Table of contents

12 November 2024, Volume 33 Issue 12 Previous issue    Next issue

COMPUTATIONAL PROGRAMS FOR PHYSICS

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ScatterX: A software for fast processing of high-throughput small-angle scattering data Fei Xie(谢飞), Mei Xie(解梅), Baoyu Song(宋宝玉), Qiaoyu Guo(郭桥雨), and Xuechen Jiao(焦学琛) Chin. Phys. B, 2024, 33 (12):  120101.  DOI: 10.1088/1674-1056/ad8b36 Abstract ( 1 )   PDF (6911KB) ( 0 )   Scattering experiments become increasingly popular in modern scientific research, including the areas of materials, biology, chemistry, physics, etc. Besides, various types of scattering facilities have been developed recently, such as lab-based x-ray scattering equipment, national synchrotron facilities and large neutron facilities. These above-mentioned trends bring up fast-increasing data amounts of scattering data, as well as different scattering types (x-ray, neutron, laser and even microwaves). To help researchers process and analyze scattering data more efficiently, we developed a general and model-free scattering data analysis software based on matrix operation, which has the unique advantage of high throughput scattering data processing, analysis and visualization. To maximize generality and efficiency, data processing is performed based on a three-dimensional matrix, where scattering curves are saved as matrices or vectors, rather than the traditional definition of paired values. It can not only realize image batch processing, background subtraction and correction, but also analyze data according to scattering theory and model, such as radius of gyration, fractal dimension and other physical quantities. In the aspect of visualization, the software allows the modify the color maps of two-dimensional scattering images and the gradual color variation of one-dimensional curves to suit efficient data communications. In all, this new software can work as a stand-alone platform for researchers to process, analyze and visualize scattering data from different research facilities without considering different file types or formats. All codes in this manuscript are open-sourced and can be easily implemented in matrix-based software, such as MATLAB, Python and Igor.

SPECIAL TOPIC — Quantum computing and quantum sensing

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A nanosecond level current pulse capture taper optical fiber probe based on micron level nitrogen-vacancy color center diamond Yuchen Bian(卞雨辰), Yangfan Mao(毛扬帆), Honghao Chen(陈鸿浩), Shiyu Ge(葛仕宇), Wentao Lu(卢文韬), Chengkun Wang(王成坤), Sihan An(安思瀚), and Guanxiang Du(杜关祥) Chin. Phys. B, 2024, 33 (12):  120301.  DOI: 10.1088/1674-1056/ad78da Abstract ( 14 )   PDF (1753KB) ( 61 )   This work demonstrates a micron-sized nanosecond current pulse probe using a quantum diamond magnetometer. A micron-sized diamond crystal affixed to a fiber tip is integrated on the end of a conical waveguide. We demonstrate real-time visualization of a single 100 nanosecond pulse and discrimination of two pulse trains of different frequencies with a coplanar waveguide and a home-made PCB circuit. This technique finds promising applications in the display of electronic stream and can be used as a pulse discriminator to simultaneously receive and demodulate multiple pulse frequencies. This method of detecting pulse current is expected to provide further detailed analysis of the internal working state of the chip.

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Automatic architecture design for distributed quantum computing Ting-Yu Luo(骆挺宇), Yu-Zhen Zheng(郑宇真), Xiang Fu(付祥), and Yu-Xin Deng(邓玉欣) Chin. Phys. B, 2024, 33 (12):  120302.  DOI: 10.1088/1674-1056/ad7c2c Abstract ( 16 )   PDF (1228KB) ( 4 )   In distributed quantum computing (DQC), quantum hardware design mainly focuses on providing as many as possible high-quality inter-chip connections. Meanwhile, quantum software tries its best to reduce the required number of remote quantum gates between chips. However, this “hardware first, software follows” methodology may not fully exploit the potential of DQC. Inspired by classical software-hardware co-design, this paper explores the design space of application-specific DQC architectures. More specifically, we propose AutoArch, an automated quantum chip network (QCN) structure design tool. With qubits grouping followed by a customized QCN design, AutoArch can generate a near-optimal DQC architecture suitable for target quantum algorithms. Experimental results show that the DQC architecture generated by AutoArch can outperform other general QCN architectures when executing target quantum algorithms.

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Nonlinear enhanced mass sensor based on optomechanical system Xin-Xin Man(满鑫鑫), Jing Sun(孙静), Wen-Zhao Zhang(张闻钊), Lijuan Luo(罗丽娟), and Guangri Jin(金光日) Chin. Phys. B, 2024, 33 (12):  120303.  DOI: 10.1088/1674-1056/ad84cf Abstract ( 15 )   PDF (915KB) ( 21 )   A high-precision and tunable mass detection scheme based on a double-oscillator optomechanical system is proposed. By designating one of the oscillators as the detection port, tiny mass signals can be probed through the frequency shift of the output spectrum, utilizing the system's optomechanically induced transparency (OMIT) effect. By solving the output of the optical mode, we demonstrate that the system exhibits two OMIT windows due to the double-oscillator coupling, with one window being strongly dependent on the mass to be detected. Characterizing the spectrum around this window enables high magnification and precise detection of the input signal under nonlinear parameter conditions. Additionally, our scheme shows resilience to environmental temperature variations and drive strength perturbations.

INSTRUMENTATION AND MEASUREMENT

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Micron-resolved quantum precision measurement of magnetic field at the Tesla level Si-Han An(安思瀚), Shi-Yu Ge(葛仕宇), Wen-Tao Lu(卢文韬), Guo-Bin Chen(陈国彬), Sheng-Kai Xia(夏圣开), Ai-Qing Chen(陈爱庆), Cheng-Kun Wang(王成坤), Lin-Yan Yu(虞林嫣), Zhi-Qiang Zhang(张致强), Yang Wang(汪洋), Gui-Jin Tang(唐贵进), Hua-Fu Cheng(程华富), and Guan-Xiang Du(杜关祥) Chin. Phys. B, 2024, 33 (12):  120305.  DOI: 10.1088/1674-1056/ad7e9b Abstract ( 21 )   PDF (879KB) ( 4 )   We develop a quantum precision measurement method for magnetic field at the Tesla level by utilizing a fiber diamond magnetometer. Central to our system is a micron-sized fiber diamond probe positioned on the surface of a coplanar waveguide made of nonmagnetic materials. Calibrated with a nuclear magnetic resonance magnetometer, this probe demonstrates a broad magnetic field range from 10 mT to 1.5 T with a nonlinear error better than 0.0028% under a standard magnetic field generator and stability better than 0.0012% at a 1.5 T magnetic field. Finally, we demonstrate quantitative mapping of the vector magnetic field on the surface of a permanent magnet using the diamond magnetometer.

GENERAL

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Quantum state estimation based on deep learning Haowen Xiao(肖皓文) and Zhiguang Han(韩枝光) Chin. Phys. B, 2024, 33 (12):  120307.  DOI: 10.1088/1674-1056/ad78d7 Abstract ( 17 )   PDF (1923KB) ( 2 )   We used deep learning techniques to construct various models for reconstructing quantum states from a given set of coincidence measurements. Through simulations, we have demonstrated that our approach generates functionally equivalent reconstructed states for a wide range of pure and mixed input states. Compared with traditional methods, our system offers the advantage of faster speed. Additionally, by training our system with measurement results containing simulated noise sources, the system shows a significant improvement in average fidelity compared with typical reconstruction methods. We also found that constraining the variational manifold to physical states, i.e., positive semi-definite density matrices, greatly enhances the quality of the reconstructed states in the presence of experimental imperfections and noise. Finally, we validated the correctness and superiority of our model by using data generated on IBM Quantum Platform, a real quantum computer.

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Tunable phonon-photon coupling induces double magnomechanically induced transparency and enhances slow light in an atom-opto-magnomechanical system M'bark Amghar, Noura Chabar, and Mohamed Amazioug Chin. Phys. B, 2024, 33 (12):  120308.  DOI: 10.1088/1674-1056/ad8cbb Abstract ( 3 )   PDF (658KB) ( 0 )   We theoretically investigate the magnomechanically induced transparency phenomenon, Fano resonance and the slow-fast light effect in the situation where an atomic ensemble is placed inside the hybrid cavity of an opto-magnomechanical system. The system is driven by dual optical and phononic drives. We show double magnomechanically induced transparency in the probe output spectrum by exploiting the phonon-photon coupling strength. Then, we study the effects of the decay rate of the cavity and the atomic ensemble on magnomechanically induced transparency. In addition, we demonstrate that effective detuning of the cavity field frequency changes the transparency window from a symmetrical to an asymmetrical profile, resembling Fano resonances. Further, the fast and slow light effects in the system are explored. We show that the slow light profile is enhanced by adjusting the phonon-photon coupling strength. This result may have potential applications in quantum information processing and communication.

SPECIAL TOPIC — Quantum computing and quantum sensing

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M2CS: A microwave measurement and control system for large-scale superconducting quantum processors Jiawei Zhang(张家蔚), Xuandong Sun(孙炫东), Zechen Guo(郭泽臣), Yuefeng Yuan(袁跃峰), Yubin Zhang(张玉斌), Ji Chu(储继), Wenhui Huang(黄文辉), Yongqi Liang(梁咏棋), Jiawei Qiu(邱嘉威), Daxiong Sun(孙大雄), Ziyu Tao(陶子予), Jiajian Zhang(张家健), Weijie Guo(郭伟杰), Ji Jiang(蒋骥), Xiayu Linpeng(林彭夏雨), Yang Liu(刘阳), Wenhui Ren(任文慧), Jingjing Niu(牛晶晶), Youpeng Zhong(钟有鹏), and Dapeng Yu(俞大鹏) Chin. Phys. B, 2024, 33 (12):  120309.  DOI: 10.1088/1674-1056/ad8a49 Abstract ( 4 )   PDF (3439KB) ( 0 )   As superconducting quantum computing continues to advance at an unprecedented pace, there is a compelling demand for the innovation of specialized electronic instruments that act as crucial conduits between quantum processors and host computers. Here, we introduce a microwave measurement and control system (M$^{2}$CS) dedicated to large-scale superconducting quantum processors. M$^{2}$CS features a compact modular design that balances overall performance, scalability and flexibility. Electronic tests of M$^{2}$CS show key metrics comparable to commercial instruments. Benchmark tests on transmon superconducting qubits further show qubit coherence and gate fidelities comparable to state-of-the-art results, confirming M$^{2}$CS's capability to meet the stringent requirements of quantum experiments running on intermediate-scale quantum processors. The compact and scalable nature of our design holds the potential to support over 1000 qubits after upgrade in stability and integration. The M$^{2}$CS architecture may also be adopted to a wider range of scenarios, including other quantum computing platforms such as trapped ions and silicon quantum dots, as well as more traditional applications like microwave kinetic inductance detectors and phased array radar systems.

GENERAL

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Coexisting and multiple scroll attractors in a Hopfield neural network with a controlled memristor Qing-Qing Ma(马青青), An-Jiang Lu(陆安江), and Zhi Huang(黄智) Chin. Phys. B, 2024, 33 (12):  120502.  DOI: 10.1088/1674-1056/ad8148 Abstract ( 13 )   PDF (2447KB) ( 1 )   A method of generating multi-double scroll attractors is proposed based on the memristor Hopfield neural network (HNN) under pulse control. First, the original hyperbolic-type memristor is added to the neural network mathematical model, and the influence of this memristor on the dynamic behavior of the new HNN is analyzed. The numerical results show that after adding the memristor, the abundant dynamic behaviors such as chaos coexistence, period coexistence and chaos period coexistence can be observed when the initial value of the system is changed. Then the logic pulse is added to the external memristor. It is found that the equilibrium point of the HNN can multiply and generate multi-double scroll attractors after the pulse stimulation. When the number of logical pulses is changed, the number of multi-double scroll attractors will also change, so that the pulse can control the generation of multi-double scroll attractors. Finally, the HNN circuit under pulsed stimulation was realized by circuit simulation, and the results verified the correctness of the numerical results.

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A fractional-order chaotic Lorenz-based chemical system: Dynamic investigation, complexity analysis, chaos synchronization, and its application to secure communication Haneche Nabil, and Hamaizia Tayeb Chin. Phys. B, 2024, 33 (12):  120503.  DOI: 10.1088/1674-1056/ad7fcf Abstract ( 17 )   PDF (3348KB) ( 0 )   Synchronization of fractional-order chaotic systems is receiving significant attention in the literature due to its applications in a variety of fields, including cryptography, optics, and secure communications. In this paper, a three-dimensional fractional-order chaotic Lorenz model of chemical reactions is discussed. Some basic dynamical properties, such as stability of equilibria, Lyapunov exponents, bifurcation diagrams, Poincaré map, and sensitivity to initial conditions, are studied. By adopting the Adomian decomposition algorithm (ADM), the numerical solution of the fractional-order system is obtained. It is found that the lowest derivative order in which the proposed system exhibits chaos is $q=0.694$ by applying ADM. The result has been validated by the existence of one positive Lyapunov exponent and by employing some phase diagrams. In addition, the richer dynamics of the system are confirmed by using powerful tools in nonlinear dynamic analysis, such as the 0-1 test and $C_{0}$ complexity. Moreover, modified projective synchronization has been implemented based on the stability theory of fractional-order systems. This paper presents the application of the modified projective synchronization in secure communication, where the information signal can be transmitted and recovered successfully through the channel. MATLAB simulations are provided to show the validity of the constructed secure communication scheme.

INSTRUMENTATION AND MEASUREMENT

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Apparatus for producing single strontium atoms in an optical tweezer array Kai Wen(文凯), Huijin Chen(陈辉锦), Xu Yan(颜煦), Zejian Ren(任泽剑), Chengdong He(何成东), Elnur Hajiyev, Preston Tsz Fung Wong(黄梓峰), and Gyu-Boong Jo Chin. Phys. B, 2024, 33 (12):  120703.  DOI: 10.1088/1674-1056/ad84d0 Abstract ( 11 )   PDF (771KB) ( 2 )   We outline an experimental setup for efficiently preparing a tweezer array of $^{88}$Sr atoms. Our setup uses permanent magnets to maintain a steady-state two-dimensional magneto-optical trap (MOT) which results in a loading rate of up to $10^{8}$ s$^{-1}$ at 5 mK for the three-dimensional blue MOT. This enables us to trap $2\times10^{6}$ $^{88}$Sr atoms at 2 μK in a narrow-line red MOT with the $^{1}$S$_{0}$ $\rightarrow$ $^{3}$P$_{1}$ intercombination transition at 689 nm. With the Sisyphus cooling and pairwise loss processes, single atoms are trapped and imaged in 813 nm optical tweezers, exhibiting a lifetime of 2.5 min. We further investigate the survival fraction of a single atom in the tweezers and characterize the optical tweezer array using a release and recapture technique. Our experimental setup serves as an excellent reference for those engaged in experiments involving optical tweezer arrays, cold atom systems, and similar research.

TOPICAL REVIEW — Stephen J. Pennycook: A research life in atomic-resolution STEM and EELS

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Combining electron microscopy with atomic-scale calculations—A personal perspective Sokrates T. Pantelides Chin. Phys. B, 2024, 33 (12):  120704.  DOI: 10.1088/1674-1056/ad8ece Abstract ( 2 )   PDF (1615KB) ( 0 )   I had the privilege and the pleasure to work closely with Stephen J. Pennycook for about twenty years, having a group of post-docs and Vanderbilt-University graduate students embedded in his electron microscopy group at Oak Ridge National Laboratory, spending on average a day per week there. We combined atomic-resolution imaging of materials, electron-energy-loss spectroscopy, and density-functional-theory calculations to explore and elucidate diverse materials phenomena, often resolving long-standing issues. This paper is a personal perspective of that journey, highlighting a few examples to illustrate the power of combining theory and microscopy and closing with an assessment of future prospects.

ATOMIC AND MOLECULAR PHYSICS

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Momentum distributions of symmetric (H2+) and asymmetric (HeH2+) molecular ions in a circularly polarized laser field under different ionization mechanisms Xin-Yu Hao(郝欣宇), Shu-Juan Yan(闫淑娟), Ying Guo(郭颖), and Jing Guo(郭静) Chin. Phys. B, 2024, 33 (12):  123401.  DOI: 10.1088/1674-1056/ad7c2b Abstract ( 16 )   PDF (964KB) ( 3 )   By numerically solving the two-dimensional (2D) time-dependent Schrödinger equation (TDSE), we present photoelectron momentum distributions (PMDs) and photoelectron angular distributions (PADs) of symmetric (${{\rm H}_{2}^{+}}$) and asymmetric (${{\rm HeH}^{2+}}$) molecular ions in circularly polarized (CP) laser pulses. By adjusting the laser wavelength, two circumstances of resonance excitation and direct ionization were considered. The ionization mechanism of the resonance excitation was mainly investigated. The results show that the PMDs of ${{\rm H}_{2}^{+}}$ and ${{\rm HeH}^{2+}}$ in the $y$-direction gradually increase with increasing intensity, and the number of PMDs lobes is in good agreement with the results predicted by the ultrafast ionization model. In the resonance excitation scenario, the PMDs of ${{\rm H}_{2}^{+}}$ are dominated by two-photon ionization, whereas the PMDs of HeH$^{2+}$ are dominated by three-photon ionization. Furthermore, the PMDs of ${{\rm HeH}^{2+}}$ are stronger in the resonance excitation scenario than those of ${{\rm H}_{2}^{+}}$, which can be explained by the time-dependent population of electrons. In addition, the molecular structure is clearly imprinted onto the PMDs.

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Determining the tilt of the Raman laser beam using an optical method for atom gravimeters Hua-Qing Luo(骆华清), Yao-Yao Xu(徐耀耀), Jia-Feng Cui(崔嘉丰), Xiao-Bing Deng(邓小兵), Min-Kang Zhou(周敏康), Xiao-Chun Duan(段小春), and Zhong-Kun Hu(胡忠坤) Chin. Phys. B, 2024, 33 (12):  123701.  DOI: 10.1088/1674-1056/ad7b00 Abstract ( 15 )   PDF (784KB) ( 1 )   The tilt of a Raman laser beam is a major systematic error in precision gravity measurement using atom interferometry. The conventional approach to evaluating this tilt error involves modulating the direction of the Raman laser beam and conducting time-consuming gravity measurements to identify the error minimum. In this work, we demonstrate a method to expediently determine the tilt of the Raman laser beam by transforming the tilt angle measurement into characterization of parallelism, which integrates the optical method of aligning the laser direction, commonly used in freely falling corner-cube gravimeters, into an atom gravimeter. A position-sensing detector (PSD) is utilized to quantitatively characterize the parallelism between the test beam and the reference beam, thus measuring the tilt precisely and rapidly. After carefully positioning the PSD and calibrating the relationship between the distance measured by the PSD and the tilt angle measured by the tiltmeter, we achieved a statistical uncertainty of less than 30 μrad in the tilt measurement. Furthermore, we compared the results obtained through this optical method with those from the conventional tilt modulation method for gravity measurement. The comparison validates that our optical method can achieve tilt determination with an accuracy level of better than 200 μrad, corresponding to a systematic error of 20 μGal in $g$ measurement. This work has practical implications for real-world applications of atom gravimeters.

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

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Analysis and measurement of vibration characteristics of a hollowing defect based on a laser self-mixing interferometer Yu-Xin Chen(陈煜昕), Jin-Bo Chen(陈金波), Peng Cao(曹鹏), You-Guang Zhao(赵有光), Jun Wang(王钧), Xu-Wei Teng(滕旭玮), and Chi Wang(王驰) Chin. Phys. B, 2024, 33 (12):  124301.  DOI: 10.1088/1674-1056/ad7e99 Abstract ( 12 )   PDF (2969KB) ( 2 )   To solve the problems with the existing methods for detecting hollowing defects, such as inconvenient operation, low efficiency and intense subjectivity, and to improve the efficiency of the acoustic-optic fusion method for detecting hollowing defects, in this paper the vibration characteristics of hollowing defects are measured and analyzed using a laser self-mixing interferometer. The ceramic tile above the hollowing defect is equivalent to a thin circular plate with peripheral fixed support. According to Kirchhoff's classical circular plate theory and the circular plate displacement function based on the improved Fourier series, a theoretical model of a circular plate is established. By solving the characteristic equation, the theoretical modal parameters of hollowing defects are obtained. Subsequently, an experimental system based on a laser self-mixing interferometer is built, and modal experiments are carried out using the hammering method. The experimental modal parameters are obtained with a professional modal analysis software. Through comparative analysis between the theoretical and experimental modal parameters, the error of the natural frequency results is found to be tiny and the mode shapes are consistent. These results provide theoretical guidance for a practical non-destructive acoustic-optic fusion method for detecting hollowing defects.

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Capture behavior of self-propelled particles into a hexatic ordering obstacle Jing-Yi Li(李静怡), Jin-Lei Shi(石金蕾), Ying-Ying Wang(王英英), Jun-Xing Pan(潘俊星), and Jin-Jun Zhang(张进军) Chin. Phys. B, 2024, 33 (12):  124501.  DOI: 10.1088/1674-1056/ad84c6 Abstract ( 12 )   PDF (1173KB) ( 1 )   Computer simulations are utilized to investigate the dynamic behavior of self-propelled particles (SPPs) within a complex obstacle environment. The findings reveal that SPPs exhibit three distinct aggregation states within the obstacle, each contingent on specific conditions. A phase diagram outlining the aggregation states concerning self-propulsion conditions is presented. The results illustrate a transition of SPPs from a dispersion state to a transition state as persistence time increases within the obstacle. Conversely, as the driving strength increases, self-propelled particles shift towards a cluster state. A systematic exploration of the interplay between driving strength, persistence time, and matching degree on the dynamic behavior of self-propelled particles is conducted. Furthermore, an analysis is performed on the spatial distribution of SPPs along the $y$-axis, capture rate, maximum capture probability, and mean-square displacement. The insights gained from this research make valuable contributions to understanding the capture and collection of active particles.

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Flow features induced by a rod-shaped microswimmer and its swimming efficiency: A two-dimensional numerical study Siwen Li(李斯文), Yuxiang Ying(应宇翔), Tongxiao Jiang(姜童晓), and Deming Nie(聂德明) Chin. Phys. B, 2024, 33 (12):  124701.  DOI: 10.1088/1674-1056/ad84c3 Abstract ( 11 )   PDF (1931KB) ( 2 )   The swimming performance of rod-shaped microswimmers in a channel was numerically investigated using the two-dimensional lattice Boltzmann method (LBM). We considered variable-length squirmer rods, assembled from circular squirmer models with self-propulsion mechanisms, and analyzed the effects of the Reynolds number (Re), aspect ratio ($\varepsilon$), squirmer-type factor ($\beta $) and blockage ratio ($\kappa$) on swimming efficiency ($\eta$) and power expenditure ($P$). The results show no significant difference in power expenditure between pushers (microswimmers propelled from the tail) and pullers (microswimmers propelled from the head) at the low Reynolds numbers adopted in this study. However, the swimming efficiency of pushers surpasses that of pullers. Moreover, as the degree of channel blockage increases (i.e., $\kappa $ increases), the squirmer rod consumes more energy while swimming, and its swimming efficiency also increases, which is clearly reflected when $\varepsilon \le 3$. Notably, squirmer rods with a larger aspect ratio $\varepsilon $ and a $\beta $ value approaching 0 can achieve high swimming efficiency with lower power expenditure. The advantages of self-propelled microswimmers are manifested when $\varepsilon > 4$ and $\beta = \pm 1$, where the squirmer rod consumes less energy than a passive rod driven by an external field. These findings underscore the potential for designing more efficient microswimmers by carefully considering the interactions between the microswimmer geometry, propulsion mechanism and fluid dynamic environment.

PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES

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Suppression of the Kelvin-Helmholtz instability by coating in the double-cone ignition scheme Yuan-Kai Xie(谢元凯), Cheng-Long Zhang(张成龙), Yi-Zhen Cheng(程翊真), and Ying-Jun Li(李英骏) Chin. Phys. B, 2024, 33 (12):  125203.  DOI: 10.1088/1674-1056/ad8551 Abstract ( 12 )   PDF (882KB) ( 1 )   In order to address the issue of gold mixing caused by the Kelvin-Helmholtz instability (KHI) in the double-cone ignition (DCI) scheme, we investigate the growth rate of the KHI at the bi-interface of the DCI scheme after applying a coating. This is done by solving the hydrodynamic equations for an ideal incompressible fluid using linear theory. Ultimately, it is discovered that applying a coating with a thickness slightly above $h=0.5(\lambda+10 μm)$ and a density somewhat lower than that of the target layer can effectively reduce the growth rate of interfacial KHI. This work provides theoretical references for studying the bi-interface KHI in the DCI scheme.

INSTRUMENTATION AND MEASUREMENT

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Influence of crystal dimension on performance of spherical crystal self-emission imager Chenglong Zhang(张成龙), Yihang Zhang(张翌航), Haochen Gu(谷昊琛), Nuo Chen(陈诺), Xiaohui Yuan(远晓辉), Zhe Zhang(张喆), Miaohua Xu(徐妙华), Yutong Li(李玉同), Yingjun Li(李英骏), and Jie Zhang(张杰) Chin. Phys. B, 2024, 33 (12):  125205.  DOI: 10.1088/1674-1056/ad84d2 Abstract ( 4 )   PDF (989KB) ( 1 )   The spherical crystal imaging system, noted for its high energy spectral resolution (monochromaticity) and spatial resolution, is extensively applied in high energy density physics and inertial confinement fusion research. This system supports studies on fast electron transport, hydrodynamic instabilities, and implosion dynamics. The x-ray source, produced through laser-plasma interaction, emits a limited number of photons within short time scales, resulting in predominantly photon-starved images. Through ray-tracing simulations, we investigated the impact of varying crystal dimensions on the performance of a spherical crystal self-emission imager. We observed that increasing the crystal dimension leads to higher imaging efficiency but at the expense of monochromaticity, causing broader spectral acceptance and reduced spatial resolution. Furthermore, we presented a theoretical model to estimate the spatial resolution of the imaging system within a specific energy spectrum range, detailing the expressions for the effective size of the crystal. The spatial resolution derived from the model closely matches the numerical simulations.

CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

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Correlation of microstructure and magnetic softness of Si-microalloying FeNiBCuSi nanocrystalline alloy revealed by nanoindentation Benjun Wang(汪本军), Wenjun Liu(刘文君), Li Liu(刘莉), Yu Wang(王玉), Yu Hang(杭宇), Xinyu Wang(王新宇), Mengen Shi(施蒙恩), Hanchen Feng(冯汉臣), Long Hou(侯龙), Chenchen Yuan(袁晨晨), Zhong Li(李忠), and Weihuo Li(李维火) Chin. Phys. B, 2024, 33 (12):  126101.  DOI: 10.1088/1674-1056/ad84c8 Abstract ( 10 )   PDF (3258KB) ( 1 )   Compared to the commercial soft-magnetic alloys, the high saturation magnetic flux density ($B_{\rm s}$) and low coercivity ($H_{\rm c}$) of post-developed novel nanocrystalline alloys tend to realize the miniaturization and lightweight of electronic products, thus attracting great attention. In this work, we designed a new FeNiBCuSi formulation with a novel atomic ratio, and the microstructure evolution and magnetic softness were investigated. Microstructure analysis revealed that the amount of Si prompted the differential chemical fluctuations of Cu element, favoring the different nucleation and growth processes of $\alpha $-Fe nanocrystals. Furthermore, microstructural defects associated with chemical heterogeneities were unveiled using the Maxwell-Voigt model with two Kelvin units and one Maxwell unit based on creeping analysis by nanoindentation. The defect, with a long relaxation time in relaxation spectra, was more likely to induce the formation of crystal nuclei that ultimately evolved into the $\alpha$-Fe nanocrystals. As a result, Fe$_{84}$Ni$_{2}$B$_{12.5}$Cu$_{1}$Si$_{0.5}$ alloy with refined uniform nanocrystalline microstructure exhibited excellent magnetic softness, including a high $B_{\rm s}$ of 1.79 T and very low $H_{\rm c}$ of 2.8 A/m. Our finding offers new insight into the influence of activated defects associated with chemical heterogeneities on the microstructures of nanocrystalline alloy with excellent magnetic softness.

SPECIAL TOPIC — Structures and properties of materials under high pressure

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Pressure-induced structural transitions and metallization in ZrSe2 Yiping Gao(高一平), Chenchen Liu(刘晨晨), Can Tian(田灿), Chengcheng Zhu(朱程程), Xiaoli Huang(黄晓丽), and Tian Cui(崔田) Chin. Phys. B, 2024, 33 (12):  126104.  DOI: 10.1088/1674-1056/ad8ec9 Abstract ( 3 )   PDF (1996KB) ( 0 )   High-pressure studies of two-dimensional materials have revealed numerous novel properties and physical mechanisms behind them. As a typical material of transition metal dichalcogenides (TMDs), ZrSe$_{2}$ exhibits high carrier mobility, rich electronic states regulated by doping, and high potential in applications at ambient pressure. However, the properties of ZrSe$_{2}$ under pressure are still not clear, especially for the structural and electrical properties. Here, we report the investigation of ZrSe$_{2}$ under pressure up to 66.5 GPa by in-situ x-ray diffraction, Raman, electrical transport measurements, and first-principles calculations. Two structural phase transitions occur in ZrSe$_{2}$ at 8.3 GPa and 31.5 GPa, from $P$-3$m$1 symmetry to $P$2$_{1}$/$m$ symmetry, and finally transformed into a non-layer $I$4/mmm symmetry structure. Pressure-induced metallic transition is observed at around 19.4 GPa in phase II which aligns well with the results of the calculation. Our work will help to improve the understanding of the evolution of the structure and electrical transport properties of two-dimensional materials.

CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

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Molecular beam epitaxial growth and physical properties of AlN/GaN superlattices with an average 50% Al composition Siqi Li(李思琦), Pengfei Shao(邵鹏飞), Xiao Liang(梁潇), Songlin Chen(陈松林), Zhenhua Li(李振华), Xujun Su(苏旭军), Tao Tao(陶涛), Zili Xie(谢自力), Bin Liu(刘斌), M. Ajmal Khan, Li Wang, T. T. Lin, Hideki Hirayama, Rong Zhang(张荣), and Ke Wang(王科) Chin. Phys. B, 2024, 33 (12):  126801.  DOI: 10.1088/1674-1056/ad84cc Abstract ( 14 )   PDF (1254KB) ( 27 )   We report molecular beam epitaxial growth and electrical and ultraviolet light emitting properties of (AlN)$m$/(GaN)$n$ superlattices (SLs), where $m$ and $n$ represent the numbers of monolayers. Clear satellite peaks observed in XRD 2$\theta $-$\omega $ scans and TEM images evidence the formation of clear periodicity and atomically sharp interfaces. For (AlN)$m$/(GaN)$n$ SLs with an average Al composition of 50%, we have obtained an electron density up to 4.48$\times10^{19}$ cm$^{-3}$ and a resistivity of 0.002 $\Omega\cdot$cm, and a hole density of 1.83$\times10^{18}$ cm$^{-3}$ with a resistivity of 3.722 $\Omega \cdot$cm, both at room temperature. Furthermore, the (AlN)$m$/(GaN)$n$ SLs exhibit a blue shift for their photoluminescence peaks, from 403 nm to 318 nm as GaN is reduced from $n=11$ to $n=4$ MLs, reaching the challenging UVB wavelength range. The results demonstrate that the (AlN)$m$/(GaN)$n$ SLs have the potential to enhance the conductivity and avoid the usual random alloy scattering of the high-Al-composition ternary AlGaN, making them promising functional components in both UVB emitter and AlGaN channel high electron mobility transistor applications.

Structures and properties of materials under high pressure

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Design of superconducting compounds at lower pressure via intercalating XH4 molecules (X = B, C, and N) into fcc lattices Yue Zhao(赵玥), Sihan Liu(刘思涵), Jiao Liu(刘骄), Tingting Gu(顾婷婷), Jian Hao(郝健), Jingming Shi(石景明), Wenwen Cui(崔文文), and Yinwei Li(李印威) Chin. Phys. B, 2024, 33 (12):  127101.  DOI: 10.1088/1674-1056/ad7c31 Abstract ( 11 )   PDF (623KB) ( 104 )   Recently, many encouraging experimental advances have been achieved in ternary hydrides superconductors under high pressure. However, the extreme pressure required is indeed a challenge for practical application, which promotes a further exploration for high temperature ($T_{\rm c}$) superconductors at relatively low pressure. Herein, we performed a systematic theoretical investigation on a series of ternary hydrides with stoichiometry $AX_2$H$_8$, which is constructed by interacting molecular $X$H$_4$ ($X=$ B, C, and N) into the fcc metal $A$ lattice under low pressure of 0-150 GPa. We uncovered five compounds which are dynamically stable below 100 GPa, e.g., AcB$_2$H$_8$ (25 GPa), LaB$_2$H$_8$ (40 GPa), RbC$_2$H$_8$ (40 GPa), CsC$_2$H$_8$ (60 GPa), and SrC$_2$H$_8$ (65 GPa). Among them, AcB$_2$H$_8$, which is energetically stable above 2.5 GPa, exhibits the highest $T_{\rm c}$ of 32 K at 25 GPa. The superconductivity originates mainly from the coupling between the electron of Ac atoms and the associated low-frequency phonons, distinct from the previous typical hydrides with H-derived superconductivity. Our results shed light on the future exploration of superconductivity among ternary compounds at low pressure.

RAPID COMMUNICATION

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Disassembling one-dimensional chains in molybdenum oxides Xian Du(杜宪), Yidian Li(李义典), Wenxuan Zhao(赵文轩), Runzhe Xu(许润哲), Kaiyi Zhai(翟恺熠), Yulin Chen(陈宇林), and Lexian Yang(杨乐仙) Chin. Phys. B, 2024, 33 (12):  127102.  DOI: 10.1088/1674-1056/ad8bb2 Abstract ( 2 )   PDF (1345KB) ( 0 )   The dimensionality of quantum materials strongly affects their physical properties. Although many emergent phenomena, such as charge-density wave and Luttinger liquid behavior, are well understood in one-dimensional (1D) systems, the generalization to explore them in higher dimensional systems is still a challenging task. In this study, we aim to bridge this gap by systematically investigating the crystal and electronic structures of molybdenum-oxide family compounds, where the contexture of 1D chains facilitates rich emergent properties. While the quasi-1D chains in these materials share general similarities, such as the motifs made up of MoO$_{{6}}$ octahedrons, they exhibit vast complexity and remarkable tunability. We disassemble the 1D chains in molybdenum oxides with different dimensions and construct effective models to excellently fit their low-energy electronic structures obtained by ab initio calculations. Furthermore, we discuss the implications of such chains on other physical properties of the materials and the practical significance of the effective models. Our work establishes the molybdenum oxides as simple and tunable model systems for studying and manipulating the dimensionality in quantum systems.

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

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Janus monolayers Fe2SSeX2(X = Ga, In, and Tl): Robust nontrivial topology with high Chern number Kang Jia(贾康), Xiao-Jing Dong(董晓晶), Pei-Ji Wang(王培吉), and Chang-Wen Zhang(张昌文) Chin. Phys. B, 2024, 33 (12):  127103.  DOI: 10.1088/1674-1056/ad7c2a Abstract ( 13 )   PDF (3239KB) ( 5 )   High-performance quantum anomalous Hall (QAH) systems are crucial materials for exploring emerging quantum physics and magnetic topological phenomena. Inspired by layered FeSe materials with excellent superconducting properties, the Janus monolayers Fe$_{2}$SSe$X_{2}$ ($X ={\rm Ga}$, In and Tl) are built by the decoration of Ga, In and Tl atoms in monolayer Fe$_{2}$SSe. In first-principles calculations, Fe$_{2}$SSe$X_{2}$ have stable structures and prefer ferromagnetic (FM) ordering, and can be considered as Weyl semimetals without spin-orbit coupling. For out-of-plane (OOP) magnetic anisotropy, large nontrivial gaps are opened and the Fe$_{2}$SSe$X_{2}$ are predicted to be large-gap QAH insulators with a high Chern number $C = 2$, proved by two chiral edge states and Berry curvature. When the magnetization is flipped, the two chiral edge states can be simultaneously changed and $C =-2$ can be obtained, revealing the fascinating behavior of chiral spin-edge state locking. It is found that the QAH properties of Fe$_{2}$SSe$X_{2}$ are robust against strain. In particular, nontrivial topological quantum states can spontaneously appear for Fe$_{2}$SSeGa$_{2}$ and Fe$_{2}$SSeIn$_{2}$ because the orientations of the easy magnetic axis are adjusted from in-plane to OOP by the biaxial strain. Our studies provide excellent candidate systems to realize QAH properties with a high Chern number, and suggest more experimental explorations combining superconductivity and topology.

RAPID COMMUNICATION

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Spin fluctuations and orbital-selective superconductivity in Ba2CuO4-y: A FLEX study Pei-Jun Zheng(郑裴俊), Ya-Min Quan(全亚民), and Liang-Jian Zou(邹良剑) Chin. Phys. B, 2024, 33 (12):  127401.  DOI: 10.1088/1674-1056/ad8cbe Abstract ( 1 )   PDF (5416KB) ( 0 )   Recently discovered Ba$_2$CuO$_{4-y}$ provides new perspectives to the study of high-temperature superconductivity. Whereas, little is known about the spin dynamics of this material. In this work, we employ the fluctuation exchange (FLEX) approximation within the framework of spin-fluctuation mediated superconductivity to examine the behavior of the spin fluctuations of a two-orbital Hubbard model for Ba$_2$CuO$_{4-y}$. Our calculations reveal an extraordinary spin resonance mode coupled to the superconducting state in the hole-underdoped regime. Furthermore, we confirm that the coupling between the electrons and this resonance mode can lead to a dip-like feature in the electronic spectrum as a feedback effect. In the hole-overdoped regime, by incorporating self energy into our calculations, we obtain orbital-dependent renormalizations and show how these self-energy effects can lead to the detailed gap structures and the orbital-selective superconductivity, which could not be obtained in a previous study using random phase approximation (RPA). This research may shed new light on searching for unconventional superconductors with higher transition temperatures.

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

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Tuning the magnetocaloric and structural properties of La0.67Sr0.28Pr0.05Mn1-xCoxO3 refrigeration materials Changji Xu(徐长吉), Xinyu Jiang(姜心雨), Zhengguang Zou(邹正光), Zhuojia Xie(谢卓家), Weijian Zhang(张伟建), and Min Feng(冯敏) Chin. Phys. B, 2024, 33 (12):  127501.  DOI: 10.1088/1674-1056/ad8550 Abstract ( 14 )   PDF (6412KB) ( 17 )   The structural, magnetic and magnetocaloric properties of perovskite manganites La$_{0.67}$Sr$_{0.28}$Pr$_{0.05}$Mn$_{1-x}$Co$_{x}$O$_{3}$ ($x = 0.05$, 0.075 and 0.10) (LSPMCO) are investigated. LSPMCO crystallizes as a rhombohedral structure with $R$-$3c$ space group. As the Co content increases, the cell volume expands, the Mn-O-Mn bond angle reduces and the length of the Mn-O bond increases. The samples show irregular submicron particles under a Zeiss scanning electron microscopy. The particle size becomes larger with increasing doping. The chemical composition of the samples is confirmed by x-ray photoelectron spectroscopy (XPS). The ferromagnetic (FM) to paramagnetic (PM) phase transition occurs near the Curie temperature ($T_{\rm C}$), and all transitions are second-order phase transitions (SMOPT) characterized by minimal thermal and magnetic hystereses. Critical behavior analysis indicates that the critical parameters of LSPMCO closely align with those predicted by the mean-field model. The $T_{\rm C}$ declines with Co doping and reaches near room temperature (302 K) at $x = 0.075$. The maximum magnetic entropy change ($-\Delta S_{\rm M}^{\max}$) at $x = 0.05$ is 4.27 J/kg$\cdot$K, and the relative cooling power (RCP) peaks at 310.81 J/K. Therefore, the system holds significant potential for development as a magnetic refrigeration material, meriting further professional and objective evaluation.

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Distance-dependent magnetization modulation induced by inter-superatomic interactions in Cr-doped Au6Te12Se8 dimers Yurou Guan(官雨柔), Nanshu Liu(刘南舒), Cong Wang(王聪), Fei Pang(庞斐), Zhihai Cheng(程志海), and Wei Ji(季威) Chin. Phys. B, 2024, 33 (12):  127502.  DOI: 10.1088/1674-1056/ad8625 Abstract ( 11 )   PDF (1227KB) ( 1 )   Individual superatoms are assembled into more complicated nanostructures to diversify their physical properties. Magnetism of assembled superatoms remains, however, ambiguous, particularly in terms of its distance dependence. Here, we report density functional theory calculations on the distance-dependent magnetism of transition metal embedded Au$_{6}$Te$_{8}$Se$_{12}$ (ATS) superatomic dimers. Among the four considered transition metals, which include V, Cr, Mn and Fe, the Cr-embedded Au$_{6}$Te$_{12}$Se$_{8}$ (Cr@ATS) is identified as the most suitable for exploring the inter-superatomic distance-dependent magnetism. We thus focused on Cr@ATS superatomic dimers and found an inter-superatomic magnetization-distance oscillation where three transitions occur for magnetic ordering and/or anisotropy at different inter-superatomic distances. As the inter-superatomic distance elongates, a ferromagnetism (FM)-to-antiferromagnetic (AFM) transition and a sequential AFM-to-FM transition occur, ascribed to competitions among Pauli repulsion and kinetic-energy-gains in formed inter-superatomic Cr-Au-Au-Cr covalent bonds and Te-Te quasi-covalent bonds. For the third transition, in-plane electronic hybridization contributes to the stabilization of the AFM configuration. This work unveils two mechanisms for tuning magnetism through non-covalent interactions and provides a strategy for manipulating magnetism in superatomic assemblies.

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Valley modulation and topological phase transition in staggered kagome ferromagnets Yuheng Xing(邢玉恒), Wenjuan Qiu(邱文娟), Xinxing Wu(吴新星), and Yue Tan(谭悦) Chin. Phys. B, 2024, 33 (12):  127503.  DOI: 10.1088/1674-1056/ad7af7 Abstract ( 13 )   PDF (1664KB) ( 4 )   Owing to their charge-free property, magnons are highly promising for achieving dissipationless transport without Joule heating, and are thus potentially applicable to energy-efficient devices. Here, we investigate valley magnons and associated valley modulations in a kagome ferromagnetic lattice with staggered exchange interaction and Dzyaloshinskii-Moriya interaction. The staggered exchange interaction breaks the spatial inversion symmetry, leading to a valley magnon Hall effect. With nonzero Dzyaloshinskii-Moriya interaction in a staggered kagome lattice, the magnon Hall effect can be observed from only one valley. Moreover, reversing the Dzyaloshinskii-Moriya interaction ($D\to -D$) and exchanging $J_{1}$ and $J_{2}$ ($J_{1} \leftrightarrow J_{2}$) can also regulate the position of the unequal valleys. With increasing Dzyaloshinskii-Moriya interaction, a series of topological phase transitions appear when two bands come to touch and split at the valleys. The valley Hall effect and topological phase transitions observed in kagome magnon lattices can be realized in thin films of insulating ferromagnets such as Lu$_{2}$V$_{2}$O$_{7}$, and will extend the basis for magnonics applications in the future.

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Optical properties of La2O3 and HfO2 for radiative cooling via multiscale simulations Lihao Wang(王礼浩), Wanglin Yang(杨旺霖), Zhongyang Wang(王忠阳), Hongchao Li(李鸿超), Hao Gong(公昊), Jingyi Pan(潘静怡), Tongxiang Fan(范同祥), and Xiao Zhou(周啸) Chin. Phys. B, 2024, 33 (12):  127801.  DOI: 10.1088/1674-1056/ad84c0 Abstract ( 2 )   PDF (2865KB) ( 0 )   Radiative cooling materials have gained prominence as a zero-energy solution for mitigating global warming. However, a comprehensive understanding of the atomic-scale optical properties and macroscopic optical performance of radiative cooling materials remains elusive, limiting insight into the underlying physics of their optical response and cooling efficacy. La$_{2}$O$_{3}$ and HfO$_{2}$, which represent rare earth and third/fourth subgroup inorganic oxides, respectively, show promise for radiative cooling applications. In this study, we used multiscale simulations to investigate the optical properties of La$_{2}$O$_{3}$ and HfO$_{2}$ across a broad spectrum. First-principles calculations revealed their dielectric functions and intrinsic refractive indices, and the results indicated that the slightly smaller bandgap of La$_{2}$O$_{3}$ compared to HfO$_{2}$ induces a higher refractive index in the solar band. Additionally, three-phonon scattering was found to provide more accurate infrared optical properties than two-phonon scattering, which enhanced the emissivity in the sky window. Monte Carlo simulations were also used to determine the macroscopic optical properties of La$_{2}$O$_{3}$ and HfO$_{2}$ coatings. Based on the simulated results, we identified that the particle size and particle volume fraction play a dominant role in the optical properties. Our findings underscore the potential of La$_{2}$O$_{3}$ and HfO$_{2}$ nanocomposites for environment-friendly cooling and offer a new approach for high-throughput screening of optical materials through multiscale simulations.

INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY

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Effects of TMIn flow rate during quantum barrier growth on multi-quantum well material properties and device performance of GaN-based laser diodes Zhenyu Chen(陈振宇), Degang Zhao(赵德刚), Feng Liang(梁锋), Zongshun Liu(刘宗顺), Jing Yang(杨静), and Ping Chen(陈平) Chin. Phys. B, 2024, 33 (12):  128102.  DOI: 10.1088/1674-1056/ad8624 Abstract ( 1 )   PDF (566KB) ( 0 )   Multidimensional influences of indium composition in barrier layers on GaN-based blue laser diodes (LDs) are discussed from both material quality and device physics perspectives. LDs with higher indium content in the barriers demonstrate a notably lower threshold current and shorter lasing wavelength compared to those with lower indium content. Our experiments reveal that higher indium content in the barrier layers can partially reduce indium composition in the quantum wells, a novel discovery. Employing higher indium content barrier layers leads to improved luminescence properties of the MQW region. Detailed analysis reveals that this improvement can be attributed to better homogeneity in the indium composition of the well layers along the epitaxy direction. InGaN barrier layers suppress the lattice mismatch between barrier and well layers, thus mitigating the indium content pulling effect in the well layers. In supplement to experimental analysis, theoretical computations are performed, showing that InGaN barrier structures can effectively enhance carrier recombination efficiency and optical confinement of LD structure, thus improving the output efficiency of GaN-based blue LDs. Combining these theoretical insights with our experimental data, we propose that higher indium content barriers effectively enhance carrier recombination efficiency and indium content homogeneity in quantum well layers, thereby improving the output performance of GaN-based blue LDs.

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Quantum-mechanical understanding on structure dependence of image potentials of single-walled boron nitride nanotubes Yu Zhang(张煜), Zhiman Zhang(张芷蔓), Weiliang Wang(王伟良), Shaolin Zhang(张绍林), and Haiming Huang(黄海鸣) Chin. Phys. B, 2024, 33 (12):  128501.  DOI: 10.1088/1674-1056/ad8071 Abstract ( 14 )   PDF (1382KB) ( 2 )   The recent discovery of field emission devices based on one-dimensional nanostructures has attracted much interest in emerging applications on next-generation flat panel displays, molecule-based sensors, and so forth. To achieve a comprehensive understanding of surface potentials at the nano-emitters during the tunneling process, in this study we systematically investigated the image potentials of single-walled boron nitride nanotubes with different edges, diameters and lengths in the frame of a composite first-principles calculation. The image potentials of zigzag single-walled boron nitride nanotubes are found to be dependent on the non-equivalent sides. Only the image potentials of isolated armchair single-walled boron nitride nanotube can be well fitted with the image potential of an ideal metal sphere of a size comparable to the tube diameter. On the contrary, the image potentials of zigzag and grounded armchair single-walled boron nitride nanotubes exhibit a strong length-dependence characteristic and are significantly different from that of an ideal metal sphere, which originates from the significant axial symmetry breaking of induced charge at the tip for the long tube. The correlation between the testing electron and electronic structure of single-walled boron nitride nanotube has also been discussed.

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Back-side stress to ease p-MOSFET degradation on e-MRAM chips Zhi-Meng Yu(于志猛), Xiao-Lei Yang(杨晓蕾), Xiao-Nan Zhao(赵晓楠), Yan-Jie Li(李艳杰), Shi-Kun He(何世坤), and Ye-Wu Wang(王业伍) Chin. Phys. B, 2024, 33 (12):  128503.  DOI: 10.1088/1674-1056/ad7c2d Abstract ( 12 )   PDF (1068KB) ( 2 )   The magnetoresistive random access memory process makes a great contribution to threshold voltage deterioration of metal-oxide-silicon field-effect transistors, especially on p-type devices. Herein, a method was proposed to reduce the threshold voltage degradation by utilizing back-side stress. Through the deposition of tensile material on the back side, positive charges generated by silicon-hydrogen bond breakage were inhibited, resulting in a potential reduction in threshold voltage shift by up to 20%. In addition, it was found that the method could only relieve silicon-hydrogen bond breakage physically, thus failing to provide a complete cure. However, it holds significant potential for applications where additional thermal budget is undesired. Furthermore, it was also concluded that the method used in this work is irreversible, with its effect sustained to the chip package phase, and it ensures competitive reliability of the resulting magnetic tunnel junction devices.

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Simulation of crowd evacuation under attack considering emotion spreading Yang Wang(王杨), Ning Ding(丁宁), Dapeng Dong(董大鹏), and Yu Zhu(朱萸) Chin. Phys. B, 2024, 33 (12):  128901.  DOI: 10.1088/1674-1056/ad84c7 Abstract ( 11 )   PDF (1041KB) ( 1 )   In recent years, attacks against crowded places such as campuses and theaters have had a frequent and negative impact on the security and stability of society. In such an event, the crowd will be subjected to high psychological stress and their emotions will rapidly spread to others. This paper establishes the attack-evacuation evacuation simulation model (AEES-SFM), based on the social force model, to consider emotion spreading under attack. In this model, (1) the attack-escape driving force is considered for the interaction between an attacker and evacuees and (2) emotion spreading among the evacuees is considered to modify the value of the psychological force. To validate the simulation, several experiments were carried out at a university in China. Comparing the simulation and experimental results, it is found that the simulation results are similar to the experimental results when considering emotion spreading. Therefore, the AEES-SFM is proved to be effective. By comparing the results of the evacuation simulation without emotion spreading, the emotion spreading model reduces the evacuation time and the number of casualties by about 30%, which is closer to the real experimental results. The results are still applicable in the case of a 40-person evacuation. This paper provides theoretical support and practical guidance for campus response to violent attacks.

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Impact of environmental factors on the coevolution of information-emotions-epidemic dynamics in activity-driven multiplex networks Liang'an Huo(霍良安), Bingjie Liu(刘炳杰), and Xiaomin Zhao(赵晓敏) Chin. Phys. B, 2024, 33 (12):  128903.  DOI: 10.1088/1674-1056/ad7df5 Abstract ( 15 )   PDF (1122KB) ( 7 )   During public health emergencies, the diffusion of negative information can exacerbate the transmission of adverse emotions, such as fear and anxiety. These emotions can adversely affect immune function and, consequently, influence the spread of the epidemic. In this study, we established a coupled model incorporating environmental factors to explore the coevolution dynamic process of information-emotions-epidemic dynamics in activity-driven multiplex networks. In this model, environmental factors refer to the external conditions or pressures that affect the spread of information, emotions, and epidemics. These factors include media coverage, public opinion, and the prevalence of diseases in the neighborhood. These layers are dynamically cross-coupled, where the environmental factors in the information layer are influenced by the emotional layer; the higher the levels of anxious states among neighboring individuals, the greater the likelihood of information diffusion. Although environmental factors in the emotional layer are influenced by both the information and epidemic layers, they come from the factors of global information and the proportion of local infections among surrounding neighbors. Subsequently, we utilized the microscopic Markov chain approach to describe the dynamic processes, thereby obtaining the epidemic threshold. Finally, conclusions are drawn through numerical modeling and analysis. The conclusions suggest that when negative information increases, the probability of the transmission of anxious states across the population increases. The transmission of anxious states increases the final size of the disease and decreases its outbreak threshold. Reducing the impact of environmental factors at both the informational and emotional levels is beneficial for controlling the scale of the spread of the epidemic. Our findings can provide a reference for improving public health awareness and behavioral decision-making, mitigating the adverse impacts of anxious states, and ultimately controlling the spread of epidemics.