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16 January 2024, Volume 33 Issue 2 Previous issue    Next issue

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TOPICAL REVIEW—Post-Moore era: Materials and device physics

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Silicon-based optoelectronic heterogeneous integration for optical interconnection Le-Liang Li(李乐良), Gui-Ke Li(李贵柯), Zhao Zhang(张钊), Jian Liu(刘剑), Nan-Jian Wu(吴南健), Kai-You Wang(王开友), Nan Qi(祁楠), and Li-Yuan Liu(刘力源) Chin. Phys. B, 2024, 33 (2):  024201.  DOI: 10.1088/1674-1056/ad0e5b Abstract ( 215 )   HTML ( 3 )   PDF (3659KB) ( 331 )   The performance of optical interconnection has improved dramatically in recent years. Silicon-based optoelectronic heterogeneous integration is the key enabler to achieve high performance optical interconnection, which not only provides the optical gain which is absent from native Si substrates and enables complete photonic functionalities on chip, but also improves the system performance through advanced heterogeneous integrated packaging. This paper reviews recent progress of silicon-based optoelectronic heterogeneous integration in high performance optical interconnection. The research status, development trend and application of ultra-low loss optical waveguides, high-speed detectors, high-speed modulators, lasers and 2D, 2.5D, 3D and monolithic integration are focused on.

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The rise of supercapacitor diodes: Current progresses and future challenges Hongyun Ma(马鸿云), Lingxiao Ma(马凌霄), Huasheng Bi(毕华盛), and Wei Lan(兰伟) Chin. Phys. B, 2024, 33 (2):  028201.  DOI: 10.1088/1674-1056/ad1171 Abstract ( 155 )   HTML ( 1 )   PDF (5565KB) ( 136 )   Supercapacitor has been widely known as a representative electrochemical energy storage device with high power density and long lifespan. Recently, with the deeper understanding of its charge storage mechanism, unidirectional-charging supercapacitor, also called supercapacitor diode (CAPode), is successfully developed based on the ion-sieving effect of its working electrode towards electrolyte ions. Because CAPode integrates mobile ion and mobile electron in one hybrid circuit, it has a great potential in the emerging fields of ion/electron coupling logic operations, human-machine interface, neural network interaction, and in vivo diagnosis and treatment. Accordingly, we herein elucidate the working mechanism and design philosophy of CAPode, and summarize the electrode materials that are suitable for constructing CAPode. Meanwhile, some other supercapacitor-based devices beyond CAPode are also introduced, and their potential applications are instructively presented. Finally, we outline the challenges and chances of CAPode-related techniques.

SPECIAL TOPIC—Post-Moore era: Materials and device physics

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Biodegradable and flexible l-carrageenan based RRAM with ultralow power consumption Jing-Yao Bian(卞景垚), Ye Tao(陶冶), Zhong-Qiang Wang(王中强), Xiao-Ning Zhao(赵晓宁), Ya Lin(林亚), Hai-Yang Xu(徐海阳), and Yi-Chun Liu(刘益春) Chin. Phys. B, 2024, 33 (2):  027301.  DOI: 10.1088/1674-1056/ad19d4 Abstract ( 169 )   HTML ( 2 )   PDF (1882KB) ( 162 )   Transient memories, which can physically disappear without leaving traceable remains over a period of normal operation, are attracting increasing attention for potential applications in the fields of data security and green electronics. Resistive random access memory (RRAM) is a promising candidate for next-generation memory. In this context, biocompatible $\iota $-carrageenan ($\iota $-car), extracted from natural seaweed, is introduced for the fabrication of RRAM devices (Ag/$\iota $-car/Pt). Taking advantage of the complexation processes between the functional groups (C-O-C, C-O-H, et al.) and Ag metal ions, a lower migration barrier of Ag ions and a high-speed switching (22.2 ns for SET operation/26 ns for RESET operation) were achieved, resulting in an ultralow power consumption of 56 fJ. And the prepared Ag/$\iota $-car/Pt RRAM devices also revealed the capacities of multilevel storage and flexibility. In addition, thanks to the hydrophilic groups of $\iota $-car molecule, the RRAM devices can be rapidly dissolved in deionized (DI) water within 13 minutes, showing excellent transient characteristics. This work demonstrates that $\iota $-car based RRAM devices have great potential for applications in secure storage applications, flexible electronics and transient electronics.

DATA PAPER

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State-selective charge exchange cross sections in collisions of highly-charged sulfur ions with helium and molecular hydrogen Xiaolong Zhu(朱小龙), Shucheng Cui(崔述成), Dadi Xing(邢大地), Jiawei Xu(徐佳伟), B. Najjari, Dongmei Zhao(赵冬梅), Dalong Guo(郭大龙), Yong Gao(高永), Ruitian Zhang(张瑞田), Maogen Su(苏茂根), Shaofeng Zhang(张少锋), and Xinwen Ma(马新文) Chin. Phys. B, 2024, 33 (2):  023401.  DOI: 10.1088/1674-1056/ad0b01 Abstract ( 167 )   HTML ( 7 )   PDF (2054KB) ( 197 )   The state-selective cross section data are useful for understanding and modeling the x-ray emission in celestial observations. In the present work, using the cold target recoil ion momentum spectroscopy, for the first time we investigated the state-selective single electron capture processes for ${\rm S}^{q+}$-He and H$_{2}$ ($q=11$-15) collision systems at an impact energy of $q\times 20 $ keV and obtained the relative state-selective cross sections. The results indicate that only a few principal quantum states of the projectile energy level are populated in a single electron capture process. In particular, the increase of the projectile charge state leads to the population of the states with higher principal quantum numbers. It is also shown that the experimental averaged $n$-shell populations are reproduced well by the over-barrier model. The database is openly available in Science Data Bank at 10.57760/sciencedb.j00113.00091.

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Databases of 2D material-substrate interfaces and 2D charged building blocks Jun Deng(邓俊), Jinbo Pan(潘金波), and Shixuan Du(杜世萱) Chin. Phys. B, 2024, 33 (2):  026101.  DOI: 10.1088/1674-1056/ad0626 Abstract ( 162 )   HTML ( 7 )   PDF (1151KB) ( 200 )   Discovery of materials using "bottom-up" or "top-down" approach is of great interest in materials science. Layered materials consisting of two-dimensional (2D) building blocks provide a good platform to explore new materials in this respect. In van der Waals (vdW) layered materials, these building blocks are charge neutral and can be isolated from their bulk phase (top-down), but usually grow on substrate. In ionic layered materials, they are charged and usually cannot exist independently but can serve as motifs to construct new materials (bottom-up). In this paper, we introduce our recently constructed databases for 2D material-substrate interface (2DMSI), and 2D charged building blocks. For 2DMSI database, we systematically build a workflow to predict appropriate substrates and their geometries at substrates, and construct the 2DMSI database. For the 2D charged building block database, 1208 entries from bulk material database are identified. Information of crystal structure, valence state, source, dimension and so on is provided for each entry with a json format. We also show its application in designing and searching for new functional layered materials. The 2DMSI database, building block database, and designed layered materials are available in Science Data Bank at https://doi.org/10.57760/sciencedb.j00113.00188.

INSTRUMENTATION AND MEASUREMENT

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Development of a monochromatic crystal backlight imager for the recent double-cone ignition experiments Chenglong Zhang(张成龙), Yihang Zhang(张翌航), Xiaohui Yuan(远晓辉), Zhe Zhang(张喆), Miaohua Xu(徐妙华), Yu Dai(戴羽), Yufeng Dong(董玉峰), Haochen Gu(谷昊琛), Zhengdong Liu(刘正东), Xu Zhao(赵旭), Yutong Li(李玉同), Yingjun Li(李英骏), Jianqiang Zhu(朱健强), and Jie Zhang(张杰) Chin. Phys. B, 2024, 33 (2):  025201.  DOI: 10.1088/1674-1056/ad1091 Abstract ( 174 )   HTML ( 2 )   PDF (2274KB) ( 126 )   We developed a monochromatic crystal backlight imaging system for the double-cone ignition (DCI) scheme, employing a spherically bent quartz crystal. This system was used to measure the spatial distribution and temporal evolution of the head-on colliding plasma from the two compressing cones in the DCI experiments. The influence of laser parameters on the x-ray backlighter intensity and spatial resolution of the imaging system was investigated. The imaging system had a spatial resolution of 10 μm when employing a CCD detector. Experiments demonstrated that the system can obtain time-resolved radiographic images with high quality, enabling the precise measurement of the shape, size, and density distribution of the plasma.

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Magnetic field regression using artificial neural networks for cold atom experiments Ziting Chen(陈子霆), Kin To Wong(黃建陶), Bojeong Seo, Mingchen Huang(黄明琛), Mithilesh K. Parit, Yifei He(何逸飞), Haoting Zhen(甄浩廷), Jensen Li, and Gyu-Boong Jo Chin. Phys. B, 2024, 33 (2):  026701.  DOI: 10.1088/1674-1056/ad0cc8 Abstract ( 158 )   HTML ( 1 )   PDF (957KB) ( 107 )   Accurately measuring magnetic fields is essential for magnetic-field sensitive experiments in areas like atomic, molecular, and optical physics, condensed matter experiments, and other areas. However, since many experiments are often conducted in an isolated environment that is inaccessible to experimentalists, it can be challenging to accurately determine the magnetic field at the target location. Here, we propose an efficient method for detecting magnetic fields with the assistance of an artificial neural network (NN). Instead of measuring the magnetic field directly at the desired location, we detect fields at several surrounding positions, and a trained NN can accurately predict the magnetic field at the target location. After training, we achieve a below 0.3% relative prediction error of magnetic field magnitude at the center of the vacuum chamber, and successfully apply this method to our erbium quantum gas apparatus for accurate calibration of magnetic field and long-term monitoring of environmental stray magnetic field. The demonstrated approach significantly simplifies the process of determining magnetic fields in isolated environments and can be applied to various research fields across a wide range of magnetic field magnitudes.

RAPID COMMUNICATION

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Remote entangling gate between a quantum dot spin and a transmon qubit mediated by microwave photons Hot! Xing-Yu Zhu(朱行宇), Le-Tian Zhu(朱乐天), Tao Tu(涂涛), and Chuan-Feng Li(李传锋) Chin. Phys. B, 2024, 33 (2):  020315.  DOI: 10.1088/1674-1056/ad1747 Abstract ( 474 )   HTML ( 11 )   PDF (729KB) ( 500 )   Spin qubits and superconducting qubits are promising candidates for realizing solid-state quantum information processors. Designing a hybrid architecture that combines the advantages of different qubits on the same chip is a highly desirable but challenging goal. Here we propose a hybrid architecture that utilizes a high-impedance SQUID array resonator as a quantum bus, thereby coherently coupling different solid-state qubits. We employ a resonant exchange spin qubit hosted in a triple quantum dot and a superconducting transmon qubit. Since this hybrid system is highly tunable, it can operate in a dispersive regime, where the interaction between the different qubits is mediated by virtual photons. By utilizing such interactions, entangling gate operations between different qubits can be realized in a short time of 30 ns with a fidelity of up to 96.5% under realistic parameter conditions. Further utilizing this interaction, remote entangled state between different qubits can be prepared and is robust to perturbations of various parameters. These results pave the way for exploring efficient fault-tolerant quantum computation on hybrid quantum architecture platforms.

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Gigahertz frequency hopping in an optical phase-locked loop for Raman lasers Dekai Mao(毛德凯), Hongmian Shui(税鸿冕), Guoling Yin(殷国玲), Peng Peng(彭鹏), Chunwei Wang(王春唯), and Xiaoji Zhou(周小计) Chin. Phys. B, 2024, 33 (2):  024209.  DOI: 10.1088/1674-1056/ad174b Abstract ( 256 )   HTML ( 5 )   PDF (984KB) ( 219 )   Raman lasers are essential in atomic physics, and the development of portable devices has posed requirements for time-division multiplexing of Raman lasers. We demonstrate an innovative gigahertz frequency hopping approach of a slave Raman laser within an optical phase-locked loop (OPLL), which finds practical application in an atomic gravimeter, where the OPLL frequently switches between near-resonance lasers and significantly detuned Raman lasers. The method merges the advantages of rapid and extensive frequency hopping with the OPLL's inherent low phase noise, and exhibits a versatile range of applications in compact laser systems, promising advancements in portable instruments.

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Angular and planar transport properties of antiferromagnetic V5S8 Hot! Xiao-Kai Wu(吴晓凯), Bin Wang(王彬), De-Tong Wu(吴德桐), Bo-Wen Chen(陈博文), Meng-Juan Mi(弭孟娟), Yi-Lin Wang(王以林), and Bing Shen(沈冰) Chin. Phys. B, 2024, 33 (2):  027503.  DOI: 10.1088/1674-1056/ad15f9 Abstract ( 330 )   HTML ( 8 )   PDF (9933KB) ( 370 )   Systemically angular and planar transport investigations are performed in layered antiferromagnetic (AF) V5S8. In this AF system, obvious anomalous Hall effect (AHE) is observed with a large Hall angle of 0.1 compared to that in ferromagnetic (FM) system. It can persist to the temperatures above AF transition and exhibit strong angular field dependence. The phase diagram reveals various magnetic states by rotating the applied field. By analyzing the anisotropic transport behavior, magnon contributions are revealed and exhibit obvious angular dependence with a spin-flop vanishing line. The observed prominent planar Hall effect and anisotropic magnetoresisitivity exhibit two-fold systematical angular dependent oscillations. These behaviors are attributed to the scattering from spin-orbital coupling instead of nontrivial topological origin. Our results reveal anisotropic interactions of magnetism and electron in V5S8, suggesting potential opportunities for the AF spintronic sensor and devices.

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Characteristics of cell motility during cell collision Yikai Ma(马一凯), Na Li(李娜), and Wei Chen(陈唯) Chin. Phys. B, 2024, 33 (2):  028702.  DOI: 10.1088/1674-1056/ad117c Abstract ( 127 )   HTML ( 3 )   PDF (1440KB) ( 115 )   Quantitative examination of cellular motion and intercellullar interactions possesses substantial relevance for both biology and medicine. However, the effects of intercellular interactions during cellular locomotion remain under-explored in experimental research. As such, this study seeks to bridge this research gap, adopting Dictyostelium discoideum (Dicty) cells as a paradigm to investigate variations in cellular motion during reciprocal collisions. We aim to attain a comprehensive understanding of how cell interactions influence cell motion. By observing and processing the motion trajectories of colliding cells under diverse chemical environments, we calculated the diffusion coefficient ($D$) and the persistence time ($\tau$), using mean square displacement. Our analysis of the relationship dynamics between $D$ and $\tau $ prior to the collisions reveals intricate and non-monotonic alterations in cell movements during collisions. By quantitatively scrutinizing the $\tau $ trend, we were able to categorize the cellular responses to interactions under different conditions. Importantly, we ascertained that the effect of cell interactions during collisions in Dicty cells emulates a classical sigmoid function. This discovery suggests that cellular responses might comply with a pattern akin to the Weber-Fechner law.

GENERAL

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Effective dynamics for a spin-1/2 particle constrained to a curved layer with inhomogeneous thickness Guo-Hua Liang(梁国华) and Pei-Lin Yin(尹佩林) Chin. Phys. B, 2024, 33 (2):  020201.  DOI: 10.1088/1674-1056/ad0715 Abstract ( 142 )   HTML ( 2 )   PDF (883KB) ( 69 )   We derive an effective Hamiltonian for a spin-1/2 particle confined within a curved thin layer with non-uniform thickness using the confining potential approach. Our analysis reveals the presence of a pseudo-magnetic field and effective spin-orbit interaction (SOI) arising from the curvature, as well as an effective scalar potential resulting from variations in thickness. Importantly, we demonstrate that the physical effect of additional SOI from thickness fluctuations vanishes in low-dimensional systems, thus guaranteeing the robustness of spin interference measurements to thickness imperfection. Furthermore, we establish the applicability of the effective Hamiltonian in both symmetric and asymmetric confinement scenarios, which is crucial for its utilization in one-side etching systems.

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Effect of applied electric fields on supralinear dendritic integration of interneuron Ya-Qin Fan(樊亚琴), Xi-Le Wei(魏熙乐), Mei-Li Lu(卢梅丽), and Guo-Sheng Yi(伊国胜) Chin. Phys. B, 2024, 33 (2):  020202.  DOI: 10.1088/1674-1056/ad09cc Abstract ( 118 )   HTML ( 1 )   PDF (991KB) ( 67 )   Evidences show that electric fields (EFs) induced by the magnetic stimulation could modulates brain activities by regulating the excitability of GABAergic interneuron. However, it is still unclear how and why the EF-induced polarization affects the interneuron response as the interneuron receives NMDA synaptic inputs. Considering the key role of NMDA receptor-mediated supralinear dendritic integration in neuronal computations, we suppose that the applied EFs could functionally modulate interneurons' response via regulating dendritic integration. At first, we build a simplified multi-dendritic circuit model with inhomogeneous extracellular potentials, which characterizes the relationship among EF-induced spatial polarizations, dendritic integration, and somatic output. By performing model-based singular perturbation analysis, it is found that the equilibrium point of fast subsystem can be used to asymptotically depict the subthreshold input-output (sI/O) relationship of dendritic integration. It predicted that EF-induced strong depolarizations on the distal dendrites reduce the dendritic saturation output by reducing driving force of synaptic input, and it shifts the steep change of sI/O curve left by reducing stimulation threshold of triggering NMDA spike. Also, the EF modulation prefers the global dendritic integration with asymmetric scatter distribution of NMDA synapses. Furthermore, we identify the respective contribution of EF-regulated dendritic integration and EF-induced somatic polarization to an action potential generation and find that they have an antagonistic effect on AP generation due to the varied NMDA spike threshold under EF stimulation.

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MetaPINNs: Predicting soliton and rogue wave of nonlinear PDEs via the improved physics-informed neural networks based on meta-learned optimization Yanan Guo(郭亚楠), Xiaoqun Cao(曹小群), Junqiang Song(宋君强), and Hongze Leng(冷洪泽) Chin. Phys. B, 2024, 33 (2):  020203.  DOI: 10.1088/1674-1056/ad0bf4 Abstract ( 166 )   HTML ( 3 )   PDF (5983KB) ( 133 )   Efficiently solving partial differential equations (PDEs) is a long-standing challenge in mathematics and physics research. In recent years, the rapid development of artificial intelligence technology has brought deep learning-based methods to the forefront of research on numerical methods for partial differential equations. Among them, physics-informed neural networks (PINNs) are a new class of deep learning methods that show great potential in solving PDEs and predicting complex physical phenomena. In the field of nonlinear science, solitary waves and rogue waves have been important research topics. In this paper, we propose an improved PINN that enhances the physical constraints of the neural network model by adding gradient information constraints. In addition, we employ meta-learning optimization to speed up the training process. We apply the improved PINNs to the numerical simulation and prediction of solitary and rogue waves. We evaluate the accuracy of the prediction results by error analysis. The experimental results show that the improved PINNs can make more accurate predictions in less time than that of the original PINNs.

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Exact solutions for magnetohydrodynamic nanofluids flow and heat transfer over a permeable axisymmetric radially stretching/shrinking sheet U. S. Mahabaleshwar, G. P. Vanitha, L. M. Pérez, Emad H. Aly, and I. Pop Chin. Phys. B, 2024, 33 (2):  020204.  DOI: 10.1088/1674-1056/ad09c9 Abstract ( 118 )   HTML ( 0 )   PDF (2417KB) ( 87 )   We report on the magnetohydrodynamic impact on the axisymmetric flow of Al2O3/Cu nanoparticles suspended in H2O past a stretched/shrinked sheet. With the use of partial differential equations and the corresponding thermophysical characteristics of nanoparticles, the physical flow process is illustrated. The resultant nonlinear system of partial differential equations is converted into a system of ordinary differential equations using the suitable similarity transformations. The transformed differential equations are solved analytically. Impacts of the magnetic parameter, solid volume fraction and stretching/shrinking parameter on momentum and temperature distribution have been analyzed and interpreted graphically. The skin friction and Nusselt number were also evaluated. In addition, existence of dual solution was deduced for the shrinking sheet and unique solution for the stretching one. Further, Al2O3/H2O nanofluid flow has better thermal conductivity on comparing with Cu/H2O nanofluid. Furthermore, it was found that the first solutions of the stream are stable and physically realizable, whereas those of the second ones are unstable.

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Analytical solution to incident angle quasi-phase-matching engineering for second harmonic generation in a periodic-poled lithium niobate crystal Li-Hong Hong(洪丽红), Ya-Ting Qiu(邱雅婷), Xiao-Ni Li(李晓霓), Bao-Qin Chen(陈宝琴), and Zhi-Yuan Li(李志远) Chin. Phys. B, 2024, 33 (2):  020301.  DOI: 10.1088/1674-1056/ad0628 Abstract ( 149 )   HTML ( 3 )   PDF (790KB) ( 125 )   Phase matching or quasi-phase matching (QPM) is of significant importance to the conversion efficiency of second harmonic generation (SHG) in artificial nonlinear crystals like lithium niobate (LN) crystal or microstructured nonlinear crystals like periodic-poled lithium niobate (PPLN) crystals. In this paper, we propose and show that the incident angle of pump laser light can be harnessed as an alternative versatile tool to engineer QPM for high-efficiency SHG in a PPLN crystal, in addition to conventional means of period adjusting or temperature tuning. A rigorous model is established and analytical solution of the nonlinear conversion efficiency under the small and large signal approximation theory is obtained at different incident angles. The variation of phase mismatching and walk-off length with incident angle or incident wavelength are also explored. Numerical simulations for a PPLN crystal with first order QPM structure are used to confirm our theoretical predictions based on the exact analytical solution of the general large-signal theory. The results show that the narrow-band tunable SHG output covers a range of 532 nm-552.8 nm at the ideal incident angle from 0° to 90°. This theoretical scheme, fully considering the reflection and transmission at the air-crystal interface, would offer an efficient theoretical system to evaluate the nonlinear frequency conversion and help to obtain the maximum SHG conversion efficiency by selecting an optimum incident wavelength and incident angle in a specially designed PPLN crystal, which would be very helpful for the design of tunable narrow-band pulse nanosecond, picosecond, and femtosecond laser devices via PPLN and other microstructured LN crystals.

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Chiral bound states in a staggered array of coupled resonators Wu-Lin Jin(金伍林), Jing Li(李静), Jing Lu(卢竞), Zhi-Rui Gong(龚志瑞), and Lan Zhou(周兰) Chin. Phys. B, 2024, 33 (2):  020302.  DOI: 10.1088/1674-1056/ad0bf0 Abstract ( 135 )   HTML ( 2 )   PDF (3424KB) ( 153 )   We study the chiral bound states in a coupled-resonator array with staggered hopping strengths, which interacts with a two-level small atom through a single coupling point or two adjacent ones. In addition to the two typical bound states found above and below the energy bands, this system presents an extraordinary chiral bound state located within the energy gap. We use the chirality to quantify the breaking of the mirror symmetry. We find that the chirality value undergoes continuous changes by tuning the coupling strengths. The preferred direction of the chirality is controlled not only by the competition between the intracell and the intercell hoppings in the coupled-resonator array, but also by the coherence between the two coupling points. In the case with one coupling point, the chirality values varies monotonously with difference between the intracell hopping and the intercell hoppings. While in the case with two coupling points, due to the coherence between the two coupling points the perfect chiral states can be obtained.

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Proposal for sequential Stern-Gerlach experiment with programmable quantum processors Meng-Jun Hu(胡孟军), Haixing Miao(缪海兴), and Yong-Sheng Zhang(张永生) Chin. Phys. B, 2024, 33 (2):  020303.  DOI: 10.1088/1674-1056/ad09ca Abstract ( 168 )   HTML ( 2 )   PDF (1324KB) ( 117 )   The historical significance of the Stern-Gerlach (SG) experiment lies in its provision of the initial evidence for space quantization. Over time, its sequential form has evolved into an elegant paradigm that effectively illustrates the fundamental principles of quantum theory. To date, the practical implementation of the sequential SG experiment has not been fully achieved. In this study, we demonstrate the capability of programmable quantum processors to simulate the sequential SG experiment. The specific parametric shallow quantum circuits, which are suitable for the limitations of current noisy quantum hardware, are given to replicate the functionality of SG devices with the ability to perform measurements in different directions. Surprisingly, it has been demonstrated that Wigner's SG interferometer can be readily implemented in our sequential quantum circuit. With the utilization of the identical circuits, it is also feasible to implement Wheeler's delayed-choice experiment. We propose the utilization of cross-shaped programmable quantum processors to showcase sequential experiments, and the simulation results demonstrate a strong alignment with theoretical predictions. With the rapid advancement of cloud-based quantum computing, such as BAQIS Quafu, it is our belief that the proposed solution is well-suited for deployment on the cloud, allowing for public accessibility. Our findings not only expand the potential applications of quantum computers, but also contribute to a deeper comprehension of the fundamental principles underlying quantum theory.

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Holevo bound independent of weight matrices for estimating two parameters of a qubit Chang Niu(牛畅) and Sixia Yu(郁司夏) Chin. Phys. B, 2024, 33 (2):  020304.  DOI: 10.1088/1674-1056/ad117d Abstract ( 165 )   HTML ( 1 )   PDF (2024KB) ( 152 )   Holevo bound plays an important role in quantum metrology as it sets the ultimate limit for multi-parameter estimations, which can be asymptotically achieved. Except for some trivial cases, the Holevo bound is implicitly defined and formulated with the help of weight matrices. Here we report the first instance of an intrinsic Holevo bound, namely, without any reference to weight matrices, in a nontrivial case. Specifically, we prove that the Holevo bound for estimating two parameters of a qubit is equivalent to the joint constraint imposed by two quantum Cramér-Rao bounds corresponding to symmetric and right logarithmic derivatives. This weightless form of Holevo bound enables us to determine the precise range of independent entries of the mean-square error matrix, i.e., two variances and one covariance that quantify the precisions of the estimation, as illustrated by different estimation models. Our result sheds some new light on the relations between the Holevo bound and quantum Cramér-Rao bounds. Possible generalizations are discussed.

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Preparing highly entangled states of nanodiamond rotation and NV center spin Wen-Liang Li(李文亮) and Duan-Lu Zhou(周端陆) Chin. Phys. B, 2024, 33 (2):  020305.  DOI: 10.1088/1674-1056/ad117a Abstract ( 146 )   HTML ( 1 )   PDF (596KB) ( 215 )   A nanodiamond with an embedded nitrogen-vacancy (NV) center is one of the experimental systems that can be coherently manipulated within current technologies. Entanglement between NV center electron spin and mechanical rotation of the nanodiamond plays a fundamental role in building a quantum network connecting these microscopic and mesoscopic degrees of motions. Here we present a protocol to asymptotically prepare a highly entangled state of the total quantum angular momentum and electron spin by adiabatically boosting the external magnetic field.

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Quantum synchronization with correlated baths Lei Li(李磊), Chun-Hui Wang(王春辉), Hong-Hao Yin(尹洪浩), Ru-Quan Wang(王如泉), and Wu-Ming Liu(刘伍明) Chin. Phys. B, 2024, 33 (2):  020306.  DOI: 10.1088/1674-1056/ad0bef Abstract ( 148 )   HTML ( 0 )   PDF (720KB) ( 154 )   We study quantum synchronization under the nonequilibrium reservoirs. We consider a two-qubit XXZ chain coupled independently to their own reservoirs modeled by the collisional model. Two reservoir particles, initially prepared in a thermal state or a state with coherence, are correlated through a unitary transformation and afterward interact locally with the two quantum subsystems. We study the quantum effect of reservoir on synchronous dynamics of system. By preparing different reservoir initial states or manipulating the reservoir particles coupling and the temperature gradient, we find that quantum entanglement of reservoir is the key to control quantum synchronization of system qubits.

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Genuine entanglement under squeezed generalized amplitude damping channels with memory Mazhar Ali Chin. Phys. B, 2024, 33 (2):  020307.  DOI: 10.1088/1674-1056/ace15f Abstract ( 127 )   HTML ( 0 )   PDF (466KB) ( 121 )   We study genuine entanglement among three qubits undergoing a noisy process that includes dissipation, squeezing, and decoherence. We obtain a general solution and analyze the asymptotic quantum states. We find that most of these asymptotic states can be genuinely entangled depending upon the parameters of the channel, memory parameter, and the parameters of the initial states. We study Greenberger-Horne-Zeilinger (GHZ) states and ${W}$ states, mixed with white noise, and determine the conditions for them to be genuinely entangled at infinity. We find that for these mixtures, it is possible to start with a bi-separable state (with a specific mixture of white noise) and end with genuine entangled states. However, the memory parameter $\mu$ must be very high. We find that in contrast to the two-qubit case, none of the three-qubit asymptotic states for $n \to \infty$ are genuinely entangled.

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Unconventional photon blockade in the two-photon Jaynes-Cummings model with two-frequency cavity drivings and atom driving Xin Liu(刘欣), Meng-Yu Tian(田梦雨), Xiao-Ning Cui(崔晓宁), and Xin-He Zhang(张馨鹤) Chin. Phys. B, 2024, 33 (2):  020308.  DOI: 10.1088/1674-1056/ad0cca Abstract ( 120 )   HTML ( 0 )   PDF (1282KB) ( 34 )   In a two-frequency cavity driving and atom driving atom-cavity system, we find the photon blockade effect. In a truncated eigenstates space, we calculate the zero-delay second-order correlation function of the cavity mode analytically and obtain an optimal condition for the photon blockade. By including three transition pathways, we find that higher excitations of the cavity mode can be further suppressed and the zero-delay second-order correlation function can be reduced additionally. Based on the master equation, we simulate the system evolution and find that the analytical solutions match well with the numerical results. Our scheme is robust with small fluctuations of parameters and may be used as a new type of single photon source.

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Protected simultaneous quantum remote state preparation scheme by weak and reversal measurements in noisy environments Mandal Manoj Kumar, Choudhury Binayak S., and Samanta Soumen Chin. Phys. B, 2024, 33 (2):  020309.  DOI: 10.1088/1674-1056/ace683 Abstract ( 111 )   HTML ( 0 )   PDF (1691KB) ( 72 )   We discuss a quantum remote state preparation protocol by which two parties, Alice and Candy, prepare a single-qubit and a two-qubit state, respectively, at the site of the receiver Bob. The single-qubit state is known to Alice while the two-qubit state which is a non-maximally entangled Bell state is known to Candy. The three parties are connected through a single entangled state which acts as a quantum channel. We first describe the protocol in the ideal case when the entangled channel under use is in a pure state. After that, we consider the effect of amplitude damping (AD) noise on the quantum channel and describe the protocol executed through the noisy channel. The decrement of the fidelity is shown to occur with the increment in the noise parameter. This is shown by numerical computation in specific examples of the states to be created. Finally, we show that it is possible to maintain the label of fidelity to some extent and hence to decrease the effect of noise by the application of weak and reversal measurements. We also present a scheme for the generation of the five-qubit entangled resource which we require as a quantum channel. The generation scheme is run on the IBMQ platform.

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Quantum algorithm for minimum dominating set problem with circuit design Haoying Zhang(张皓颖), Shaoxuan Wang(王绍轩), Xinjian Liu(刘新建), Yingtong Shen(沈颖童), and Yukun Wang(王玉坤) Chin. Phys. B, 2024, 33 (2):  020310.  DOI: 10.1088/1674-1056/ad02e5 Abstract ( 135 )   HTML ( 0 )   PDF (1001KB) ( 76 )   Using quantum algorithms to solve various problems has attracted widespread attention with the development of quantum computing. Researchers are particularly interested in using the acceleration properties of quantum algorithms to solve NP-complete problems. This paper focuses on the well-known NP-complete problem of finding the minimum dominating set in undirected graphs. To expedite the search process, a quantum algorithm employing Grover's search is proposed. However, a challenge arises from the unknown number of solutions for the minimum dominating set, rendering direct usage of original Grover's search impossible. Thus, a swap test method is introduced to ascertain the number of iterations required. The oracle, diffusion operators, and swap test are designed with achievable quantum gates. The query complexity is $O(1.414^n)$ and the space complexity is $O(n)$. To validate the proposed approach, qiskit software package is employed to simulate the quantum circuit, yielding the anticipated results.

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Gray code based gradient-free optimization algorithm for parameterized quantum circuit Anqi Zhang(张安琪), Chunhui Wu(武春辉), and Shengmei Zhao(赵生妹) Chin. Phys. B, 2024, 33 (2):  020311.  DOI: 10.1088/1674-1056/ad09cd Abstract ( 134 )   HTML ( 1 )   PDF (730KB) ( 29 )   A Gray code based gradient-free optimization (GCO) algorithm is proposed to update the parameters of parameterized quantum circuits (PQCs) in this work. Each parameter of PQCs is encoded as a binary string, named as a gene, and a genetic-based method is adopted to select the offsprings. The individuals in the offspring are decoded in Gray code way to keep Hamming distance, and then are evaluated to obtain the best one with the lowest cost value in each iteration. The algorithm is performed iteratively for all parameters one by one until the cost value satisfies the stop condition or the number of iterations is reached. The GCO algorithm is demonstrated for classification tasks in Iris and MNIST datasets, and their performance are compared by those with the Bayesian optimization algorithm and binary code based optimization algorithm. The simulation results show that the GCO algorithm can reach high accuracies steadily for quantum classification tasks. Importantly, the GCO algorithm has a robust performance in the noise environment.

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Simulation of optimal work extraction for quantum systems with work storage Peng-Fei Song(宋鹏飞) and Dan-Bo Zhang(张旦波) Chin. Phys. B, 2024, 33 (2):  020312.  DOI: 10.1088/1674-1056/ad09d0 Abstract ( 116 )   HTML ( 1 )   PDF (658KB) ( 39 )   The capacity to extract work from a quantum heat machine is not only of practical value but also lies at the heart of understanding quantum thermodynamics. In this paper, we investigate optimal work extraction for quantum systems with work storage, where extracting work is completed by a unitary evolution on the composite system. We consider the physical requirement of energy conservation both strictly and on average. For both, we construct their corresponding unitaries and propose variational quantum algorithms for optimal work extraction. We show that maximal work extraction in general can be feasible when energy conservation is satisfied on average. We demonstrate with numeral simulations using a continuous-variable work storage. Our work show an implementation of a variational quantum computing approach for simulating work extraction in quantum systems.

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Improved decoy-state quantum key distribution with uncharacterized heralded single-photon sources Le-Chen Xu(徐乐辰), Chun-Hui Zhang(张春辉), Xing-Yu Zhou(周星宇), and Qin Wang(王琴) Chin. Phys. B, 2024, 33 (2):  020313.  DOI: 10.1088/1674-1056/ad062a Abstract ( 154 )   HTML ( 0 )   PDF (1256KB) ( 114 )   Encoding system plays a significant role in quantum key distribution (QKD). However, the security and performance of QKD systems can be compromised by encoding misalignment due to the inevitable defects in realistic devices. To alleviate the influence of misalignments, a method exploiting statistics from mismatched basis is proposed to enable uncharacterized sources to generate secure keys in QKD. In this work, we propose a scheme on four-intensity decoy-state quantum key distribution with uncharacterized heralded single-photon sources. It only requires the source states are prepared in a two-dimensional Hilbert space, and can thus reduce the complexity of practical realizations. Moreover, we carry out corresponding numerical simulations and demonstrate that our present four-intensity decoy-state scheme can achieve a much higher key rate compared than a three-intensity decoy-state method, and meantime it can obtain a longer transmission distance compared than the one using weak coherent sources.

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Dynamical nonlinear excitations induced by interaction quench in a two-dimensional box-trapped Bose-Einstein condensate Zhen-Xia Niu(牛真霞) and Chao Gao(高超) Chin. Phys. B, 2024, 33 (2):  020314.  DOI: 10.1088/1674-1056/ad1179 Abstract ( 153 )   HTML ( 0 )   PDF (3082KB) ( 133 )   Manipulating nonlinear excitations, including solitons and vortices, is an essential topic in quantum many-body physics. A new progress in this direction is a protocol proposed in [Phys. Rev. Res. 2 043256 (2020)] to produce dark solitons in a one-dimensional atomic Bose-Einstein condensate (BEC) by quenching inter-atomic interaction. Motivated by this work, we generalize the protocol to a two-dimensional BEC and investigate the generic scenario of its post-quench dynamics. For an isotropic disk trap with a hard-wall boundary, we find that successive inward-moving ring dark solitons (RDSs) can be induced from the edge, and the number of RDSs can be controlled by tuning the ratio of the after- and before-quench interaction strength across different critical values. The role of the quench played on the profiles of the density, phase, and sound velocity is also investigated. Due to the snake instability, the RDSs then become vortex-antivortex pairs with peculiar dynamics managed by the initial density and the after-quench interaction. By tuning the geometry of the box traps, demonstrated as polygonal ones, more subtle dynamics of solitons and vortices are enabled. Our proposed protocol and the discovered rich dynamical effects on nonlinear excitations can be realized in near future cold-atom experiments.

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Memory effect in time fractional Schrödinger equation Chuanjin Zu(祖传金) and Xiangyang Yu(余向阳) Chin. Phys. B, 2024, 33 (2):  020501.  DOI: 10.1088/1674-1056/ad02e6 Abstract ( 149 )   HTML ( 0 )   PDF (922KB) ( 65 )   A significant obstacle impeding the advancement of the time fractional Schrödinger equation lies in the challenge of determining its precise mathematical formulation. In order to address this, we undertake an exploration of the time fractional Schrödinger equation within the context of a non-Markovian environment. By leveraging a two-level atom as an illustrative case, we find that the choice to raise i to the order of the time derivative is inappropriate. In contrast to the conventional approach used to depict the dynamic evolution of quantum states in a non-Markovian environment, the time fractional Schrödinger equation, when devoid of fractional-order operations on the imaginary unit i, emerges as a more intuitively comprehensible framework in physics and offers greater simplicity in computational aspects. Meanwhile, we also prove that it is meaningless to study the memory of time fractional Schrödinger equation with time derivative 1 < α ≤ 2. It should be noted that we have not yet constructed an open system that can be fully described by the time fractional Schrödinger equation. This will be the focus of future research. Our study might provide a new perspective on the role of time fractional Schrödinger equation.

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Symmetric Brownian motor subjected to Lévy noise Kao Jia(贾考), Lan Hu(胡兰), and Linru Nie(聂林如) Chin. Phys. B, 2024, 33 (2):  020502.  DOI: 10.1088/1674-1056/ace8fa Abstract ( 137 )   HTML ( 0 )   PDF (637KB) ( 32 )   In the past few years, attention has mainly been focused on the symmetric Brownian motor (BM) with Gaussian noises, whose current and energy conversion efficiency are very low. Here, we investigate the operating performance of the symmetric BM subjected to Lévy noise. Through numerical simulations, it is found that the operating performance of the motor can be greatly improved in asymmetric Lévy noise. Without any load, the Lévy noises with smaller stable indexes can let the motor give rise to a much greater current. With a load, the energy conversion efficiency of the motor can be enhanced by adjusting the stable indexes of the Lévy noises with symmetry breaking. The results of this research are of great significance for opening up BM's intrinsic physical mechanism and promoting the development of nanotechnology.

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A chaotic hierarchical encryption/watermark embedding scheme for multi-medical images based on row-column confusion and closed-loop bi-directional diffusion Zheyi Zhang(张哲祎), Jun Mou(牟俊), Santo Banerjee, and Yinghong Cao(曹颖鸿) Chin. Phys. B, 2024, 33 (2):  020503.  DOI: 10.1088/1674-1056/ad0775 Abstract ( 142 )   HTML ( 1 )   PDF (26773KB) ( 152 )   Security during remote transmission has been an important concern for researchers in recent years. In this paper, a hierarchical encryption multi-image encryption scheme for people with different security levels is designed, and a multi-image encryption (MIE) algorithm with row and column confusion and closed-loop bi-directional diffusion is adopted in the paper. While ensuring secure communication of medical image information, people with different security levels have different levels of decryption keys, and differentiated visual effects can be obtained by using the strong sensitivity of chaotic keys. The highest security level can obtain decrypted images without watermarks, and at the same time, patient information and copyright attribution can be verified by obtaining watermark images. The experimental results show that the scheme is sufficiently secure as an MIE scheme with visualized differences and the encryption and decryption efficiency is significantly improved compared to other works.

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Multiple mixed state variable incremental integration for reconstructing extreme multistability in a novel memristive hyperchaotic jerk system with multiple cubic nonlinearity Meng-Jiao Wang(王梦蛟) and Lingfang Gu(辜玲芳) Chin. Phys. B, 2024, 33 (2):  020504.  DOI: 10.1088/1674-1056/acddd0 Abstract ( 148 )   HTML ( 0 )   PDF (3781KB) ( 72 )   Memristor-based chaotic systems with infinite equilibria are interesting because they generate extreme multistability. Their initial state-dependent dynamics can be explained in a reduced-dimension model by converting the incremental integration of the state variables into system parameters. However, this approach cannot solve memristive systems in the presence of nonlinear terms other than the memristor term. In addition, the converted state variables may suffer from a degree of divergence. To allow simpler mechanistic analysis and physical implementation of extreme multistability phenomena, this paper uses a multiple mixed state variable incremental integration (MMSVII) method, which successfully reconstructs a four-dimensional hyperchaotic jerk system with multiple cubic nonlinearities except for the memristor term in a three-dimensional model using a clever linear state variable mapping that eliminates the divergence of the state variables. Finally, the simulation circuit of the reduced-dimension system is constructed using Multisim simulation software and the simulation results are consistent with the MATLAB numerical simulation results. The results show that the method of MMSVII proposed in this paper is useful for analyzing extreme multistable systems with multiple higher-order nonlinear terms.

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Pedestrian lane formation with following-overtaking model and measurement of system order Bi-Lu Li(李碧璐), Zheng Li(李政), Rui Zhou(周睿), and Shi-Fei Shen(申世飞) Chin. Phys. B, 2024, 33 (2):  020505.  DOI: 10.1088/1674-1056/ad09d1 Abstract ( 127 )   HTML ( 0 )   PDF (3291KB) ( 68 )   Pedestrian self-organizing movement plays a significant role in evacuation studies and architectural design. Lane formation, a typical self-organizing phenomenon, helps pedestrian system to become more orderly, the majority of following behavior model and overtaking behavior model are imprecise and unrealistic compared with pedestrian movement in the real world. In this study, a pedestrian dynamic model considering detailed modelling of the following behavior and overtaking behavior is constructed, and a method of measuring the lane formation and pedestrian system order based on information entropy is proposed. Simulation and analysis demonstrate that the following and avoidance behaviors are important factors of lane formation. A high tendency of following results in good lane formation. Both non-selective following behavior and aggressive overtaking behavior cause the system order to decrease. The most orderly following strategy for a pedestrian is to overtake the former pedestrian whose speed is lower than approximately 70% of his own. The influence of the obstacle layout on pedestrian lane and egress efficiency is also studied with this model. The presence of a small obstacle does not obstruct the walking of pedestrians; in contrast, it may help to improve the egress efficiency by guiding the pedestrian flow and mitigating the reduction of pedestrian system orderliness.

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Compression and stretching of ring vortex in a bulk nonlinear medium Xian-Jing Lai(来娴静), Xiao-Ou Cai(蔡晓鸥), Ya-Bin Shao(邵雅斌), and Yue-Yue Wang(王悦悦) Chin. Phys. B, 2024, 33 (2):  020506.  DOI: 10.1088/1674-1056/ad01a0 Abstract ( 116 )   HTML ( 0 )   PDF (751KB) ( 34 )   We explore the nonlinear gain coupled Schrödinger system through the utilization of the variables separation method and ansatz technique. By employing these approaches, we generate hierarchies of explicit dissipative vector vortices (DVVs) that possess diverse vorticity values. Numerous fundamental characteristics of the DVVs are examined, encompassing amplitude profiles, energy fluxes, parameter effects, as well as linear and dynamic stability.

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Robust free-space optical frequency transfer in time-varying link distances conditions Zhou Tong(童周), Lei Liu(刘雷), Jia-Liang Wang(王家亮), Qian Cao(操前), Zhi-Cheng Jin(金志成), Kang Ying(应康), Shen-Sheng Han(韩申生), Zheng-Fu Han(韩正甫), and You-Zhen Gui(桂有珍) Chin. Phys. B, 2024, 33 (2):  020601.  DOI: 10.1088/1674-1056/ad0718 Abstract ( 167 )   HTML ( 0 )   PDF (2076KB) ( 135 )   Future inter-satellite clock comparison on high orbit will require optical time and frequency transmission technology between moving objects. Here, we demonstrate robust optical frequency transmission under the condition of variable link distance. This variable link is accomplished by the relative motion of a single telescope fixed on the experimental platform to a corner-cube reflector (CCR) installed on a sliding guide. Two acousto-optic modulators with different frequencies are used to separate forward signal from backward signal. With active phase noise suppression, when the CCR moves back and forth at a constant velocity of 20 cm/s and an acceleration of 20 cm/s2, we achieve the best frequency stability of 1.9×10-16 at 1 s and 7.9×10-19 at 1000 s indoors. This work paves the way for future studying optical frequency transfer between ultra-high-orbit satellites.

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Coherent optical frequency transfer via 972-km fiber link Xue Deng(邓雪), Xiang Zhang(张翔), Qi Zang(臧琦), Dong-Dong Jiao(焦东东), Dan Wang(王丹), Jie Liu(刘杰), Jing Gao(高静), Guan-Jun Xu (许冠军), Rui-Fang Dong(董瑞芳), Tao Liu(刘涛), and Shou-Gang Zhang(张首刚) Chin. Phys. B, 2024, 33 (2):  020602.  DOI: 10.1088/1674-1056/ad0629 Abstract ( 178 )   HTML ( 0 )   PDF (1150KB) ( 157 )   We demonstrate coherent optical frequency dissemination over a distance of 972 km by cascading two spans where the phase noise is passively compensated for. Instead of employing a phase discriminator and a phase locking loop in the conventional active phase control scheme, the passive phase noise cancellation is realized by feeding double-trip beat-note frequency to the driver of the acoustic optical modulator at the local site. This passive scheme exhibits fine robustness and reliability, making it suitable for long-distance and noisy fiber links. An optical regeneration station is used in the link for signal amplification and cascaded transmission. The phase noise cancellation and transfer instability of the 972-km link is investigated, and transfer instability of 1.1×10-19 at 104 s is achieved. This work provides a promising method for realizing optical frequency distribution over thousands of kilometers by using fiber links.

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Detection accuracy of target accelerations based on vortex electromagnetic wave in keyhole space Kai Guo(郭凯), Shuang Lei(雷爽), Yi Lei(雷艺), Hong-Ping Zhou(周红平), and Zhong-Yi Guo(郭忠义) Chin. Phys. B, 2024, 33 (2):  020603.  DOI: 10.1088/1674-1056/ad071a Abstract ( 133 )   HTML ( 0 )   PDF (988KB) ( 30 )   The influence of the longitudinal acceleration and the angular acceleration of detecting target based on vortex electromagnetic waves in keyhole space are analyzed. The spectrum spreads of different orbital angular momentum (OAM) modes in different non-line-of-sight situations are simulated. The errors of target accelerations in detection are calculated and compared based on the OAM spectra spreading by using two combinations of composite OAM modes in the keyhole space. According to the research, the effects about spectrum spreads of higher OAM modes are more obvious. The error in detection is mainly affected by OAM spectrum spreading, which can be reduced by reasonably using different combinations of OAM modes in different practical situations. The above results provide a reference idea for investigating keyhole effect when vortex electromagnetic wave is used to detect accelerations.

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Response optimization of a three-axis sensitive SERF magnetometer for closed-loop operation Yuanrui Zhou(周原锐), Yongze Sun(孙永泽), Xixi Wang(汪茜茜), Jianan Qin(秦佳男), Xue Zhang(张雪), and Yanzhang Wang(王言章) Chin. Phys. B, 2024, 33 (2):  020701.  DOI: 10.1088/1674-1056/ad0b00 Abstract ( 163 )   HTML ( 0 )   PDF (1991KB) ( 45 )   Most triaxial-vectorial magnetic field measurements with spin-exchange relaxation free (SERF) atomic magnetometer (AM) are based on the quasi-steady-state solution of the Bloch equation. However, the responding speed of these methods is greatly limited because the frequency of the modulation signal should be slow enough to ensure the validity of the quasi-steady-state solution. In this work, a new model to describe the response of the three-axis sensitive SERF AM with high modulation frequency is presented and verified. The response of alkali-atomic spin to high-frequency modulation field is further investigated by solving the Bloch equation in a modulation-frequency-dependence manner. This solution is well verified by our experiments and can offer a reference for selection of modulation frequencies. The result shows a potential to achieve a SERF AM operating in a geomagnetic field without heavy aluminum shielding when the modulation frequencies are selected properly.

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Fast compressed sensing spectral measurement with adaptive gradient multiscale resolution Ruo-Ming Lan(蓝若明), Xue-Feng Liu(刘雪峰), Tian-Ping Li(李天平), and Cheng-Jie Bai(白成杰) Chin. Phys. B, 2024, 33 (2):  020702.  DOI: 10.1088/1674-1056/ad09cf Abstract ( 112 )   HTML ( 0 )   PDF (633KB) ( 70 )   We propose a fast, adaptive multiscale resolution spectral measurement method based on compressed sensing. The method can apply variable measurement resolution over the entire spectral range to reduce the measurement time by over 75% compared to a global high-resolution measurement. Mimicking the characteristics of the human retina system, the resolution distribution follows the principle of gradually decreasing. The system allows the spectral peaks of interest to be captured dynamically or to be specified a priori by a user. The system was tested by measuring single and dual spectral peaks, and the results of spectral peaks are consistent with those of global high-resolution measurements.

ATOMIC AND MOLECULAR PHYSICS

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Generating attosecond pulses with controllable polarization from cyclic H32+ molecules by bichromatic circular fields Si-Qi Zhang(张思琪), Bing Zhang(张冰), Bo Yan(闫博), Xiang-Qian Jiang(姜向前), and Xiu-Dong Sun(孙秀冬) Chin. Phys. B, 2024, 33 (2):  023301.  DOI: 10.1088/1674-1056/ad062b Abstract ( 146 )   HTML ( 3 )   PDF (1069KB) ( 91 )   We investigate the polarization properties of harmonics from the cyclic H32+ molecular ions in tailored bichromatic counter-rotating circularly polarized (BCCP) fields by solving the time-dependent Schrödinger equation. The allowed harmonics and their helicities are associated with the symmetry compatibility of the field-target systems, and large intensity difference between adjacent harmonics with opposite helicities appears in a wide spectral range when the BCCP field is at certain rotation angles. We try to explain the intensity difference by using a recombination model based on the quantum-orbit theory and by analyzing the ionization pathways. Moreover, to synthesize attosecond pulse trains with tunable polarization, the intensity difference is manipulated by introducing a seed XUV field, and by changing the relative amplitude ratio as well as the helicity of BCCP fields.

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Structure, electronic, and nonlinear optical properties of superalkaline M3O (M = Li, Na) doped cyclo[18]carbon Xiao-Dong Liu(刘晓东), Qi-Liang Lu(卢其亮), and Qi-Quan Luo(罗其全) Chin. Phys. B, 2024, 33 (2):  023601.  DOI: 10.1088/1674-1056/ace036 Abstract ( 165 )   HTML ( 1 )   PDF (2800KB) ( 68 )   Cyclo[18]carbon has received considerable attention thanks to its novel geometric configuration and special electronic structure. Superalkalis have low ionization energy. Doping a superalkali in cyclo[18]carbon is an effective method to improve the optical properties of the system because considerable electron transfer occurs. In this paper, the geometry, bonding properties, electronic structure, absorption spectrum, and nonlinear optical (NLO) properties of superalkaline $M_{3}$O ($M={\rm Li}$, Na)-doped cyclo[18]carbon were studied by using density functional theory. $M_{3}$O and the C$_{18}$ rings are not coplanar. The C$_{18}$ ring still exhibits alternating long and short bonds. The charge transfer between $M_{3}$O and C$_{18}$ forms stable [$M_{3}$O]$^{+}$[C$_{18}$]$^{-}$ ionic complexes. C$_{18}$$M_{3}$O ($M={\rm Li}$, Na) shows striking optical nonlinearity, i.e., their first- and second-order hyperpolarizability ($\beta_{\rm vec}$ and $\gamma_{\vert \vert }$) increase considerably at $\lambda = 1907$ nm and 1460 nm.

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In situ calibrated angle between the quantization axis and the propagating direction of the light field for trapping neutral atoms Rui-Jun Guo(郭瑞军), Xiao-Dong He(何晓东), Cheng Sheng(盛诚), Kun-Peng Wang(王坤鹏), Peng Xu(许鹏), Min Liu(刘敏), Jin Wang(王谨), Xiao-Hong Sun(孙晓红), Yong Zeng(曾勇), and Ming-Sheng Zhan(詹明生) Chin. Phys. B, 2024, 33 (2):  023701.  DOI: 10.1088/1674-1056/acf11d Abstract ( 138 )   HTML ( 0 )   PDF (791KB) ( 34 )   The recently developed magic-intensity trapping technique of neutral atoms efficiently mitigates the detrimental effect of light shifts on atomic qubits and substantially enhances the coherence time. This technique relies on applying a bias magnetic field precisely parallel to the wave vector of a circularly polarized trapping laser field. However, due to the presence of the vector light shift experienced by the trapped atoms, it is challenging to precisely define a parallel magnetic field, especially at a low bias magnetic field strength, for the magic-intensity trapping of 85Rb qubits. In this work, we present a method to calibrate the angle between the bias magnetic field and the trapping laser field with the compensating magnetic fields in the other two directions orthogonal to the bias magnetic field direction. Experimentally, with a constant-depth trap and a fixed bias magnetic field, we measure the respective resonant frequencies of the atomic qubits in a linearly polarized trap and a circularly polarized one via the conventional microwave Rabi spectra with different compensating magnetic fields and obtain the corresponding total magnetic fields via the respective resonant frequencies using the Breit-Rabi formula. With known total magnetic fields, the angle is a function of the other two compensating magnetic fields. Finally, the projection value of the angle on either of the directions orthogonal to the bias magnetic field direction can be reduced to 0(4)° by applying specific compensating magnetic fields. The measurement error is mainly attributed to the fluctuation of atomic temperature. Moreover, it also demonstrates that, even for a small angle, the effect is strong enough to cause large decoherence of Rabi oscillation in a magic-intensity trap. Although the compensation method demonstrated here is explored for the magic-intensity trapping technique, it can be applied to a variety of similar precision measurements with trapped neutral atoms.

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Efficient loading of cesium atoms in a magnetic levitated dimple trap Guoqing Zhang(张国庆), Guosheng Feng(冯国胜), Yuqing Li(李玉清), Jizhou Wu(武寄洲), and Jie Ma(马杰) Chin. Phys. B, 2024, 33 (2):  023702.  DOI: 10.1088/1674-1056/ad0b03 Abstract ( 141 )   HTML ( 0 )   PDF (944KB) ( 36 )   We report a detailed study of magnetically levitated loading of ultracold 133Cs atoms in a dimple trap. The atomic sample was produced in a combined red-detuned optical dipole trap and dimple trap formed by two small waist beams crossing a horizontal plane. The magnetic levitation for the 133Cs atoms forms an effective potential for a large number of atoms in a high spatial density. Dependence of the number of atoms loaded and trapped in the dimple trap on the magnetic field gradient and bias field is in good agreement with the theoretical analysis. This method has been widely used to obtain the Bose-Einstein condensation atoms for many atomic species.

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

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A flexible ultra-broadband multi-layered absorber working at 2 GHz-40 GHz printed by resistive ink Tao Wang(汪涛), Yu-Lun Yan(闫玉伦), Gong-Hua Chen(陈巩华), Ying Li(李迎), Jun Hu(胡俊), and Jian-Bo Mao(毛剑波) Chin. Phys. B, 2024, 33 (2):  024101.  DOI: 10.1088/1674-1056/acea64 Abstract ( 153 )   HTML ( 4 )   PDF (1799KB) ( 90 )   A flexible extra broadband metamaterial absorber (MMA) stacked with five layers working at 2 GHz-40 GHz is investigated. Each layer is composed of polyvinyl chloride (PVC), polyimide (PI), and a frequency selective surface (FSS), which is printed on PI using conductive ink. To investigate this absorber, both one-dimensional analogous circuit analysis and three-dimensional full-wave simulation based on a physical model are provided. Various crucial electromagnetic properties, such as absorption, effective impedance, complex permittivity and permeability, electric current distribution and magnetic field distribution at resonant peak points, are studied in detail. Analysis shows that the working frequency of this absorber covers entire S, C, X, Ku, K and Ka bands with a minimum thickness of 0.098 λmax (λmax is the maximum wavelength in the absorption band), and the fractional bandwidth (FBW) reaches 181.1%. Moreover, the reflection coefficient is less than -10 dB at 1.998 GHz-40.056 GHz at normal incidence, and the absorptivity of the plane wave is greater than 80% when the incident angle is smaller than 50°. Furthermore, the proposed absorber is experimentally validated, and the experimental results show good agreement with the simulation results, which demonstrates the potential applicability of this absorber at 2 GHz-40 GHz.

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Wideband low-scattering metasurface with an in-band reconfigurable transparent window Ying Zhu(朱瑛), Weixu Yang(杨维旭), Kun Duan(段坤), Tian Jiang(姜田), Junming Zhao(赵俊明), Ke Chen(陈克), and Yijun Feng(冯一军) Chin. Phys. B, 2024, 33 (2):  024102.  DOI: 10.1088/1674-1056/ad0119 Abstract ( 136 )   HTML ( 1 )   PDF (4885KB) ( 215 )   Active metasurfaces with dynamically reconfigurable functionalities are highly demanded in various practical applications. Here, we propose a wideband low-scattering metasurface that can realize an in-band reconfigurable transparent window by altering the operation states of the PIN diodes loaded on the structures. The metasurface is composed of a band-pass frequency selective surface (FSS) sandwiched between two polarization conversion metasurfaces (PCMs). PIN diodes are integrated into the FSS to switch the transparent window, while a checkerboard configuration is applied in PCMs for the diffusive-reflective function. A sample with 20×20 elements is designed, fabricated, and experimentally verified. Both simulated and measured results show that the in-band functions can be dynamically switched between beam-splitting scattering and high transmission by controlling the biasing states of the diodes, while low backscattering can be attained outside the passband. Furthermore, the resonant structures of FSS also play the role of feeding lines, thus significantly eliminating extra interference compared with conventional feeding networks. We envision that the proposed metasurface may provide new possibilities for the development of an intelligent stealth platform and its antenna applications.

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Design and fabrication of compound varifocal lens driven by polydimethylsiloxane film elastic deformation Wen-Hao Miao(缪文浩), Ze-Feng Han(韩泽峰), Rui Zhao(赵瑞), Zhong-Cheng Liang(梁忠诚), Song-Feng Kou(寇松峰), and Rong-Qing Xu(徐荣青) Chin. Phys. B, 2024, 33 (2):  024103.  DOI: 10.1088/1674-1056/ad09ce Abstract ( 125 )   HTML ( 0 )   PDF (2163KB) ( 49 )   A compound varifocal lens based on electromagnetic drive technology is designed and fabricated, where the polydimethylsiloxane (PDMS) film acts as a driving component, while the PDMS biconvex lens and the plane-concave lens form a coaxial compound lens system. The plane-concave lens equipped with driving coils is installed directly above the PDMS lens surrounded by the annular magnet. When different currents are applied, the annular magnet moves up and down, driving the PDMS film to undergo elastic deformation, and then resulting in longitudinal movement of the PDMS lens. The position change of the PDMS lens changes the focal length of the compound lens system. To verify the feasibility and practicability of this design, a prototype of our compound lens system is fabricated in experiment. Our proposed compound lens shows that its zoom ability reaches 9.28 mm when the current ranges from -0.20 A to 0.21 A.

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Design of tightly linked dual ring antenna and imaging of magnetic field distribution using a diamond fiber probe Qing-Yun Ye(叶青云), Ya-Wen Xue(薛雅文), Fei-Yue He(何飞越), Xu-Tong Zhao(赵旭彤), Yu-Chen Bian(卞雨辰), Wen-Tao Lu(卢文韬), Jin-Xu Wang(王金旭), Hong-Hao Chen(陈鸿浩), Sheng-Kai Xia(夏圣开), Ming-Jing Zeng(曾明菁), and Guan-Xiang Du(杜关祥) Chin. Phys. B, 2024, 33 (2):  024202.  DOI: 10.1088/1674-1056/ad0772 Abstract ( 225 )   HTML ( 0 )   PDF (2285KB) ( 171 )   A tightly linked dual ring antenna is designed, and it is specifically tailored for uniformly coupling the microwave magnetic field to the nitrogen-vacancy (NV) center. The designed antenna operates at a center frequency of about 2.87 GHz, with a bandwidth of around 200 MHz, allowing it to address multiple resonance peaks in the optically detected magnetic resonance (ODMR) spectrum in an external magnetic field. Moreover, the antenna generates a fairly uniform magnetic field in a range with a radius of 0.75 mm. High resolution imaging of the magnetic field distribution on the surface of the antenna is conducted by using a fiber diamond probe. We also investigate the effect of magnetic field uniformity on the linewidth of ODMR, so as to provide insights into reducing the inhomogeneous broadening of ODMR.

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Optimal and robust control of population transfer in asymmetric quantum-dot molecules Yu Guo(郭裕), Songshan Ma(马松山), and Chuan-Cun Shu(束传存) Chin. Phys. B, 2024, 33 (2):  024203.  DOI: 10.1088/1674-1056/ad0627 Abstract ( 160 )   HTML ( 0 )   PDF (2413KB) ( 100 )   We present an optimal and robust quantum control method for efficient population transfer in asymmetric double quantum-dot molecules. We derive a long-duration control scheme that allows for highly efficient population transfer by accurately controlling the amplitude of a narrow-bandwidth pulse. To overcome fluctuations in control field parameters, we employ a frequency-domain quantum optimal control theory method to optimize the spectral phase of a single pulse with broad bandwidth while preserving the spectral amplitude. It is shown that this spectral-phase-only optimization approach can successfully identify robust and optimal control fields, leading to efficient population transfer to the target state while concurrently suppressing population transfer to undesired states. The method demonstrates resilience to fluctuations in control field parameters, making it a promising approach for reliable and efficient population transfer in practical applications.

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Spatial quantum coherent modulation with perfect hybrid vector vortex beam based on atomic medium Yan Ma(马燕), Xin Yang(杨欣), Hong Chang(常虹), Xin-Qi Yang(杨鑫琪), Ming-Tao Cao(曹明涛), Xiao-Fei Zhang(张晓斐), Hong Gao(高宏), Rui-Fang Dong(董瑞芳), and Shou-Gang Zhang(张首刚) Chin. Phys. B, 2024, 33 (2):  024204.  DOI: 10.1088/1674-1056/ad0f86 Abstract ( 199 )   HTML ( 0 )   PDF (1664KB) ( 151 )   The perfect hybrid vector vortex beam (PHVVB) with helical phase wavefront structure has aroused significant concern in recent years, as its beam waist does not expand with the topological charge (TC). In this work, we investigate the spatial quantum coherent modulation effect with PHVVB based on the atomic medium, and we observe the absorption characteristic of the PHVVB with different TCs under variant magnetic fields. We find that the transmission spectrum linewidth of PHVVB can be effectively maintained regardless of the TC. Still, the width of transmission peaks increases slightly as the beam size expands in hot atomic vapor. This distinctive quantum coherence phenomenon, demonstrated by the interaction of an atomic medium with a hybrid vector-structured beam, might be anticipated to open up new opportunities for quantum coherence modulation and accurate magnetic field measurement.

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Dependence of Rydberg-atom-based sensor performance on different Rydberg atom populations in one atomic-vapor cell Bo Wu(武博), Jiawei Yao(姚佳伟), Fengchuan Wu(吴逢川), Qiang An(安强), and Yunqi Fu(付云起) Chin. Phys. B, 2024, 33 (2):  024205.  DOI: 10.1088/1674-1056/ad0b04 Abstract ( 138 )   HTML ( 0 )   PDF (867KB) ( 133 )   The atomic-vapor cell is a vital component for Rydberg atomic microwave sensors, and impacts on overall capability of Rydberg sensors. However, the conventional analysis approach on effect of vapor-cell length contains two implicit assumptions, that is, the same atomic population density and buffer gas pressure, which make it unable to accurately capture actual response about effect of Rydberg-atom-based sensor performance on different Rydberg atom populations. Here, utilizing a stepped cesium atomic-vapor cell with five different dimensions at the same atomic population density and buffer gas pressure, the height and full width at half maximum of electromagnetically induced transparency (EIT) signal, and the sensitivity of the atomic superheterodyne sensor are comprehensively investigated under conditions of the same Rabi frequencies (saturated laser power). It is identified that EIT signal height is proportional to the cell length, full width at half maximum and sensitivity grow with the increment of cell length to a certain extent. Employing the coherent integration signal theory and atomic linear expansion coefficient method, theoretical analysis of the EIT height and sensitivity are further investigated. The results could shed new light on understanding and design of ultrahigh-sensitivity Rydberg atomic microwave sensors and find promising applications in quantum measurement, communication, and imaging.

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Broadband bidirectional Brillouin-Raman random fiber laser with ultra-narrow linewidth Qian Yang(杨茜), Yang Li(李阳), Hui Zou(邹辉), Jie Mei(梅杰), En-Ming Xu(徐恩明), and Zu-Xing Zhang(张祖兴) Chin. Phys. B, 2024, 33 (2):  024206.  DOI: 10.1088/1674-1056/ad09cb Abstract ( 157 )   HTML ( 0 )   PDF (2756KB) ( 74 )   We present a Brillouin-Raman random fiber laser (BRRFL) with full-open linear cavity structure to generate broadband Brillouin frequency comb (BFC) with double Brillouin-frequency-shift spacing. The incorporation of a regeneration portion consisting of an erbium-doped fiber and a single-mode fiber enables the generation of broadband BFC. The dynamics of broadband BFC generation changing with the pump power (EDF and Raman) and Brillouin pump (BP) wavelength are investigated in detail, respectively. Under suitable conditions, the bidirectional BRRFL proposed can produce a flat-amplitude BFC with 40.7-nm bandwidth ranging from 1531 nm to 1571.7 nm, and built-in 242-order Brillouin Stokes lines (BSLs) with double Brillouin-frequency-shift spacing. Moreover, the linewidth of single BSL is experimentally measured to be about 2.5 kHz. The broadband bidirectional narrow-linewidth BRRFL has great potential applications in optical communication, optical sensing, spectral measurement, and so on.

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Effect of sample temperature on femtosecond laser ablation of copper Wei-Jie Dang(党伟杰), Yu-Tong Chen(陈雨桐), An-Min Chen(陈安民), and Ming-Xing Jin(金明星) Chin. Phys. B, 2024, 33 (2):  024207.  DOI: 10.1088/1674-1056/ad028f Abstract ( 139 )   HTML ( 0 )   PDF (1424KB) ( 23 )   We conduct an experimental study supported by theoretical analysis of single laser ablating copper to investigate the interactions between laser and material at different sample temperatures, and predict the changes of ablation morphology and lattice temperature. For investigating the effect of sample temperature on femtosecond laser processing, we conduct experiments on and simulate the thermal behavior of femtosecond laser irradiating copper by using a two-temperature model. The simulation results show that both electron peak temperature and the relaxation time needed to reach equilibrium increase as initial sample temperature rises. When the sample temperature rises from 300 K to 600 K, the maximum lattice temperature of the copper surface increases by about 6500 K under femtosecond laser irradiation, and the ablation depth increases by 20%. The simulated ablation depths follow the same general trend as the experimental values. This work provides some theoretical basis and technical support for developing femtosecond laser processing in the field of metal materials.

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Properties of focused Laguerre-Gaussian beam propagating in anisotropic ocean turbulence Xinguang Wang(王新光), Yangbin Ma(马洋斌), Qiujie Yuan(袁邱杰), Wei Chen(陈伟), Le Wang(王乐), and Shengmei Zhao(赵生妹) Chin. Phys. B, 2024, 33 (2):  024208.  DOI: 10.1088/1674-1056/ad053c Abstract ( 174 )   HTML ( 2 )   PDF (3355KB) ( 84 )   We analyze the properties of a focused Laguerre-Gaussian (LG) beam propagating through anisotropic ocean turbulence based on the Huygens-Fresnel principle. Under the Rytov approximation theory, we derive the analytical formula of the channel capacity of the focused LG beam in the anisotropic ocean turbulence, and analyze the relationship between the capacity and the light source parameters as well as the turbulent ocean parameters. It is found that the focusing mirror can greatly enhance the channel capacity of the system at the geometric focal plane in oceanic turbulence. The results also demonstrate that the communication link can obtain high channel capacity by adopting longer beam wavelength, greater initial beam waist radius, and larger number of transmission channels. Further, the capacity of the system increases with the decrease of the mean squared temperature dissipation rate, temperature-salinity contribution ratio and turbulence outer scale factor, and with the increase of the kinetic energy dissipation rate per unit mass of fluid, turbulence inner scale factor and anisotropy factor. Compared to a Hankel-Bessel beam with diffraction-free characteristics and unfocused LG beam, the focused LG beam shows superior anti-turbulence interference properties, which provide a theoretical reference for research and development of underwater optical communication links using focused LG beams.

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Behaviors of cavitation bubbles driven by high-intensity ultrasound Chen-Yang Huang(黄晨阳), Fan Li(李凡), Shi-Yi Feng(冯释毅), Cheng-Hui Wang(王成会), Shi Chen(陈时), Jing Hu(胡静), Xin-Rui He(何芯蕊), and Jia-Kai Song(宋家凯) Chin. Phys. B, 2024, 33 (2):  024301.  DOI: 10.1088/1674-1056/ad0717 Abstract ( 146 )   HTML ( 3 )   PDF (2709KB) ( 86 )   In a multi-bubble system, the bubble behavior is modulated by the primary acoustic field and the secondary acoustic field. To explore the translational motion of bubbles in cavitation liquids containing high-concentration cavitation nuclei, evolutions of bubbles are recorded by a high-speed camera, and translational trajectories of several representative bubbles are traced. It is found that translational motion of bubbles is always accompanied by the fragmentation and coalescence of bubbles, and for bubbles smaller than 10 μ, the possibility of bubble coalescence is enhanced when the spacing of bubbles is less than 30 μ. The measured signals and their spectra show the presence of strong negative pressure, broadband noise, and various harmonics, which implies that multiple interactions of bubbles appear in the region of high-intensity cavitation. Due to the strong coupling effect, the interaction between bubbles is random. A simplified triple-bubble model is developed to explore the interaction patterns of bubbles affected by the surrounding bubbles. Patterns of bubble interaction, such as attraction, repulsion, stable spacing, and rebound of bubbles, can be predicted by the theoretical analysis, and the obtained results are in good agreement with experimental observations. Mass exchange between the liquid and bubbles as well as absorption in the cavitation nuclei also plays an important role in multi-bubble cavitation, which may account for the weakening of the radial oscillations of bubbles.

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Numerical simulation for the initial state of avalanche in polydisperse particle systems Ren Han(韩韧), Ting Li(李亭), Zhipeng Chi(迟志鹏), Hui Yang(杨晖), and Ran Li(李然) Chin. Phys. B, 2024, 33 (2):  024501.  DOI: 10.1088/1674-1056/ad117b Abstract ( 134 )   HTML ( 1 )   PDF (1204KB) ( 68 )   Numerical simulation is employed to investigate the initial state of avalanche in polydisperse particle systems. Nucleation and propagation processes are illustrated for pentadisperse and triadisperse particle systems, respectively. In these processes, particles involved in the avalanche grow slowly in the early stage and explosively in the later stage, which is clearly different from the continuous and steady growth trend in the monodisperse system. By examining the avalanche propagation, the number growth of particles involved in the avalanche and the slope of the number growth, the initial state can be divided into three stages: T1 (nucleation stage), T2 (propagation stage), T3 (overall avalanche stage). We focus on the characteristics of the avalanche in the T2 stage, and find that propagation distances increase almost linearly in both axial and radial directions in polydisperse systems. We also consider the distribution characteristics of the average coordination number and average velocity for the moving particles. The results support that the polydisperse particle systems are more stable in the T2 stage.

PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES

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Long radial coherence of electron temperature fluctuations in non-local transport in HL-2A plasmas Zhongbing Shi(石中兵), Kairui Fang(方凯锐), Jingchun Li(李景春), Xiaolan Zou(邹晓岚), Zhaoyang Lu(卢兆旸), Jie Wen(闻杰), Zhanhui Wang(王占辉), Xuantong Ding(丁玄同), Wei Chen(陈伟), Zengchen Yang(杨曾辰), Min Jiang(蒋敏), Xiaoquan Ji(季小全), Ruihai Tong(佟瑞海), Yonggao Li(李永高), Peiwan Shi(施陪万), Wulyv Zhong(钟武律), and Min Xu(许敏) Chin. Phys. B, 2024, 33 (2):  025202.  DOI: 10.1088/1674-1056/ad1093 Abstract ( 149 )   HTML ( 2 )   PDF (4139KB) ( 101 )   The dynamics of long-wavelength ($k_\theta<1.4$ cm$^{-1}$), broadband (20 kHz-200 kHz) electron temperature fluctuations ($\tilde T_{\rm e}/T_{\rm e}$) of plasmas in gas-puff experiments are observed for the first time in HL-2A tokamak. In a relatively low density ($n_{\rm e}(0) \simeq 0.91 \times10^{19}$$\rm m^{-3}$-$1.20 \times10^{19}$$\rm m^{-3}$) scenario, after gas-puffing the core temperature increases and the edge temperature drops. On the contrary, temperature fluctuation drops at the core and increases at the edge. Analyses show the non-local emergence is accompanied with a long radial coherent length of turbulent fluctuations. While in a higher density ($n_{\rm e}(0) \simeq 1.83 \times10^{19}$ m$^{-3}$-$2.02 \times10^{19}$ m$^{-3}$) scenario, the phenomena are not observed. Furthermore, compelling evidence indicates that $\bm{E} \times \bm{B}$ shear serves as a substantial contributor to this extensive radial interaction. This finding offers a direct explanatory link to the intriguing core-heating phenomenon witnessed within the realm of non-local transport.

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Differences between two methods to derive a nonlinear Schrödinger equation and their application scopes Yu-Xi Chen(陈羽西), Heng Zhang(张恒), and Wen-Shan Duan(段文山) Chin. Phys. B, 2024, 33 (2):  025203.  DOI: 10.1088/1674-1056/ad082b Abstract ( 124 )   HTML ( 0 )   PDF (2994KB) ( 34 )   The present paper chooses a dusty plasma as an example to numerically and analytically study the differences between two different methods of obtaining nonlinear Schrödinger equation (NLSE). The first method is to derive a Korteweg-de Vries (KdV)-type equation and then derive the NLSE from the KdV-type equation, while the second one is to directly derive the NLSE from the original equation. It is found that the envelope waves from the two methods have different dispersion relations, different group velocities. The results indicate that two envelope wave solutions from two different methods are completely different. The results also show that the application scope of the envelope wave obtained from the second method is wider than that of the first one, though both methods are valuable in the range of their corresponding application scopes. It is suggested that, for other systems, both methods to derive NLSE may be correct, but their nonlinear wave solutions are different and their application scopes are also different.

CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

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Theoretical characterization of the adsorption configuration of pyrrole on Si(100) surface by x-ray spectroscopy Hao-Qing Li(李好情), Jing Ming(明静), Zhi-Ang Jiang(姜志昂), Hai-Bo Li(李海波), Yong Ma(马勇), and Xiu-Neng Song(宋秀能) Chin. Phys. B, 2024, 33 (2):  026102.  DOI: 10.1088/1674-1056/aceaeb Abstract ( 116 )   HTML ( 1 )   PDF (1060KB) ( 34 )   The possible configurations of pyrrole absorbed on a Si(100) surface have been investigated by x-ray photoelectron spectroscopy (XPS) and near-edge x-ray absorption fine structure (NEXAFS) spectra. The C-1s XPS and NEXAFS spectra of these adsorption configurations have been calculated by using the density functional theory (DFT) method and full-core hole (FCH) approximation to investigate the relationship between the adsorption configurations and the spectra. The result shows that the XPS and NEXAFS spectra are structurally dependent on the configurations of pyrrole absorbed on the Si(100) surface. Compared with the XPS, the NEXAFS spectra are relatively sensitive to the adsorption configurations and can accurately identify them. The NEXAFS decomposition spectra produced by non-equivalent carbon atoms have also been calculated and show that the spectral features vary with the diverse types of carbon atoms and their structural environments.

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Floquet spectrum and universal dynamics of a periodically driven two-atom system Wenzhu Xie(谢文柱), Zhengqiang Zhou(周正强), Xuan Li(李轩), Simiao Cui(崔思淼), and Mingyuan Sun(孙明远) Chin. Phys. B, 2024, 33 (2):  026702.  DOI: 10.1088/1674-1056/ad0623 Abstract ( 149 )   HTML ( 3 )   PDF (28512KB) ( 105 )   We investigate the Floquet spectrum and excitation properties of a two-ultracold-atom system with periodically driven interaction in a three-dimensional harmonic trap. The interaction between the atoms is changed by varying the s-wave scattering length in two ways, the cosine and the square-wave modulations. It is found that as the driving frequency increases, the Floquet spectrum exhibits two main features for both modulations, the accumulating and the spreading of the quasienergy levels, which further lead to different dynamical behaviors. The accumulation is associated with collective excitations and the persistent growth of the energy, while the spread indicates that the energy is bounded at all times. The initial scattering length, the driving frequency and amplitude can all significantly change the Floquet spectrum as well as the dynamics. However, the corresponding relation between them is valid universally. Finally, we propose a mechanism for selectively exciting the system to one specific state by using the avoided crossing of two quasienergy levels, which could guide preparation of a desired state in experiments.

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Effect of surface modification on the radiation stability of diamond ohmic contacts Lian-Xi Mu(牟恋希), Shang-Man Zhao(赵上熳), Peng Wang(王鹏), Xiao-Lu Yuan(原晓芦), Jin-Long Liu(刘金龙), Zhi-Fu Zhu(朱志甫), Liang-Xian Chen(陈良贤), Jun-Jun Wei(魏俊俊), Xiao-Ping Ou-Yang(欧阳晓平), and Cheng-Ming Li(李成明) Chin. Phys. B, 2024, 33 (2):  026801.  DOI: 10.1088/1674-1056/ace61e Abstract ( 142 )   HTML ( 0 )   PDF (967KB) ( 88 )   The ohmic contact interface between diamond and metal is essential for the application of diamond detectors. Surface modification can significantly affect the contact performance and eliminate the interface polarization effect. However, the radiation stability of a diamond detector is also sensitive to surface modification. In this work, the influence of surface modification technology on a diamond ohmic contact under high-energy radiation was investigated. Before radiation, the specific contact resistivities ($\rho_{\rm c}$) between Ti/Pt/Au-hydrogen-terminated diamond (H-diamond) and Ti/Pt/Au-oxygen-terminated diamond (O-diamond) were $2.0 \times 10^{-4}$ $\Omega \cdot $cm$^{2}$ and $4.3 \times 10^{-3}$ $\Omega \cdot $cm$^{2}$, respectively. After 10 MeV electron radiation, the $\rho_{\rm c}$ of Ti/Pt/Au H-diamond and Ti/Pt/Au O-diamond were $5.3 \times 10^{-3}$ $\Omega \cdot $cm$^{2}$ and $9.1 \times 10^{-3}$ $ \Omega \cdot $cm$^{2}$, respectively. The rates of change of $\rho_{\rm c}$ of H-diamond and O-diamond after radiation were 2550% and 112%, respectively. The electron radiation promotes bond reconstruction of the diamond surface, resulting in an increase in $\rho_{\rm c}$.

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Growth and characterization of Bi(110)/CrTe2 heterostructures: Exploring interplay between magnetism and topology Zhenyu Yuan(袁震宇), Fazhi Yang(杨发枝), Baiqing Lv(吕佰晴), Yaobo Huang(黄耀波), Tian Qian(钱天), Jinpeng Xu(徐金朋), and Hong Ding(丁洪) Chin. Phys. B, 2024, 33 (2):  026802.  DOI: 10.1088/1674-1056/ad082a Abstract ( 140 )   HTML ( 4 )   PDF (3637KB) ( 169 )   The interplay between topology and magnetism is vital for realizing exotic quantum phenomena, significant examples including quantum anomalous Hall effect, axion insulators, and high-order topological states. These states host great potential for future applications in high-speed and low-consumption electronic devices. Despite being extensively investigated, practical platforms are still scarce. In this work, with molecular beam epitaxy (MBE), we provide the first experimental report on high-quality Bi(110)/CrTe$_{2}$ magnetic heterostructure. By employing in-situ high-resolution scanning tunneling microscopy, we are able to examine the interaction between magnetism and topology. There is a potential edge state at an energy level above the Fermi level, but no edge states observed near the Fermi level The absence of high-order topological corner states near $E_{\rm F}$ highlights the importance of lattice matching and interface engineering in designing high-order topological states. Our study provides key insights into the interplay between two-dimensional magnetic and topological materials and offers an important dimension for engineering magnetic topological states.

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

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Band structures of strained kagome lattices Luting Xu(徐露婷) and Fan Yang(杨帆) Chin. Phys. B, 2024, 33 (2):  027101.  DOI: 10.1088/1674-1056/ad0291 Abstract ( 205 )   HTML ( 6 )   PDF (1764KB) ( 174 )   Materials with kagome lattices have attracted significant research attention due to their nontrivial features in energy bands. We theoretically investigate the evolution of electronic band structures of kagome lattices in response to uniaxial strain using both a tight-binding model and an antidot model based on a periodic muffin-tin potential. It is found that the Dirac points move with applied strain. Furthermore, the flat band of unstrained kagome lattices is found to develop into a highly anisotropic shape under a stretching strain along y direction, forming a partially flat band with a region dispersionless along ky direction while dispersive along kx direction. Our results shed light on the possibility of engineering the electronic band structures of kagome materials by mechanical strain.

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Angle-resolved photoemission study of NbGeSb with non-symmorphic symmetry Huan Ma(马欢), Ning Tan(谭宁), Xuchuan Wu(吴徐传), Man Li(李满), Yiyan Wang(王义炎), Hongyan Lu(路洪艳), Tianlong Xia(夏天龙), and Shancai Wang(王善才) Chin. Phys. B, 2024, 33 (2):  027102.  DOI: 10.1088/1674-1056/ad0ccf Abstract ( 173 )   HTML ( 0 )   PDF (8717KB) ( 150 )   We investigate the electronic structure of NbGeSb with non-symmorphic symmetry. We employ angle-resolved photoemission spectroscopy (ARPES) to observe and identify the bulk and surface states over the Brillouin zone. By utilizing high-energy photons, we identify the bulk Fermi surface and bulk nodal line along the direction $X$-$R$, while the Fermi surface of the surface state is observed by using low-energy photons. We observe the splitting of surface bands away from the high-symmetry point $\overline{{X}}$. The density functional theory calculations on bulk and 1 to 5-layer slab models, as well as spin textures of NbGeSb, verify that the band splitting could be attributed to the Rashba-like spin-orbit coupling caused by space-inversion-symmetry breaking at the surface. These splitted surface bands cross with each other, forming two-dimensional Weyl-like crossings that are protected by mirror symmetry. Our findings provide insights into the two-dimensional topological and symmetry-protected band inversion of surface states.

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Spin transport characteristics modulated by the GeBi interlayer in Y3Fe5O12/GeBi/Pt heterostructures Mingming Li(李明明), Lei Zhang(张磊), Lichuan Jin(金立川), and Haizhong Guo(郭海中) Chin. Phys. B, 2024, 33 (2):  027201.  DOI: 10.1088/1674-1056/ace3aa Abstract ( 139 )   HTML ( 0 )   PDF (1360KB) ( 91 )   For the past few years, germanium-based semiconductor spintronics has attracted considerable interest due to its potential for integration into mainstream semiconductor technology. The main challenges in the development of modern semiconductor spintronics are the generation, detection, and manipulation of spin currents. Here, the transport characteristics of a spin current generated by spin pumping through a GeBi semiconductor barrier in Y3Fe5O12/GeBi/Pt heterostructures were investigated systematically. The effective spin-mixing conductance and inverse spin Hall voltage to quantitatively describe the spin transport characteristics were extracted. The spin-injection efficiency in the Y3Fe5O12/GeBi/Pt heterostructures is comparable to that of the Y3Fe5O12/Pt bilayer, and the inverse spin Hall voltage exponential decays with the increase in the barrier thickness. Furthermore, the band gap of the GeBi layer was tuned by changing the Bi content. The spin-injection efficiency at the YIG/semiconductor interface and the spin transportation within the semiconductor barrier are related to the band gap of the GeBi layer. Our results may be used as guidelines for the fabrication of efficient spin transmission structures and may lead to further studies on the impacts of different kinds of barrier materials.

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Light-modulated graphene-based φ0 Josephson junction and -φ0 to φ0 transition Renxiang Cheng(程任翔), Miao Yu(于苗), Hong Wang(汪洪), Deliang Cao(曹德亮), Xingao Li(李兴鳌), Fenghua Qi(戚凤华), and Xingfei Zhou(周兴飞) Chin. Phys. B, 2024, 33 (2):  027302.  DOI: 10.1088/1674-1056/ad04c5 Abstract ( 111 )   HTML ( 0 )   PDF (1148KB) ( 115 )   We investigate the chiral edge states-induced Josephson current-phase relation in a graphene-based Josephson junction modulated by the off-resonant circularly polarized light and the staggered sublattice potential. By solving the Bogoliubov-de Gennes equation, a $\varphi_{0}$ Josephson junction is induced in the coaction of the off-resonant circularly polarized light and the staggered sublattice potential, which arises from the fact that the center of-mass wave vector of Cooper pair becomes finite and the opposite center of-mass wave vector to compensate is lacking in the nonsuperconducting region. Interestingly, when the direction of polarization of light is changed, $-\varphi_{0}$ to $\varphi_{0}$ transition generates, which generalizes the concept of traditional $0$-$\pi$ transition. Our findings provide a purely optical way to manipulate a phase-controllable Josephson device and guidelines for future experiments to confirm the presence of graphene-based $\varphi_{0}$ Josephson junction.

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Disorder effects in NbTiN superconducting resonators Wei-Tao Lyu(吕伟涛), Qiang Zhi(支强), Jie Hu(胡洁), Jing Li(李婧), and Sheng-Cai Shi(史生才) Chin. Phys. B, 2024, 33 (2):  027401.  DOI: 10.1088/1674-1056/ad03dc Abstract ( 136 )   HTML ( 0 )   PDF (1298KB) ( 50 )   Disordered superconducting materials like NbTiN possess a high kinetic inductance fraction and an adjustable critical temperature, making them a good choice for low-temperature detectors. Their energy gap ($\varDelta$), critical temperature ($T_{\rm c}$), and quasiparticle density of states (QDOS) distribution, however, deviate from the classical BCS theory due to the disorder effects. The Usadel equation, which takes account of elastic scattering, non-elastic scattering, and electro-phonon coupling, can be applied to explain and describe these deviations. This paper presents numerical simulations of the disorder effects based on the Usadel equation to investigate their effects on the $\varDelta $, $T_{\rm c}$, QDOS distribution, and complex conductivity of the NbTiN film. Furthermore, NbTiN superconducting resonators with coplanar waveguide (CPW) structures are fabricated and characterized at different temperatures to validate our numerical simulations. The pair-breaking parameter $\alpha $ and the critical temperature in the pure state $T_{\rm c}^{\rm P}$ of our NbTiN film are determined from the experimental results and numerical simulations. This study has significant implications for the development of low-temperature detectors made of disordered superconducting materials.

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Oscillation of Dzyaloshinskii-Moriya interaction driven by weak electric fields Runze Chen(陈润泽), Anni Cao(曹安妮), Xinran Wang(王馨苒), Yang Liu(柳洋), Hongxin Yang(杨洪新), and Weisheng Zhao(赵巍胜) Chin. Phys. B, 2024, 33 (2):  027501.  DOI: 10.1088/1674-1056/ad0f85 Abstract ( 146 )   HTML ( 2 )   PDF (2423KB) ( 101 )   Dzyaloshinskii-Moriya interaction (DMI) is under extensive investigation considering its crucial status in chiral magnetic orders, such as Néel-type domain wall (DW) and skyrmions. It has been reported that the interfacial DMI originating from Rashba spin-orbit coupling (SOC) can be linearly tuned with strong external electric fields. In this work, we experimentally demonstrate that the strength of DMI exhibits rapid fluctuations, ranging from 10% to 30% of its original value, as a function of applied electric fields in Pt/Co/MgO heterostructures within the small field regime (<10-2 V/nm). Brillouin light scattering (BLS) experiments have been performed to measure DMI, and first-principles calculations show agreement with this observation, which can be explained by the variation in orbital hybridization at the Co/MgO interface in response to the weak electric fields. Our results on voltage control of DMI (VCDMI) suggest that research related to the voltage control of magnetic anisotropy for spin-orbit torque or the motion control of skyrmions might also have to consider the role of the external electric field on DMI as small voltages are generally used for the magnetoresistance detection.

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Magnetic proximity effect in the two-dimensional ε-Fe2O3/NbSe2 heterojunction Bingyu Che(车冰玉), Guojing Hu(胡国静), Chao Zhu(朱超), Hui Guo(郭辉), Senhao Lv(吕森浩), Xuanye Liu(刘轩冶), Kang Wu(吴康), Zhen Zhao(赵振), Lulu Pan(潘禄禄), Ke Zhu(祝轲), Qi Qi(齐琦), Yechao Han(韩烨超), Xiao Lin(林晓), Zi'an Li(李子安), Chengmin Shen(申承民), Lihong Bao(鲍丽宏), Zheng Liu(刘政), Jiadong Zhou(周家东), Haitao Yang(杨海涛), and Hong-Jun Gao(高鸿钧) Chin. Phys. B, 2024, 33 (2):  027502.  DOI: 10.1088/1674-1056/ad09d2 Abstract ( 155 )   HTML ( 1 )   PDF (2719KB) ( 117 )   Two-dimensional (2D) magnet/superconductor heterostructures can promote the design of artificial materials for exploring 2D physics and device applications by exotic proximity effects. However, plagued by the low Curie temperature and instability in air, it is hard to realize practical applications for the reported layered magnetic materials at present. In this paper, we developed a space-confined chemical vapor deposition method to synthesize ultrathin air-stable ε-Fe2O3 nanosheets with Curie temperature above 350 K. The ε-Fe2O3/NbSe2 heterojunction was constructed to study the magnetic proximity effect on the superconductivity of the NbSe2 multilayer. The electrical transport results show that the subtle proximity effect can modulate the interfacial spin-orbit interaction while undegrading the superconducting critical parameters. Our work paves the way to construct 2D heterojunctions with ultrathin nonlayered materials and layered van der Waals (vdW) materials for exploring new physical phenomena.

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Electronic property and topological phase transition in a graphene/CoBr2 heterostructure Yuan-Xiu Qin(秦元秀), Sheng-Shi Li(李胜世), Wei-Xiao Ji(纪维霄), and Chang-Wen Zhang(张昌文) Chin. Phys. B, 2024, 33 (2):  027901.  DOI: 10.1088/1674-1056/ad0f8a Abstract ( 149 )   HTML ( 0 )   PDF (2169KB) ( 78 )   Recently, significant experimental advancements in achieving topological phases have been reported in van der Waals (vdW) heterostructures involving graphene. Here, using first-principles calculations, we investigate graphene/CoBr$_{2}$ (Gr/CoBr$_{2}$) heterostructures and find that an enhancement of in-plane magnetic anisotropy (IMA) energy in monolayer CoBr$_{2}$ can be accomplished by reducing the interlayer distance of the vdW heterostructures. In addition, we clarify that the enhancement of IMA energy primarily results from two factors: one is the weakness of the Co-d$_{xy}$ and Co-d$_{x^{2}-y^{2}}$ orbital hybridization and the other is the augmentation of the Co-d$_{yz}$ and Co-d$_{z^{2}}$ orbital hybridization. Meanwhile, calculation results suggest that the Kosterlitz-Thouless phase transition temperature ($T_{\rm KT}$) of a 2D $XY$ magnet Gr/CoBr$_{2}$ (23.8 K) is higher than that of a 2D $XY$ monolayer CoBr$_{2}$ (1.35 K). By decreasing the interlayer distances, the proximity effect is more pronounced and band splitting appears. Moreover, by taking into account spin-orbit coupling, a band gap of approximately 14.3 meV and the quantum anomalous Hall effect (QAHE) are attained by decreasing the interlayer distance by 1.0 Å. Inspired by the above conclusions, we design a topological field transistor device model. Our results support that the vdW interlayer distance can be used to modulate the IMA energy and QAHE of materials, providing a pathway for the development of new low-power spintronic devices.

INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY

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Purification of copper foils driven by single crystallization Jin-Zong Kou(寇金宗), Meng-Ze Zhao(赵孟泽), Xing-Guang Li(李兴光), Meng-Lin He(何梦林), Fang-You Yang(杨方友), Ke-Hai Liu(刘科海), Qing-Qiu Cheng(成庆秋), Yun-Long Ren(任云龙), Can Liu(刘灿), Ying Fu(付莹), Mu-Hong Wu(吴慕鸿), Kai-Hui Liu(刘开辉), and En-Ge Wang(王恩哥) Chin. Phys. B, 2024, 33 (2):  028101.  DOI: 10.1088/1674-1056/ad0ec5 Abstract ( 166 )   HTML ( 0 )   PDF (1038KB) ( 109 )   High-purity copper (Cu) with excellent thermal and electrical conductivity, is crucial in modern technological applications, including heat exchangers, integrated circuits, and superconducting magnets. The current purification process is mainly based on the zone/electrolytic refining or anion exchange, however, which excessively relies on specific integrated equipment with ultra-high vacuum or chemical solution environment, and is also bothered by external contaminants and energy consumption. Here we report a simple approach to purify the Cu foils from 99.9% (3N) to 99.99% (4N) by a temperature-gradient thermal annealing technique, accompanied by the kinetic evolution of single crystallization of Cu. The success of purification mainly relies on (i) the segregation of elements with low effective distribution coefficient driven by grain-boundary movements and (ii) the high-temperature evaporation of elements with high saturated vapor pressure. The purified Cu foils display higher flexibility (elongation of 70%) and electrical conductivity (104% IACS) than that of the original commercial rolled Cu foils (elongation of 10%, electrical conductivity of ～ 100% IACS). Our results provide an effective strategy to optimize the as-produced metal medium, and therefore will facilitate the potential applications of Cu foils in precision electronic products and high-frequency printed circuit boards.

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Molecular dynamics simulations on the interactions between nucleic acids and a phospholipid bilayer Hot! Yao Xu(徐耀), Shu-Wei Huang(黄舒伟), Hong-Ming Ding(丁泓铭), and Yu-Qiang Ma(马余强) Chin. Phys. B, 2024, 33 (2):  028701.  DOI: 10.1088/1674-1056/ad1178 Abstract ( 236 )   HTML ( 6 )   PDF (4235KB) ( 215 )   Recently, lipid nanoparticles (LNPs) have been extensively investigated as non-viral carriers of nucleic acid vaccines due to their high transport efficiency, safety, and straightforward production and scalability. However, the molecular mechanism underlying the interactions between nucleic acids and phospholipid bilayers within LNPs remains elusive. In this study, we employed the all-atom molecular dynamics simulation to investigate the interactions between single-stranded nucleic acids and a phospholipid bilayer. Our findings revealed that hydrophilic bases, specifically G in single-stranded RNA (ssRNA) and single-stranded DNA (ssDNA), displayed a higher propensity to form hydrogen bonds with phospholipid head groups. Notably, ssRNA exhibited stronger binding energy than ssDNA. Furthermore, divalent ions, particularly Ca2+, facilitated the binding of ssRNA to phospholipids due to their higher binding energy and lower dissociation rate from phospholipids. Overall, our study provides valuable insights into the molecular mechanisms underlying nucleic acid-phospholipid interactions, with potential implications for the nucleic acids in biotherapies, particularly in the context of lipid carriers.

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Spatial search weighting information contained in cell velocity distribution Yikai Ma(马一凯), Na Li(李娜), and Wei Chen(陈唯) Chin. Phys. B, 2024, 33 (2):  028703.  DOI: 10.1088/1674-1056/ad09d3 Abstract ( 121 )   HTML ( 0 )   PDF (5732KB) ( 94 )   Cell migration plays a significant role in physiological and pathological processes. Understanding the characteristics of cell movement is crucial for comprehending biological processes such as cell functionality, cell migration, and cell-cell interactions. One of the fundamental characteristics of cell movement is the specific distribution of cell speed, containing valuable information that still requires comprehensive understanding. This article investigates the distribution of mean velocities along cell trajectories, with a focus on optimizing the efficiency of cell food search in the context of the entire colony. We confirm that the specific velocity distribution in the experiments corresponds to an optimal search efficiency when spatial weighting is considered. The simulation results indicate that the distribution of average velocity does not align with the optimal search efficiency when employing average spatial weighting. However, when considering the distribution of central spatial weighting, the specific velocity distribution in the experiment is shown to correspond to the optimal search efficiency. Our simulations reveal that for any given distribution of average velocity, a specific central spatial weighting can be identified among the possible central spatial weighting that aligns with the optimal search strategy. Additionally, our work presents a method for determining the spatial weights embedded in the velocity distribution of cell movement. Our results have provided new avenues for further investigation of significant topics, such as relationship between cell behavior and environmental conditions throughout their evolutionary history, and how cells achieve collective cooperation through cell-cell communication.

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Effect of cognitive training on brain dynamics Guiyang Lv(吕贵阳), Tianyong Xu(徐天勇), Feiyan Chen(陈飞燕), Ping Zhu(朱萍), Miao Wang(王淼), and Guoguang He(何国光) Chin. Phys. B, 2024, 33 (2):  028704.  DOI: 10.1088/1674-1056/ad09c8 Abstract ( 120 )   HTML ( 1 )   PDF (1161KB) ( 32 )   The human brain is highly plastic. Cognitive training is usually used to modify functional connectivity of brain networks. Moreover, the structures of brain networks may determine its dynamic behavior which is related to human cognitive abilities. To study the effect of functional connectivity on the brain dynamics, the dynamic model based on functional connections of the brain and the Hindmarsh-Rose model is utilized in this work. The resting-state fMRI data from the experimental group undergoing abacus-based mental calculation (AMC) training and from the control group are used to construct the functional brain networks. The dynamic behavior of brain at the resting and task states for the AMC group and the control group are simulated with the above-mentioned dynamic model. In the resting state, there are the differences of brain activation between the AMC group and the control group, and more brain regions are inspired in the AMC group. A stimulus with sinusoidal signals to brain networks is introduced to simulate the brain dynamics in the task states. The dynamic characteristics are extracted by the excitation rates, the response intensities and the state distributions. The change in the functional connectivity of brain networks with the AMC training would in turn improve the brain response to external stimulus, and make the brain more efficient in processing tasks.

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Dynamics and synchronization in a memristor-coupled discrete heterogeneous neuron network considering noise Xun Yan(晏询), Zhijun Li(李志军), and Chunlai Li(李春来) Chin. Phys. B, 2024, 33 (2):  028705.  DOI: 10.1088/1674-1056/ad062c Abstract ( 132 )   HTML ( 1 )   PDF (1966KB) ( 130 )   Research on discrete memristor-based neural networks has received much attention. However, current research mainly focuses on memristor-based discrete homogeneous neuron networks, while memristor-coupled discrete heterogeneous neuron networks are rarely reported. In this study, a new four-stable discrete locally active memristor is proposed and its nonvolatile and locally active properties are verified by its power-off plot and DC V-I diagram. Based on two-dimensional (2D) discrete Izhikevich neuron and 2D discrete Chialvo neuron, a heterogeneous discrete neuron network is constructed by using the proposed discrete memristor as a coupling synapse connecting the two heterogeneous neurons. Considering the coupling strength as the control parameter, chaotic firing, periodic firing, and hyperchaotic firing patterns are revealed. In particular, multiple coexisting firing patterns are observed, which are induced by different initial values of the memristor. Phase synchronization between the two heterogeneous neurons is discussed and it is found that they can achieve perfect synchronous at large coupling strength. Furthermore, the effect of Gaussian white noise on synchronization behaviors is also explored. We demonstrate that the presence of noise not only leads to the transition of firing patterns, but also achieves the phase synchronization between two heterogeneous neurons under low coupling strength.

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Dynamical behavior of memristor-coupled heterogeneous discrete neural networks with synaptic crosstalk Minglin Ma(马铭磷), Kangling Xiong(熊康灵), Zhijun Li(李志军), and Shaobo He(贺少波) Chin. Phys. B, 2024, 33 (2):  028706.  DOI: 10.1088/1674-1056/aceee9 Abstract ( 135 )   HTML ( 2 )   PDF (5152KB) ( 106 )   Synaptic crosstalk is a prevalent phenomenon among neuronal synapses, playing a crucial role in the transmission of neural signals. Therefore, considering synaptic crosstalk behavior and investigating the dynamical behavior of discrete neural networks are highly necessary. In this paper, we propose a heterogeneous discrete neural network (HDNN) consisting of a three-dimensional KTz discrete neuron and a Chialvo discrete neuron. These two neurons are coupled mutually by two discrete memristors and the synaptic crosstalk is considered. The impact of crosstalk strength on the firing behavior of the HDNN is explored through bifurcation diagrams and Lyapunov exponents. It is observed that the HDNN exhibits different coexisting attractors under varying crosstalk strengths. Furthermore, the influence of different crosstalk strengths on the synchronized firing of the HDNN is investigated, revealing a gradual attainment of phase synchronization between the two discrete neurons as the crosstalk strength decreases.

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Epidemic threshold influenced by non-pharmaceutical interventions in residential university environments Zechao Lu(卢泽超), Shengmei Zhao(赵生妹), Huazhong Shu(束华中), and Long-Yan Gong(巩龙延) Chin. Phys. B, 2024, 33 (2):  028707.  DOI: 10.1088/1674-1056/ace2b0 Abstract ( 117 )   HTML ( 0 )   PDF (1175KB) ( 40 )   The control of highly contagious disease spreading in campuses is a critical challenge. In residential universities, students attend classes according to a curriculum schedule, and mainly pack into classrooms, dining halls and dorms. They move from one place to another. To simulate such environments, we propose an agent-based susceptible-infected-recovered model with time-varying heterogeneous contact networks. In close environments, maintaining physical distancing is the most widely recommended and encouraged non-pharmaceutical intervention. It can be easily realized by using larger classrooms, adopting staggered dining hours, decreasing the number of students per dorm and so on. Their real-world influence remains uncertain. With numerical simulations, we obtain epidemic thresholds. The effect of such countermeasures on reducing the number of disease cases is also quantitatively evaluated.

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Origin of tradeoff between movement velocity and attachment duration of kinesin motor on a microtubule Yuying Liu(刘玉颖) and Zhiqiang Zhang(张志强) Chin. Phys. B, 2024, 33 (2):  028708.  DOI: 10.1088/1674-1056/ad1177 Abstract ( 145 )   HTML ( 0 )   PDF (940KB) ( 32 )   Kinesin-1 motor protein is a homodimer containing two identical motor domains connected by a common long coiled-coil stalk via two flexible neck linkers. The motor can step on a microtubule with a velocity of about 1 μm·s-1 and an attachment duration of about 1 s under physiological conditions. The available experimental data indicate a tradeoff between velocity and attachment duration under various experimental conditions, such as variation of the solution temperature, variation of the strain between the two motor domains, and so on. However, the underlying mechanism of the tradeoff is unknown. Here, the mechanism is explained by a theoretical study of the dynamics of the motor under various experimental conditions, reproducing quantitatively the available experimental data and providing additional predictions. How the various experimental conditions lead to different decreasing rates of attachment duration versus velocity is also explained.

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An extended social force model on unidirectional flow considering psychological and behavioral impacts of hazard source Kaifeng Deng(邓凯丰), Meng Li(李梦), Xiangmin Hu(胡祥敏), and Tao Chen(陈涛) Chin. Phys. B, 2024, 33 (2):  028901.  DOI: 10.1088/1674-1056/ad1173 Abstract ( 145 )   HTML ( 0 )   PDF (1831KB) ( 89 )   An accurate assessment of the evacuation efficiency in case of disasters is of vital importance to the safety design of buildings and street blocks. Hazard sources not only physically but psychologically affect the pedestrians, which may further alter their behavioral patterns. This effect is especially significant in narrow spaces, such as corridors and alleys. This study aims to integrate a non-spreading hazard source into the social force model following the results from a previous experiment and simulation, and to simulate unidirectional pedestrian flows over various crowd densities and clarity-intensity properties of the hazard source. The integration include a virtual repulsion force from the hazard source and a decay on the social force term. The simulations reveal (i) that the hazard source creates virtual bottlenecks that suppress the flow, (ii) that the inter-pedestrian push forms a stabilisation phase on the flow-density curve within medium-to-high densities, and (iii) that the pedestrians are prone to a less orderly and stable pattern of movement in low clarity-intensity scenarios, possibly with lateral collisions passing the hazard source.

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Source localization in signed networks with effective distance Zhi-Wei Ma(马志伟), Lei Sun(孙蕾), Zhi-Guo Ding(丁智国), Yi-Zhen Huang(黄宜真), and Zhao-Long Hu(胡兆龙) Chin. Phys. B, 2024, 33 (2):  028902.  DOI: 10.1088/1674-1056/ad1482 Abstract ( 145 )   HTML ( 3 )   PDF (1126KB) ( 69 )   While progress has been made in information source localization, it has overlooked the prevalent friend and adversarial relationships in social networks. This paper addresses this gap by focusing on source localization in signed network models. Leveraging the topological characteristics of signed networks and transforming the propagation probability into effective distance, we propose an optimization method for observer selection. Additionally, by using the reverse propagation algorithm we present a method for information source localization in signed networks. Extensive experimental results demonstrate that a higher proportion of positive edges within signed networks contributes to more favorable source localization, and the higher the ratio of propagation rates between positive and negative edges, the more accurate the source localization becomes. Interestingly, this aligns with our observation that, in reality, the number of friends tends to be greater than the number of adversaries, and the likelihood of information propagation among friends is often higher than among adversaries. In addition, the source located at the periphery of the network is not easy to identify. Furthermore, our proposed observer selection method based on effective distance achieves higher operational efficiency and exhibits higher accuracy in information source localization, compared with three strategies for observer selection based on the classical full-order neighbor coverage.

CORRIGENDUM

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Corrigendum to “Atomic-scale electromagnetic theory bridging optics in microscopic world and macroscopic world” Zhi-Yuan Li(李志远) and Jianfeng Chen(陈剑锋) Chin. Phys. B, 2024, 33 (2):  029901.  DOI: 10.1088/1674-1056/ad19d8 Abstract ( 138 )   HTML ( 0 )   PDF (461KB) ( 22 )   The signs of the electric field markers in Figs. 2 and 4 of the paper [Chin. Phys. B 32 104211 (2023)] have been corrected. These modifications do not affect the results derived in the paper.