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14 February 2023, Volume 32 Issue 3 Previous issue    Next issue

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DATA PAPER

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Measuring stellar populations, dust attenuation and ionized gas at kpc scales in 10010 nearby galaxies using the integral field spectroscopy from MaNGA Niu Li(李牛) and Cheng Li(李成) Chin. Phys. B, 2023, 32 (3):  039801.  DOI: 10.1088/1674-1056/acb0ba Abstract ( 87 )   PDF (1004KB) ( 24 )   As one of the three major experiments of the fourth-generation Sloan Digital Sky Survey (SDSS-IV), the Mapping Nearby Galaxies at Apatch Point Observatory (MaNGA) survey has obtained high-quality integral field spectroscopy (IFS) with a resolution of 1-2 kpc for ～104 galaxies in the local universe during its six-year operation from July 2014 through August 2020. It is crucial to reliably measure the physical properties of the different components in each spectrum before one can use the data for any scientific study. In the past years we have made lots of efforts to develop a novel technique of full spectral fitting, which estimates a model-independent dust attenuation curve from each spectrum, thus allowing us to break the degeneracy between dust attenuation and stellar population properties when fitting the spectrum with stellar population synthesis models. We have applied our technique to the final data release of MaNGA, and obtained measurements of stellar population properties and emission line parameters, as well as the kinematics and dust attenuation of both stellar and ionized gas components. In this paper we describe our technique and the content and format of our data products. The whole dataset is publicly available in Science Data Bank with the link https://doi.org/10.57760/sciencedb.j00113.00088.

RAPID COMMUNICATION

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Transition frequencies between 2S and 2P states of lithium-like ions Hot! Liming Wang(王黎明), Tongtong Liu(刘仝彤), Weiqing Yang(杨为青), and Zong-Chao Yan Chin. Phys. B, 2023, 32 (3):  033102.  DOI: 10.1088/1674-1056/acad6f Abstract ( 92 )   PDF (584KB) ( 58 )   The Schrödinger equation for the $2$S and $2$P states of the lithium-like ions $Z=5$-7, 9-10 is solved by using the Rayleigh-Ritz variational method in Hylleraas coordinates. The leading-order relativistic and QED corrections are calculated perturbatively and higher-order corrections are estimated. The transition frequencies between the $2{\rm S}_{1/2}$ and $2{\rm P}_J$ ($J=1/2, 3/2$) states are determined and compared with experimental and other theoretical results. Specifically, isotope shifts are also calculated for B$^{2+}$.

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Atomic optical spatial mode extractor for vector beams based on polarization-dependent absorption Hong Chang(常虹), Xin Yang(杨欣), Jinwen Wang(王金文), Yan Ma(马燕), Xinqi Yang(杨鑫琪), Mingtao Cao(曹明涛), Xiaofei Zhang(张晓斐), Hong Gao(高宏), Ruifang Dong(董瑞芳), and Shougang Zhang(张首刚) Chin. Phys. B, 2023, 32 (3):  034207.  DOI: 10.1088/1674-1056/acac19 Abstract ( 77 )   PDF (8912KB) ( 59 )   Vector beams with spiral phase and spatially varying polarization profiles have many applications from optical micromanipulation to materials processing. Here, we propose and demonstrate an atomic spatial mode extracting scheme for the vector beam based on polarization-dependent absorption in the atom vapor. By employing the linear polarization pump beam which induces polarization sensitive absorption in the atomic ensemble, a counter-propagated weak probe vector beam is extracted by spatial absorption, and extracted part still maintains the original polarization and the vortex phase. The topological charges of the extracted mode are verified by interfering with the Gaussian beam, and it can be found that the orbital angular momentum is conserved in the extracting process. Our work will have potential applications in non-destructive spatial mode identification, and is also useful for studying higher-dimensional quantum information based on atomic ensembles.

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Superconductivity in epitaxially grown LaVO3/KTaO3(111) heterostructures Hot! Yuan Liu(刘源), Zhongran Liu(刘中然), Meng Zhang(张蒙), Yanqiu Sun(孙艳秋), He Tian(田鹤), and Yanwu Xie(谢燕武) Chin. Phys. B, 2023, 32 (3):  037305.  DOI: 10.1088/1674-1056/acac1b Abstract ( 104 )   PDF (1230KB) ( 65 )   Complex oxide heterointerfaces can host a rich of emergent phenomena, and epitaxial growth is usually at the heart of forming these interfaces. Recently, a strong crystalline-orientation-dependent two-dimensional superconductivity was discovered at interfaces between KTaO3 single-crystal substrates and films of other oxides. Unexpectedly, rare of these oxide films was epitaxially grown. Here, we report the existence of superconductivity in epitaxially grown LaVO3/KTaO3(111) heterostructures, with a superconducting transition temperature of ～ 0.5 K. Meanwhile, no superconductivity was detected in the (001)- and (110)-orientated LaVO3/KTaO3 heterostructures down to 50 mK. Moreover, we find that for the LaVO3/KTaO3(111) interfaces to be conducting, an oxygen-deficient growth environment and a minimum LaVO3 thickness of ～ 0.8 nm (～ 2 unit cells) are needed.

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Reconstruction and functionalization of aerogels by controlling mesoscopic nucleation to greatly enhance macroscopic performance Hot! Chen-Lu Jiao(焦晨璐), Guang-Wei Shao(邵光伟), Yu-Yue Chen(陈宇岳), and Xiang-Yang Liu(刘向阳) Chin. Phys. B, 2023, 32 (3):  038103.  DOI: 10.1088/1674-1056/acb912 Abstract ( 150 )   PDF (7614KB) ( 106 )   This work presents a strategy for the mesoscopic engineering of hierarchically structured sodium alginate (SA) aerogels to enhance the macroscopic performance. The strategy was implemented by meso-functionalizing and reorganizing SA aerogels via controlled heterogeneous nucleation, in which microcrystalline cellulose-manganese dioxide (MCC-MnO2) nano-crystallites worked as template. Due to the short rod-like structure and abundant hydroxyl groups of MCC-MnO2, the organized mesostructure of SA aerogels was reconstructed during the assembly of SA molecule chains, which gave rise to a significant enhancement in macroscopic performance of SA areogels. For instance, the functionalized and reconstructed MCC-MnO2/SA aerogels acquired a more than 70% increase in mechanical strength with an excellent deformation recovery. Furthermore, an almost double enhancement of removal capacity for metal ions (i.e., Cu2+ and Pb2+) and organic dyes (i.e., congo red and methylene blue) was obtained for MnO2/SA aerogels, with an 87% repossession of the pollutants removal performance after 5 operation cycles.

GENERAL

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Application of the body of revolution finite-element method in a re-entrant cavity for fast and accurate dielectric parameter measurements Tianqi Feng(冯天琦), Chengyong Yu(余承勇), En Li(李恩), and Yu Shi(石玉) Chin. Phys. B, 2023, 32 (3):  030101.  DOI: 10.1088/1674-1056/ac7f91 Abstract ( 43 )   PDF (1170KB) ( 26 )   In dielectrometry, traditional analytical and numerical algorithms are difficultly employed in complex resonant cavities. For a special kind of structure (a rotating resonant cavity), the body of revolution finite-element method (BOR-FEM) is employed to calculate the resonant parameters and dielectric parameters. In this paper, several typical resonant structures are selected for analysis and verification. Compared with the resonance parameter values in the literature and the simulation results of commercial software, the error of the BOR-FEM calculation is less than 0.9% and a single solution time is less than 1 s. Reentrant coaxial resonant cavities loaded with dielectric materials are analyzed using this method and compared with simulation results, showing good agreement. Finally, in this paper, the established BOR-FEM method is successfully applied with a machined cavity for the accurate measurement of the complex dielectric constant of dielectric materials. The test specimens were machined from polytetrafluoroethylene, fused silica and Al2O3, and the test results showed good agreement with the literature reference values.

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Inverse stochastic resonance in modular neural network with synaptic plasticity Yong-Tao Yu(于永涛) and Xiao-Li Yang(杨晓丽) Chin. Phys. B, 2023, 32 (3):  030201.  DOI: 10.1088/1674-1056/aca602 Abstract ( 43 )   PDF (4176KB) ( 29 )   This work explores the inverse stochastic resonance (ISR) induced by bounded noise and the multiple inverse stochastic resonance induced by time delay by constructing a modular neural network, where the modified Oja's synaptic learning rule is employed to characterize synaptic plasticity in this network. Meanwhile, the effects of synaptic plasticity on the ISR dynamics are investigated. Through numerical simulations, it is found that the mean firing rate curve under the influence of bounded noise has an inverted bell-like shape, which implies the appearance of ISR. Moreover, synaptic plasticity with smaller learning rate strengthens this ISR phenomenon, while synaptic plasticity with larger learning rate weakens or even destroys it. On the other hand, the mean firing rate curve under the influence of time delay is found to exhibit a decaying oscillatory process, which represents the emergence of multiple ISR. However, the multiple ISR phenomenon gradually weakens until it disappears with increasing noise amplitude. On the same time, synaptic plasticity with smaller learning rate also weakens this multiple ISR phenomenon, while synaptic plasticity with larger learning rate strengthens it. Furthermore, we find that changes of synaptic learning rate can induce the emergence of ISR phenomenon. We hope these obtained results would provide new insights into the study of ISR in neuroscience.

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Adaptive multi-step piecewise interpolation reproducing kernel method for solving the nonlinear time-fractional partial differential equation arising from financial economics Ming-Jing Du(杜明婧), Bao-Jun Sun(孙宝军), and Ge Kai(凯歌) Chin. Phys. B, 2023, 32 (3):  030202.  DOI: 10.1088/1674-1056/ac9368 Abstract ( 31 )   PDF (1531KB) ( 14 )   This paper is aimed at solving the nonlinear time-fractional partial differential equation with two small parameters arising from option pricing model in financial economics. The traditional reproducing kernel (RK) method which deals with this problem is very troublesome. This paper proposes a new method by adaptive multi-step piecewise interpolation reproducing kernel (AMPIRK) method for the first time. This method has three obvious advantages which are as follows. Firstly, the piecewise number is reduced. Secondly, the calculation accuracy is improved. Finally, the waste time caused by too many fragments is avoided. Then four numerical examples show that this new method has a higher precision and it is a more timesaving numerical method than the others. The research in this paper provides a powerful mathematical tool for solving time-fractional option pricing model which will play an important role in financial economics.

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An incommensurate fractional discrete macroeconomic system: Bifurcation, chaos, and complexity Abderrahmane Abbes, Adel Ouannas, and Nabil Shawagfeh Chin. Phys. B, 2023, 32 (3):  030203.  DOI: 10.1088/1674-1056/ac7296 Abstract ( 49 )   PDF (10205KB) ( 19 )   This study proposes a novel fractional discrete-time macroeconomic system with incommensurate order. The dynamical behavior of the proposed macroeconomic model is investigated analytically and numerically. In particular, the zero equilibrium point stability is investigated to demonstrate that the discrete macroeconomic system exhibits chaotic behavior. Through using bifurcation diagrams, phase attractors, the maximum Lyapunov exponent and the 0-1 test, we verified that chaos exists in the new model with incommensurate fractional orders. Additionally, a complexity analysis is carried out utilizing the approximation entropy (ApEn) and C0 complexity to prove that chaos exists. Finally, the main findings of this study are presented using numerical simulations.

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Bidirectional visible light absorber based on nanodisk arrays Qi Wang(王琦), Fei-Fan Zhu(朱非凡), Rui Li(李瑞), Shi-Jie Zhang(张世杰), and Da-Wei Zhang(张大伟) Chin. Phys. B, 2023, 32 (3):  030205.  DOI: 10.1088/1674-1056/ac8afa Abstract ( 30 )   PDF (688KB) ( 13 )   A perfect bidirectional broadband visible light absorber composed of titanium nitride and tungsten nanodisk arrays is proposed. The average absorption of the absorber exceeds 89% at 400 nm-800 nm when light is normally incident on the front-side. Illumination from the opposite direction (back-side) results in absorption of more than 75%. Through the theoretical analysis of the electric and magnetic fields, the physical mechanism of the broadband perfect absorption is attributed to the synergy of localized surface plasmons, propagating surface plasmons, and plasmonic resonant cavity modes. Furthermore, the absorber also exhibits excellent polarization-independence performance and a high angular tolerance of ～ 30° for both front- and back-side incidence. The designed bidirectional broadband visible light absorber here has wide application prospects in the fields of solar cells and ink-free printing.

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Formalism of rotating-wave approximation in high-spin system with quadrupole interaction Wen-Kui Ding(丁文魁) and Xiao-Guang Wang(王晓光) Chin. Phys. B, 2023, 32 (3):  030301.  DOI: 10.1088/1674-1056/aca392 Abstract ( 59 )   PDF (494KB) ( 27 )   We investigate the rotating wave approximation applied in the high-spin quantum system driven by a linearly polarized alternating magnetic field in the presence of quadrupole interactions. The conventional way to apply the rotating wave approximation in a driven high-spin system is to assume the dynamics being restricted in the reduced Hilbert space. However, when the driving strength is relatively strong or the driving is off resonant, the leakage from the target resonance subspace cannot be neglected for a multi-level quantum system. We propose the correct formalism to apply the rotating wave approximation in the full Hilbert space by taking this leakage into account. By estimating the operator fidelity of the time propagator, our formalism applied in the full Hilbert space unambiguously manifests great advantages over the conventional method applied in the reduced Hilbert space.

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Floquet scattering through a parity-time symmetric oscillating potential Xuzhen Cao(曹序桢), Zhaoxin Liang(梁兆新), and Ying Hu(胡颖) Chin. Phys. B, 2023, 32 (3):  030302.  DOI: 10.1088/1674-1056/aca39a Abstract ( 51 )   PDF (1260KB) ( 34 )   We investigate the scattering of a particle from a trapping potential that is subjected to weak, parity-time symmetric periodic drivings. Using the Floquet theory, we derive the scattering matrix and calculate the transmittance of the incident particle. When the driving is purely coherent, our calculation recovers the known result and the transmission spectrum shows the familiar, bound-state-induced Fano resonances. When the driving is purely incoherent, we find the Fano resonances still occur, but the lineshape of each resonance is reversed compared to the coherent-driving counterpart. Intriguingly, the transmission resonances disappear when both the coherent and incoherent driving fields are present with equal amplitudes. This phenomena can be seen as a manifestation of the non-reciprocal coupling of Floquet channels in the frequency domain. Notably, when the frequency up-conversion is absent, the transmission is such as if there is no driving at all, even when the driving strength increases.

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High-fidelity universal quantum gates for hybrid systems via the practical photon scattering Jun-Wen Luo(罗竣文) and Guan-Yu Wang(王冠玉) Chin. Phys. B, 2023, 32 (3):  030303.  DOI: 10.1088/1674-1056/ac8734 Abstract ( 60 )   PDF (1509KB) ( 20 )   High-fidelity quantum logic gates are essential in quantum computation, and both photons and electron spins in quantum dots (QDs) have their own unique advantages in implementing quantum computation. It is of critical significance to achieve high-fidelity quantum gates for photon-QD hybrid systems. Here, we propose two schemes for implementing high-fidelity universal quantum gates including Toffoli gate and Fredkin gate for photon-QD hybrid systems, utilizing the practical scattering of a single photon off a QD-cavity system. The computation errors from the imperfections involved in the practical scattering are detected and prevented from arising in the final results of the two gates. Accordingly, the unity fidelity of each quantum gate is obtained in the nearly realistic condition, and the requirement for experimental realization is relaxed. Furthermore, the quantum circuits for the two gates are compact and no auxiliary qubits are required, which would also be the advantages regarding their experimental feasibility. These features indicate that our schemes may be useful in the practical quantum computation tasks.

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Unified entropy entanglement with tighter constraints on multipartite systems Qi Sun(孙琪), Tao Li(李陶), Zhi-Xiang Jin(靳志祥), and Deng-Feng Liang(梁登峰) Chin. Phys. B, 2023, 32 (3):  030304.  DOI: 10.1088/1674-1056/aca399 Abstract ( 53 )   PDF (530KB) ( 31 )   Monogamy and polygamy relations characterize the distributions of entanglement in multipartite systems. We provide a characterization of multiqubit entanglement constraints in terms of unified-$(q,s)$ entropy. A class of tighter monogamy inequalities of multiqubit entanglement based on the $\alpha$-th power of unified-$(q,s)$ entanglement for $\alpha\geq 1$ and a class of polygamy inequalities in terms of the $\beta$-th power of unified-$(q,s)$ entanglement of assistance are established in this paper. Our results present a general class of the monogamy and polygamy relations for bipartite entanglement measures based on unified-$(q,s)$ entropy, which are tighter than the existing ones. What is more, some usual monogamy and polygamy relations, such as monogamy and polygamy relations based on entanglement of formation, Renyi-$q$ entanglement of assistance and Tsallis-$q$ entanglement of assistance, can be obtained from these results by choosing appropriate parameters $(q,s)$ in unified-$(q,s)$ entropy entanglement. Typical examples are also presented for illustration.

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Non-Markovianity of an atom in a semi-infinite rectangular waveguide Jing Zeng(曾静), Yaju Song(宋亚菊), Jing Lu(卢竞), and Lan Zhou(周兰) Chin. Phys. B, 2023, 32 (3):  030305.  DOI: 10.1088/1674-1056/acac18 Abstract ( 41 )   PDF (1006KB) ( 32 )   We investigate the non-Markovianity (NM) of a waveguide QED with a two-level atom as the system and a semi-infinite rectangular waveguide as the environment, where the transverse magnetic (TM$_{mn}$) modes define the quantum channels of guided photons. The perfect mirror imposed by the finite end exerts a retarded feedback mechanism to allow for information backflow, which leads to NM dynamics. For the energy separation of the atom far away from the cutoff frequencies of transverse modes, the delay differential equations are obtained with single-excitation initial in the atom. Our attention is focused on the effects of multiple quantum channels involved in guiding photons on the degree of non-Markovian behavior. An asymptotic value of the non-Markovianity $\mathcal{N}_{1}$ can be found as the atom-mirror distance is large enough, however, the asymptotic value of $\mathcal{N}_{2}$ of the atom interacting with the effective double-modes is lower than that of the atom interacting with the effective single-mode. We also show that $\mathcal{N}_{1}$ is a constant, and the analytical expression for $\mathcal{N}_{2}$ is related to the parameters associated with the modes, which is related to the interference of the two modes.

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Performance analysis of quantum key distribution using polarized coherent-states in free-space channel Zengte Zheng(郑增特), Ziyang Chen(陈子扬), Luyu Huang(黄露雨),Xiangyu Wang(王翔宇), and Song Yu(喻松) Chin. Phys. B, 2023, 32 (3):  030306.  DOI: 10.1088/1674-1056/ac7450 Abstract ( 23 )   PDF (1583KB) ( 8 )   In free space channel, continuous-variable quantum key distribution (CV-QKD) using polarized coherent-states can not only make the signal state more stable and less susceptible to interference based on the polarization non-sensitive of the free-space channel, but also reduce the noise introduced by phase interference. However, arbitrary continuous modulation can not be carried out in the past polarization coding, resulting in that the signal state can not obtain arbitrary continuous value in Poincare space, and the security analysis of CV-QKD using polarized coherent-states in free space is not complete. Here we propose a new modulation method to extend the modulation range of signal states with an optical-fiber-based polarization controller. In particular, in terms of the main influence factors in the free-space channel, we utilize the beam extinction and elliptical model when considering the transmittance and adopt the formulation of secret key rate. In addition, the performance of the proposed scheme under foggy weather is also taken into consideration to reveal the influence of severe weather. Numerical simulation shows that the proposed scheme is seriously affected by attenuation under foggy weather. The protocol fails when visibility is less than 1 km. At the same time, the wavelength can affect the performance of the proposed scheme. Specifically, under foggy weather, the longer the wavelength, the smaller the attenuation coefficient, and the better the transmission performance. Our proposed scheme can expand the modulation range of signal state, and supplement the security research of the scheme in the free-space channel, thus can provide theoretical support for subsequent experiments.

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Security of the traditional quantum key distribution protocolswith finite-key lengths Bao Feng(冯宝), Hai-Dong Huang(黄海东), Yu-Xiang Bian(卞宇翔), Wei Jia(贾玮), Xing-Yu Zhou(周星宇), and Qin Wang(王琴) Chin. Phys. B, 2023, 32 (3):  030307.  DOI: 10.1088/1674-1056/ac9b33 Abstract ( 31 )   PDF (536KB) ( 12 )   Quantum key distribution (QKD) in principle can provide unconditional secure communication between distant parts. However, when finite-key length is taken into account, the security can only be ensured within certain security level. In this paper, we adopt the Chernoff bound analysis method to deal with finite-key-size effects, carrying out corresponding investigations on the relationship between the key generation rate and security parameters for different protocols, including BB84, measurement-device-independent and twin-field QKD protocols. Simulation results show that there exists a fundamental limit between the key rate and the security parameters. Therefore, this study can provide valuable references for practical application of QKD, getting a nice balance between the key generation rate and the security level.

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Electrical manipulation of a hole ‘spin’-orbit qubit in nanowire quantum dot: The nontrivial magnetic field effects Rui Li(李睿) and Hang Zhang(张航) Chin. Phys. B, 2023, 32 (3):  030308.  DOI: 10.1088/1674-1056/ac873b Abstract ( 44 )   PDF (639KB) ( 13 )   Strong ‘spin’-orbit coupled one-dimensional hole gas is achievable in a Ge nanowire in the presence of a strong magnetic field. The strong magnetic field lifts the two-fold degeneracy in the hole subband dispersions, so that the effective low-energy subband dispersion exhibits strong spin-orbit coupling. Here, we study the electrical spin manipulation in a Ge nanowire quantum dot for both the lowest and second lowest hole subband dispersions. Using a finite square well to model the quantum dot confining potential, we calculate exactly the level splitting of the spin-orbit qubit and the Rabi frequency in the electric-dipole spin resonance. The spin-orbit coupling modulated longitudinal g-factor gso is not only non-vanishing but also magnetic field dependent. Moreover, the spin-orbit couplings of the lowest and second lowest subband dispersions have opposite magnetic dependences, so that the results for these two subband dispersions are totally different. It should be noticed that we focus only on the properties of the hole ‘spin’ instead of the real hole spin.

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A color image encryption algorithm based on hyperchaotic map and DNA mutation Xinyu Gao(高昕瑜), Bo Sun(孙博), Yinghong Cao(曹颖鸿), Santo Banerjee, and Jun Mou(牟俊) Chin. Phys. B, 2023, 32 (3):  030501.  DOI: 10.1088/1674-1056/ac8cdf Abstract ( 39 )   PDF (18891KB) ( 13 )   We devise a color image encryption scheme via combining hyperchaotic map, cross-plane operation and gene theory. First, the hyperchaotic map used in the encryption scheme is analyzed and studied. On the basis of the dynamics of hyperchaotic map, a color image encryption scheme is designed. At the end of the encryption process, a DNA mutation operation is used to increase the encoding images' randomness and to improve the encryption algorithm's security. Finally, simulation experiments, performance analysis, and attack tests are performed to prove the effectiveness and security of the designed algorithm. This work provides the possibility of applying chaos theory and gene theory in image encryption.

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Modulational instability of a resonantly polariton condensate in discrete lattices Wei Qi(漆伟), Xiao-Gang Guo(郭晓刚), Liang-Wei Dong(董亮伟), and Xiao-Fei Zhang(张晓斐) Chin. Phys. B, 2023, 32 (3):  030502.  DOI: 10.1088/1674-1056/ac891a Abstract ( 53 )   PDF (1317KB) ( 23 )   We study modulational instability of a resonantly polariton condensate in a discrete lattice. Employing a discrete gain-saturation model, we derive the dispersion relation for the modulational instability by means of the linear-stability analysis. Effects of the pumping strength, the nonlinearity, the strength of the detuning, and the coupling strength on the modulation instability are investigated. It is found that the interplay between these parameters will dramatically change the modulational instability condition. We believe that the predicted results in this work can be useful for future possible experiment of exciton-polariton condensate in lattices.

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Performance optimization on finite-time quantum Carnot engines and refrigerators based on spin-1/2 systems driven by a squeezed reservoir Haoguang Liu(刘浩广), Jizhou He(何济洲), and Jianhui Wang(王建辉) Chin. Phys. B, 2023, 32 (3):  030503.  DOI: 10.1088/1674-1056/aca207 Abstract ( 45 )   PDF (599KB) ( 22 )   We investigate the finite-time performance of a quantum endoreversible Carnot engine cycle and its inverse operation — Carnot refrigeration cycle, employing a spin-$1/2$ system as the working substance. The thermal machine is alternatively driven by a hot boson bath of inverse temperature $\beta_{\rm h}$ and a cold boson bath at inverse temperature $\beta_{\rm c}(>\beta_{\rm h})$. While for the engine model the hot bath is constructed to be squeezed, in the refrigeration cycle the cold bath is established to be squeezed, with squeezing parameter $r$. We obtain the analytical expressions for both efficiency and power in heat engines and for coefficient of performance and cooling rate in refrigerators. We find that, in the high-temperature limit, the efficiency at maximum power is bounded by the analytical value $\eta_+=1-\sqrt{\text{sech}(2r)(1-\eta_{\rm C})}$, and the coefficient of performance at the maximum figure of merit is limited by $ \varepsilon_+=\frac{\sqrt{\text{sech}(2r)(1+\varepsilon_{\rm C}})}{\sqrt{\text{sech}(2r)(1+\varepsilon_{\rm C})-\varepsilon_{\rm C}}}-1$, where $\eta_{\rm C}=1-\beta_{\rm h}/\beta_{\rm c}$ and $\varepsilon_{\rm C}=\beta_{\rm h}/(\beta_{\rm c}-\beta_{\rm h})$ are the respective Carnot values of the engines and refrigerators. These analytical results are identical to those obtained from the Carnot engines based on harmonic systems, indicating that the efficiency at maximum power and coefficient at maximum figure of merit are independent of the working substance.

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Asymmetric image encryption algorithm based ona new three-dimensional improved logistic chaotic map Guo-Dong Ye(叶国栋), Hui-Shan Wu(吴惠山), Xiao-Ling Huang(黄小玲), and Syh-Yuan Tan Chin. Phys. B, 2023, 32 (3):  030504.  DOI: 10.1088/1674-1056/ac7dbb Abstract ( 22 )   PDF (4562KB) ( 15 )   Based on some analyses of existing chaotic image encryption frameworks and a new designed three-dimensional improved logistic chaotic map (3D-ILM), an asymmetric image encryption algorithm using public-key Rivest-Shamir-Adleman (RSA) is presented in this paper. In the first stage, a new 3D-ILM is proposed to enhance the chaotic behavior considering analysis of time sequence, Lyapunov exponent, and Shannon entropy. In the second stage, combined with the public key RSA algorithm, a new key acquisition mathematical model (MKA) is constructed to obtain the initial keys for the 3D-ILM. Consequently, the key stream can be produced depending on the plain image for a higher security. Moreover, a novel process model (NPM) for the input of the 3D-ILM is built, which is built to improve the distribution uniformity of the chaotic sequence. In the third stage, to encrypt the plain image, a pre-process by exclusive OR (XOR) operation with a random matrix is applied. Then, the pre-processed image is performed by a permutation for rows, a downward modulo function for adjacent pixels, a permutation for columns, a forward direction XOR addition-modulo diffusion, and a backward direction XOR addition-modulo diffusion to achieve the final cipher image. Moreover, experiments show that the the proposed algorithm has a better performance. Especially, the number of pixels change rate (NPCR) is close to ideal case 99.6094%, with the unified average changing intensity (UACI) close to 33.4634%, and the information entropy (IE) close to 8.

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Soliton molecules, T-breather molecules and some interaction solutions in the (2+1)-dimensional generalized KDKK equation Yiyuan Zhang(张艺源), Ziqi Liu(刘子琪), Jiaxin Qi(齐家馨), and Hongli An(安红利) Chin. Phys. B, 2023, 32 (3):  030505.  DOI: 10.1088/1674-1056/ac89d9 Abstract ( 28 )   PDF (2127KB) ( 7 )   By employing the complexification method and velocity resonant principle to $N$-solitons of the $(2+1)$-dimensional generalized Konopelchenko-Dubrovsky-Kaup-Kupershmidt (KDKK) equation, we obtain the soliton molecules, $T$-breather molecules, $T$-breather-$L$-soliton molecules and some interaction solutions when $N\leq6$. Dynamical behaviors of these solutions are discussed analytically and graphically. The method adopted can be effectively used to construct soliton molecules and $T$-breather molecules of other nonlinear evolution equations. The results obtained may be helpful for experts to study the related phenomenon in oceanography and atmospheric science.

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All-optical switches based on three-soliton inelastic interaction and its application in optical communication systems Shubin Wang(王树斌), Xin Zhang(张鑫), Guoli Ma(马国利), and Daiyin Zhu(朱岱寅) Chin. Phys. B, 2023, 32 (3):  030506.  DOI: 10.1088/1674-1056/acad6c Abstract ( 21 )   PDF (5318KB) ( 17 )   In high-speed optical communication systems, in order to improve the communication rate, the distance between pulses must be compressed, which will cause the problem of the interaction between optical pulses in optical communication systems, which has been widely concerned by researches. In this paper, the bilinear method will be used to analyze the coupled high-order nonlinear Schrödinger equations and obtain their three-soliton solutions. Then, the influence of the relevant parameters in the three-soliton solution on the soliton inelastic interaction is studied. In addition, the constraint conditions of each parameter in the three-soliton solution are analyzed, the inelastic interaction properties of optical solitons under different parameter conditions are obtained, and the relevant laws of the inelastic interaction of solitons are studied. The results will have potential applications in the soliton control, all-optical switching and optical computing.

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Suppression of laser power error in a miniaturized atomic co-magnetometer based on split ratio optimization Wei-Jia Zhang(张伟佳), Wen-Feng Fan(范文峰), Shi-Miao Fan(范时秒), and Wei Quan(全伟) Chin. Phys. B, 2023, 32 (3):  030701.  DOI: 10.1088/1674-1056/ac81b1 Abstract ( 26 )   PDF (913KB) ( 10 )   A miniaturized atomic spin-exchange relaxation-free (SERF) co-magnetometer measures angular velocity using a balanced polarimetry technique which is easily affected by the laser power. A laser power closed-loop control system is usually used to suppress the fluctuation of the laser power. Although this method can greatly eliminate the fluctuation of the in-loop laser power (the feedback laser), it cannot fully eliminate the fluctuation of the out-of-loop laser power (the signal measurement laser). This leads to SERF gyroscope laser power error, which reduces the inertial measurement accuracy. In this paper, the influence mechanism of the split ratio (the ratio of the in-loop laser power to the out-of-loop laser power) on the out-of-loop laser power control accuracy is analyzed by establishing a laser power transmission model inside and outside the loop. Moreover, a method is developed to improve the out-of-loop laser power stability by optimizing the split ratio. Comparative experiments showed that the relative Allan standard deviation of the out-of-loop laser power decreased from 5.48×10-6 to 2.62×10-6 at 100 s, and decreased by an order of magnitude from 1.76×10-5 to 3.30×10-6 at 1000 s. Correspondingly, the rate ramp coefficient in the Allan standard deviation curve of the SERF gyroscope test data decreased from 1.312 [(°/h)/h] to 0.246 [(°/h)/h]. And the bias stability increased from 0.032 °/h to 0.019 °/h. Therefore, the proposed method can improve the long-term stability of the probe laser power and effectively suppress the laser power error of the SERF gyroscope.

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Fiber cladding dual channel surface plasmon resonance sensor based on S-type fiber Yong Wei(魏勇), Xiaoling Zhao(赵晓玲), Chunlan Liu(刘春兰), Rui Wang(王锐), Tianci Jiang(蒋天赐), Lingling Li(李玲玲), Chen Shi(石晨), Chunbiao Liu(刘纯彪), and Dong Zhu(竺栋) Chin. Phys. B, 2023, 32 (3):  030702.  DOI: 10.1088/1674-1056/ac7e3b Abstract ( 31 )   PDF (4596KB) ( 14 )   Fiber cladding surface plasmon resonance (SPR) sensors have few structures, and a clad SPR sensor based on S-type fiber is proposed in this paper. This new type of fiber cladding SPR sensor was formed by electrofusing an S-shaped structure on the fiber to couple the light in the fiber core to the cladding. In this paper, the effects of fiber parameters on the performance of the sensor were studied by simulation and experiment. Based on the conclusion that the smaller the core diameter is, the closer the working band of the SPR resonance is to long wavelengths, and that the geometric characteristics mean that a multimode fiber can receive the fiber cladding light from a small core diameter few-mode fiber, a dual channel SPR sensor with a double S-type fiber cascade was proposed. In the refractive index detection range of 1.333-1.385 refractive index units (RIU), the resonant working band of channel I is 627.66 nm-759.78 nm, with an average sensitivity of 2540.77 nm/RIU, and the resonant working band of channel II is 518.24 nm-658.2 nm, with an average sensitivity of 2691.54 nm/RIU. The processing method for the S-type fiber cladding SPR sensor is simple, effectively solving the problem of this type of SPR sensor structure and the difficult realization of a dual channel. The sensor is expected to be used in the fields of medical treatment and biological analysis.

ATOMIC AND MOLECULAR PHYSICS

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Ridge regression energy levels calculation of neutral ytterbium (Z = 70) Yushu Yu(余雨姝), Chen Yang(杨晨), and Gang Jiang(蒋刚) Chin. Phys. B, 2023, 32 (3):  033101.  DOI: 10.1088/1674-1056/acac08 Abstract ( 48 )   PDF (580KB) ( 16 )   In view of the difficulty in calculating the atomic structure parameters of high-Z elements, the Hartree-Fock with relativistic corrections (HFR) theory in combination with the ridge regression (RR) algorithm rather than the Cowan code's least squares fitting (LSF) method is proposed and applied. By analyzing the energy level structure parameters of the HFR theory and using the fitting experimental energy level extrapolation method, some excited state energy levels of the Yb I (Z=70) atom including the 4f open shell are calculated. The advantages of the ridge regression algorithm are demonstrated by comparing it with Cowan code's LSF results. In addition, the results obtained by the new method are compared with the experimental results and other theoretical results to demonstrate the reliability and accuracy of our approach.

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Phase-coherence dynamics of frequency-comb emission via high-order harmonic generation in few-cycle pulse trains Chang-Tong Liang(梁畅通), Jing-Jing Zhang(张晶晶), and Peng-Cheng Li(李鹏程) Chin. Phys. B, 2023, 32 (3):  033201.  DOI: 10.1088/1674-1056/acac0f Abstract ( 54 )   PDF (1979KB) ( 47 )   Frequency-comb emission via high-order harmonic generation (HHG) provides an alternative method for the coherent vacuum ultraviolet (VUV) and extreme ultraviolet (XUV) radiation at ultrahigh repetition rates. In particular, the temporal and spectral features of the HHG were shown to carry profound insight into frequency-comb emission dynamics. Here we present an ab initio investigation of the temporal and spectral coherence of the frequency comb emitted in HHG of He atom driven by few-cycle pulse trains. We find that the emission of frequency combs features a destructive and constructive coherences caused by the phase interference of HHG, leading to suppression and enhancement of frequency-comb emission. The results reveal intriguing and substantially different nonlinear optical response behaviors for frequency-comb emission via HHG. The dynamical origin of frequency-comb emission is clarified by analyzing the phase coherence in HHG processes in detail. Our results provide fresh insight into the experimental realization of selective enhancement of frequency comb in the VUV-XUV regimes.

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Quantum control of ultrafast magnetic field in H32+ molecules by tricircular polarized laser pulses Qing-Yun Xu(徐清芸), Yong-Lin He(何永林), Zhi-Jie Yang(杨志杰), Zhi-Xian Lei(雷志仙),Shu-Juan Yan(闫淑娟), Xue-Shen Liu(刘学深), and Jing Guo(郭静) Chin. Phys. B, 2023, 32 (3):  033202.  DOI: 10.1088/1674-1056/ac90b6 Abstract ( 42 )   PDF (1695KB) ( 39 )   We present a scheme to control the generated ultrafast magnetic field in $\rm H_{3}^{2+}$ molecules using multi-frequency tricircular pulses composed of co- and counter-rotating bicircular pulses. Simulations show that the field amplitude and the wavelength are two significant factors for magnetic field generation by tricircular pulses. Specifically, the strength of the magnetic field is linearly related to the field amplitude at $\lambda_0 = 50 $ nm, while at $\lambda_0 = 70 $ nm, the strength first increases and then decreases with the amplitude, this can be attributed to the resonance between the ground and excited states. Moreover, the phase and helicity of bicircular pulses are shown to have important effects on the magnetic field. The dependence of the magnetic field on the phase arises from the interference effect between multiple ionization pathways. These findings illustrate a guiding principle for controlling the magnetic field in molecular systems for future research in ultrafast magneto-optics.

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A theoretical study of fragmentation dynamics of water dimer by proton impact Zhi-Ping Wang(王志萍), Xue-Fen Xu(许雪芬), Feng-Shou Zhang(张丰收), and Xu Wang(王旭) Chin. Phys. B, 2023, 32 (3):  033401.  DOI: 10.1088/1674-1056/ac8340 Abstract ( 55 )   PDF (787KB) ( 16 )   To investigate the collision processes of proton with the water dimer (H2O)2 at 50 eV, the time-dependent density functional theory coupled with molecular dynamics nonadiabatically is applied. Six specific collision orientations with various impact parameters are considered. The reaction channels, the mass distribution and the fragmentation mass spectrum are explored. Among all launched samples, the probability of the channel of non-charge transfer scattering and charge transfer scattering is about 80%, hinting that the probability of fragmentation is about 20%. The reaction channel of proton exchange process 2 is taken as an example to exhibit the detailed microscopic dynamics of the collision process by inspecting the positions, the respective distance, the number of loss of electrons and the evolution of the electron density. The study of the mass distribution and the fragmentation mass spectrum shows that among all possible fragments, the fragment with mass 36 has the highest relative abundance of 65%. The relative abundances of fragments with masses 1, 35, and 34 are 20%, 13%, and 1.5%, respectively. For the total electron capture cross section, the present calculations agree with the available measurements and calculations over the energy range from 50 eV to 12 keV.

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

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Fast population transfer with a superconducting qutrit via non-Hermitian shortcut to adiabaticity Xin-Ping Dong(董新平), Zhi-Bo Feng(冯志波), Xiao-Jing Lu(路晓静), Ming Li(李明), and Zheng-Yin Zhao(赵正印) Chin. Phys. B, 2023, 32 (3):  034201.  DOI: 10.1088/1674-1056/ac8926 Abstract ( 40 )   PDF (581KB) ( 14 )   Non-Hermitian dissipation dynamics, capable of turning the conventionally detrimental decoherence effects to useful resources for state engineering, is highly attractive to quantum information processing. In this work, an effective scheme is developed for implementing fast population transfer with a superconducting qutrit via the non-Hermitian shortcut to adiabaticity (STA). We first deal with a Λ-configuration interaction between the qutrit and microwave drivings, in which the dephasing-assisted qubit state inversion requiring an overlarge dephasing rate is constructed non-adiabatically. After introducing a feasible ancillary driving that directly acts upon the qubit states, the target state transfer can be well realized but with an accessible qubit dephasing rate. Moreover, a high fidelity could be numerically obtained in the considered system. The strategy could provide a new route towards the non-Hermitian shortcut operations on superconducting quantum circuits.

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Impact of amplified spontaneous emission noise on the SRS threshold of high-power fiber amplifiers Wei Liu(刘伟), Shuai Ren(任帅), Pengfei Ma(马鹏飞), and Pu Zhou(周朴) Chin. Phys. B, 2023, 32 (3):  034202.  DOI: 10.1088/1674-1056/ac833e Abstract ( 35 )   PDF (1461KB) ( 10 )   Impact of amplified spontaneous emission (ASE) noise on the stimulated Raman scattering (SRS) threshold of high-power fiber amplifiers is demonstrated numerically through a spectral evolution approach. The simulation results confirm that ASE noise in the Raman wavelength band could reduce the SRS threshold of high-power fiber amplifiers significantly. As for ASE noise originated the main amplifier, it becomes stronger and reduces the SRS threshold at shorter operation wavelength below 1052 nm. As for ASE noise originated from the seed laser, it reduces the SRS threshold at different operation wavelength under the condition that the Raman ratio is over -90 dB in the seed laser. The theoretical method and results in this work could provide a well reference to extend the operation wavelength of high-power fiber lasers.

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Mid-infrared lightly Er3+-doped CaF2 laser under acousto-optical modulation Yuan-Hao Zhao(赵元昊), Meng-Yu Zong(宗梦雨), Jia-Hao Dong(董佳昊), Zhen Zhang(张振), Jing-Jing Liu(刘晶晶), Jie Liu(刘杰), and Liang-Bi Su(苏良碧) Chin. Phys. B, 2023, 32 (3):  034203.  DOI: 10.1088/1674-1056/aca4c0 Abstract ( 38 )   PDF (1226KB) ( 10 )   A 1.7-at.% Er:CaF2 crystal was synthesized by temperature gradient method. The Er:CaF2 crystal was applied in acousto-optically Q-switched laser at mid-infrared region for the first time. Using a TeO2-based crystal as Q-switcher, we obtained a laser diode (LD) end-pumped Er:CaF2 laser with the highest single pulse energy up to 0.49 mJ and maximum peak power of 0.56 kW under 6.34-W absorbed pump power. The implication of these results is that the low-doped Er:CaF2 crystal exhibits promising optical properties in solid-state lasers.

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Spectral shift of solid high-order harmonics from different channels in a combined laser field Dong-Dong Cao(曹冬冬), Xue-Fei Pan(潘雪飞), Jun Zhang(张军), and Xue-Shen Liu(刘学深) Chin. Phys. B, 2023, 32 (3):  034204.  DOI: 10.1088/1674-1056/aca4bf Abstract ( 65 )   PDF (2434KB) ( 37 )   We investigate theoretically the spectral shift of the high-order harmonic generation (HHG) in ZnO driven by a combined laser field by solving the two-band semiconductor Bloch equations (SBEs) in the velocity gauge. The combined laser field is synthesized by a fundamental laser pulse and its seventh-frequency laser pulse. When the seventh-frequency laser pulse is added to the rising or falling parts of the fundamental laser field, we find that the spectral blueshift or redshift appears, which is due to the unequal contribution of the rising and falling parts in the fundamental laser field to the harmonics. By analyzing the time-dependent conduction band population in k space, we found that, in addition to the tunneling ionization channel, there is also the resonant electron injection channels which is induced by the seventh-frequency laser pulse. The harmonics generated by the different channels show the spectral redshift or the spectral blueshift, respectively. Through analyzing the k-integrated transient conduction band population of the electrons from different channels, we found that if there is a certain delay in the process of the electron excitation, it will lead to the delay in the harmonic emission, which results in the spectral redshift of the harmonics.

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A kind of multiwavelength erbium-doped fiber laser based on Lyot filter Zhehai Zhou(周哲海), Jingyi Wu(吴婧仪), Kunlong Min(闵昆龙), Shuang Zhao(赵爽), and Huiyu Li(李慧宇) Chin. Phys. B, 2023, 32 (3):  034205.  DOI: 10.1088/1674-1056/ac872b Abstract ( 31 )   PDF (2119KB) ( 8 )   A multiwavelength tunable ring-cavity erbium-doped fiber laser (EDFL) based on a Lyot filter was presented. For the proposed Lyot filter, a comb filter consisting of an EDF-polarization-maintaining fiber (EDF-PMF), a polarization controller (PC), and a circulator with four ports was used to suppress the mode competition. The light transmission direction was guaranteed by the circulator. For the proposed fiber laser, tunable single, dual, triple, quadruple, quintuple, sextuple, and septuple wavelengths were realized. A single-wavelength laser output with an optical signal-to-noise ratio (SNR) of up to 30.56 dB was realized, and a tuning range of 1590.54 nm to 1599.54 nm was achieved by tuning the PC. The stability of the single, dual, triple, and quadruple-wavelength center power fluctuations was less than 0.05 dB, 0.98 dB, 5.07 dB, and 7.71 dB respectively. When the laser was operated in the multiwavelength condition, the SNR was more than 20.97 dB. The proposed erbium-doped fiber laser is suitable for fiber-sensing system applications.

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Continuous-wave optical enhancement cavity with 30-kW average power Xing Liu(柳兴), Xin-Yi Lu(陆心怡), Huan Wang(王焕), Li-Xin Yan(颜立新), Ren-Kai Li(李任恺), Wen-Hui Huang(黄文会), Chuan-Xiang Tang(唐传祥), Ronic Chiche, and Fabian Zomer Chin. Phys. B, 2023, 32 (3):  034206.  DOI: 10.1088/1674-1056/ac873e Abstract ( 24 )   PDF (2590KB) ( 14 )   Optical enhancement cavity (OEC) is a powerful tool for fundamental research and diagnostics. In this paper, the progress of a continuous-wave OEC to realize of megawatt cavity for a novel light source based on a steady-state microbunching (SSMB) mechanism, is reported. After efficiently suppressing all external noise and optimizing the alignment, mode-matching, and polarization matching, stable and long-term locking is achieved with the help of two feedback loops. The modal instability phenomenon caused by the surface thermoelastic deformation is observed. A pair of D-shape mirrors are utilized to remove the high-order modes. Finally, an intra-cavity average power of 30 kW is reached.

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Numerical simulation of a truncated cladding negative curvature fiber sensor based on the surface plasmon resonance effect Zhichao Zhang(张志超), Jinhui Yuan(苑金辉), Shi Qiu(邱石), Guiyao Zhou(周桂耀), Xian Zhou(周娴), Binbin Yan(颜玢玢), Qiang Wu(吴强), Kuiru Wang(王葵如), and Xinzhu Sang(桑新柱) Chin. Phys. B, 2023, 32 (3):  034208.  DOI: 10.1088/1674-1056/ac785e Abstract ( 33 )   PDF (1788KB) ( 14 )   A refractive index (RI) sensor based on the surface plasmon resonance effect is proposed using a truncated cladding negative curvature fiber (TC-NCF). The influences of the TC-NCF structure parameters on the sensing performances are investigated and compared with the traditional NCF. The simulation results show that the proposed TC-NCF RI sensor has an ultra-wide detection range from 1.16 to 1.43. The maximum wavelength sensitivity reaches 12400 nm/RIU, and the corresponding R2 of the polynomial fitting equation is 0.9999. The maximum and minimum resolutions are 2.56×10-5 and 8.06×10-6, respectively. In addition, the maximum amplitude sensitivity can reach -379.1 RIU-1 when the RI is chosen as 1.43. The proposed TC-NCF RI sensor could be useful in biochemical medicine, environmental monitoring, and food safety.

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Anti-symmetric sampled grating quantum cascade laser for mode selection Qiangqiang Guo(郭强强), Jinchuan Zhang(张锦川), Fengmin Cheng(程凤敏), Ning Zhuo(卓宁), Shenqiang Zhai(翟慎强), Junqi Liu(刘俊岐), Lijun Wang(王利军),Shuman Liu(刘舒曼), and Fengqi Liu(刘峰奇) Chin. Phys. B, 2023, 32 (3):  034209.  DOI: 10.1088/1674-1056/ac7291 Abstract ( 49 )   PDF (1830KB) ( 12 )   For mode selection in a quantum cascade laser (QCL), we demonstrate an anti-symmetric sampled grating (ASG). The wavelength of the -1-th mode of this laser has been blue-shifted more than 75 nm (～ 10 cm-1) compared with that of an ordinary sampled grating laser with an emission wavelength of approximately 8.6 μm, when the periodicities within both the base grating and the sample grating are kept constant. Under this condition, an improvement in the continuous tuning capability of the QCL array is ensured. The ASG structure is fabricated in holographic exposure and optical photolithography, thereby enhancing its flexibility, repeatability, and cost-effectiveness. The wavelength modulation capability of the two channels of the grating is insensitive to the variations in channel size, assuming that the overall waveguide width remains constant. The output wavelength can be tailored freely within a certain range by adjusting the width of the ridge and the material of the cladding layer.

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Ghost imaging based on the control of light source bandwidth Zhao-Qi Liu(刘兆骐), Yan-Feng Bai(白艳锋), Xuan-Peng-Fan Zou(邹璇彭凡), Li-Yu Zhou(周立宇), Qin Fu(付芹), and Xi-Quan Fu(傅喜泉) Chin. Phys. B, 2023, 32 (3):  034210.  DOI: 10.1088/1674-1056/ac6edd Abstract ( 26 )   PDF (2010KB) ( 9 )   A scheme to improve the quality in ghost imaging (GI) by controlling the bandwidth of light source (BCGI) is proposed. The theoretical and numerical results show that the reconstruction result with high quality can be obtained by adjusting the bandwidth range of the light source appropriately, and the selection criterion of the bandwidth is analyzed by the power distribution of the imaging target. A proof-of-principle experiment is implemented to verify the theoretical and numerical results. In addition, the BCGI also presents better anti-noise performance when compared with some popular GI methods.

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A three-band perfect absorber based on a parallelogram metamaterial slab with monolayer MoS2 Wen-Jing Zhang(张雯婧), Qing-Song Liu(刘青松), Bo Cheng(程波), Ming-Hao Chao(晁明豪),Yun Xu(徐云), and Guo-Feng Song(宋国峰) Chin. Phys. B, 2023, 32 (3):  034211.  DOI: 10.1088/1674-1056/ac9047 Abstract ( 17 )   PDF (872KB) ( 6 )   As a two-dimensional (2D) material, monolayer MoS2 which limits its optical applications has a low absorption efficiency. In this paper, we propose a three-band perfect metamaterial absorber in the visible light range based on monolayer MoS2. The peak absorptivity of the structure at each resonance wavelength is nearly perfect, moreover, the light absorption of monolayer MoS2 is obviously enhanced at the three resonant wavelengths. The dielectric-dielectric-metal structure we designed produces the coupling of Fabry-Perot resonance and high-order diffraction guided-mode resonance at different absorption peaks, which has been proved by the slab waveguide theory. In addition, the multi-modal absorption phenomenon is explained by extracting the equivalent impedance. The results show that we can adjust the absorption peak wavelength by regulating the parameters of the structure. This structure not only provides an idea for enhancing the interaction between light and two-dimensional materials but also has potential applications for optical detection devices.

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Giant saturation absorption of tungsten trioxide film prepared based on the seedless layer hydrothermal method Xiaoguang Ma(马晓光), Fangzhen Hu(胡芳珍), Xi Chen(陈希), Yimeng Wang(王艺盟), Xiaojian Hao(郝晓剑), Min Gu(顾敏), and Qiming Zhang(张启明) Chin. Phys. B, 2023, 32 (3):  034212.  DOI: 10.1088/1674-1056/acaf2a Abstract ( 25 )   PDF (1204KB) ( 6 )   Nonlinear materials have gained wide interest as saturable absorbers and pulse compression for pulsed laser applications due to their unique optical properties. This work investigates the third-order nonlinear phenomenon of tungsten trioxide (WO$_{3}$) thin films. The giant nonlinear absorption and nonlinear refractive index of WO$_{3}$ thin films were characterized by $Z$-scan method at 800 nm. We experimentally observed the giant saturable absorption (SA) and nonlinear refractive index of WO$_{3}$ thin films prepared by the seedless layer hydrothermal method, with SA coefficient being as high as $-2.59\times 10 ^{5}$ cm$\cdot$GW$^{-1}$. The SA coefficient is at least one order of magnitude larger than those of the conventional semiconductors. The nonlinear refractive index $n_{2}$ of WO$_{3}$ film has been observed for the first time in recent studies and the corresponding coefficient can be up to 1.793 cm$^{2}\cdot$GW$^{-1}$. The large third-order nonlinear optical (NLO) response enables WO$_{3}$ thin films to be promising candidates for optoelectronic and photonic applications in the near-infrared domain.

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A 3-5 μm broadband YBCO high-temperature superconducting photonic crystal Gang Liu(刘刚), Yuanhang Li(李远航), Baonan Jia(贾宝楠), Yongpan Gao(高永潘), Lihong Han(韩利红), Pengfei Lu(芦鹏飞), and Haizhi Song(宋海智) Chin. Phys. B, 2023, 32 (3):  034213.  DOI: 10.1088/1674-1056/acb760 Abstract ( 16 )   PDF (1230KB) ( 7 )   Photonic crystal structures have excellent optical properties, so they are widely studied in conventional optical materials. Recent research shows that high-temperature superconducting periodic structures have natural photonic crystal features and they are favourable candidates for single-photon detection. Considering that superconductors have completely different properties from conventional optical materials, we study the energy level diagram and mid-infrared 3 μm-5 μm transmission spectrum of two-dimensional superconducting photonic crystals in both superconducting and quenched states with the finite element method. The energy level diagram of the circular crystal column superconducting structure shows that the structure has a large band gap width in both states. At the same fill factor, the circular crystal column superconducting structure has a larger band gap width than the others structures. For lattice structures, the zero transmission point of the square lattice structure is robust to the incident angle and environmental temperature. Our research has guiding significance for the design of new material photonic crystals, photon modulation and detection.

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Response characteristics of drill-string guided wave in downhole acoustic telemetry Ao-Song Zhao(赵傲耸), Hao Chen(陈浩), Xiao He(何晓), Xiu-Ming Wang(王秀明), and Xue-Shen Cao(曹雪砷) Chin. Phys. B, 2023, 32 (3):  034301.  DOI: 10.1088/1674-1056/ac8e98 Abstract ( 46 )   PDF (1988KB) ( 11 )   Modeling of a drill-string acoustic channel has been an important topic in downhole telemetry for a long time. The propagation of drill-string guided waves in the borehole contains excitation, attenuation, and mode conversion issues that have not been considered by existing modeling methods. In this article, we formulate a hybrid modeling method to investigate the response characteristics of a fundamental-mode drill-string wave in various borehole environments. This hybrid method provides channel functions, including transmitting and receiving deployments, periodicity of the structure, and formation property changes. The essential physics of the drill-string wave propagation is captured with a one-dimensional model. The analytical solutions of the wavefield in multilayered cylindrical structures are introduced into a propagation matrix to express drill-string-wave interactions with the borehole environments. The effectiveness of the proposed method is confirmed through comparison with the finite-difference method. In addition, by designing numerical models, we investigate the conversion effect of the drill-string wave at the tool joint. We demonstrate that the conversion intensity of the drill-string wave is positively correlated not only with the cross-sectional area of the tool joint but also with the wave impedance of the outer formation. Hard formation outside the borehole reduces the energy leakage while intensifying the conversion of drill-string waves to Stoneley waves, and the opposite is true for the drill string in an infinite fluid. The converted Stoneley waves interfere with the drill-string waves, resulting in variations of bandgap distribution, which challenges the reliability of the data transmission.

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Acoustic propagation uncertainty in internal wave environments using an ocean-acoustic joint model Fei Gao(高飞), Fanghua Xu(徐芳华), Zhenglin Li(李整林), Jixing Qin(秦继兴), and Qinya Zhang(章沁雅) Chin. Phys. B, 2023, 32 (3):  034302.  DOI: 10.1088/1674-1056/ac89dc Abstract ( 30 )   PDF (5640KB) ( 15 )   An ocean-acoustic joint model is developed for research of acoustic propagation uncertainty in internal wave environments. The internal waves are numerically produced by tidal forcing over a continental slope using an ocean model. Three parameters (i.e., internal wave, source depth, and water depth) contribute to the dynamic waveguide environments, and result in stochastic sound fields. The sensitivity of the transmission loss (TL) to environment parameters, statistical characteristics of the TL variation, and the associated physical mechanisms are investigated by the Sobol sensitivity analysis method, the Monte Carlo sampling, and the coupled normal mode theory, respectively. The results show that the TL is most sensitive to the source depth in the near field, resulted from the initial amplitudes of higher-order modes; while in middle and far fields, the internal waves are responsible for more than 80% of the total acoustic propagation contribution. In addition, the standard deviation of the TL in the near field and the shallow layer is smaller than those in the middle and far fields and the deep layer.

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Tunable topological interface states and resonance states of surface waves based on the shape memory alloy Shao-Yong Huo(霍绍勇), Long-Chao Yao(姚龙超), Kuan-Hong Hsieh(谢冠宏), Chun-Ming Fu(符纯明), Shih-Chia Chiu(邱士嘉), Xiao-Chao Gong(龚小超), and Jian Deng(邓健) Chin. Phys. B, 2023, 32 (3):  034303.  DOI: 10.1088/1674-1056/ac8727 Abstract ( 17 )   PDF (2214KB) ( 7 )   Topological interface state (TIS) of elastic wave has attracted significant research interest due to its potential prospects in strengthening acoustic energy and enhancing the signal accuracy of damage identification and quantification. However, previous implementations on the interface modes of surface waves are limited to the non-adjustable frequency band and unalterable mode width. Here, we demonstrate the tunable TIS and topological resonance state (TRS) of Rayleigh wave by using a shape memory alloy (SMA) stubbed semi-infinite one-dimensional (1D) solid phononic crystals (PnCs), which simultaneously possesses the adjustable mode width. The mechanism of tunability stems from the phase transformation of the SMA between the martensite at low temperature and the austenite at high temperature. The tunable TIS of Rayleigh wave is realized by combining two bandgap-opened PnCs with different Zak phases. The TRS with adjustable mode width is achieved in the heterostructures by adding PnCs with Dirac point to the middle of two bandgap-opened PnCs with different Zak phases, which exhibits the extraordinary robustness in contrast to the ordinary Fabry-Pérot resonance state. This research provides new possibilities for the highly adjustable Rayleigh wave manipulation and find promising applications such as tunable energy harvesters, wide-mode filters, and high-sensitivity Rayleigh wave detectors.

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Effect of bio-tissue deformation behavior due to intratumoral injection on magnetic hyperthermia Yundong Tang(汤云东), Jian Zou(邹建), Rodolfo C.C. Flesch, and Tao Jin(金涛) Chin. Phys. B, 2023, 32 (3):  034304.  DOI: 10.1088/1674-1056/ac744c Abstract ( 22 )   PDF (4255KB) ( 17 )   Thermal damage of malignant tissue is generally determined not only by the characteristics of bio-tissues and nanoparticles but also the nanofluid concentration distributions due to different injection methods during magnetic hyperthermia. The latter has more advantages in improving the therapeutic effect with respect to the former since it is a determining factor for the uniformity of nanofluid concentration distribution inside the tumor region. This study investigates the effect of bio-tissue deformation due to intratumoral injection on the thermal damage behavior and treatment temperature distribution during magnetic hyperthermia, in which both the bio-tissue deformation due to nanofluid injection and the mass diffusion after injection behavior are taken into consideration. The nanofluid flow behavior is illustrated by two different theoretical models in this study, which are Navier-Stokes equation inside syringe needle and modified Darcy's law inside bio-tissue. The diffusion behavior after nanofluid injection is expressed by a modified convection-diffusion equation. A proposed three-dimensional liver model based on the angiographic data is set to be the research object in this study, in which all bio-tissues are assumed to be deformable porous media. Simulation results demonstrate that the injection point for syringe needle can generally achieve the maximum value in the tissue pressure, deformation degree, and interstitial flow velocity during the injection process, all of which then drop sharply with the distance away from the injection center. In addition to the bio-tissue deformation due to injection behavior, the treatment temperature is also highly relevant to determine both the diffusion duration and blood perfusion rate due to the thermal damage during the therapy.

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Wideband frequency-dependent dielectric properties of rat tissues exposed to low-intensity focused ultrasound in the microwave frequency range Xue Wang(王雪), Shi-Xie Jiang, Lin Huang(黄林), Zi-Hui Chi(迟子惠), Dan Wu(吴丹), and Hua-Bei Jiang Chin. Phys. B, 2023, 32 (3):  034305.  DOI: 10.1088/1674-1056/ac7453 Abstract ( 9 )   PDF (1304KB) ( 4 )   Tissue dielectric properties can vary upon the incident of an acoustic wave. The goal of this study is to quantify this change due to the acoustoelectric effect (AE), and to obtain the frequency-dependent dielectric properties of tissues exposed to low-intensity focused ultrasound (LIFU). The dielectric properties of the blood, brain, chest muscle, heart, kidney, leg muscle, liver, lung, pancreas, and spleen of rats were measured by an open-ended coaxial probe method. The acoustic intensity of LIFU focus was 2.97 MPa (67.6 W/cm2), 3.95 MPa (120 W/cm2), and 5.17 MPa (204 W/cm2), respectively, and the measurement frequency band was 0.1-7.08 GHz. The measurement results show that with the LIFU modulation, the conductivity and dielectric constant decreased in the high-frequency band, and on the contrary, they increased in the low-frequency band, and the larger the acoustic intensity was, the more obvious the phenomenon was. This work contributes to a better understanding of the mechanisms by which ultrasound acts on the dielectric properties of biological tissues. It is expected that the findings from this study will provide a basis that the response of tissue to LIFU modulation can be monitored by noninvasive techniques such as microwave-induced thermoacoustic imaging (MTI) and microwave imaging, present a new idea for improving the endogenous contrast between different biological tissues in MTI and acoustoelectric imaging, and possibly lead to the development of a new imaging method based on the relaxation time of tissue after LIFU modulation.

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Reconfigurable source illusion device for airborne sound using an enclosed adjustable piezoelectric metasurface Yi-Fan Tang(唐一璠) and Shu-Yu Lin(林书玉) Chin. Phys. B, 2023, 32 (3):  034306.  DOI: 10.1088/1674-1056/ac9fc0 Abstract ( 23 )   PDF (4413KB) ( 11 )   Source illusion is an important issue in acoustic fields that has significant applications in various practical scenarios. Recent progress in acoustic metasurfaces has broken the limitation of manipulating large-scale waves at subwavelength scales and enables a better illusion capability, while there is still a problem that most previous studies are hampered by a lack of tuning capability. Here we propose a reconfigurable source illusion device capable of providing azimuthally-dependent phase delay in real-time via changing the static voltage distribution. The resulting device is implemented by employing an adjustable piezoelectric metasurface with a subwavelength thickness that can achieve a full 2π -phase shift while maintaining efficient transmittance. The effectiveness of our mechanism is demonstrated via two distinctive source illusion phenomena of shifting and transforming a simple point source without changing the device geometry. We anticipate that our methodology, which does not require a large device size or a complicated phased array, will open up new avenues for the miniaturization and integration of source illusion devices and may promote their on-chip applications in a variety of fields, such as acoustic camouflage and manipulation precision.

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Resistance law of a rod penetrating a multilayer granular raft Zonglin Li(李宗霖), Qiang Tian(田强), and Haiyan Hu(胡海岩) Chin. Phys. B, 2023, 32 (3):  034501.  DOI: 10.1088/1674-1056/aca5ff Abstract ( 44 )   PDF (2800KB) ( 13 )   This paper presents an experimental study on the resistance law of a rod vertically penetrating different kinds of multilayer granular rafts with a constant velocity so as to reveal the mechanical properties of the multilayer granular rafts. The resistance was quasi-static under the chosen velocity. Experiments were conducted with different granular thicknesses, rod diameters and combinations of particles and liquids. The study shows that the resistance-displacement relation of the rod has three smooth stages. In the first stage, the resistance rapidly increased. In the second stage, the resistance curve maintained an almost constant slope. In the third stage, the resistance smoothly changed with its slope continuously increasing. Based on the corresponding physical models for each stage, the study reveals the exponential dependence of the load-bearing capacity of the multilayer granular raft on its thickness, and clarifies the capillary effects on the resistance law. The study extends the knowledge of the granular raft from monolayer to multilayer structure.

PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES

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Intense low-noise terahertz generation by relativistic laser irradiating near-critical-density plasma Shijie Zhang(张世杰), Weimin Zhou(周维民), Yan Yin(银燕), Debin Zou(邹德滨), Na Zhao(赵娜), Duan Xie(谢端), and Hongbin Zhuo(卓红斌) Chin. Phys. B, 2023, 32 (3):  035201.  DOI: 10.1088/1674-1056/ac872c Abstract ( 31 )   PDF (927KB) ( 6 )   Low-noise terahertz (THz) radiation over 100 MV/cm generation by a linearly-polarized relativistic laser pulse interacting with a near-critical-density (NCD) plasma slab is studied by theory and particle-in-cell (PIC) simulations. A theoretical model is established to examine the dipole-like radiation emission. The THz radiation is attributed to the single-cycle low-frequency surface current, which is longitudinally constrained by the quasi-equilibrium established by the laser ponderomotive force and the ponderomotively induced electrostatic force. Through theoretical analysis, the spatiotemporal characteristics, polarization property of the THz radiation, and the relation between the radiation strength with the initial parameters of driving laser and plasma are obtained, which are in good consistence with the PIC simulation results. Furthermore, it is found by PIC simulations that the generation of thermal electrons can be suppressed within the appropriate parameter regime, resulting in a clear THz radiation waveform. The appropriate parameter region is given for generating a low-noise intense THz radiation with peak strength reaching 100 MV/cm, which could find potential applications in nonlinear THz physics.

CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

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Atomic simulations of primary irradiation damage in U-Mo-Xe system Wen-Hong Ouyang(欧阳文泓), Jian-Bo Liu(刘剑波), Wen-Sheng Lai(赖文生),Jia-Hao Li(李家好), and Bai-Xin Liu(柳百新) Chin. Phys. B, 2023, 32 (3):  036101.  DOI: 10.1088/1674-1056/ac9366 Abstract ( 15 )   PDF (1253KB) ( 8 )   To shed a light on Xe bubble nucleation in U-Mo fuel from the view of primary irradiation damage, a reported U-Mo-Xe potential under the framework of embedded atom method has been modified within the range of short and intermediate atomic distance. The modified potential can better describe the interactions between energetic particles, and can accurately reproduce the threshold displacement energy surface calculated by the first-principles method. Then, molecular dynamics simulations of primary irradiation damage in U-Mo-Xe system have been conducted under different contents. The raise of Xe concentration brings about a remarkable promotion in residual defect quantity and generates bubbles in more over-pressured state, which suggests an acceleration of irradiation damage under the accumulation of the fission gas. Meanwhile, the addition of Mo considerably reduces the residual defect count and hinders irradiation-induced Xe diffusion especially at high contents of Xe, corroborating the importance of high Mo content in mitigation of irradiation damage and swelling behavior in U-Mo fuel. In particular, the variation of irradiation damage with respect to contents suggests a necessity of taking into account the influence of local components on defect evolution in mesoscale simulations.

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Investigation of spatial structure and sympathetic cooling in the 9Be+–40Ca+ bi-component Coulomb crystals Min Li(李敏), Yong Zhang(张勇), Qian-Yu Zhang(张乾煜), Wen-Li Bai(白文丽), Sheng-Guo He(何胜国), Wen-Cui Peng(彭文翠), and Xin Tong(童昕) Chin. Phys. B, 2023, 32 (3):  036402.  DOI: 10.1088/1674-1056/ac70b2 Abstract ( 32 )   PDF (2506KB) ( 6 )   We study the spatial structure and sympathetic cooling of the bi-component Coulomb crystal (CC), which consists of approximate 450 9Be+ ions and 450 40Ca+ ions with a mass ratio of 0.225 in a segmented linear ion trap. By two-dimensional imaging of the bi-component CC, the 9Be+ ions are found to be surrounded by the 40Ca+ ions in the radial direction with a separation ratio of ～ 2.0, and the axial length of the 9Be+ ions occupied area is much larger than that of the 40Ca+ ions occupied area. Combined with the previous experimental results, the structure of the 9Be+-40Ca+ CC shows the larger the difference in the mass-charge ratio, the larger the separation between the two species. The comparison of the fluorescence spectra of the 9Be+ ions in the bi-component CC and the pure CC indicates that the 9Be+ ions can be sympathetically cooled and stably localized by the laser-cooled 40Ca+ ions during the recording of the fluorescence spectrum.

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Atomistic insights into early stage corrosion of bcc Fe surfaces in oxygen dissolved liquid lead-bismuth eutectic (LBE-O) Ting Zhou(周婷), Xing Gao(高星), Zhiwei Ma(马志伟), Hailong Chang(常海龙), Tielong Shen(申铁龙), Minghuan Cui(崔明焕), and Zhiguang Wang(王志光) Chin. Phys. B, 2023, 32 (3):  036801.  DOI: 10.1088/1674-1056/ac834b Abstract ( 31 )   PDF (1068KB) ( 5 )   Classical molecular dynamics simulations with global neural network machine learning potential are used to study early stage oxidation and dissolution behaviors of bcc Fe surfaces contacting with stagnant oxygen dissolved liquid lead-bismuth eutectic (LBE-O). Both static and dynamic simulation results indicate that the early stage oxidation and dissolution behaviors of bcc Fe show strong orientation dependence under the liquid LBE environments, which may explain the experimental observations of uneven interface between iron-based materials and liquid LBE. Our investigations show that it is the delicate balance between the oxide growth and metal dissolution that leads to the observed corrosion anisotropy for bcc Fe contacting with liquid LBE-O.

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Strain engineering and hydrogen effect for two-dimensional ferroelectricity in monolayer group-IV monochalcogenides MX (M =Sn, Ge; X=Se, Te, S) Maurice Franck Kenmogne Ndjoko, Bi-Dan Guo(郭必诞), Yin-Hui Peng(彭银辉), and Yu-Jun Zhao(赵宇军) Chin. Phys. B, 2023, 32 (3):  036802.  DOI: 10.1088/1674-1056/ac744e Abstract ( 38 )   PDF (2518KB) ( 14 )   Two-dimensional (2D) ferroelectric compounds are a special class of materials that meet the need for devices miniaturization, which can lead to a wide range of applications. Here, we investigate ferroelectric properties of monolayer group-IV monochalcogenides $MX$ ($M ={\rm Sn}$, Ge; $X={\rm Se}$, Te, S) via strain engineering, and their effects with contaminated hydrogen are also discussed. GeSe, GeTe, and GeS do not go through transition up to the compressive strain of -5%, and consequently have good ferroelectric parameters for device applications that can be further improved by applying strain. According to the calculated ferroelectric properties and the band gaps of these materials, we find that their band gap can be adjusted by strain for excellent photovoltaic applications. In addition, we have determined the most stable hydrogen occupancy location in the monolayer SnS and SnTe. It reveals that H prefers to absorb on SnS and SnTe monolayers as molecules rather than atomic H. As a result, hydrogen molecules have little effect on the polarization and electronic structure of monolayer SnTe and SnS.

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Rational design of Fe/Co-based diatomic catalysts for Li-S batteries by first-principles calculations Xiaoya Zhang(张晓雅), Yingjie Cheng(程莹洁), Chunyu Zhao(赵春宇), Jingwan Gao(高敬莞), Dongxiao Kan(阚东晓), Yizhan Wang(王义展), Duo Qi(齐舵), and Yingjin Wei(魏英进) Chin. Phys. B, 2023, 32 (3):  036803.  DOI: 10.1088/1674-1056/aca6da Abstract ( 56 )   PDF (1398KB) ( 17 )   Fe/Co-based diatomic catalysts decorated on an N-doped graphene substrate are investigated by first-principles calculations to improve the electrochemical properties of Li-S batteries. Our results demonstrate that FeCoN8@Gra not only possesses moderate adsorption energies towards Li2Sn species, but also exhibits superior catalytic activity for both reduction and oxidation reactions of the sulfur cathode. Moreover, the metallic property of the diatomic catalysts can be well maintained after Li2Sn adsorption, which could help the sulfur cathode to maintain high conductivity during the whole charge-discharge process. Given these exceptional properties, it is expected that FeCoN8@Gra could be a promising diatomic catalyst for Li-S batteries and afford insights for further development of advanced Li-S batteries.

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Coexisting lattice contractions and expansions with decreasing thicknesses of Cu (100) nano-films Simin An(安思敏), Xingyu Gao(高兴誉), Xian Zhang(张弦), Xin Chen(陈欣), Jiawei Xian(咸家伟), Yu Liu(刘瑜), Bo Sun(孙博), Haifeng Liu(刘海风), and Haifeng Song(宋海峰) Chin. Phys. B, 2023, 32 (3):  036804.  DOI: 10.1088/1674-1056/ac76b5 Abstract ( 15 )   PDF (1014KB) ( 7 )   Lattice parameters are a basic quantity in material characterization, and a slight alteration in lattice parameters directly affects the properties of materials. However, there are still considerable controversies as to whether lattice expansion or contraction occurs in metallic nanomaterials with size reduction. Here, the size dependences of the lattice parameter and surface free energy of clean Cu (100) films are investigated via simulations. Lattice parameters of the exposed surfaces contract, whereas lattice expansion occurs along the direction perpendicular to the surfaces with decreasing film thicknesses. This is striking since the metallic bonds usually lack strong directionality, and it is always regarded that the lattice variations in all directions are consistent. The contraction parallel to the surface is more severe than the expansion perpendicular to the surface in films. The lattices change from cubic to tetragonal with decreasing film thickness. Consequently, common contractions and occasional expansions of the lattice parameters of Cu nanoparticles have been observed in previous experiments. Increasing free energy and surface free energy with decreasing thicknesses is the thermodynamic origin of the lattice variations. Our study therefore provides a comprehensive physical basis for the surface effects on the lattice variations.

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

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Coexistence of giant Rashba spin splitting and quantum spin Hall effect in H-Pb-F Wenming Xue(薛文明), Jin Li(李金), Chaoyu He(何朝宇), Tao Ouyang(欧阳滔), Xiongying Dai(戴雄英), and Jianxin Zhong(钟建新) Chin. Phys. B, 2023, 32 (3):  037101.  DOI: 10.1088/1674-1056/aca7eb Abstract ( 38 )   PDF (1742KB) ( 17 )   Rashba spin splitting (RSS) and quantum spin Hall effect (QSHE) have attracted enormous interest due to their great significance in the application of spintronics. In this work, we theoretically proposed a new two-dimensional (2D) material H-Pb-F with coexistence of giant RSS and quantum spin Hall effec by using the ab initio calculations. Our results show that H-Pb-F possesses giant RSS (1.21 eV·Å) and the RSS can be tuned up to 4.16 eV·Å by in-plane biaxial strain, which is a huge value among 2D materials. Furthermore, we also noticed that H-Pb-F is a 2D topological insulator (TI) duo to the strong spin-orbit coupling (SOC) interaction, and the large topological gap is up to 1.35 eV, which is large enough for for the observation of topological edge states at room temperature. The coexistence of giant RSS and quantum spin Hall effect greatly broadens the potential application of H-Pb-F in the field of spintronic devices.

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Plasmonic hybridization properties in polyenes octatetraene molecules based on theoretical computation Nan Gao(高楠), Guodong Zhu(朱国栋), Yingzhou Huang(黄映洲), and Yurui Fang(方蔚瑞) Chin. Phys. B, 2023, 32 (3):  037102.  DOI: 10.1088/1674-1056/ac891c Abstract ( 36 )   PDF (3564KB) ( 7 )   Relationship of plasmonic properties of multiple clusters to molecular interactions and properties of a single cluster or molecule have become increasingly important due to the continuous emergence of molecular and cluster devices or systems. A hybrid phenomenon similar to plasmonic nanoparticle hybridization exists between two molecules with plasmon excitation modes. We use linear-response time-dependent density functional theory, real-time propagation time-dependent density functional theory, the plasmonicity index, and transition contribution maps (TCMs) to identify the plasmon excitation modes for the linear polyenes octatetraene with -OH and -NH2 groups and analyze the hybridization characteristics using charge transitions. The results show that molecular plasmon hybridization exists when the two molecules are coupled. The TCM analysis shows that the plasmon modes and hybridization result from collective and single-particle excitation. The plasmon mode is stronger, and the individual properties of the molecules are maintained after coupling when there is extra charge depose in the molecules because the electrons are moving in the molecules. This study provides new insights into the molecular plasmon hybridization of coupled molecules.

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Prediction of one-dimensional CrN nanostructure as a promising ferromagnetic half-metal Wenyu Xiang(相文雨), Yaping Wang(王亚萍), Weixiao Ji(纪维霄), Wenjie Hou(侯文杰),Shengshi Li(李胜世), and Peiji Wang(王培吉) Chin. Phys. B, 2023, 32 (3):  037103.  DOI: 10.1088/1674-1056/acb200 Abstract ( 32 )   PDF (2674KB) ( 18 )   Searching for one-dimensional (1D) nanostructure with ferromagnetic (FM) half-metallicity is of significance for the development of miniature spintronic devices. Here, based on the first-principles calculations, we propose that the 1D CrN nanostructure is a FM half-metal, which can generate the fully spin-polarized current. The ab initio molecular dynamic simulation and the phonon spectrum calculation demonstrate that the 1D CrN nanostructure is thermodynamically stable. The partially occupied Cr-d orbitals endow the nanostructure with FM half-metallicity, in which the half-metallic gap (Δs) reaches up to 1.58 eV. The ferromagnetism in the nanostructure is attributed to the superexchange interaction between the magnetic Cr atoms, and a sizable magnetocrystalline anisotropy energy (MAE) is obtained. Moreover, the transverse stretching of nanostructure can effectively modulate Δs and MAE, accompanied by the preservation of half-metallicity. A nanocable is designed by encapsulating the CrN nanostructure with a BN nanotube, and the intriguing magnetic and electronic properties of the nanostructure are retained. These novel characteristics render the 1D CrN nanostructure as a compelling candidate for exploiting high-performance spintronic devices.

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High-temperature ferromagnetism and strong π-conjugation feature in two-dimensional manganese tetranitride Ming Yan(闫明), Zhi-Yuan Xie(谢志远), and Miao Gao(高淼) Chin. Phys. B, 2023, 32 (3):  037104.  DOI: 10.1088/1674-1056/acae7b Abstract ( 50 )   PDF (956KB) ( 24 )   Two-dimensional (2D) magnetic materials have attracted tremendous research interest because of the promising application in the next-generation microelectronic devices. Here, by the first-principles calculations, we propose a two-dimensional ferromagnetic material with high Curie temperature, manganese tetranitride MnN4 monolayer, which is a square-planar lattice made up of only one layer of atoms. The structure is demonstrated to be stable by the phonon spectra and the molecular dynamic simulations, and the stability is ascribed to the π-d conjugation between π orbital of N=N bond and d orbital of Mn. More interestingly, the MnN4 monolayer displays robust 2D ferromagnetism, which originates from the strong exchange couplings between Mn atoms due to the π-d conjugation. The high critical temperature of 247 K is determined by solving the Heisenberg model using the Monte Carlo method.

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Reverse gate leakage mechanism of AlGaN/GaN HEMTs with Au-free gate Xin Jiang(蒋鑫), Chen-Hao Li(李晨浩), Shuo-Xiong Yang(羊硕雄), Jia-Hao Liang(梁家豪), Long-Kun Lai(来龙坤), Qing-Yang Dong(董青杨), Wei Huang(黄威),Xin-Yu Liu(刘新宇), and Wei-Jun Luo(罗卫军) Chin. Phys. B, 2023, 32 (3):  037201.  DOI: 10.1088/1674-1056/ac8735 Abstract ( 65 )   PDF (1115KB) ( 26 )   The reverse gate leakage mechanism of W-gate and TiN-gate AlGaN/GaN high-electron-mobility transistors (HEMTs) with N2 plasma surface treatment is investigated using current-voltage (I-V) and capacitance-voltage (C-V) characteristics and theoretical calculation analysis. It is found that the main reverse gate leakage mechanism of both devices is the trap-assisted tunneling (TAT) mechanism in the entire reverse bias region (-30 V to 0 V). It is also found that the reverse gate leakage current of the W-gate AlGaN/GaN HEMTs is smaller than that of the TiN gate at high reverse gate bias voltage. Moreover, the activation energies of the extracted W-gate and TiN-gate AlGaN/GaN HEMTs are 0.0551 eV-0.127 eV and 0.112 eV-0.201 eV, respectively.

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Quantitative measurement of the charge carrier concentration using dielectric force microscopy Junqi Lai(赖君奇), Bowen Chen(陈博文), Zhiwei Xing(邢志伟), Xuefei Li(李雪飞), Shulong Lu(陆书龙), Qi Chen(陈琪), and Liwei Chen(陈立桅) Chin. Phys. B, 2023, 32 (3):  037202.  DOI: 10.1088/1674-1056/aca7e6 Abstract ( 69 )   PDF (1173KB) ( 14 )   The charge carrier concentration profile is a critical factor that determines semiconducting material properties and device performance. Dielectric force microscopy (DFM) has been previously developed to map charge carrier concentrations with nanometer-scale spatial resolution. However, it is challenging to quantitatively obtain the charge carrier concentration, since the dielectric force is also affected by the mobility. Here, we quantitative measured the charge carrier concentration at the saturation mobility regime via the rectification effect-dependent gating ratio of DFM. By measuring a series of n-type GaAs and GaN thin films with mobility in the saturation regime, we confirmed the decreased DFM-measured gating ratio with increasing electron concentration. Combined with numerical simulation to calibrate the tip-sample geometry-induced systematic error, the quantitative correlation between the DFM-measured gating ratio and the electron concentration has been established, where the extracted electron concentration presents high accuracy in the range of 4×1016 - 1×1018 cm-3. We expect the quantitative DFM to find broad applications in characterizing the charge carrier transport properties of various semiconducting materials and devices.

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Spin- and valley-polarized Goos-Hänchen-like shift in ferromagnetic mass graphene junction with circularly polarized light Mei-Rong Liu(刘美荣), Zheng-Fang Liu(刘正方), Ruo-Long Zhang(张若龙), Xian-Bo Xiao(肖贤波), and Qing-Ping Wu(伍清萍) Chin. Phys. B, 2023, 32 (3):  037301.  DOI: 10.1088/1674-1056/ac89e2 Abstract ( 52 )   PDF (1677KB) ( 16 )   We investigate the band structure and Goos-Hänchen-like shift in ferromagnetic mass graphene junction modulated by the circularly polarized light. It is found that both spin and valley-related energy gaps can be opened by employing the circularly polarized light and the exchange field in mass graphene. The valley-polarized Goos-Hänchen-like shift can be identified in the presence of circularly polarized light, and the spin-polarized Goos-Hänchen-like shift can be realized with introduction of exchange field in mass graphene. Furthermore, the spin and valley polarization-related Goos-Hänchen-like shift can be achieved by combination of circularly polarized light and exchange field in mass graphene. It is hopeful that our work will be more conducive for future applications in graphene polarization transport devices.

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Design and research of normally-off β-Ga2O3/4H-SiC heterojunction field effect transistor Meixia Cheng(程梅霞), Suzhen Luan(栾苏珍), Hailin Wang(王海林), and Renxu Jia(贾仁需) Chin. Phys. B, 2023, 32 (3):  037302.  DOI: 10.1088/1674-1056/aca39c Abstract ( 77 )   PDF (867KB) ( 61 )   Ga$_{2}$O$_{3}$ is difficult to achieve p-type doping, which further hinders the development of Ga$_{2}$O$_{3}$-based power devices and is not conducive to the development of new devices with high power density and low power consumption. This paper expounds a $\beta $-Ga$_{2}$O$_{3}$/4H-SiC heterojunction lateral metal-oxide-semiconductor field-effect transistor (HJFET), which can make better use of the characteristics of PN junction by adding p-doped SiC in the channel region. Compared with the conventional devices, the threshold voltage of the heterojunction metal-oxide-semiconductor field-effect transistor (MOSFET) is greatly improved, and normally-off operation is realized, showing a positive threshold voltage of 0.82 V. Meanwhile, the off-state breakdown voltage of the device is up to 1817 V, and the maximum transconductance is 15.3 mS/mm. The optimal PFOM is obtained by simulating the thickness, length and doping of the SiC in each region of the epitaxial layer. This structure provides a feasible idea for high performance $\beta $-Ga$_{2}$O$_{3 }$ MOSFET.

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Low-resistance ohmic contacts on InAlN/GaN heterostructures with MOCVD-regrown n+-InGaN and mask-free regrowth process Jingshu Guo(郭静姝), Jiejie Zhu(祝杰杰), Siyu Liu(刘思雨), Jielong Liu(刘捷龙), Jiahao Xu(徐佳豪), Weiwei Chen(陈伟伟), Yuwei Zhou(周雨威), Xu Zhao(赵旭), Minhan Mi(宓珉瀚), Mei Yang(杨眉), Xiaohua Ma(马晓华), and Yue Hao(郝跃) Chin. Phys. B, 2023, 32 (3):  037303.  DOI: 10.1088/1674-1056/ac891b Abstract ( 32 )   PDF (836KB) ( 26 )   This paper studied the low-resistance ohmic contacts on InAlN/GaN with metal-organic chemical vapor deposition (MOCVD) regrowth technique. The 150-nm regrown n+-InGaN exhibits a low sheet resistance of 31 Ω/□, resulting in an extremely low contact resistance of 0.102 Ω·mm between n+-InGaN and InAlN/GaN channels. Mask-free regrowth process was also used to significantly improve the sheet resistance of InAlN/GaN with MOCVD regrown ohmic contacts. Then, the diffusion mechanism between n+-InGaN and InAlN during regrowth process was investigated with electrical and structural characterizations, which could benefit the further process optimization.

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Thermoelectric signature of Majorana zero modes in a T-typed double-quantum-dot structure Cong Wang(王聪) and Xiao-Qi Wang(王晓琦) Chin. Phys. B, 2023, 32 (3):  037304.  DOI: 10.1088/1674-1056/ac92d3 Abstract ( 26 )   PDF (2024KB) ( 2 )   The thermoelectric effect of the system is theoretically investigated, by coupling Majorana zero mode to the T-typed double-quantum-dot-structure in different ways. It is found that when a single Majorana zero mode is coupled to one of the quantum dots (QDs), the thermoelectric efficiency is suppressed due to the leakage of Majorana zero modes into the QDs. When the Majorana zero mode is coupled to QD2, the suppression of the thermoelectric efficiency is more serious than that of QD1. Furthermore, when two Majorana zero modes are introduced simultaneously, suppression of the thermoelectric effect still takes place. We believe that such results can be candidates for the detection of Majorana bound states and help us understand the role of Majorana zero mode in thermoelectricity.

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Single-layer intrinsic 2H-phase LuX2 (X = Cl, Br, I) with large valley polarization and anomalous valley Hall effect Chun-Sheng Hu(胡春生), Yun-Jing Wu(仵允京), Yuan-Shuo Liu(刘元硕), Shuai Fu(傅帅),Xiao-Ning Cui(崔晓宁), Yi-Hao Wang(王易昊), and Chang-Wen Zhang(张昌文) Chin. Phys. B, 2023, 32 (3):  037306.  DOI: 10.1088/1674-1056/ac89d6 Abstract ( 61 )   PDF (2201KB) ( 20 )   Manipulation of the valley degree of freedom provides a new path for quantum information technology, but the real intrinsic large valley-polarization materials are rarely reported up to date. Here, we perform first-principles calculations to predict a class of 2H-phase single layer (SL) materials Lu$X_{2}$ ($X ={\rm Cl}$, Br, I) to be ideal candidates. SL-Lu$X_{2}$ are ferrovalley materials with a giant valley-polarization of 55 meV-148 meV as a result of its large spin-orbital coupling (SOC) and intrinsic ferromagnetism (FM). The magnetic transition temperatures of SL-LuI$_{2}$ and SL-LuCl$_{2}$ are estimated to be 89 K-124 K, with a sizable magnetic anisotropy at out-of-plane direction. Remarkably, the anomalous valley Hall effect (AVHE) can be controlled in SL-Lu$X_{2}$ when an external electric field is applied. Moreover, the intrinsic valley-polarization of SL-LuI$_{2}$ is highly robust for biaxial strain. These findings provide a promising ferrovalley material system for the experimentation of valleytronics and subsequent applications.

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Abnormal magnetoresistance effect in the Nb/Si superconductor-semiconductor heterojunction Zhi-Wei Hu(胡志伟) and Xiang-Gang Qiu(邱祥冈) Chin. Phys. B, 2023, 32 (3):  037401.  DOI: 10.1088/1674-1056/ac8af7 Abstract ( 39 )   PDF (835KB) ( 22 )   Ultrathin superconducting Nb films of about 8 nm thick have been deposited on heavily doped Si substrates through DC magnetron sputtering and then the high-quality Nb/Si superconductor-semiconductor heterojunctions have been fabricated by electron beam lithography and reactive ion etching. An abnormal magnetoresistance effect, which manifests itself as a zero field resistance peak under a magnetic field applied perpendicular to the interface, has been distinctly observed when the Nb film is in the superconductiing state. By considering the heterojunction interface being equivalent to the structure of superconductor-barrier layer-superconductor configuration, we could generally understand this unusual effect based on the Andreev reflection mechanism. Our results can be of help for the future development on compatibility and scalability of the silicon-based nanoscale superconducting devices for integrated circuits and superconducting quantum electronics.

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Flux pinning evolution in multilayer Pb/Ge/Pb/Ge/Pb superconducting systems Li-Xin Gao(高礼鑫), Xiao-Ke Zhang(张晓珂), An-Lei Zhang(张安蕾), Qi-Ling Xiao(肖祁陵), Fei Chen(陈飞), and Jun-Yi Ge(葛军饴) Chin. Phys. B, 2023, 32 (3):  037402.  DOI: 10.1088/1674-1056/ac89e1 Abstract ( 25 )   PDF (3754KB) ( 5 )   Multicomponent superconductors exhibit nontrivial vortex behaviors due to the various vortex-vortex interactions, including the competing one in the recently proposed type-1.5 superconductor. However, potential candidate that can be used to study the multicomponent superconductivity is rare. Here, we prepared an artificial superconducting multilayer to act as an alternative approach to study multicomponent superconductivity. The additional repulsive length and the coupling strength among superconducting films were regulated by changing the thickness of the insulting layer. The magnetization measurements were performed to clarify the effect of the competition between the repulsive vortex interactions on the macroscopic superconductivity. The vortex phase diagram and the optimum critical current density have been determined. Furthermore, a second magnetization effect is observed, and is attributed to the upper layer, which provides the weak pinning sites to localize the flux lines. The pinning behaviors switches to the mixed type with the increase of the insulting layer thicknesses. Our results open a new perspective to the study and related applications of the multilayer superconducting systems.

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Vortex bound states influenced by the Fermi surface anisotropy Delong Fang(方德龙) Chin. Phys. B, 2023, 32 (3):  037403.  DOI: 10.1088/1674-1056/ac8f32 Abstract ( 27 )   PDF (1483KB) ( 3 )   The spatial distribution of vortex bound states is often anisotropic, which is correlated with the underlying property of materials. In this work, we examine the effects of Fermi surface anisotropy on vortex bound states. The large-scale calculation of vortex bound states is introduced in the presence of fourfold or twofold Fermi surface by solving the Bogoliubov-de Gennes (BdG) equations. Two kinds of quasiparticles' behaviors can be extracted from the local density of states (LDOS) around a vortex. The angle-dependent quasiparticles will move from high energy to low energy when the angle varies from curvature maxima to minima of the Fermi surface, while the angle-independent quasiparticles tend to stay at a relatively higher energy. In addition, the weight of angle-dependent quasiparticles can be enhanced by the increasing anisotropy degree of Fermi surface.

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Li2NiSe2: A new-type intrinsic two-dimensional ferromagnetic semiconductor above 200 K Li-Man Xiao(肖丽蔓), Huan-Cheng Yang(杨焕成), and Zhong-Yi Lu(卢仲毅) Chin. Phys. B, 2023, 32 (3):  037501.  DOI: 10.1088/1674-1056/aca39f Abstract ( 45 )   PDF (2669KB) ( 23 )   By using first-principles electronic structure calculations, we propose a two-dimensional ferromagnetic semiconductor Li2NiSe2 with a Curie temperature above 200 K. The structure of monolayer Li2NiSe2 is dynamically stable, which is derived from the synthesized prototype compound Li2NiO2 and can be denoted as Li-decorated 1T-type NiSe2. The Ni-Se-Ni ferromagnetic superexchange dominates the magnetic couplings between the Ni atoms, which can be understood in the frame of the Goodenough-Kanamori-Anderson (GKA) rules. Our systematic study of monolayer Li2NiSe2 enables its promising applications in spintronics and suggests a new choice to design two-dimensional ferromagnetic semiconductors.

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Orbital torque of Cr-induced magnetization switching in perpendicularly magnetized Pt/Co/Pt/Cr heterostructures Hongfei Xie(谢宏斐), Yuhan Chang(常宇晗), Xi Guo(郭玺), Jianrong Zhang(张健荣), Baoshan Cui(崔宝山), Yalu Zuo(左亚路), and Li Xi(席力) Chin. Phys. B, 2023, 32 (3):  037502.  DOI: 10.1088/1674-1056/aca6d7 Abstract ( 46 )   PDF (1957KB) ( 22 )   The spin-orbit torque via the spin Hall effect of heavy metals has shown promising prospect in driving the magnetization switching in spintronic devices due to the generated spin current from heavy metals. Recently, the 3d-light metals have been predicted the ability to generate orbital current and the associated orbital torques from the orbital Hall effect. However, few experiments have been carried out since it is quite hard to directly detect the orbital current-generated orbital torque. Here, we report an effective method to demonstrate the strong orbital torques in light metal Cr through a conversion process from orbital current to spin current by introducing the Pt interfacial layer in perpendicularly magnetized symmetric Pt/Co/Pt structures. A quite large and monotonically growth of orbital torque efficiency in Pt/Co/Pt/Cr with the increase of the thickness of Cr layer is obtained with the largest effective orbital torque efficiency around 2.6 Oe/(MA·cm-2) (1 Oe=79.5775 A·m-1). The ability of orbital torque to drive the magnetization switching is also reported with the critical switching current density down to the order of 106 A·cm-2. Our findings prove the efficiency for switching the magnetization from light metal Cr layers through the orbital Hall effect.

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Enhanced and tunable Imbert-Fedorov shift based on epsilon-near-zero response of Weyl semimetal Ji-Peng Wu(伍计鹏), Yuan-Jiang Xiang(项元江), and Xiao-Yu Dai(戴小玉) Chin. Phys. B, 2023, 32 (3):  037503.  DOI: 10.1088/1674-1056/ac7f92 Abstract ( 50 )   PDF (6459KB) ( 14 )   We theoretically investigate the reflected spatial Imbert-Fedorov (IF) shift of transverse-electric (TE)-polarized beam illuminating on a bulk Weyl semimetal (WSM). The spatial IF shift is enhanced significantly at two different frequencies close to the epsilon-near-zero (ENZ) frequency, where large values of reflection coefficients $|r_{\rm pp}| / | r_{\rm ss}|$ are obtained due to the ENZ response induced different rapid increasing trends of $|r_{\rm pp}|$ and $| r_{\rm ss}|$. Particularly, the tunable ENZ effect with tilt degree of Weyl cones and Fermi energy enables the enhanced spatial IF shift at different frequencies. The enhanced spatial IF shift also shows the adjustability of WSM thickness, incident angle and Weyl node separation. Our findings provide easy and available methods to enlarge and adjust the reflected IF shift of TE-polarized light with a WSM.

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Structural evolution-enabled BiFeO3 modulated by strontium doping with enhanced dielectric, optical and superparamagneticproperties by a modified sol-gel method Sharon V S, Veena Gopalan E, and Malini K A Chin. Phys. B, 2023, 32 (3):  037504.  DOI: 10.1088/1674-1056/ac785b Abstract ( 34 )   PDF (886KB) ( 7 )   Multiferroic (BFO) nanoparticles doped with strontium with the general formula Bi$_{1-x}$Sr$_{x}$FeO$_{3}$ ($x=0$, 0.3, 0.5, 0.7) were synthesized using a modified sol-gel auto-combustion process. The structural, electrical, optical, and magnetic properties of the samples are discussed. The structural analysis, carried out using the x-ray powder diffraction technique, shows a structural transition from rhombohedral ($R$-$3c$) to cubic ($Pm$-$3m$) for the doping amount of strontium (Sr) equal to $x=0.3$. Morphological analysis of the prepared samples were carried out using scanning electron microscopy (SEM). Frequency-dependent dielectric constant and ac conductivity were studied. The doped samples, with improved dielectric properties, can be used to fabricate different optoelectronic devices. Strong dielectric dispersion and broad relaxation were exhibited by all the samples. Cole-Cole plots were employed as an effective tool to study the dispersion parameters, namely, the optical dielectric constant, static dielectric constant, relaxation time, and spreading factor. The activation energy was calculated from the relaxation peaks and Cole-Cole plots, which were found to be compatible with each other. The bandgap of the samples was calculated using diffuse reflectance spectral (DRS) analysis. Sharp and strong photoluminescence in the IR region was observed in the samples, similar to ZnO, which was reported for the first time. Room-temperature and low-temperature magnetization studies point towards the superparamagnetic nature of the samples, with an improvement in magnetic properties with doping. The antiferromagnetic behavior of bulk bismuth ferrite transforms to superparamagnetic in nature for both pure and Sr-substituted bismuth ferrite nanoparticles due to the close dimensions of crystallite size with magnetic domains leading to the break-down of the frustrated spin cycloidal moment.

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Spin pumping by higher-order dipole-exchange spin-wave modes Peng Wang(王鹏) Chin. Phys. B, 2023, 32 (3):  037601.  DOI: 10.1088/1674-1056/ac8922 Abstract ( 44 )   PDF (1034KB) ( 15 )   Spin pumping (SP) and inverse spin Hall effect (ISHE) driven by parametrically-excited dipole-exchange spin waves in a yttrium iron garnet film have been systematically investigated. The measured voltage spectrum exhibits a feature of the field-induced transition from parallel pumping to perpendicular pumping because of the inhomogeneous excitation geometry. Thanks to the high precision of the SP-ISHE detection, two sets of fine structures in the voltage spectrum are observed, which can correspond well to two kinds of critical points in the multimode spin-wave spectrum for magnetic films. One is the q = 0 point of each higher-order dispersion branch, and the other is the local minimum due to the interplay between the dipolar and exchange interactions. These fine structures on the voltage spectrum confirm the spin pumping by higher-order dipole-exchange spin-wave modes, and are helpful for probing the multimode spin-wave spectrum.

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Ferroelectricity induced by the absorption of water molecules on double helix SnIP Dan Liu(刘聃), Ran Wei(魏冉), Lin Han(韩琳), Chen Zhu(朱琛), and Shuai Dong(董帅) Chin. Phys. B, 2023, 32 (3):  037701.  DOI: 10.1088/1674-1056/ac7f8e Abstract ( 34 )   PDF (3433KB) ( 11 )   We study the ferroelectricity in a one-dimensional (1D) system composed of a double helix SnIP with absorbing water molecules. Our ab initio calculations reveal two factors that are critical to the electrical polarization. The first one is the orientation of polarized water molecules staying in the R2 region of SnIP. The second one is the displacement of I atom which roots from subtle interaction with absorbed water molecules. A reasonable scenario of polarization flipping is proposed in this study. In the scenario, the water molecule is rolling-up with keeping the magnitude of its electrical dipole and changing its direction, meanwhile, the displacement of I atoms is also reversed. Highly tunable polarization can be achieved by applying strain, with 26.5% of polarization enhancement by applying tensile strain, with only 4% degradation is observed with 4% compressive strain. Finally, the direct band gap is also found to be correlated with strain.

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Atomic-scale insights of indium segregation and its suppression by GaAs insertion layer in InGaAs/AlGaAs multiple quantum wells Shu-Fang Ma(马淑芳), Lei Li(李磊), Qing-Bo Kong(孔庆波), Yang Xu(徐阳), Qing-Ming Liu(刘青明), Shuai Zhang(张帅), Xi-Shu Zhang(张西数), Bin Han(韩斌), Bo-Cang Qiu(仇伯仓), Bing-She Xu(许并社), and Xiao-Dong Hao(郝晓东) Chin. Phys. B, 2023, 32 (3):  037801.  DOI: 10.1088/1674-1056/ac70b5 Abstract ( 31 )   PDF (2613KB) ( 8 )   The In segregation and its suppression in InGaAs/AlGaAs quantum well are investigated by using high-resolution x-ray diffraction (XRD) and photoluminescence (PL), combined with the state-of-the-art aberration corrected scanning transmission electron microscopy (Cs-STEM) techniques. To facility our study, we grow two multiple quantum wells (MQWs) samples, which are almost identical except that in sample B a thin GaAs layer is inserted in each of the InGaAs well and AlGaAs barrier layer comparing to pristine InGaAs/AlGaAs MQWs (sample A). Our study indeed shows the direct evidences that In segregation occurs in the InGaAs/AlGaAs interface, and the effect of the GaAs insertion layer on suppressing the segregation of In atoms is also demonstrated on the atomic-scale. Therefore, the atomic-scale insights are provided to understand the segregation behavior of In atoms and to unravel the underlying mechanism of the effect of GaAs insertion layer on the improvement of crystallinity, interface roughness, and further an enhanced optical performance of InGaAs/AlGaAs QWs.

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Crystal and electronic structure of a quasi-two-dimensional semiconductor Mg3Si2Te6 Chaoxin Huang(黄潮欣), Benyuan Cheng(程本源), Yunwei Zhang(张云蔚), Long Jiang(姜隆), Lisi Li(李历斯), Mengwu Huo(霍梦五), Hui Liu(刘晖), Xing Huang(黄星), Feixiang Liang(梁飞翔), Lan Chen(陈岚), Hualei Sun(孙华蕾), and Meng Wang(王猛) Chin. Phys. B, 2023, 32 (3):  037802.  DOI: 10.1088/1674-1056/aca393 Abstract ( 58 )   PDF (1360KB) ( 15 )   We report the synthesis and characterization of a Si-based ternary semiconductor Mg3Si2Te6, which exhibits a quasi-two-dimensional structure, where the trigonal Mg2Si2Te6 layers are separated by Mg ions. Ultraviolet-visible absorption spectroscopy and density functional theory calculations were performed to investigate the electronic structure. The experimentally determined direct band gap is 1.39 eV, consistent with the value of the density function theory calculations. Our results reveal that Mg3Si2Te6 is a direct gap semiconductor, which is a potential candidate for near-infrared optoelectronic devices.

INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY

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Suppression and compensation effect of oxygen on the behavior of heavily boron-doped diamond films Li-Cai Hao(郝礼才), Zi-Ang Chen(陈子昂), Dong-Yang Liu(刘东阳), Wei-Kang Zhao(赵伟康),Ming Zhang(张鸣), Kun Tang(汤琨), Shun-Ming Zhu(朱顺明), Jian-Dong Ye(叶建东),Rong Zhang(张荣), You-Dou Zheng(郑有炓), and Shu-Lin Gu(顾书林) Chin. Phys. B, 2023, 32 (3):  038101.  DOI: 10.1088/1674-1056/ac7f8a Abstract ( 34 )   PDF (935KB) ( 8 )   This work investigates the suppression and compensation effect of oxygen on the behaviors and characteristics of heavily boron-doped microwave plasma chemical vapor deposition (MPCVD) diamond films. The suppression effect of oxygen on boron incorporation is observed by an improvement in crystal quality when oxygen is added during the diamond doping process. A relatively low hole concentration is expected and verified by Hall effect measurements due to the compensation effect of oxygen as a deep donor in diamond. A low acceptor concentration, high compensation donor concentration and relatively larger acceptor ionization energy are then induced by the incorporation of oxygen; however, a heavily boron-doped diamond film with high crystal quality can also be expected. The formation of an oxygen-boron complex structure instead of oxygen substitution, as indicated by the results of x-ray photoelectron spectroscopy, is suggested to be more responsible for the observed enhanced compensation effect due to its predicted low formation energy. Meanwhile, density functional theory calculations show that the boron-oxygen complex structure is easily formed in diamond with a formation energy of -0.83 eV. This work provides a comprehensive understanding of oxygen compensation in heavily boron-doped diamond.

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Tuning the particle size, physical properties, and photocatalytic activity of Ag3PO4 materials by changing the Ag+/PO43- ratio Hung N M, Oanh L T M, Chung D P, Thang D V, Mai V T, Hang L T, and Minh N V Chin. Phys. B, 2023, 32 (3):  038102.  DOI: 10.1088/1674-1056/ac84ce Abstract ( 16 )   PDF (1053KB) ( 3 )   This study demonstrates the influence of the Ag+/PO43- ratio in precursor solution on the crystal structural formation, morphology, physical properties, and photocatalytic performance of a Ag3PO4 photocatalyst that is fabricated, using a facile precipitation method, from AgNO3 and Na2HPO4·12H2O. The material characterizations were carried out using x-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDX), Brunauer-Emmett-Teller (BET) surface area, Fourier transform infrared (FTIR) absorption, Raman scattering, x-ray photoelectron spectroscopy (XPS), UV-vis absorption, and photoluminescence (PL). The results show that Ag3PO4 crystallizes better when the excess PO43- content increases, and the lattice parameters decrease slightly, while the crystal diameter and the particle size increase. This change is also observed in the Raman scattering and FTIR spectra with the increase in the vibration frequency of the [PO4] group. The compression of the [PO4] unit was also confirmed in the XPS spectra with the shift of P 2p peaks toward higher binding energy. The photocatalytic results showed that the samples synthesized from excess PO43- solution exhibited higher photocatalytic performance compared to the sample with a Ag+/PO43- ratio of 3:1. A sample prepared from the precursor solution with a Ag+/PO43- ratio of 3:1.5 was optimal for RhB decomposition under both visible light and natural sunlight, completely decomposing 10 ppm RhB after 15 minutes of xenon lamp irradiation and after 60 minutes under solar light irradiation. This is attributed to the high crystallinity, small particle size and low electron-hole recombination rate of the sample.

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Observation of size-dependent boundary effects in non-Hermitian electric circuits Luhong Su(苏鹭红), Cui-Xian Guo(郭翠仙), Yongliang Wang(王永良), Li Li(李力), Xinhui Ruan(阮馨慧), Yanjing Du(杜燕京), Shu Chen(陈澍), and Dongning Zheng(郑东宁) Chin. Phys. B, 2023, 32 (3):  038401.  DOI: 10.1088/1674-1056/aca9c4 Abstract ( 52 )   PDF (2396KB) ( 17 )   The non-Hermitian systems with the non-Hermitian skin effect(NHSE) are very sensitive to the imposed boundary conditions and lattice sizes, which lead to size-dependent non-Hermitian skin effects. Here, we report the experimental observation of NHSE with different boundary conditions and different lattice sizes in the unidirectional hopping model based on a circuit platform. The circuit admittance spectra and corresponding eigenstates are very sensitive to the presence of the boundary. Meanwhile, our experimental results show how the lattice sizes and boundary terms together affect the strength of NHSE. Therefore, our electric circuit provides a good platform to observe size-dependent boundary effects in non-Hermitian systems.

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High performance carrier stored trench bipolar transistor with dual shielding structure Jin-Ping Zhang(张金平), Hao-Nan Deng(邓浩楠), Rong-Rong Zhu(朱镕镕), Ze-Hong Li(李泽宏), and Bo Zhang(张波) Chin. Phys. B, 2023, 32 (3):  038501.  DOI: 10.1088/1674-1056/ac873d Abstract ( 70 )   PDF (734KB) ( 24 )   We propose a novel high performance carrier stored trench bipolar transistor (CSTBT) with dual shielding structure (DSS-CSTBT). The proposed DSS-CSTBT features a double trench structure with different trench profiles in the surface, in which a shallow gate trench is shielded by a deep emitter trench and a thick oxide layer under it. Compared with the conventional CSTBT (con-CSTBT), the proposed DSS-CSTBT not only alleviates the negative impact of the shallow gate trench and highly doped CS layer on the breakdown voltage (BV), but also well reduces the gate-collector capacitance $C_{\rm GC}$, gate charge $Q_{\rm G}$, and turn-off loss $E_{\rm OFF}$ of the device. Furthermore, lower turn-on loss $E_{\rm ON}$ and gate drive loss $E_{\rm DR}$ are also obtained. Simulation results show that with the same CS layer doping concentration $N_{\rm CS}=1.5\times10^{16 }$ cm$^{-3}$, the BV increases from 1312 V of the con-CSTBT to 1423 V of the proposed DSS-CSTBT with oxide layer thickness under gate ($T_{\rm og2}$) of 1 μm. Moreover, compared with the con-CSTBT, the $C_{\rm GC}$ at $V_{\rm CE} $ of 25 V and miller plateau charge ($Q_{\rm GC}$) for the proposed DSS-CSTBT with $T_{\rm og2}$ of 1 μm are reduced by 79.4% and 74.3%, respectively. With the $V_{\rm GE} $ increases from 0 V to 15 V, the total $Q_{\rm G}$ for the proposed DSS-CSTBT with $T_{\rm og2}$ of 1 μm is reduced by 49.5%. As a result, at the same on-state voltage drop ($V_{\rm CEON}$) of 1.55 V, the $E_{\rm ON}$ and $E_{\rm OFF}$ are reduced from 20.3 mJ/cm$^{2}$ and 19.3 mJ/cm$^{2}$ for the con-CSTBT to 8.2 mJ/cm$^{2}$ and 9.7 mJ/cm$^{2}$ for the proposed DSS-CSTBT with $T_{\rm og2}$ of 1 μm, respectively. The proposed DSS-CSTBT not only significantly improves the trade-off relationship between the $V_{\rm CEON}$ and $E_{\rm OFF }$ but also greatly reduces the $E_{\rm ON}$.

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Analysis of high-temperature performance of 4H-SiC avalanche photodiodes in both linear and Geiger modes Xing-Ye Zhou(周幸叶), Yuan-Jie Lv(吕元杰), Hong-Yu Guo(郭红雨), Guo-Dong Gu(顾国栋), Yuan-Gang Wang(王元刚), Shi-Xiong Liang(梁士雄), Ai-Min Bu(卜爱民), and Zhi-Hong Feng(冯志红) Chin. Phys. B, 2023, 32 (3):  038502.  DOI: 10.1088/1674-1056/ac9820 Abstract ( 13 )   PDF (979KB) ( 4 )   The high-temperature performance of 4H-SiC ultraviolet avalanche photodiodes (APDs) in both linear and Geiger modes is extensively investigated. During the temperature-dependent measurements, a fixed bias voltage is adopted for the device samples, which is much more practical and important for high-temperature applications. The results show that the fabricated 4H-SiC APDs are very stable and reliable at high temperatures. As the temperature increases from room temperature to 425 K, the dark current at 95% of the breakdown voltage increases slightly and remains lower than 40 pA. In Geiger mode, our 4H-SiC APDs can be self-quenched in a passive-quenching circuit, which is expected for high-speed detection systems. Moreover, an interesting phenomenon is observed for the first time: the single-photon detection efficiency shows a non-monotonic variation as a function of temperature. The physical mechanism of the variation in high-temperature performance is further analyzed. The results in this work can provide a fundamental reference for researchers in the field of 4H-SiC APD ultraviolet detectors.

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High-performance extended short-wavelength infrared PBn photodetectors based on InAs/GaSb/AlSb superlattices Junkai Jiang(蒋俊锴), Faran Chang(常发冉), Wenguang Zhou(周文广), Nong Li(李农), Weiqiang Chen(陈伟强), Dongwei Jiang(蒋洞微), Hongyue Hao(郝宏玥), Guowei Wang(王国伟), Donghai Wu(吴东海), Yingqiang Xu(徐应强), and Zhi-Chuan Niu(牛智川) Chin. Phys. B, 2023, 32 (3):  038503.  DOI: 10.1088/1674-1056/acaa2e Abstract ( 63 )   PDF (1413KB) ( 26 )   High performance short-wavelength infrared PBn photodetectors based on InAs/GaSb/AlSb superlattices on GaSb substrate have been demonstrated. At 300 K, the device exhibits a 50% cut-off wavelength of $\sim 2.1 $μm as predicted from the band structure calculation; the device responsivity peaks at 0.85 A/W, corresponding to a quantum efficiency (QE) of 56% for 2.0 μm-thick absorption region. The dark current density of 1.03$ \times 10^{-3}$ A/cm$^{2}$ is obtained under 50 mV applied bias. The device exhibits a saturated dark current shot noise limited specific detectivity ($D^{\ast }$) of 3.29$\times10^{10}$cm$\cdot$Hz$^{1/2}$/W (at a peak responsivity of 2.0 μm) under $-50$ mV applied bias.

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Hopf bifurcation and phase synchronization in memristor-coupled Hindmarsh-Rose and FitzHugh-Nagumo neurons with two time delays Zhan-Hong Guo(郭展宏), Zhi-Jun Li(李志军), Meng-Jiao Wang(王梦蛟), and Ming-Lin Ma(马铭磷) Chin. Phys. B, 2023, 32 (3):  038701.  DOI: 10.1088/1674-1056/aca601 Abstract ( 33 )   PDF (3885KB) ( 24 )   A memristor-coupled heterogenous neural network consisting of two-dimensional (2D) FitzHugh-Nagumo (FHN) and Hindmarsh-Rose (HR) neurons with two time delays is established. Taking the time delays as the control parameters, the existence of Hopf bifurcation near the stable equilibrium point in four cases is derived theoretically, and the validity of the Hopf bifurcation condition is verified by numerical analysis. The results show that the two time delays can make the stable equilibrium point unstable, thus leading to periodic oscillations induced by Hopf bifurcation. Furthermore, the time delays in FHN and HR neurons have different effects on the firing activity of neural network. Complex firing patterns, such as quiescent state, chaotic spiking, and periodic spiking can be induced by the time delay in FHN neuron, while the neural network only exhibits quiescent state and periodic spiking with the change of the time delay in HR neuron. Especially, phase synchronization between the heterogeneous neurons is explored, and the results show that the time delay in HR neurons has a greater effect on blocking the synchronization than the time delay in FHN neuron. Finally, the theoretical analysis is verified by circuit simulations.

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Super-resolution reconstruction algorithm for terahertz imaging below diffraction limit Ying Wang(王莹), Feng Qi(祁峰), Zi-Xu Zhang(张子旭), and Jin-Kuan Wang(汪晋宽) Chin. Phys. B, 2023, 32 (3):  038702.  DOI: 10.1088/1674-1056/aca9c7 Abstract ( 45 )   PDF (2580KB) ( 14 )   Terahertz (THz) imaging has drawn significant attention because THz wave has a unique capability to transient, ultra-wide spectrum and low photon energy. However, the low resolution has always been a problem due to its long wavelength, limiting their application of fields practical use. In this paper, we proposed a complex one-shot super-resolution (COSSR) framework based on a complex convolution neural network to restore superior THz images at 0.35 times wavelength by extracting features directly from a reference measured sample and groundtruth without the measured PSF. Compared with real convolution neural network-based approaches and complex zero-shot super-resolution (CZSSR), COSSR delivers at least 6.67, 0.003, and 6.96% superior higher imaging efficacy in terms of peak signal to noise ratio (PSNR), mean square error (MSE), and structural similarity index measure (SSIM), respectively, for the analyzed data. Additionally, the proposed method is experimentally demonstrated to have a good generalization and to perform well on measured data. The COSSR provides a new pathway for THz imaging super-resolution (SR) reconstruction below the diffraction limit.

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Effect of autaptic delay signal on spike-timing precision of single neuron Xuan Ma(马璇), Yaya Zhao(赵鸭鸭), Yafeng Wang(王亚峰), Yueling Chen(陈月玲), and Hengtong Wang(王恒通) Chin. Phys. B, 2023, 32 (3):  038703.  DOI: 10.1088/1674-1056/ac7451 Abstract ( 38 )   PDF (2184KB) ( 15 )   Experimental and theoretical studies have reported that the precise firing of neurons is crucial for sensory representation. Autapse serves as a special synapse connecting neuron and itself, which has also been found to improve the accuracy of neuronal response. In current work, the effect of autaptic delay signal on the spike-timing precision is investigated on a single autaptic Hodgkin-Huxley neuron in the present of noise. The simulation results show that both excitatory and inhibitory autaptic signals can effectively adjust the precise spike time of neurons with noise by choosing the appropriate coupling strength g and time delay of autaptic signal τ. The g-τ parameter space is divided into two regions: one is the region where the spike-timing precision is effectively regulated; the other is the region where the neuronal firing is almost not regulated. For the excitatory and inhibitory autapse, the range of parameters causing the accuracy of neuronal firing is different. Moreover, it is also found that the mechanisms of the spike-timing precision regulation are different for the two kinds of autaptic signals.

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Investigations of moiré artifacts induced by flux fluctuations in x-ray dark-field imaging Zhi-Li Wang(王志立), Zi-Han Chen(陈子涵), Yao Gu(顾瑶), Heng Chen(陈恒), and Xin Ge(葛昕) Chin. Phys. B, 2023, 32 (3):  038704.  DOI: 10.1088/1674-1056/ac946a Abstract ( 16 )   PDF (923KB) ( 4 )   X-ray dark-field imaging using a grating interferometer has shown potential benefits for a variety of applications in recent years. X-ray dark-field image is commonly retrieved by using discrete Fourier transform from the acquired phase-stepping data. The retrieval process assumes a constant phase step size and a constant flux for each stepped grating position. However, stepping errors and flux fluctuations inevitably occur due to external vibrations and/or thermal drift during data acquisition. Previous studies have shown that those influences introduce errors in the acquired phase-stepping data, which cause obvious moiré artifacts in the retrieved refraction image. This work investigates moiré artifacts in x-ray dark-field imaging as a result of flux fluctuations. For the retrieved mean intensity, amplitude, visibility and dark-field images, the dependence of moiré artifacts on flux fluctuation factors is theoretically derived respectively by using a first-order Taylor series expansion. Results of synchrotron radiation experiments verify the validity of the derived analytical formulas. The spatial frequency characteristics of moiré artifacts are analyzed and compared to those induced by phase-stepping errors. It illustrates that moiré artifacts can be estimated by a weighted mean of flux fluctuation factors, with the weighting factors dependent on the moiré phase and different greatly for each retrieved image. Furthermore, moiré artifacts can even be affected by object's features not displayed in the particular contrast. These results can be used to interpret images correctly, identify sources of moiré artifacts, and develop dedicated algorithms to remove moiré artifacts in the retrieved multi-contrast images.

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Topological phase transition in network spreading Fuzhong Nian(年福忠) and Xia Zhang(张霞) Chin. Phys. B, 2023, 32 (3):  038901.  DOI: 10.1088/1674-1056/ac7bfa Abstract ( 38 )   PDF (3640KB) ( 8 )   This paper investigates information spreading from the perspective of topological phase transition. Firstly, a new hybrid network is constructed based on the small-world networks and scale-free networks. Secondly, the attention mechanism of online users in information spreading is studied from four aspects: social distance, individual influence, content richness, and individual activity, and a dynamic evolution model of connecting with spreading is designed. Eventually, numerical simulations are conducted in three types of networks to verify the validity of the proposed dynamic evolution model. The simulation results show that topological structure and node influence in different networks have undergone phase transition, which is consistent with the phenomenon that followers and individual influence in real social networks experience phase transition within a short period. The infection density of networks with the dynamic evolution rule changes faster and reaches higher values than that of networks without the dynamic evolution rule. Furthermore, the simulation results are compared with the real data, which shows that the infection density curve of the hybrid networks is closer to that of the real data than that of the small-world networks and scale-free networks, verifying the validity of the model proposed in this paper.