the composite material, the concentration of free electrons in VO$_{2}$(M) increases, causing the phase transition to occur at a lower temperature of 52.2 $^\circ$C. With the embedded SiO$_{2}$ array, the solar modulation efficiency is enhanced to 25.4 %, and the visible light modulation efficiency increases by nearly 7 times. Additionally, the grating effect of the photonic crystal significantly diffracts light around the 600 nm wavelength, reducing the strong absorption of VO$_{2}$(M) in the shortwave range and diluting its inherent brown-yellow color. By embedding the SiO$_{2}$ array into the VO$_2$(M)-Ag composite film, this approach simultaneously achieves a reduction in phase transition temperature, enhancement of solar modulation efficiency, and color adjustment of the film, providing a reference for the practical application of VO$_{2}$ in smart windows.

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

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ARPES study of Y2O2Bi single crystals: Intrinsic electronic structure of Bi square nets Yun-Bo Wu(吴云波), Tong-Rui Li(李彤瑞), Zhi-Peng Cao(曹志鹏), Zhan-Feng Liu(刘站锋), Yu-Liang Li(李昱良), Zheng-Ming Shang(尚政明), Xin Zheng(郑新), Hui Tian(田慧), Zong-Yi Wang(王宗一), Yu-Tong Bi(毕雨桐), Hao-Yang Zhou(周浩洋), Yi Liu(刘毅), Guo-Bin Zhang(张国斌), Zheng-Tai Liu(刘正太), Da-Wei Shen(沈大伟), Li-Dong Zhang(张李东), Sheng-Tao Cui(崔胜涛), and Zhe Sun(孙喆) Chin. Phys. B, 2026, 35 (4):  047101.  DOI: 10.1088/1674-1056/ae04d9 Abstract ( 29 )   PDF (5465KB) ( 7 )   The Bi square net, a structural motif in a diverse array of layered compounds, has emerged as a desirable system for investigating the interplay between strong spin—orbit coupling, reduced dimensionality, and magnetism. We present a comprehensive study of Y2O2Bi single crystals using high-resolution angle-resolved photoemission spectroscopy (ARPES) and density functional theory (DFT) calculations to elucidate the intrinsic electronic structure of the Bi square net. Our findings reveal a pronounced two-dimensional character of the electronic states, with the Bi square net dominating the low-energy electronic structure. While Y2O2Bi itself exhibits no topological features, DFT calculations on related Bi square net compounds reveal that the surrounding crystal environment can induce non-trivial topology, as exemplified by the topological insulator LiBi. This comparative study establishes a crucial benchmark for understanding Bi square net physics and informs the design of future Bi square net-based quantum materials.

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PT phase transition and non-Hermitian skin effect in vacancy-induced subbands of the Haldane model with gain and loss Cui-Xian Guo(郭翠仙), Xiao-Ming Zhao(赵小明), and Su-Peng Kou(寇谡鹏) Chin. Phys. B, 2026, 35 (4):  047103.  DOI: 10.1088/1674-1056/ae44f4 Abstract ( 7 )   PDF (5437KB) ( 2 )   Defects can profoundly alter the properties of quantum materials, inducing emergent phenomena beyond the scope of their parent counterparts. Here, we construct effective models to investigate the properties of vacancy-induced subbands in the Haldane model with gain and loss, revealing that their behaviors are critically dependent on the spatial configuration of the vacancy array. Specifically, a sequence of parity-time ($\mathcal{PT}$) phase transitions occurs for the one-dimensional vacancy array across different sublattices, whereas the non-Hermitian skin effect (NHSE) — with its nontrivial spectral winding — manifests in a chain confined to a single sublattice. Notably, the NHSE arises in this subband even though the parent system lacks it. Our results demonstrate that vacancy defect engineering serves as a powerful approach to generate subsystems whose properties are decoupled from the parent Hamiltonian.

RAPID COMMUNICATION

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Manipulating the electronic structure and superconductivity of Li2B3C by biaxial strain Yuhao Gu(顾雨豪), Yihao Wang(王奕淏), and Shuxian Hu(胡淑贤) Chin. Phys. B, 2026, 35 (4):  047401.  DOI: 10.1088/1674-1056/ae5594 Abstract ( 30 )   PDF (5884KB) ( 10 )   Strain is a clean and efficient method to manipulate physical properties without changing the chemical composition. In this paper, we perform a systematic first-principles study of how biaxial strain manipulates the electronic structure and phonon-mediated superconductivity of Li2B3C with its optimal configuration. Here we introduce a descriptor $\Delta\varepsilon$, defined as the energy offset between the B—B bridge $\sigma$-bonding band maximum and the Fermi level. We screen the biaxial-strained Li2B3C structures in the range of -5% to +5% and retain those with $\Delta\varepsilon>0.05$ eV for subsequent electron-phonon coupling (EPC) calculations. The maximum Tc=44.72 K occurs at +5% $a$-axis strain and -5% $b$-axis strain. We then elucidate the microscopic mechanism underlying the strain response of the electronic structure by analyzing the corresponding changes of the structure and tight-binding parameters. Taking the optimal biaxial-strained Li2B3C as an example, we analyze its phonon properties and discuss the origin of its strong EPC. Our work provides reliable theoretical guidance for manipulating electronic structure and superconductivity by strain, and sheds new light on high-$T_{\rm c}$ superconductivity induced by metallic $\sigma$-bonding electrons.

SPECIAL TOPIC — Advanced magnonics

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Analogous Faraday effect of spin waves propagating in ferromagnetic nanotubes Li Zhou(周利), Zhixuan Ren(任芷萱), and Ming Yan(颜明) Chin. Phys. B, 2026, 35 (4):  047501.  DOI: 10.1088/1674-1056/ae1ff7 Abstract ( 17 )   PDF (526KB) ( 3 )   We present a micromagnetic study of magnetization dynamics in ferromagnetic nanotubes. The sample is radially magnetized in equilibrium with the presence of a strong anisotropy. Micromagnetic simulations reveal that spin waves (SWs) propagating in the tube exhibit a novel effect, analogous to the well-known Faraday magneto-optic effect. Specifically, the location of the nodes/antinodes of the standing waves formed in the azimuthal direction undergoes a continuous rotation during the wave propagation under the influence of an external magnetic field. The physical mechanism is essentially the same as the Faraday effect, i.e., the breaking of the chiral symmetry by the external field. A qualitative explanation is presented by analytically solving the equation of motion of magnetization taking into account the exchange interaction. Our results may bear potential applications in the development of future spintronic devices based on SW propagation.

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Engineering nonreciprocal damping and polarization of spin waves in ferromagnetic domain wall via Dzyaloshinskii-Moriya interaction and spin-transfer torque Xiang Liu(刘想), Xiguang Wang(王希光), Zhixiong Li(李志雄), Xiufeng Han(韩秀峰), and Guanghua Guo(郭光华) Chin. Phys. B, 2026, 35 (4):  047502.  DOI: 10.1088/1674-1056/ae2771 Abstract ( 6 )   PDF (1179KB) ( 0 )   anipulation of spin-wave polarization is fundamental for designing novel magnonic devices based on the polarization coding technique. Here, we demonstrate the generation of left-handed polarized spin waves (LPSWs) in a ferromagnetic domain wall and their polarization modulation through the combined effect of the Dzyaloshinskii-Moriya interaction (DMI) and spin-polarized electric current. A phase diagram delineating the stability regions of left- and right-handed polarized spin waves (RPSWs) is constructed as a function of DMI strength and current density. Our results reveal a pronounced DMI-induced nonreciprocal damping effect, predominantly manifested in RPSWs while leaving LPSWs largely unaffected. This phenomenon enables effective filtering of RPSWs in one direction, allowing the realization of pure LPSW propagation as well as elliptically polarized spin waves with tunable eccentricity. Our work provides a viable method for controlling spin-wave polarization and nonreciprocal propagation in ferromagnetic systems.

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Hybridization between chiral nutation modes in ferrimagnets Yihang Duan(段懿航) and Ka Shen(沈卡) Chin. Phys. B, 2026, 35 (4):  047504.  DOI: 10.1088/1674-1056/ae3c8c Abstract ( 2 )   PDF (1721KB) ( 0 )   The hybridization between ferrimagnetic magnons of different chiralities holds potentials for applications in the design of magnonic devices. Whereas the nutation mode observed in the ferromagnetic film also possesses opposite chirality to precessional magnon mode, in the present work, we study the interplay of the nutation modes and chiral magnons in ferrimagnets with both parallel and antiparallel magnetic configurations based on the inertial Landau-Lifshitz-Gilbert equation. While the two configurations show some general features, such as the individual excitation of the nutation modes and the repulsion between nutation modes and conventional modes, the antiparallel configuration also exhibits a hybridization between two nutation modes and distinct dissipation behaviors, compared to the parallel configuration. A theoretical mode analysis was performed based on a perturbation approach, which nicely reproduces the observations in the simulation and clarifies the key role of the magnetic anisotropy in mode hybridization. Our findings offer a more comprehensive understanding of inertial effects in ferrimagnets, and could be useful for understanding experimental studies on ferrimagnets with non-negligible magnetic inertia.

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Efficient magnon transport and magnon torque through the epitaxial antiferromagnetic insulator α-Fe2O3 Donglin Song(宋东霖), Fanyu Meng(孟凡毓), Mingyang Sun(孙铭扬), Hongrui Ni(倪泓睿), Jinhao Zou(邹锦豪), Zichen Yao(姚子忱), Zhenlong Guo(郭振龙), Yichi Zhang(张一驰), Liyan Zhang(张丽艳), Hongliang Bai(白洪亮), Wenping Zhou(周文平), and Yi Wang(王译) Chin. Phys. B, 2026, 35 (4):  047505.  DOI: 10.1088/1674-1056/ae48c1 Abstract ( 2 )   PDF (892KB) ( 0 )   Magnons, as key carriers of spin angular momentum, enable spin transport without charge movement in magnetic insulators, thereby greatly reducing Joule heating in spintronic devices. Magnon-mediated spin torque (i.e., magnon torque) provides an alternative approach for efficient magnetization manipulation. However, magnon transmission through antiferromagnetic insulators still suffers from notable propagation losses, limiting the efficiency of magnon torque. Here, we fabricate high-quality epitaxial $\alpha $-Fe$_{2}$O$_{3}$ thin films by magnetron sputtering that exhibit strong antiferromagnetic ordering, and successfully demonstrate highly efficient magnon transport and magnon torque in Pt/$\alpha $-Fe$_{2}$O$_{3}$/NiFe devices at room temperature. It is observed that magnons propagate through a 20-nm-thick $\alpha $-Fe$_{2}$O$_{3}$ layer with a significantly enhanced transmission efficiency of 75 %, about 2.5 times higher than that in previously reported NiO-based magnonic devices. Consequently, a pronounced magnon torque is exerted on the adjacent ferromagnetic layer. Our work demonstrates that $\alpha $-Fe$_{2}$O$_{3}$ is a promising antiferromagnetic material for efficient magnon channels, advancing the study of energy-efficient, high-speed magnonic devices.

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

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Strain-engineered anisotropic conductance enhancement in corrugated monolayer MoS2 Yimai Jiang(蒋伊麦), Jianing Tan(谭家宁), Meng Ge(葛蒙), and Gang Ouyang(欧阳钢) Chin. Phys. B, 2026, 35 (4):  047701.  DOI: 10.1088/1674-1056/ae0d59 Abstract ( 25 )   PDF (1106KB) ( 4 )   To enhance the transport properties of monolayer MoS$_{2}$ (ML-MoS$_{2}$)-based electronic devices, we systematically investigate the curvature-dependent electronic structure and carrier mobility in a corrugated ML-MoS$_{2}$ using density functional theory and the non-equilibrium Green's function method. We reveal that localized strain induces a polarized electric field, which modifies the band structure and delocalizes the electronic states, thereby significantly improving charge transport efficiency. The conductance along the zigzag direction exhibits 10$^{7}$-fold enhancement with increasing curvature. At a maximum local strain of 10%, the electronic mobility reaches 613.68 cm$^{2}\cdot$V$^{-1}\cdot$s$^{-1}$, representing a 9.1-fold improvement over planar ML-MoS$_{2}$. Our results agree well with available evidence and provide crucial insights for designing high-performance devices via strain engineering.

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Topological edge state coupled mode-induced tetra-band tunable spin-dependent perfect absorption Ji-Peng Wu(伍计鹏), Xi-Rui Zeng(曾玺瑞), Yu-Lei Liao(廖煜磊), Rong-Zhou Zeng(曾荣周), Hong Wen(文鸿), Xiao-Yu Dai(戴小玉), and Yuan-Jiang Xiang(项元江) Chin. Phys. B, 2026, 35 (4):  047801.  DOI: 10.1088/1674-1056/ae00b2 Abstract ( 8 )   PDF (607KB) ( 2 )   When discussing the spin-dependent optical perfect absorption (PA) phenomenon in a micro-nano structure, the designed structure should contain symmetry-breaking compositions that generally require an applied magnetic field. Fortunately, the multi-Weyl semimetal (mWSM) with natural time-reversal symmetry breaking property provides feasible schemes to investigate the spin-dependent PA without an external magnetic field. Recently, most existing schemes are primarily restricted to single- or dual-band spin-dependent PA in mWSM-based systems. Here, we present a heterostructure comprising five one-dimensional photonic crystals (PCs) and four identical mWSM layers to discuss the tetra-band spin-dependent PA. Results show that, due to the topological edge state-coupled mode and the nonzero off-diagonal term of mWSM, the PA of left-hand circularly polarized and right-hand circularly polarized light is attained at four distinct frequencies, respectively. More importantly, the tetra-band spin-dependent PA phenomenon can be regulated effectively via the tilt degree of Weyl cones, Fermi energy, topological charge, Weyl nodes separation, mWSM thickness, and the periods of the middle three PCs. This study provides an efficient scheme to achieve tetra-band adjustable spin-dependent PA without an external magnetic field, which may have potential applications in spin-dependent photonic devices.

INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY

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High-mobility, low-resistive boron-doped diamond material realized by oxygen assistance Gengyou Zhao(赵耕右), Kun Tang(汤琨), Kai Yang(杨凯), Bo Feng(冯博), Liangxue Gu(顾梁雪), Xiang Xiong(熊翔), Tao Tao(陶涛), Bin Liu(刘斌), Jiandong Ye(叶建东), Rong Zhang(张荣), Youdou Zheng(郑有炓), and Shulin Gu(顾书林) Chin. Phys. B, 2026, 35 (4):  048101.  DOI: 10.1088/1674-1056/ae0636 Abstract ( 18 )   PDF (1379KB) ( 5 )   The effect of trace oxygen on the light-doping behavior of boron in diamond films during microwave plasma chemical vapor deposition was experimentally investigated. Boron-doped diamond films were grown continuously under different oxygen concentrations [oxygen/carbon (O/C) $=$ 0%-5%]. When oxygen was added during the diamond doping process, improvements in crystal quality and surface morphology were observed, and residual nitrogen was significantly suppressed. However, further increasing the oxygen concentration could lead to surface defects. We evaluated and discussed the carrier mobility, carrier concentration and boron content of the samples. At room temperature, under the condition of O/C $=$ 4%, the maximum hole mobility reached 1400 cm$^{2}\cdot $V$^{-1}\cdot $s$^{-1}$, and a higher carrier concentration of 1.5 $\times10^{15}$ cm$^{-3}$ was obtained, which is an excellent result compared with all previous studies. In addition, the characteristic peaks that appeared in both low-temperature photoluminescence spectra and absorption spectra were analyzed, and it was found that the characteristic peak at 4.7 eV (270 nm) may correspond to a boron-nitrogen complex, supplementing the effect of boron-doped diamond on defect formation. These findings demonstrate the potential of controlling the boron concentration in diamond films using oxygen concentration in a plasma environment and open avenues for future applications in advanced optoelectronic devices.

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Host-dependent Eu2+/Eu3+ co-luminescence and excitation-tunable multicolor emission of Eu-doped AeF2 (Ae = Ca, Sr, Ba, Ca0.5Sr0.5, Ca0.33Sr0.33Ba0.33) single crystals Xiaobo Huang(黄孝波), Ying Quan(全颖), Wudi Wang(王无敌), Qingguo Wang(王庆国), Xiaodong Xu(徐晓东), Huili Tang(唐慧丽), and Jun Xu(徐军) Chin. Phys. B, 2026, 35 (4):  048102.  DOI: 10.1088/1674-1056/ae0562 Abstract ( 18 )   PDF (892KB) ( 2 )   This study successfully grew a series of mixed-valence Eu$^{2+}$/Eu$^{3+}$ co-activated alkaline-earth fluoride single crystals (CaF$_{2}$, SrF$_{2}$, BaF$_{2}$, Ca$_{0.5}$Sr$_{0.5}$F$_{2}$, and the medium-entropy Ca$_{0.33}$Sr$_{0.33}$Ba$_{0.33}$F$_{2}$) using the vertical Bridgman method. During the high-temperature growth process, Eu$^{3+}$ undergoes spontaneous reduction to form Eu$^{2+}$. X-ray photoelectron spectroscopy (XPS) confirmed the coexistence of both valence states, and their relative ratio exhibits a strong host-dependence; for instance, Eu$^{2+}$ is predominant in SrF$_{2}$, while Eu$^{3+}$ is dominant in BaF$_{2}$. Under ultraviolet excitation, all crystals simultaneously exhibit the broadband emission of Eu$^{2+}$ (400—550 nm) and the narrow-line emission of Eu$^{3+}$ (585—710 nm). The Eu$^{2+}$ emission peak systematically red-shifts from 440 nm in CaF$_{2}$ to 485 nm in BaF$_{2}$ as the host cation radius increases. Efficient resonant energy transfer from Eu$^{2+}$ to Eu$^{3+}$ is evidenced by spectral overlap and opposing fluorescence lifetime trends. By controlling the host's composition, the emission chromaticity of the crystals can be continuously tuned from the deep-blue of CaF$_{2}$ (0.1720, 0.0382) to the warm-white of BaF$_{2}$ (0.4135, 0.3516) under 299 nm excitation. Notably, the medium-entropy Eu: Ca$_{0.33}$Sr$_{0.33}$Ba$_{0.33}$F$_{2}$ crystal can achieve a shift in emission tone from neutral white to warm white simply by changing the excitation wavelength. These findings provide a new design strategy for developing single-activator, wide-gamut, tunable luminescent materials for next-generation solid-state lighting and display technologies.

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High-pressure synthesis and sequential ferrimagnetic ordering and spin glass transition of an Fe/Ru disordered quadruple perovskite CeCu3Fe2Ru2O12 Sumei Li(李素梅), Gaochao Zhao(赵高超), Meng Wang(王萌), Lihua Yin(尹利华), Peng Tong(童鹏), Xuebin Zhu(朱雪斌), Jie Yang(杨杰), and Yuping Sun(孙玉平) Chin. Phys. B, 2026, 35 (4):  048103.  DOI: 10.1088/1674-1056/ae0399 Abstract ( 14 )   PDF (1396KB) ( 3 )   We successfully prepared an $A$-site-ordered quadruple perovskite oxide CeCu$_{3}$Fe$_{2}$Ru$_{2}$O$_{12}$ by using a high-pressure method (10 GPa, 1400 K). The compound crystallizes in the Im$\bar{3}$ space group, with $A$-site ordering of Ce and Cu ions in a ratio of 1:3, but $B$-site disordered distribution of Fe and Ru ions. Bond-value-sum calculations and x-ray photoelectron spectroscopy measurement manifest that the charge distribution is Ce$^{3.5+}$Cu$^{2+}_{3}$Fe$^{3+}_{2}$Ru$^{4.25+}_{2}$O$_{12}$. A ferrimagnetic phase transition occurs at $T_{\rm C} = 73.6 $ K followed by a spin glass behavior at 50.3 K consistent with the conventional dynamical scaling power law. Electrical transport measurement shows that the intrinsic electrical behavior is semiconducting and the resistivity obey the adiabatic small-polaron model. The specific heat follows a $T^2$ law instead of traditional phonon-dominated $T^{3}$ behavior implying a finite energy gap in the excitation spectrum.

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Effect of a deep virtual guard ring on performance of a miniaturized high-photosensitivity silicon single-photon avalanche diode Enle Zhou(周恩乐), Dajing Bian(卞大井), and Yue Xu(徐跃) Chin. Phys. B, 2026, 35 (4):  048501.  DOI: 10.1088/1674-1056/ae0164 Abstract ( 24 )   PDF (1106KB) ( 5 )   We developed a miniaturized high-sensitivity single-photon avalanche diode (SPAD) device based on 180 nm bipolar complementary metal-oxide-semiconductor double-diffused metal-oxide-semiconductor technology and investigated the effect of a deep virtual guard ring (VGR) on device performance. To mitigate the degradation in photon detection efficiency (PDE) and dark count rate (DCR) induced by device scaling, we innovatively implemented a P-type implant/high-voltage n-well SPAD structure. This configuration deepens and widens the multiplication region to broaden the spectral response, while the specialized adoption of the P-type epitaxial VGR technology suppresses premature edge breakdown and reduces dark noise. Furthermore, a unique layout was devised to maximize the photosensitive area and increase the fill factor of the device. Through technology computer-aided design simulations, the effect of the guard ring width on the electric field distribution inside the device was systematically studied. Experimental results demonstrate that the fill factor of the device reaches 31.5% when the pitch is scaled down to 8.5 μm. The novel device achieves a high peak PDE of 24% at 555 nm and an ultralow DCR of 0.41 cps$\cdotμ $m$^{-2}$ at 5 V excess bias voltage.

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Cryogenic low-noise amplifiers of low power dissipation for space terahertz astronomy Jie Liu(刘洁), Dong Liu(刘冬), Kun Zhang(张坤), Ming Yao(姚明), Jun-Da Jin(金骏达), Qi-Jun Yao(姚骑均), Jing Li(李婧), and Sheng-Cai Shi(史生才) Chin. Phys. B, 2026, 35 (4):  048502.  DOI: 10.1088/1674-1056/ae0019 Abstract ( 7 )   PDF (509KB) ( 2 )   ryogenic low-noise amplifiers (CLNAs) are of particular interest for applications such as radio astronomy and quantum information science. Here we report on the design and characterization of low-power-dissipation wideband CLNAs for a terahertz spectrometer onboard China's Space Station Telescope (CSST). A simple small-signal and noise model is established based on the DC and RF characteristics of SiGe heterojunction-bipolar-transistors (HBTs) adopted for this development. The developed SiGe HBT CLNAs at 4 K demonstrate an average noise temperature of 4.5 K and a gain of exceeding 35 dB in the frequency range of 0.1 GHz-1.1 GHz. With the power dissipation as low as 3 mW, the average noise temperature is still as low as 6.8 K. The combination of low power dissipation and low noise temperature is rather beneficial to applications in space instruments and complex systems.

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Enhancement of rectification by quantum interference in co-oligomer molecular diodes Han-Shuang Zhang(张含双), Han Ma(马晗), Hui-Qing Zhang(张惠晴), Xiao-Bei Zhang(张晓蓓), Jun-Feng Ren(任俊峰), Guang-Ping Zhang(张广平), and Gui-Chao Hu(胡贵超) Chin. Phys. B, 2026, 35 (4):  048504.  DOI: 10.1088/1674-1056/ae0b3d Abstract ( 0 )   PDF (526KB) ( 0 )   We investigate the rectification property theoretically in co-oligomer diodes integrating a destructive quantum interference (DQI) feature. The results demonstrate that compared to a similar co-oligomer diode without DQI, the rectification ratio is enhanced by one order of magnitude in the presence of the DQI feature. Mechanism analysis indicates that the high rectification ratio benefits from the strong suppression of transmission in the off-state of the diode by the DQI dip. The strong rectification is attributed to the distinctly asymmetric shift of the DQI dip under bias voltages, which comes out as a result of both bias-induced shift of eigenvalues and redistribution of wave functions of all orbitals. The effect of energy level alignment between the two segments of the co-oligomer on the rectification is also discussed. This work provides a valid way to enhance the performance of intrinsic co-oligomer diodes, a promising approach for molecular circuit design.

SPECIAL TOPIC — Biophysical circuits: Modeling & applications in neuroscience

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Frequency-tunable spiking dynamics of Chua corsage memristors Qijian Wu(吴奇键), Peipei Jin(靳培培), Xiameng Wu(吴夏萌), Meiyuan Gu(顾梅园), Wei Zhou(周玮), Yujiao Dong(董玉姣), Yan Liang(梁燕), and Long Chen(陈龙) Chin. Phys. B, 2026, 35 (4):  048703.  DOI: 10.1088/1674-1056/ae3c95 Abstract ( 25 )   PDF (6450KB) ( 24 )   Brain-inspired computing relies on neuronal spiking frequency as a foundational element for information encoding. Bi-directional spiking enables the processing and encoding of multimodal information. The Chua corsage memristor (CCM), endowed with the edge of chaos, can generate spiking dynamics and can be synthesized using only off-the-shelf electronic components, making it suitable for both theoretical analysis and hardware demonstration of frequency-tunable spiking dynamics. This paper employs second- and third-order neuron circuits constructed with a CCM sibling, namely the odd-symmetric CCM, to explore the frequency-tunable characteristics of bi-directional spiking. A quantitative method for calculating the output spiking frequency of neurons is proposed. Simulation results verify the validity of this method. The neuron hardware circuits are implemented using a homemade odd-symmetric CCM circuit board. The experimental results confirm the frequency-tunable spiking of the odd-symmetric CCM-based neurons and reveal the effect of the excitation voltage on the system dynamics.