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10 March 2023, Volume 32 Issue 4 Previous issue    Next issue

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SPECIAL TOPIC—Smart design of materials and design of smart materials

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Fast prediction of the mechanical response for layered pavement under instantaneous large impact based on random forest regression Ming-Jun Li(励明君), Lina Yang(杨哩娜), Deng Wang(王登), Si-Yi Wang(王斯艺), Jing-Nan Tang(唐静楠), Yi Jiang(姜毅), and Jie Chen(陈杰) Chin. Phys. B, 2023, 32 (4):  046203.  DOI: 10.1088/1674-1056/acb76a Abstract ( 315 )   HTML ( 217 )   PDF (5791KB) ( 198 )   The layered pavements usually exhibit complicated mechanical properties with the effect of complex material properties under external environment. In some cases, such as launching missiles or rockets, layered pavements are required to bear large impulse load. However, traditional methods cannot non-destructively and quickly detect the internal structural of pavements. Thus, accurate and fast prediction of the mechanical properties of layered pavements is of great importance and necessity. In recent years, machine learning has shown great superiority in solving nonlinear problems. In this work, we present a method of predicting the maximum deflection and damage factor of layered pavements under instantaneous large impact based on random forest regression with the deflection basin parameters obtained from falling weight deflection testing. The regression coefficient R2 of testing datasets are above 0.94 in the process of predicting the elastic moduli of structural layers and mechanical responses, which indicates that the prediction results have great consistency with finite element simulation results. This paper provides a novel method for fast and accurate prediction of pavement mechanical responses under instantaneous large impact load using partial structural parameters of pavements, and has application potential in non-destructive evaluation of pavement structure.

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Prediction of lattice thermal conductivity with two-stage interpretable machine learning Jinlong Hu(胡锦龙), Yuting Zuo(左钰婷), Yuzhou Hao(郝昱州), Guoyu Shu(舒国钰), Yang Wang(王洋), Minxuan Feng(冯敏轩), Xuejie Li(李雪洁), Xiaoying Wang(王晓莹), Jun Sun(孙军), Xiangdong Ding(丁向东), Zhibin Gao(高志斌), Guimei Zhu(朱桂妹), and Baowen Li(李保文) Chin. Phys. B, 2023, 32 (4):  046301.  DOI: 10.1088/1674-1056/acbaf4 Abstract ( 533 )   HTML ( 238 )   PDF (2150KB) ( 424 )   Thermoelectric and thermal materials are essential in achieving carbon neutrality. However, the high cost of lattice thermal conductivity calculations and the limited applicability of classical physical models have led to the inefficient development of thermoelectric materials. In this study, we proposed a two-stage machine learning framework with physical interpretability incorporating domain knowledge to calculate high/low thermal conductivity rapidly. Specifically, crystal graph convolutional neural network (CGCNN) is constructed to predict the fundamental physical parameters related to lattice thermal conductivity. Based on the above physical parameters, an interpretable machine learning model-sure independence screening and sparsifying operator (SISSO), is trained to predict the lattice thermal conductivity. We have predicted the lattice thermal conductivity of all available materials in the open quantum materials database (OQMD) (https://www.oqmd.org/). The proposed approach guides the next step of searching for materials with ultra-high or ultra-low lattice thermal conductivity and promotes the development of new thermal insulation materials and thermoelectric materials.

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Forecasting solar still performance from conventional weather data variation by machine learning method Wenjie Gao(高文杰), Leshan Shen(沈乐山), Senshan Sun(孙森山), Guilong Peng(彭桂龙), Zhen Shen(申震), Yunpeng Wang(王云鹏), AbdAllah Wagih Kandeal, Zhouyang Luo(骆周扬), A. E. Kabeel, Jianqun Zhang(张坚群), Hua Bao(鲍华), and Nuo Yang(杨诺) Chin. Phys. B, 2023, 32 (4):  048801.  DOI: 10.1088/1674-1056/ac989f Abstract ( 592 )   HTML ( 244 )   PDF (1066KB) ( 242 )   Solar stills are considered an effective method to solve the scarcity of drinkable water. However, it is still missing a way to forecast its production. Herein, it is proposed that a convenient forecasting model which just needs to input the conventional weather forecasting data. The model is established by using machine learning methods of random forest and optimized by Bayesian algorithm. The required data to train the model are obtained from daily measurements lasting 9 months. To validate the accuracy model, the determination coefficients of two types of solar stills are calculated as 0.935 and 0.929, respectively, which are much higher than the value of both multiple linear regression (0.767) and the traditional models (0.829 and 0.847). Moreover, by applying the model, we predicted the freshwater production of four cities in China. The predicted production is approved to be reliable by a high value of correlation (0.868) between the predicted production and the solar insolation. With the help of the forecasting model, it would greatly promote the global application of solar stills.

INVITED REVIEW

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Recent progress on the planar Hall effect in quantum materials Jingyuan Zhong(钟景元), Jincheng Zhuang(庄金呈), and Yi Du(杜轶) Chin. Phys. B, 2023, 32 (4):  047203.  DOI: 10.1088/1674-1056/acb91a Abstract ( 393 )   HTML ( 6 )   PDF (3789KB) ( 230 )   The planar Hall effect (PHE), which originates from anisotropic magnetoresistance, presents a qualitative and simple approach to characterize electronic structures of quantum materials by applying an in-plane rotating magnetic field to induce identical oscillations in both longitudinal and transverse resistances. In this review, we focus on the recent research on the PHE in various quantum materials, including ferromagnetic materials, topological insulators, Weyl semimetals, and orbital anisotropic matters. Firstly, we briefly introduce the family of Hall effect and give a basic deduction of PHE formula with the second-order resistance tensor, showing the mechanism of the characteristic π-period oscillation in trigonometric function form with a π/4 phase delay between the longitudinal and transverse resistances. Then, we will introduce the four main mechanisms to realize PHE in quantum materials. After that, the origin of the anomalous planar Hall effect (APHE) results, of which the curve shapes deviate from that of PHE, will be reviewed and discussed. Finally, the challenges and prospects for this field of study are discussed.

INSTRUMENTATION AND MEASUREMENT

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Precision measurement and suppression of low-frequency noise in a current source with double-resonance alignment magnetometers Jintao Zheng(郑锦韬), Yang Zhang(张洋), Zaiyang Yu(鱼在洋),Zhiqiang Xiong(熊志强), Hui Luo(罗晖), and Zhiguo Wang(汪之国) Chin. Phys. B, 2023, 32 (4):  040601.  DOI: 10.1088/1674-1056/ac9361 Abstract ( 327 )   HTML ( 3 )   PDF (1068KB) ( 234 )   Low-noise high-stability current sources have essential applications such as neutron electric dipole moment measurement and high-stability magnetometers. Previous studies mainly focused on frequency noise above 0.1 Hz while less on the low-frequency noise/drift. We use double resonance alignment magnetometers (DRAMs) to measure and suppress the low-frequency noise of a homemade current source (CS) board. The CS board noise level is suppressed by about 10 times in the range of 0.001-0.1 Hz and is reduced to $100 \mathrm{nA/}\sqrt {\mathrm{Hz}} $ at 0.001 Hz. The relative stability of CS board can reach $2.2\times {10}^{-8}$. In addition, the DRAM shows a better resolution and accuracy than a commercial 7.5-digit multimeter when measuring our homemade CS board. Further, by combining the DRAM with a double resonance orientation magnetometer, we may realize a low-noise CS in the 0.001-1000 Hz range.

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Measurements of Majorana transition frequency shift in caesium atomic fountain clocks Jun-Ru Shi(施俊如), Xin-Liang Wang(王心亮), Fan Yang(杨帆), Yang Bai(白杨), Yong Guan(管勇), Si-Chen Fan(范思晨), Dan-Dan Liu(刘丹丹), Jun Ruan(阮军), and Shou-Gang Zhang(张首刚) Chin. Phys. B, 2023, 32 (4):  040602.  DOI: 10.1088/1674-1056/ac8344 Abstract ( 246 )   HTML ( 2 )   PDF (830KB) ( 269 )   The caesium atomic fountain clock is a primary frequency standard. During its operation, a Majorana transition frequency shift will occur once a magnetic field at some special locations along the atomic trajectory is singular. In this study, by developing a physical model, we analyzed the magnetic field requirements for atomic adiabatic transition and calculated the influence of the Majorana atomic transition on the atomic state via a quantum method. Based on the simulation results for the magnetic field in the fountain clock, we applied the Monte Carlo method to simulate the relationship between the Majorana transition frequency shift and the magnetic field at the entrance of the magnetic shielding, as well as the initial atomic population. Measurement of the Majorana transition frequency shift was realized by state-selecting asymmetrically populated atoms. The relationship between the Majorana transition frequency shift and the axial magnetic field at the entrance of the magnetic shielding was obtained. The measured results were essentially consistent with the calculated results. Thus, the magnetic field at the entrance of the magnetic shielding was configured, and the Majorana transition frequency shift of the fountain clock was calculated to be 4.57×10-18.

RAPID COMMUNICATION

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Nonreciprocal negative refraction in a dense hot atomic medium Hai Yi(易海), Hongjun Zhang(张红军), and Hui Sun(孙辉) Chin. Phys. B, 2023, 32 (4):  044202.  DOI: 10.1088/1674-1056/acae7a Abstract ( 328 )   HTML ( 5 )   PDF (1353KB) ( 204 )   We investigate the electromagnetic properties of a four-level dense atomic gas medium with Doppler effect. It is shown that the relative permittivity and relative permeability of the medium can be negative simultaneously with low absorption in the same detuning interval on account of electromagnetically induced transparency. Furthermore, with the suitable parameters, the nonreciprocal negative refraction can be obtained due to the Doppler effect, and the nonreciprocity frequency band can be regulated by adjusting the temperature, the intensity of the control field and the atomic density in this hot atomic medium.

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Tunable phonon-atom interaction in a hybrid optomechanical system Hot! Yao Li(李耀), Chuang Li(李闯), Jiandong Zhang(张建东), Ying Dong(董莹), and Huizhu Hu(胡慧珠) Chin. Phys. B, 2023, 32 (4):  044213.  DOI: 10.1088/1674-1056/acb9ea Abstract ( 535 )   HTML ( 23 )   PDF (738KB) ( 429 )   We theoretically analyze a hybrid system consisting of a levitated neutral atom and a nanoparticle coupled to a cavity. The mechanical oscillator and the atom are effectively coupled to each other through the cavity photons as a bus. By adjusting the driving lasers, we can conveniently switch the phonon-atom coupling between Jaynes-Cummings (JC) and anti-JC forms, which can be used to manipulate the motional states of the mechanical oscillator. As an application, we prepare a superposition state of the mechanical oscillator via the effective phonon-atom interaction and investigate the effects of dissipation on the state generation.

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Modeling of thermal conductivity for disordered carbon nanotube networks Hot! Hao Yin(殷浩), Zhiguo Liu(刘治国), and Juekuan Yang(杨决宽) Chin. Phys. B, 2023, 32 (4):  044401.  DOI: 10.1088/1674-1056/acb0be Abstract ( 392 )   HTML ( 7 )   PDF (861KB) ( 232 )   Several theoretical models have been developed so far to predict the thermal conductivities of carbon nanotube (CNT) networks. However, these models overestimated the thermal conductivity significantly. In this paper, we claimed that a CNT network can be considered as a contact thermal resistance network. In the contact thermal resistance network, the temperature of an individual CNT is nonuniform and the intrinsic thermal resistance of CNTs can be ignored. Compared with the previous models, the model we proposed agrees well with the experimental results of single-walled CNT networks.

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Quantitative analysis of the morphing wing mechanism of raptors: Morphing kinematics of Falco peregrinus wing Di Tang(唐迪), Jinqi Che(车婧琦), Weijie Jin(金伟杰), Yahui Cui(崔亚辉), Zhongyong Fan(范忠勇), Yin Yang(杨茵), and Dawei Liu(刘大伟) Chin. Phys. B, 2023, 32 (4):  044703.  DOI: 10.1088/1674-1056/aca201 Abstract ( 257 )   HTML ( 4 )   PDF (2668KB) ( 270 )   Raptors are getting more attention from researchers because of their excellent flight abilities. And the excellent wing morphing ability is critical for raptors to achieve high maneuvering flight, which can be a good bionic inspiration for unmanned aerial vehicles (UAV) design. However, morphing wing motions of Falco peregrinus with multi postures cannot be consulted since such a motion database was nonexistent. This study aimed to provide data reference for future research in wing morphing kinetics. We used the computed tomography (CT) approach to obtain nine critical postures of the Falco peregrinus wing skeleton, followed with motion analysis of each joint and bone. Based on the obtained motion database, a six-bar kinematic model was proposed to regenerate wing motions with a high fidelity.

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Magneto-volume effect in FenTi13-n clusters during thermal expansion Jian Huang(黄建), Yanyan Jiang(蒋妍彦), Zhichao Li(李志超), Di Zhang(张迪), Junping Qian(钱俊平), and Hui Li(李辉) Chin. Phys. B, 2023, 32 (4):  046501.  DOI: 10.1088/1674-1056/acaf2e Abstract ( 313 )   HTML ( 9 )   PDF (2072KB) ( 140 )   Ab initio molecular dynamics calculations have been carried out to search for the ground state structure of Fe$_{n}$Ti$_{13-n}$ clusters and measure the thermal expansion of Fe$_{n}$Ti$_{13-n}$. The volume of Fe$_{n}$Ti$_{13-n}$ clusters during thermal expansion is jointly determined by anharmonic interaction and magneto-volume effect. It has been found that Fe$_{6}$Ti$_{7}$, Fe$_{9}$Ti$_{4}$, Fe$_{11}$Ti$_{2}$, and Fe$_{13}$ clusters can exhibit the remarkable magneto-volume effect with abnormal volume behaviors and magnetic moment behaviors during thermal expansion. A prerequisite for the magneto-volume effect of Fe$_{n}$Ti$_{13-n}$ clusters during thermal expansion has been revealed and the magnitude of the magneto-volume is also approximately determined. Furthermore, the magneto-volume behaviors of Fe$_{n}$Ti$_{13-n}$ clusters are qualitatively characterized by the energy contour map. Our results shed light on the mechanism of the magneto-volume effect in Fe$_{n}$Ti$_{13-n}$ clusters during thermal expansion, which can guide the design of nanomaterials with zero expansion or even controllable expansion properties.

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First-principles study of the bandgap renormalization and optical property of β-LiGaO2 Dangqi Fang(方党旗) Chin. Phys. B, 2023, 32 (4):  047101.  DOI: 10.1088/1674-1056/acb9ef Abstract ( 329 )   HTML ( 10 )   PDF (1103KB) ( 185 )   The $\beta$-LiGaO$_{2}$ with an orthorhombic wurtzite-derived structure is a candidate ultrawide direct-bandgap semiconductor. In this work, using the non-adiabatic Allen-Heine-Cardona approach, we investigate the bandgap renormalization arising from electron-phonon coupling. We find a sizable zero-point motion correction of $-0.362 $ eV to the gap at $\varGamma $, which is dominated by the contributions of long-wavelength longitudinal optical phonons. The bandgap of $\beta $-LiGaO$_{2}$ decreases monotonically with increasing temperature. We investigate the optical spectra by comparing the model Bethe-Salpether equation method with the independent-particle approximation. The calculated optical spectra including electron-hole interactions exhibit strong excitonic effects, in qualitative agreement with the experiment. The contributing interband transitions and the binding energy for the excitonic states are analyzed.

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Conductive path and local oxygen-vacancy dynamics: Case study of crosshatched oxides Hot! Z W Liang(梁正伟), P Wu(吴平), L C Wang(王利晨), B G Shen(沈保根), and Zhi-Hong Wang(王志宏) Chin. Phys. B, 2023, 32 (4):  047303.  DOI: 10.1088/1674-1056/acb421 Abstract ( 342 )   HTML ( 8 )   PDF (3660KB) ( 189 )   By employing scanning probe microscopy, conductive path and local oxygen-vacancy dynamics have been investigated in crosshatched La0.7Sr0.3MnO3 thin films grown onto flat and vicinal LaAlO3(001) single crystal substrates. Consistent with prior studies, the crosshatch topography was observed first by dynamical force microscopy as the epi-stain started to release with increasing film thickness. Second, by using conductive atomic force microscopy (CAFM), conductive crosshatch and dots (locally aligned or random) were unravelled, however, not all of which necessarily coincided with that shown in the in situ atomic force microscopy. Furthermore, the current-voltage responses were probed by CAFM, revealing the occurrence of threshold and/or memristive switchings. Our results demonstrate that the resistive switching relies on the evolution of the local profile and concentration of oxygen vacancies, which, in the crosshatched films, are modulated by both the misfit and threading dislocations.

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Strong spin frustration and magnetism in kagomé antiferromagnets LnCu3(OH)6Br3 (Ln=Nd, Sm, and Eu) Hot! Jin-Qun Zhong(钟金群), Zhen-Wei Yu(余振伟), Xiao-Yu Yue(岳小宇), Yi-Yan Wang(王义炎), Hui Liang(梁慧), Yan Sun(孙燕), Dan-Dan Wu(吴丹丹), Zong-Ling Ding(丁宗玲), Jin Sun(孙进), Xue-Feng Sun(孙学峰), and Qiu-Ju Li(李秋菊) Chin. Phys. B, 2023, 32 (4):  047505.  DOI: 10.1088/1674-1056/acb9e8 Abstract ( 564 )   HTML ( 159 )   PDF (2462KB) ( 589 )   To study the effects of lanthanide ions on the geometrically frustrated antiferromagnets and their magnetic properties, we grew high-quality single crystals of $Ln$Cu$_{3}$(OH)$_{6}$Br$_{3}$ ($Ln={\rm Nd}$, Sm, and Eu) by hydrothermal method and studied their crystal structures and magnetic properties. The refinements of the crystal structure referred to the powder x-ray diffraction data show that $Ln$Cu$_{3}$(OH)$_{6}$Br$_{3}$ adopt a Kapellasite-type layer structure, which is isostructural to their chlorine analogue. Magnetic susceptibilities demonstrate that $Ln$Cu$_{3}$(OH)$_{6}$Br$_{3}$ have strong antiferromagnetic coupling and a pronounced magnetic frustration effect. Magnetization measurements indicate canted antiferromagnetic ordering of Cu$^{2+}$ ions around 16 K within the kagomé plane and weak ferromagnetic coupling. Moreover, shoulder-like anomalies in specific heat around 16 K could be a signature of emergent of magnetic ordering. The low-temperature negative magnetization and specific heat of $Ln$Cu$_{3}$(OH)$_{6}$Br$_{3}$ ($Ln={\rm Nd}$, Sm, and Eu) indicate that $Ln^{3+}$ ions induce more exotic magnetic ground state properties.

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Adaptive genetic algorithm-based design of gamma-graphyne nanoribbon incorporating diamond-shaped segment with high thermoelectric conversion efficiency Jingyuan Lu(陆静远), Chunfeng Cui(崔春凤), Tao Ouyang(欧阳滔), Jin Li(李金), Chaoyu He(何朝宇), Chao Tang(唐超), and Jianxin Zhong(钟建新) Chin. Phys. B, 2023, 32 (4):  048401.  DOI: 10.1088/1674-1056/acb768 Abstract ( 331 )   HTML ( 3 )   PDF (3398KB) ( 167 )   The gamma-graphyne nanoribbons ($\gamma $-GYNRs) incorporating diamond-shaped segment (DSSs) with excellent thermoelectric properties are systematically investigated by combining nonequilibrium Green's functions with adaptive genetic algorithm. Our calculations show that the adaptive genetic algorithm is efficient and accurate in the process of identifying structures with excellent thermoelectric performance. In multiple rounds, an average of 476 candidates (only 2.88% of all 16512 candidate structures) are calculated to obtain the structures with extremely high thermoelectric conversion efficiency. The room temperature thermoelectric figure of merit ($ZT$) of the optimal $\gamma $-GYNR incorporating DSSs is 1.622, which is about 5.4 times higher than that of pristine $\gamma $-GYNR (length 23.693 nm and width 2.660 nm). The significant improvement of thermoelectric performance of the optimal $\gamma $-GYNR is mainly attributed to the maximum balance of inhibition of thermal conductance (proactive effect) and reduction of thermal power factor (side effect). Moreover, through exploration of the main variables affecting the genetic algorithm, it is revealed that the efficiency of the genetic algorithm can be improved by optimizing the initial population gene pool, selecting a higher individual retention rate and a lower mutation rate. The results presented in this paper validate the effectiveness of genetic algorithm in accelerating the exploration of $\gamma $-GYNRs with high thermoelectric conversion efficiency, and could provide a new development solution for carbon-based thermoelectric materials.

GENERAL

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Positon and hybrid solutions for the (2+1)-dimensional complex modified Korteweg-de Vries equations Feng Yuan(袁丰) and Behzad Ghanbari Chin. Phys. B, 2023, 32 (4):  040201.  DOI: 10.1088/1674-1056/ac935b Abstract ( 263 )   HTML ( 2 )   PDF (2995KB) ( 194 )   Solving nonlinear partial differential equations have attracted intensive attention in the past few decades. In this paper, the Darboux transformation method is used to derive several positon and hybrid solutions for the (2+1)-dimensional complex modified Korteweg-de Vries equations. Based on the zero seed solution, the positon solution and the hybrid solutions of positon and soliton are constructed. The composition of positons is studied, showing that multi-positons of (2+1)-dimensional equations are decomposed into multi-solitons as well as the (1+1)-dimensions. Moreover, the interactions between positon and soliton are analyzed. In addition, the hybrid solutions of b-positon and breather are obtained using the plane wave seed solution, and their evolutions with time are discussed.

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Conformable fractional heat equation with fractional translation symmetry in both time and space W S Chung, A Gungor, J Kříž, B C Lütfüoǧlu, and H Hassanabadi Chin. Phys. B, 2023, 32 (4):  040202.  DOI: 10.1088/1674-1056/ac935f Abstract ( 263 )   HTML ( 2 )   PDF (460KB) ( 70 )   We investigate the fractional heat equation with fractional translation in both time and position with different fractional orders. As examples, we consider a rod and an α-disk with an initial constant temperature and discuss their cooling processes in the examined formalism.

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Riemann-Hilbert approach of the complex Sharma-Tasso-Olver equation and its N-soliton solutions Sha Li(李莎), Tiecheng Xia(夏铁成), and Hanyu Wei(魏含玉) Chin. Phys. B, 2023, 32 (4):  040203.  DOI: 10.1088/1674-1056/ac960a Abstract ( 247 )   HTML ( 2 )   PDF (696KB) ( 47 )   We study the complex Sharma-Tasso-Olver equation using the Riemann-Hilbert approach. The associated Riemann-Hilbert problem for this integrable equation can be naturally constructed by considering the spectral problem of the Lax pair. Subsequently, in the case that the Riemann-Hilbert problem is irregular, the N-soliton solutions of the equation can be deduced. In addition, the three-dimensional graphic of the soliton solutions and wave propagation image are graphically depicted and further discussed.

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Local density of optical states calculated by the mode spectrum in stratified media Ting Fu(傅廷), Jingxuan Chen(陈静瑄), Xueyou Wang(王学友), Yingqiu Dai(戴迎秋), Xuyan Zhou(周旭彦), Yufei Wang(王宇飞), Mingjin Wang(王明金), and Wanhua Zheng(郑婉华) Chin. Phys. B, 2023, 32 (4):  040204.  DOI: 10.1088/1674-1056/acaf2c Abstract ( 271 )   HTML ( 3 )   PDF (1683KB) ( 161 )   The local density of optical states (LDOS) is an important physical concept, which can characterize the spontaneous emission of microcavities. In order to calculate the LDOS, the relationship between the mode spectrum and the LDOS is established. Then, based on the transfer matrix method and the effective resonator model, the leaky loss of the leaky mode and the mode spectrum in the one-dimensional photonic bandgap crystal waveguide are calculated, results of which indicate that the mode spectrum can characterize the leaky loss of the leaky mode. At last, the density of optical states (DOS), and the LDOS in each layer are calculated. The partial DOS and the partial LDOS in the quantum well, related to the fundamental leaky mode, can be used to find out the optimal location of the quantum well in the defect layer to couple more useful photons into the lasing mode for lasers.

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Couple stress and Darcy Forchheimer hybrid nanofluid flow on a vertical plate by means of double diffusion Cattaneo-Christov analysis Hamdi Ayed Chin. Phys. B, 2023, 32 (4):  040205.  DOI: 10.1088/1674-1056/ac7bfb Abstract ( 240 )   HTML ( 2 )   PDF (2725KB) ( 62 )   A three-dimensional Darcy Forchheimer mixed convective flow of a couple stress hybrid nanofluid flow through a vertical plate by means of the double diffusion Cattaneo-Christov model is presented in this study. The influence of high-order velocity slip flow, as well as a passive and active control, is also considered. The motive of the research is to develop a computational model, using cobalt ferrite (CoFe2O4) and copper (Cu) nanoparticles (NPs) in the carrier fluid water, to magnify the energy and mass communication rate and boost the efficiency and performance of thermal energy conduction for a variety of commercial and biological purposes. The proposed model becomes more significant, with an additional effect of non-Fick's mass flux and Fourier's heat model to report the energy and mass passage rate. The results are obtained through the computational strategy parametric continuation method. The figures are plotted to reveal the physical sketch of the obtained solution, while the statistical assessment has been evaluated through tables. It has been observed that the dispersion of Cu and CoFe2O4 NPs to the base fluid significantly enhances the velocity and thermal conductivity of water, which is the most remarkable property of these NPs from the industrial point of view.

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Meshfree-based physics-informed neural networks for the unsteady Oseen equations Keyi Peng(彭珂依), Jing Yue(岳靖), Wen Zhang(张文), and Jian Li(李剑) Chin. Phys. B, 2023, 32 (4):  040207.  DOI: 10.1088/1674-1056/ac9cb9 Abstract ( 315 )   HTML ( 2 )   PDF (1993KB) ( 87 )   We propose the meshfree-based physics-informed neural networks for solving the unsteady Oseen equations. Firstly, based on the ideas of meshfree and small sample learning, we only randomly select a small number of spatiotemporal points to train the neural network instead of forming a mesh. Specifically, we optimize the neural network by minimizing the loss function to satisfy the differential operators, initial condition and boundary condition. Then, we prove the convergence of the loss function and the convergence of the neural network. In addition, the feasibility and effectiveness of the method are verified by the results of numerical experiments, and the theoretical derivation is verified by the relative error between the neural network solution and the analytical solution.

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New light fields based on integration theory within the Weyl ordering product of operators Ke Zhang(张科), Lan-Lan Li(李兰兰), Da-Wei Guo(郭大伟), and Hong-Yi Fan(范洪义) Chin. Phys. B, 2023, 32 (4):  040301.  DOI: 10.1088/1674-1056/ac7e34 Abstract ( 288 )   HTML ( 4 )   PDF (468KB) ( 89 )   The development of quantum optics theory based on the method of integration within an ordered product of operators (IWOP) has greatly stimulated the study of quantum states in the light field, especially non-Gaussian states with various non-classical properties. In this paper, the two-mode squeezing operator is derived with integral theory within the Weyl ordering product of operators using a combinatorial field in which one mode is a chaotic field and the other mode is a vacuum field. The density operator of the new light field, its entanglement property and photon number distribution are analyzed. We also note that tracing a three-mode pure state can yield this new light field. These methods represent a theoretical approach to investigating new density operators of light fields.

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Quantum entangled fractional Fourier transform based on the IWOP technique Ke Zhang(张科), Lan-Lan Li(李兰兰), Pan-Pan Yu(余盼盼), Ying Zhou(周莹),Da-Wei Guo(郭大伟), and Hong-Yi Fan(范洪义) Chin. Phys. B, 2023, 32 (4):  040302.  DOI: 10.1088/1674-1056/ac7e32 Abstract ( 265 )   HTML ( 7 )   PDF (558KB) ( 109 )   In our previous papers, the classical fractional Fourier transform theory was incorporated into the quantum theoretical system using the theoretical method of quantum optics, and the calculation produced quantum mechanical operators corresponding to the generation of fractional Fourier transform. The core function of the coordinate-momentum exchange operators in the addition law of fractional Fourier transform was analyzed too. In this paper, the bivariate operator Hermite polynomial theory and the technique of integration within an ordered product of operators (IWOP) are used to establish the entanglement fractional Fourier transform theory to the extent of quantum. A new function generating formula and an operator for generating quantum entangled fractional Fourier transform are obtained using the fractional Fourier transform relationship in a pair of conjugated entangled state representations.

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An optimized infinite time-evolving block decimation algorithm for lattice systems Junjun Xu(许军军) Chin. Phys. B, 2023, 32 (4):  040303.  DOI: 10.1088/1674-1056/ac92d4 Abstract ( 266 )   HTML ( 2 )   PDF (571KB) ( 144 )   The infinite time-evolving block decimation algorithm (iTEBD) provides an efficient way to determine the ground state and dynamics of the quantum lattice systems in the thermodynamic limit. In this paper we suggest an optimized way to take the iTEBD calculation, which takes advantage of additional reduced decompositions to speed up the calculation. The numerical calculations show that for a comparable computation time our method provides more accurate results than the traditional iTEBD, especially for lattice systems with large on-site degrees of freedom.

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Lorentz quantum computer Wenhao He(何文昊), Zhenduo Wang(王朕铎), and Biao Wu(吴飙) Chin. Phys. B, 2023, 32 (4):  040304.  DOI: 10.1088/1674-1056/acad6a Abstract ( 332 )   HTML ( 6 )   PDF (587KB) ( 199 )   A theoretical model of computation is proposed based on Lorentz quantum mechanics. Besides the standard qubits, this model has an additional bit, which we call hyperbolic bit (or hybit in short). A set of basic logical gates are constructed and their universality is proved. As an application, a search algorithm is designed for this computer model and is found to be exponentially faster than Grover's search algorithm.

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Quantum dynamical resource theory under resource non-increasing framework Si-Ren Yang(杨思忍) and Chang-Shui Yu(于长水) Chin. Phys. B, 2023, 32 (4):  040305.  DOI: 10.1088/1674-1056/aca398 Abstract ( 298 )   HTML ( 2 )   PDF (539KB) ( 161 )   We define the resource non-increasing (RNI) framework to study the dynamical resource theory. With this definition, we propose several potential quantification candidates under various free operation sets. For explicit demonstrations, we quantify the quantum dynamical coherence in the scenarios with and without post-selective measurements. Correspondingly, we show that the maximally incoherent operations (MIO) and the incoherent operations (IO) in the static coherence resource theory are free in the sense of dynamical coherence. We also provide operational meanings for the measures by the quantum discrimination tasks. Moreover, for the dynamical total coherence, we also present convenient measures and give the analytic calculation for the amplitude damping channel.

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Generation of microwave photon perfect W states of three coupled superconducting resonators Xin-Ke Li(李新克), Yuan Zhou(周原), Guang-Hui Wang(王光辉), Dong-Yan Lv(吕东燕),Fazal Badshah, and Hai-Ming Huang(黄海铭) Chin. Phys. B, 2023, 32 (4):  040306.  DOI: 10.1088/1674-1056/aca394 Abstract ( 270 )   HTML ( 2 )   PDF (1074KB) ( 112 )   We propose an efficient method for the generation of perfect W states on three microwave superconducting resonators, of which the two nearest neighbors are coupled by a symmetric direct current superconducting quantum interference device (dc-SQUID). With suitable external magnetic fluxes applied to the dc-SQUID symmetry loops, on-chip tunable interactions between neighboring resonators can be realized, and different perfect W states can be deterministically created on-demand in one step. Numerical simulations show that high-fidelity target states can be generated and our scheme is robust against imperfect parameter tuning and environment-induced decoherence. The present work may have potential applications for implementing quantum computation and quantum information processing based on microwave photons.

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Enhanced topological superconductivity in an asymmetrical planar Josephson junction Erhu Zhang(张二虎) and Yu Zhang(张钰) Chin. Phys. B, 2023, 32 (4):  040307.  DOI: 10.1088/1674-1056/acaa29 Abstract ( 304 )   HTML ( 3 )   PDF (1729KB) ( 149 )   As a platform for holding Majorana zero models (MZMs), the two-dimensional planar topological Josephson junction that can be used as carriers for topological quantum computing faces some challenges. One is a combination of mirror and time-reversal symmetries may make the system hold multiple pairs of MZMs. The other is that a soft gap dominated by a large momentum occurs in a clean system. To solve these problems, asymmetric junction can be introduced. Breaking this symmetry changes the symmetry class from class BDI to class D, and only a single pair of MZMs can be left at the boundary of the system. We numerically study four cases that create an asymmetric system and find out different superconducting pairing potential, different coupling coefficients between two-dimensional electron gases (2DEGs) and two superconducting bulks, different widths of two superconducting bulks make the gap of the system decrease at the optimal value, but make the gap at the minimum value increases. And the zigzag-shape quasi-one-dimensional junction eliminates the large momentum parallel to the junction and enhances the gap at the large momentum. However, the zigzag-shape junction cannot increase the gap at the region of multiple pairs of MZMs in a symmetric system. We show that by combining zigzag-shape junction with different coupling coefficients, the system can maintain a large gap (≈0.2 Δ) in a wide region of the parameter space.

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Quantum speed limit of a single atom in a squeezed optical cavity mode Ya-Jie Ma(马雅洁), Xue-Chen Gao(高雪晨), Shao-Xiong Wu(武少雄), and Chang-Shui Yu(于长水) Chin. Phys. B, 2023, 32 (4):  040308.  DOI: 10.1088/1674-1056/acbd2b Abstract ( 238 )   HTML ( 2 )   PDF (3310KB) ( 110 )   We theoretically study the quantum speed limit of a single atom trapped in a Fabry-Perot microresonator. The cavity mode will be squeezed when a driving laser is applied to the second-order nonlinear medium, and the effective Hamiltonian can be obtained under the Bogoliubov squeezing transformation. The analytical expression of the evolved atom state can be obtained by using the non-Hermitian Schrödinger equation for the initial excited state, and the quantum speed limit time coincides very well for both the analytical expression and the master equation method. From the perspective of quantum speed limit, it is more conducive to accelerate the evolution of the quantum state for the large detuning, strong driving, and coupling strength. For the case of the initial superposition state, the form of the initial state has more influence on the evolution speed. The quantum speed limit time is not only dependent on the system parameters but also determined by the initial state.

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Genuine Einstein-Podolsky-Rosen steering of generalized three-qubit states via unsharp measurements Yuyu Chen(陈玉玉), Fenzhuo Guo(郭奋卓), Shihui Wei(魏士慧), and Qiaoyan Wen(温巧燕) Chin. Phys. B, 2023, 32 (4):  040309.  DOI: 10.1088/1674-1056/acac14 Abstract ( 318 )   HTML ( 4 )   PDF (696KB) ( 172 )   We aim to explore all possible scenarios of ($ 1 \rightarrow 2 $) (where one wing is untrusted and the others two wings are trusted) and ($ 2 \rightarrow 1 $) (where two wings are untrusted, and one wing is trusted) genuine tripartite Einstein-Podolsky-Rosen (EPR) steering. The generalized Greenberger-Horne-Zeilinger (GHZ) state is shared between three spatially separated parties, Alice, Bob and Charlie. In both ($ 1 \rightarrow 2 $) and ($ 2 \rightarrow 1 $), we discuss the untrusted party and trusted party performing a sequence of unsharp measurements, respectively. For each scenario, we deduce an upper bound on the number of sequential observers who can demonstrate genuine EPR steering through the quantum violation of tripartite steering inequality. The results show that the maximum number of observers for the generalized GHZ states can be the same with that of the maximally GHZ state in a certain range of state parameters. Moreover, both the sharpness parameters range and the state parameters range in the scenario of ($ 1 \rightarrow 2 $) steering are larger than those in the scenario of ($ 2 \rightarrow 1 $) steering.

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Dynamics of lump chains for the BKP equation describing propagation of nonlinear waves Zhonglong Zhao(赵忠龙), Lingchao He(和玲超), and Abdul-Majid Wazwaz Chin. Phys. B, 2023, 32 (4):  040501.  DOI: 10.1088/1674-1056/acb0c1 Abstract ( 322 )   HTML ( 4 )   PDF (7801KB) ( 215 )   A large member of lump chain solutions of the (2+1)-dimensional Bogoyavlenskii-Kadomtsev-Petviashvili (BKP) equation are constructed by means of the τ-function in the form of Grammian. The lump chains are formed by periodic arrangement of individual lumps and travel with distinct group and velocities. An analytical method related dominant regions of polygon is developed to analyze the interaction dynamics of the multiple lump chains. The degenerate structures of parallel, superimposed, and molecular lump chains are presented. The interaction solutions between lump chains and kink-solitons are investigated, where the kink-solitons lie on the boundaries of dominant region determined by the constant term in the τ-function. Furthermore, the hybrid solutions consisting of lump chains and individual lumps controlled by the parameter with high rank and depth are investigated. The analytical method presented in this paper can be further extended to other integrable systems to explore complex wave structures.

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Unstable periodic orbits analysis in the Qi system Lian Jia(贾莲), Chengwei Dong(董成伟), Hantao Li(李瀚涛), and Xiaohong Sui(眭晓红) Chin. Phys. B, 2023, 32 (4):  040502.  DOI: 10.1088/1674-1056/aca9c3 Abstract ( 301 )   HTML ( 2 )   PDF (6093KB) ( 170 )   We use the variational method to extract the short periodic orbits of the Qi system within a certain topological length. The chaotic dynamical behaviors of the Qi system with five equilibria are analyzed by the means of phase portraits, Lyapunov exponents, and Poincaré maps. Based on several periodic orbits with different sizes and shapes, they are encoded systematically with two letters or four letters for two different sets of parameters. The periodic orbits outside the attractor with complex topology are discovered by accident. In addition, the bifurcations of cycles and the bifurcations of equilibria in the Qi system are explored by different methods respectively. In this process, the rule of orbital period changing with parameters is also investigated. The calculation and classification method of periodic orbits in this study can be widely used in other similar low-dimensional dissipative systems.

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Lie symmetry analysis and invariant solutions for the (3+1)-dimensional Virasoro integrable model Hengchun Hu(胡恒春) and Yaqi Li(李雅琦) Chin. Phys. B, 2023, 32 (4):  040503.  DOI: 10.1088/1674-1056/ac9de6 Abstract ( 299 )   HTML ( 1 )   PDF (667KB) ( 116 )   Lie symmetry analysis is applied to a (3+1)-dimensional Virasoro integrable model and the corresponding similarity reduction equations are obtained with the different infinitesimal generators. Invariant solutions with arbitrary functions for the (3+1)-dimensional Virasoro integrable model, including the interaction solution between a kink and a soliton, the lump-type solution and periodic solutions, have been studied analytically and graphically.

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Diffusive field coupling-induced synchronization between neural circuits under energy balance Ya Wang(王亚), Guoping Sun(孙国平), and Guodong Ren(任国栋) Chin. Phys. B, 2023, 32 (4):  040504.  DOI: 10.1088/1674-1056/ac7bff Abstract ( 296 )   HTML ( 2 )   PDF (683KB) ( 135 )   When charged bodies come up close to each other, the field energy is diffused and their states are regulated under bidirectional field coupling. For biological neurons, the diversity in intrinsic electric and magnetic field energy can create synaptic connection for fast energy balance and synaptic current is passed across the synapse channel; as a result, energy is pumped and exchanged to induce synchronous firing modes. In this paper, a capacitor is used to connect two neural circuits and energy propagation is activated along the coupling channel. The intrinsic field energy in the two neural circuits is exchanged and the coupling intensity is controlled adaptively using the Heaviside function. Some field energy is saved in the coupling channel and is then sent back to the coupled neural circuits to reach energy balance. Therefore the circuits can reach possible energy balance and complete synchronization. It is possible that the diffusive energy of the coupled neurons inspires the synaptic connections to grow stronger for possible energy balance.

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Feedback control and quantum error correction assisted quantum multi-parameter estimation Hai-Yuan Hong(洪海源), Xiu-Juan Lu(鲁秀娟), and Sen Kuang(匡森) Chin. Phys. B, 2023, 32 (4):  040603.  DOI: 10.1088/1674-1056/ac8721 Abstract ( 252 )   HTML ( 2 )   PDF (564KB) ( 147 )   Quantum metrology provides a fundamental limit on the precision of multi-parameter estimation, called the Heisenberg limit, which has been achieved in noiseless quantum systems. However, for systems subject to noises, it is hard to achieve this limit since noises are inclined to destroy quantum coherence and entanglement. In this paper, a combined control scheme with feedback and quantum error correction (QEC) is proposed to achieve the Heisenberg limit in the presence of spontaneous emission, where the feedback control is used to protect a stabilizer code space containing an optimal probe state and an additional control is applied to eliminate the measurement incompatibility among three parameters. Although an ancilla system is necessary for the preparation of the optimal probe state, our scheme does not require the ancilla system to be noiseless. In addition, the control scheme in this paper has a low-dimensional code space. For the three components of a magnetic field, it can achieve the highest estimation precision with only a 2-dimensional code space, while at least a 4-dimensional code space is required in the common optimal error correction protocols.

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Numerical study on THz radiation of two-dimensional plasmon resonance of GaN HEMT array Hongyang Guo(郭宏阳), Ping Zhang(张平), Shengpeng Yang(杨生鹏), Shaomeng Wang(王少萌), and Yubin Gong(宫玉彬) Chin. Phys. B, 2023, 32 (4):  040701.  DOI: 10.1088/1674-1056/acb0bb Abstract ( 295 )   HTML ( 2 )   PDF (2888KB) ( 145 )   The GaN high electron mobility transistor (HEMT) has been considered as a potential terahertz (THz) radiation source, yet the low radiation power level restricts their applications. The HEMT array is thought to improve the coupling efficiency between two-dimensional (2D) plasmons and THz radiation. In this work, we investigate the plasma oscillation, electromagnetic radiation, and the integration characteristics of GaN HEMT targeting at a high THz radiation power source. The quantitative radiation power and directivity are obtained for integrated GaN HEMT array with different array periods and element numbers. With the same initial plasma oscillation phase among the HEMT units, the radiation power of the two-element HEMT array can achieve 4 times as the single HEMT radiation power when the array period is shorter than 1/8 electromagnetic wavelength. In addition, the radiation power of the HEMT array varies almost linearly with the element number, the smaller array period can lead to the greater radiation power. It shows that increasing the array period could narrow the main radiated lobe width while weaken the radiation power. Increasing the element number can improve both the radiation directivity and power. We also synchronize the plasma wave phases in the HEMT array by adopting an external Gaussian plane wave with central frequency the same as the plasmon resonant frequency, which solves the problem of the radiation power reduction caused by the asynchronous plasma oscillation phases among the elements. The study of the radiation power amplification of the one-dimensional (1D) GaN HEMT array provides useful guidance for the research of compact high-power solid-state terahertz sources.

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A compact and closed-loop spin-exchange relaxation-free atomic magnetometer for wearable magnetoencephalography Qing-Qian Guo(郭清乾), Tao Hu(胡涛), Xiao-Yu Feng(冯晓宇), Ming-Kang Zhang(张明康), Chun-Qiao Chen(陈春巧), Xin Zhang(张欣), Ze-Kun Yao(姚泽坤), Jia-Yu Xu(徐佳玉),Qing Wang(王青), Fang-Yue Fu(付方跃), Yin Zhang(张寅), Yan Chang(常严), and Xiao-Dong Yang(杨晓冬) Chin. Phys. B, 2023, 32 (4):  040702.  DOI: 10.1088/1674-1056/ac7e38 Abstract ( 340 )   HTML ( 2 )   PDF (2834KB) ( 212 )   Atomic magnetometers operated in the spin-exchange relaxation-free (SERF) regime are the promising sensor to replace superconducting quantum interference devices (SQUIDs) in the biomagnetism field. The SERF magnetometer with compact size and good performance is crucial to the new generation of wearable magnetoencephalography (MEG) system. In this paper, we developed a compact and closed-loop SERF magnetometer with the dimensions of 15.0×22.0×30.0 mm3 based on a single-beam configuration. The bandwidth of the magnetometer was extended to 675 Hz while the sensitivity was maintained at 22 fT/Hz1/2. A nearly 3-fold enhancement of the bandwidth was obtained in comparison with the open-loop control. The implementation of the closed-loop control also greatly improved the dynamic range, enabling the magnetometer to be robust against the disturbance of the ambient field. Moreover, the magnetometer was successfully applied for the detection of human α -rhythm and auditory evoked fields (AEFs), which demonstrated the potential to be extended to multi-channel MEG measurements for future neuroscience studies.

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A robust method for performance evaluation of the vapor cell for magnetometry Zhi Liu(柳治), Sheng Zou(邹升), Kaifeng Yin(尹凯峰), Tao Shi(石韬),Junjian Tang(唐钧剑), and Heng Yuan(袁珩) Chin. Phys. B, 2023, 32 (4):  040703.  DOI: 10.1088/1674-1056/aca6d5 Abstract ( 254 )   HTML ( 3 )   PDF (824KB) ( 124 )   A robust performance evaluation method for vapor cells used in magnetometers is proposed in this work. The performance of the vapor cell determines the sensitivity of the magnetic measurement, which is the core parameter of a magnetometer. After establishing the relationship between intrinsic sensitivity and the total relaxation rate, the total relaxation rate of the vapor cell can be obtained to represent the intrinsic sensitivity of the magnetometer by fitting the parameters of the magnetic resonance experiments. The method for measurement of the total relaxation rate based on the magnetic resonance experiment proposed in this work is robust and insensitive to ambient noise. Experiments show that, compared with conventional sensitivity measurement, the total relaxation rate affected by magnetic noise below 0.9 nT, pump light frequency noise below 1.5 GHz, pump light power noise below 9%, probe light power noise below 3% and temperature fluctuation of 150 ±3 ℃ deviates by less than 2% from the noise-free situation. This robust performance evaluation method for vapor cells is conducive to the construction of a multi-channel high-spatial-resolution cardio-encephalography system.

ATOMIC AND MOLECULAR PHYSICS

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A simple semiempirical model for the static polarizability of electronically excited atoms and molecules Alexander S Sharipov, Alexey V Pelevkin, and Boris I Loukhovitski Chin. Phys. B, 2023, 32 (4):  043301.  DOI: 10.1088/1674-1056/ac8342 Abstract ( 276 )   HTML ( 2 )   PDF (855KB) ( 165 )   We present a semiempirical analytical model for the static polarizability of electronically excited atoms and molecules, which requires very few readily accessible input data, including the ground-state polarizability, elemental composition, ionization potential, and spin multiplicities of excited and ground states. This very simple model formulated in a semiclassical framework is based on a number of observed trends in polarizability of electronically excited compounds. To adjust the model, both accurate theoretical predictions and reliable measurements previously reported elsewhere for a broad range of multielectron species in the gas phase are utilized. For some representative compounds of general concern that have not yet attracted sufficient research interest, the results of our multireference second-order perturbation theory calculations are additionally engaged. We show that the model we developed has reasonable (given the considerable uncertainties in the reference data) accuracy in predicting the static polarizability of electronically excited species of arbitrary size and excitation energy. These findings can be useful for many applications, where there is a need for inexpensive and quick assessments of the static gas-phase polarizability of excited electronic states, in particular, when building the complex nonequilibrium kinetic models to describe the observed optical refractivity (dielectric permittivity) of nonthermal reacting gas flows.

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

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Plasma density transition-based electron injection in laser wake field acceleration driven by a flying focus laser Pan-Fei Geng(耿盼飞), Min Chen(陈民), Xiang-Yan An(安相炎), Wei-Yuan Liu(刘维媛), Xin-Zhe Zhu(祝昕哲), Jian-Long Li(李建龙), Bo-Yuan Li(李博原), and Zheng-Ming Sheng(盛政明) Chin. Phys. B, 2023, 32 (4):  044101.  DOI: 10.1088/1674-1056/acae79 Abstract ( 304 )   HTML ( 5 )   PDF (8187KB) ( 264 )   By using a high-intensity flying focus laser, the dephasingless [Phys. Rev. Lett. 124 134802 (2020)] or phase-locked [Nat. Photon. 14 475 (2020)] laser wakefield acceleration (LWFA) can be realized, which may overcome issues of laser diffraction, pump depletion, and electron dephasing which are always suffered in usual LWFA. The scheme thus has the potentiality to accelerate electrons to TeV energy in a single acceleration stage. However, the controlled electron injection has not been self-consistently included in such schemes. Only external injection was suggested in previous theoretical studies, which requires other accelerators and is relatively difficulty to operate. Here, we numerically study the actively controlled density transition injection in phase-locked LWFA to get appropriate density profiles for amount of electron injection. The study shows that compared with LWFA driven by lasers with fixed focus, a larger plasma density gradient is necessary. Electrons experience both transverse and longitudinal loss during acceleration due to the superluminal group velocity of the driver and the variation of the wakefield structure. Furthermore, the periodic deformation and fracture of the flying focus laser in the high-density plasma plateau make the final injected charge also depend on the beginning position of the density downramp. Our studies show a possible way for amount of electron injection in LWFA driven by flying focus lasers.

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Propagation and focusing characteristics of the Bessel-Gaussian beam with the spiral phase term of new power-exponent-phase Aotian Wang(王傲天), Lianghong Yu(於亮红), Jinfeng Li(李进峰), and Xiaoyan Liang(梁晓燕) Chin. Phys. B, 2023, 32 (4):  044201.  DOI: 10.1088/1674-1056/acb1fe Abstract ( 321 )   HTML ( 3 )   PDF (2727KB) ( 257 )   A new type of beam called the NPEP-BG (a Bessel-Gaussian (BG) beam with a spiral phase term of a new power-exponent-phase (NPEP)) is theoretically studied in this paper. The results show that the number of singularities of the phase and side lobes of the intensity of this beam were equal to the topological charges (TCs) and the beam has the characteristics of self-healing during propagation. The NPEP-BG beam combined the partial characteristics of the new power-exponent-phase vortex (NPEPV) and the Bessel-Gaussian beam. At the focus of the beam, the characteristic like a perfect vortex beam was present, in which the focal radius is stable and independent of the topological charge. There are multi-focal spots around a ring in the focal plane, meaning that the NPEP-BG beam has a potential for application in multi-particle manipulation.

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Nonreciprocal wide-angle bidirectional absorber based on one-dimensional magnetized gyromagnetic photonic crystals You-Ming Liu(刘又铭), Yuan-Kun Shi(史源坤), Ban-Fei Wan(万宝飞), Dan Zhang(张丹), and Hai-Feng Zhang(章海锋) Chin. Phys. B, 2023, 32 (4):  044203.  DOI: 10.1088/1674-1056/ac921d Abstract ( 264 )   HTML ( 4 )   PDF (7715KB) ( 106 )   We propose magnetized gyromagnetic photonic crystals (MGPCs) composed of indium antimonide (InSb) and yttrium iron garnet ferrite (YIGF) layers, which possess the properties of nonreciprocal wide-angle bidirectional absorption. Periodical defects in the MGPCs work as filters. Absorption bands (ABs) for the positive and negative propagations arise from the optical Tamm state and resonance in cavities respectively, and they prove to share no overlaps in the studied frequency range. Given ω=2.0138 THz, for the positive propagation, the ABs in the high-frequency range are localized in the interval between 0.66ω and 0.88ω. In the angular range, the ABs for the TE and TM waves reach 60° and 51°, separately. For the negative propagation, the ABs in the low-frequency range are localized in the interval between 0.13ω and 0.3ω. The ABs extend to 60° for the TE waves and 80.4° for the TM waves. There also exists a narrow frequency band in a lower frequency range. The relevant factors, which include the external temperature, the magnetic fields applied to the YIGF, the refractive index of the impedance matching layer, and the defect thickness, are adjusted to investigate the effects on the ABs. All the numerical simulations are based on the transfer matrix method. This work provides an approach to designs of isolators and so on.

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A probability theory for filtered ghost imaging Zhong-Yuan Liu(刘忠源), Shao-Ying Meng(孟少英), and Xi-Hao Chen(陈希浩) Chin. Phys. B, 2023, 32 (4):  044204.  DOI: 10.1088/1674-1056/ac981e Abstract ( 290 )   HTML ( 4 )   PDF (899KB) ( 39 )   Based on probability density functions, we present a theoretical model to explain filtered ghost imaging (FGI) we first proposed and experimentally demonstrated in 2017 [Opt. Lett. 42 5290 (2017)]. An analytic expression for the joint intensity probability density functions of filtered random speckle fields is derived according to their probability distributions. Moreover, the normalized second-order intensity correlation functions are calculated for the three cases of low-pass, bandpass and high-pass filterings to study the resolution and visibility in the FGI system. Numerical simulations show that the resolution and visibility predicted by our model agree well with the experimental results, which also explains why FGI can achieve a super-resolution image and better visibility than traditional ghost imaging.

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Light manipulation by dual channel storage in ultra-cold Rydberg medium Xue-Dong Tian(田雪冬), Zi-Jiao Jing(景梓骄), Feng-Zhen Lv(吕凤珍),Qian-Qian Bao(鲍倩倩), and Yi-Mou Liu(刘一谋) Chin. Phys. B, 2023, 32 (4):  044205.  DOI: 10.1088/1674-1056/ac946c Abstract ( 281 )   HTML ( 2 )   PDF (3410KB) ( 113 )   We investigate the light propagation dynamics in ultra-cold Rydberg medium with inverted-Y configuration based on the superatom theory. It is viable to store light information in two types of atomic spin coherence (trivial spin coherence and Rydberg spin coherence), which makes the system a prospective platform for versatile light manipulation. A normal feature is to realize efficient light storage with simultaneous resonant control fields applied. An intriguing feature is to split light into two beams with different intensities and statistical properties if the control fields are applied separately. The beam of light retrieved from the Rydberg spin coherence is severely attenuated and shows anti-bunching character accompanied by the cooperative optical nonlinearity. Moreover, generation and manipulation of beating signal are achievable by applying the non-resonant control fields.

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Mode characteristics of VCSELs with different shape and size oxidation apertures Xin-Yu Xie(谢新宇), Jian Li(李健), Xiao-Lang Qiu(邱小浪), Yong-Li Wang(王永丽), Chuan-Chuan Li(李川川), and Xin Wei(韦欣) Chin. Phys. B, 2023, 32 (4):  044206.  DOI: 10.1088/1674-1056/ac9821 Abstract ( 358 )   HTML ( 3 )   PDF (1512KB) ( 236 )   Vertical cavity surface emitting laser (VCSELs) as the ideal light source for rubidium (Rb) and cesium (Cs) atomic clocks is analyzed for its mode and polarization control. We fabricated three kinds of shapes: triangular, elliptic, and circular oxidation apertures which also have different sizes. We formed three different shape oxide apertures by wet-oxidation with 36 μm-39 μm circular mesa. Our results show that triangular oxidized-VCSEL has the advantages of mode and polarization selection over elliptic and circular oxide apertures. When triangular oxide-confined VCSELs emit in single mode, the measured side mode suppression ratio (SMSR) is larger than 20 dB and orthogonal polarization suppression ratio achieves 10 dB. Resonant blueshift of VCSELs with triangular and elliptic apertures is observed with the decrease of aperture size.

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Angular insensitive nonreciprocal ultrawide band absorption in plasma-embedded photonic crystals designed with improved particle swarm optimization algorithm Yi-Han Wang(王奕涵) and Hai-Feng Zhang(章海锋) Chin. Phys. B, 2023, 32 (4):  044207.  DOI: 10.1088/1674-1056/ac8929 Abstract ( 258 )   HTML ( 2 )   PDF (4279KB) ( 160 )   Using an improved particle swarm optimization algorithm (IPSO) to drive a transfer matrix method, a nonreciprocal absorber with an ultrawide absorption bandwidth and angular insensitivity is realized in plasma-embedded photonic crystals arranged in a structure composed of periodic and quasi-periodic sequences on a normalized scale. The effective dielectric function, which determines the absorption of the plasma, is subject to the basic parameters of the plasma, causing the absorption of the proposed absorber to be easily modulated by these parameters. Compared with other quasi-periodic sequences, the Octonacci sequence is superior both in relative bandwidth and absolute bandwidth. Under further optimization using IPSO with 14 parameters set to be optimized, the absorption characteristics of the proposed structure with different numbers of layers of the smallest structure unit N are shown and discussed. IPSO is also used to address angular insensitive nonreciprocal ultrawide bandwidth absorption, and the optimized result shows excellent unidirectional absorbability and angular insensitivity of the proposed structure. The impacts of the sequence number of quasi-periodic sequence M and collision frequency of plasma1 ν1 to absorption in the angle domain and frequency domain are investigated. Additionally, the impedance match theory and the interference field theory are introduced to express the findings of the algorithm.

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Diffraction deep neural network based orbital angular momentum mode recognition scheme in oceanic turbulence Hai-Chao Zhan(詹海潮), Bing Chen(陈兵), Yi-Xiang Peng(彭怡翔), Le Wang(王乐), Wen-Nai Wang(王文鼐), and Sheng-Mei Zhao(赵生妹) Chin. Phys. B, 2023, 32 (4):  044208.  DOI: 10.1088/1674-1056/ac935e Abstract ( 334 )   HTML ( 3 )   PDF (848KB) ( 318 )   Orbital angular momentum (OAM) has the characteristics of mutual orthogonality between modes, and has been applied to underwater wireless optical communication (UWOC) systems to increase the channel capacity. In this work, we propose a diffractive deep neural network (DDNN) based OAM mode recognition scheme, where the DDNN is trained to capture the features of the intensity distribution of the OAM modes and output the corresponding azimuthal indices and radial indices. The results show that the proposed scheme can recognize the azimuthal indices and radial indices of the OAM modes accurately and quickly. In addition, the proposed scheme can resist weak oceanic turbulence (OT), and exhibit excellent ability to recognize OAM modes in a strong OT environment. The DDNN-based OAM mode recognition scheme has potential applications in UWOC systems.

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Propagation of light near the band edge in one-dimensional multilayers Yang Tang(唐洋), Lingjie Fan(范灵杰), Yanbin Zhang(张彦彬), Tongyu Li(李同宇), Tangyao Shen(沈唐尧), and Lei Shi(石磊) Chin. Phys. B, 2023, 32 (4):  044209.  DOI: 10.1088/1674-1056/ac892b Abstract ( 313 )   HTML ( 2 )   PDF (606KB) ( 76 )   Optical systems offer rich modulation in light propagation, but sufficient quantitative descriptions lack when highly complex structures are considered since practical structures contain defects or imperfections. Here, we utilize a method combining a data-fitting method and a time-resolved system to describe light propagation near the band edges in one-dimensional structures. Calculations after optimization of the method show little deviation to the measurements.

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Effective dynamics and quantum state engineering by periodic kicks Zhi-Cheng Shi(施志成), Zhen Chen(陈阵), Jian-Hui Wang(王建辉), Yan Xia(夏岩), and X X Yi(衣学喜) Chin. Phys. B, 2023, 32 (4):  044210.  DOI: 10.1088/1674-1056/ac7bfc Abstract ( 260 )   HTML ( 3 )   PDF (3207KB) ( 57 )   We study the kick dynamics of periodically driven quantum systems, and provide a time-independent effective Hamiltonian with the analytical form to reasonably describe the effective dynamics in a long timescale. It is shown that the effective coupling strength can be much larger than the coupling strength of the original system in some parameter regions, which stems from the zero time duration of kicks. Furthermore, different regimes can be transformed from and to each other in the same three-level system by only modulating the period of periodic kicks. In particular, the population of excited states can be selectively suppressed in periodic kicks, benefiting from the large detuning regime of the original system. Finally, some applications and physical implementation of periodic kicks are demonstrated in quantum systems. These unique features would make periodic kicks become a powerful tool for quantum state engineering.

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Spontaneous emission from Λ-type three-level atom driven by bichromatic field in anisotropic double-band photonic crystals Kai Ling(凌凯), Li Jiang(姜丽), Ren-Gang Wan(万仁刚), and Zhi-Hai Yao(姚治海) Chin. Phys. B, 2023, 32 (4):  044211.  DOI: 10.1088/1674-1056/aca39b Abstract ( 282 )   HTML ( 2 )   PDF (987KB) ( 166 )   The spontaneous emission property of Λ-type three-level atom driven by the bichromatic field in the anisotropic double-band photonic crystal is calculated by n-times iteration method. The influence of different parameters on atomic spontaneous emission is studied, and the phenomena of atomic spontaneous emission are explained in the dressed state representation. It is found that the spontaneous emission spectra of the atom driven by the bichromatic field presents a multi-peak comb structure. The position of the emission peak is determined by the initial state of the atom, and the interval between the neighboring emission peaks is the detuning δ of the bichromatic field. When the ratio between Rabi frequency intensity and the detuning δ of the bichromatic field remains unchanged, the intensity of each emitted peak remains invariant. The spontaneously emitted peak can be annihilated in the band gap and enhanced near the band edge in the anisotropic photonic crystals. Meanwhile, we also observe the fluorescence quenching phenomenon in the spontaneous emission spectra. The research in this paper provides the theoretical guidance for the control of atomic spontaneous emission.

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Design and simulation of a silicon-based hybrid integrated optical gyroscope system Dao-Xin Sun(孙道鑫), Dong-Liang Zhang(张东亮), Li-Dan Lu(鹿利单), Tao Xu(徐涛),Xian-Tong Zheng(郑显通), Zhe-Hai Zhou(周哲海), and Lian-Qing Zhu(祝连庆) Chin. Phys. B, 2023, 32 (4):  044212.  DOI: 10.1088/1674-1056/ac81a9 Abstract ( 294 )   HTML ( 1 )   PDF (1608KB) ( 393 )   By combining a silicon-based lithium niobate modulator and a silicon-based Si3N4 resonator with silicon-based photonics technology, a highly systematic design of a hybrid integrated optical gyroscope with enhanced reciprocity sensitivity and a dual micro-ring structure is proposed for the first time in this paper. The relationship between the device's structural parameters and optical performance is also analyzed by constructing a complete simulation link, which provides a theoretical design reference to improve the system's sensitivity. When the wavelength is 1550 nm, the conversion frequency of the dual-ring optical path is 50 MHz, the coupling coefficient is 0.2, and the radius R is 1000 μm, the quality factor of the silicon-based Si3N4 resonator is 2.58×105, which is 1.58 times that of the silicon-on-insulator resonator. Moreover, the effective number of times the light travels around the ring before leaving the micro-ring is 5.93, which is 1.62 times that of the silicon-on-insulator resonator. The work fits the gyro dynamic output diagram, and solves the problem of low sensitivity at low speed by setting the phase offset. This results provide a basis for the further optimization of design and chip processing of the integrated optical gyroscope.

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Nonlinear wave propagation in acoustic metamaterials with bilinear nonlinearity Shiqi Liang(梁诗琪), Jiehui Liu(刘杰惠), Yun Lai(赖耘), and Xiaozhou Liu(刘晓宙) Chin. Phys. B, 2023, 32 (4):  044301.  DOI: 10.1088/1674-1056/ac9783 Abstract ( 298 )   HTML ( 1 )   PDF (1747KB) ( 151 )   Nonlinear phononic crystals have attracted great interest because of their unique properties absent in linear phononic crystals. However, few researches have considered the bilinear nonlinearity as well as its consequences in acoustic metamaterials. Hence, we introduce bilinear nonlinearity into acoustic metamaterials, and investigate the propagation behaviors of the fundamental and the second harmonic waves in the nonlinear acoustic metamaterials by discretization method, revealing the influence of the system parameters. Furthermore, we investigate the influence of partially periodic nonlinear acoustic metamaterials on the second harmonic wave propagation, and the results suggest that pass-band and band-gap can be transformed into each other under certain conditions. Our findings could be beneficial to the band gap control in nonlinear acoustic metamaterials.

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Extension of sound field reconstruction based on element radiation superposition method in a sparsity framework Yuan Gao(高塬), Bo-Quan Yang(杨博全), Sheng-Guo Shi(时胜国), and Hao-Yang Zhang(张昊阳) Chin. Phys. B, 2023, 32 (4):  044302.  DOI: 10.1088/1674-1056/ac8e55 Abstract ( 228 )   HTML ( 1 )   PDF (3939KB) ( 67 )   Nearfield acoustic holography (NAH) is a powerful tool for realizing source identification and sound field reconstruction. The wave superposition (WS)-based NAH is appropriate for the spatially extended sources and does not require the complex numerical integrals. Equivalent source method (ESM), as a classical WS approach, is widely used due to its simplicity and efficiency. In the ESM, a virtual source surface is introduced, on which the virtual point sources are taken as the assumed sources, and an optimal retreat distance needs to be considered. A newly proposed WS-based approach, the element radiation superposition method (ERSM), uses piston surface source as the assumed source with no need to choose a virtual source surface. To satisfy the application conditions of piston pressure formula, the sizes of pistons are assumed to be as small as possible, which results in a large number of pistons and sampling points. In this paper, transfer matrix modes (TMMs), which are composed of the singular vectors of the vibro-acoustic transfer matrix, are used as the sparse basis of piston normal velocities. Then, the compressive ERSM based on TMMs is proposed. Compared with the conventional ERSM, the proposed method maintains a good pressure reconstruction when the number of sampling points and pistons are both reduced. Besides, the proposed method is compared with the compressive ESM in a mathematical sense. Both simulations and experiments for a rectangular plate demonstrate the advantage of the proposed method over the existing methods.

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Guide and control of thermal conduction with isotropic thermodynamic parameters based on a rotary-concentrating device Mao Liu(刘帽) and Quan Yan(严泉) Chin. Phys. B, 2023, 32 (4):  044402.  DOI: 10.1088/1674-1056/ac9cc1 Abstract ( 285 )   HTML ( 1 )   PDF (1226KB) ( 202 )   A rotary-concentrating device for thermal conduction is constructed to control and guide thermal energy transmitting in elastic plates. The designed device has the ability of concentrating for thermal conduction and controlling the processes of thermal diffusion in a plate. The multilayered isotropic material properties of the rotary-concentrating device are derived based on the transformation and rotary medium method and a rotation parameter to control the thermal diffusion process is introduced. The efficiency of the rotary-concentrating device for thermal conduction is verified. Stability of temperature fields in a plate with the rotary-concentrating device is analyzed to study the performance of rotary-concentrating. Numerical examples show that the constructed rotary-concentrating device for thermal conduction can effectively rotate and focus on the thermal energy into the device for a wide range of diffusion temperatures, which can enhance the thermal conduction. Therefore, this study can provide a theoretical support for potential applications in fields of energy harvesting and thermal conduction control.

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A stochastic two-dimensional intelligent driver car-following model with vehicular dynamics Hong-Sheng Qi(祁宏生) and Yu-Yan Ying(应雨燕) Chin. Phys. B, 2023, 32 (4):  044501.  DOI: 10.1088/1674-1056/ac8f3c Abstract ( 264 )   HTML ( 2 )   PDF (6110KB) ( 181 )   The law of vehicle movement has long been studied under the umbrella of microscopic traffic flow models, especially the car-following (CF) models. These models of the movement of vehicles serve as the backbone of traffic flow analysis, simulation, autonomous vehicle development, etc. Two-dimensional (2D) vehicular movement is basically stochastic and is the result of interactions between a driver's behavior and a vehicle's characteristics. Current microscopic models either neglect 2D noise, or overlook vehicle dynamics. The modeling capabilities, thus, are limited, so that stochastic lateral movement cannot be reproduced. The present research extends an intelligent driver model (IDM) by explicitly considering both vehicle dynamics and 2D noises to formulate a stochastic 2D IDM model, with vehicle dynamics based on the stochastic differential equation (SDE) theory. Control inputs from the vehicle include the steer rate and longitudinal acceleration, both of which are developed based on an idea from a traditional intelligent driver model. The stochastic stability condition is analyzed on the basis of Lyapunov theory. Numerical analysis is used to assess the two cases: (i) when a vehicle accelerates from a standstill and (ii) when a platoon of vehicles follow a leader with a stop-and-go speed profile, the formation of congestion and subsequent dispersion are simulated. The results show that the model can reproduce the stochastic 2D trajectories of the vehicle and the marginal distribution of lateral movement. The proposed model can be used in both a simulation platform and a behavioral analysis of a human driver in traffic flow.

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Phase-field-crystal simulation of nano-single crystal microcrack propagation under different orientation angles Dunwei Peng(彭敦维), Yunpeng Zhang(张云鹏), Xiaolin Tian(田晓林), Hua Hou(侯华), and Yuhong Zhao(赵宇宏) Chin. Phys. B, 2023, 32 (4):  044601.  DOI: 10.1088/1674-1056/acb41d Abstract ( 264 )   HTML ( 2 )   PDF (8592KB) ( 194 )   The propagation mechanism of microcracks in nanocrystalline single crystal systems under uniaxial dynamic and static tension is investigated using the phase-field-crystal method. Both dynamic and static stretching results show that different orientation angles can induce the crack propagation mode, microscopic morphology, the free energy, crack area change, and causing fracture failure. Crack propagation mode depends on the dislocation activity near the crack tip. Brittle propagation of the crack occurs due to dislocation always at crack tip. Dislocation is emitted at the front end of the crack tip and plastic deformation occurs, which belongs to ductile propagation. The orientation angles of 9° and 14° are brittle-ductile mixed propagation, while the orientation angles of 19° and 30° are brittle propagation and no dislocation is formed under dynamic tension. The vacancy and vacancy connectivity phenomenon would appear when the orientation angle is 14° under static tension, and the crack would be ductile propagation. While the orientation angle is 19° and 30°, the crack propagates in a certain direction, which is a kind of brittle propagation. This work has some practical significance in preventing material fracture failure and improving material performance.

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Micro sliding friction model considering periodic variation stress distribution of contact surface and experimental verification Sheng-Hao Lu(卢晟昊), Jing-Yu Han(韩靖宇), and Shao-Ze Yan(阎绍泽) Chin. Phys. B, 2023, 32 (4):  044602.  DOI: 10.1088/1674-1056/ac9043 Abstract ( 277 )   HTML ( 0 )   PDF (2347KB) ( 52 )   Micro sliding phenomenon widely exists in the operation process of mechanical systems, and the micro sliding friction mechanism is always a research hotspot. In this work, based on the total reflection method, a measuring device for interface contact behavior under two-dimensional (2D) vibration is built. The stress distribution is characterized by the light intensity distribution of the contact image, and the interface contact behavior in the 2D vibration process is studied. It is found that the vibration angle of the normal direction of the contact surface and its fluctuation affect the interface friction coefficient, the tangential stiffness, and the fluctuation amplitude of the stress distribution. Then they will affect the change of friction state and energy dissipation in the process of micro sliding. Further, an improved micro sliding friction model is proposed based on the experimental analysis, with the nonlinear change of contact parameters caused by the normal contact stress distribution fluctuation taken into account. This model considers the interface tangential stiffness fluctuation, friction coefficient hysteresis, and stress distribution fluctuation, whose simulation results are consistent well with the experimental results. It is found that considering the nonlinear effect of a certain contact parameter alone may bring a greater error to the prediction of friction behavior. Only by integrating multiple contact parameters can the accuracy of friction prediction is improved.

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Flow and clogging in a horizontal silo with a rotary obstacle Cong-Cong Xu(徐聪聪), Qing-Fan Shi(史庆藩), Wei Liu(刘伟), and Ning Zheng(郑宁) Chin. Phys. B, 2023, 32 (4):  044701.  DOI: 10.1088/1674-1056/ac7a19 Abstract ( 252 )   HTML ( 0 )   PDF (3347KB) ( 150 )   The external perturbation applied to a silo and the placement of an immobile obstacle before an exit are two common and effective ways to diminish clogging in the hopper/silo flow. Here, we incorporate the local perturbation into a fixed obstacle, and experimentally explore the effects of a rotary obstacle on clogging and the flowing characteristics in the horizontal silo flow driven by a conveyor belt. Even with a low spin rate, the total blocking probability that a particle constructs a stable blocking arch with its neighbors significantly drops. Correspondingly, the average flow rate of the particles through the exit abruptly rises, at least 1 order of magnitude better than that with an immobile obstacle and approaching the flow rate of continuous flow. The rotation enhances the breakage of clogging arches, which is responsible for improving the flowability in the horizontal silo. In addition, there always exists an optimal obstacle position at which the total blocking probability is minimal and the average flow rate peaks, regardless of the spin rate. Finally, clogging is relieved with the increase of the driving velocity of the conveyor belt, showing a "fast is fast" effect that is opposite to the "fast is slow" effect in other systems such as crowd evacuation and gravity-driven hoppers.

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Simulation of single bubble dynamic process in pool boiling process under microgravity based on phase field method Chang-Sheng Zhu(朱昶胜), Bo-Rui Zhao(赵博睿), Yao Lei(雷瑶), and Xiu-Ting Guo(郭秀婷) Chin. Phys. B, 2023, 32 (4):  044702.  DOI: 10.1088/1674-1056/aca209 Abstract ( 273 )   HTML ( 0 )   PDF (793KB) ( 167 )   We use the phase field method to track the gas-liquid interface based on the gas-liquid two-phase flow in the pool boiling process, and study the bubble nucleation, growth, deformation, departure and other dynamic behaviors on the heating surface under microgravity. By simulating the correlation between liquid undercooling and bubble dynamics, we find that the bubble growth time increases with the increase of liquid undercooling, but the effect of liquid undercooling on bubble height is not significant. Meanwhile, the gas-liquid-solid three-phase contact angle and the gravity level will also have an effect on the bubble growth time and bubble height. With the increase of the contact angle, the bubble growth time and bubble height when the bubble departs also increase. While the effect of gravity level is on the contrary, the smaller the gravity level is, the larger the bubble height and bubble growth time when the bubble separates.

PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES

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Gas- and plasma-driven hydrogen permeation behavior of stagnant eutectic-solid GaInSn/Fe double-layer structure Wen-Na Jing(荆文娜), Jian-Xing Liu(刘建星), Heng-Xin Guo(郭恒鑫), Si-Shu Wang(王思蜀), Hai-Lin Bi(毕海林), Bo Chen(陈波), Jian-Jun Chen(陈建军), Hong-Bin Wang(王宏彬), Jian-Jun Wei(韦建军), Zong-Biao Ye(叶宗标), and Fu-Jun Gou(芶富均) Chin. Phys. B, 2023, 32 (4):  045201.  DOI: 10.1088/1674-1056/ac9365 Abstract ( 223 )   HTML ( 0 )   PDF (1705KB) ( 25 )   Gas-driven permeation (GDP) and plasma-driven permeation (PDP) of hydrogen gas through GaInSn/Fe are systematically investigated in this work. The permeation parameters of hydrogen through GaInSn/Fe, including diffusivity, Sieverts' constant, permeability, and surface recombination coefficient are obtained. The permeation flux of hydrogen through GaInSn/Fe shows great dependence on external conditions such as temperature, hydrogen pressure, and thickness of liquid GaInSn. Furthermore, the hydrogen permeation behavior through GaInSn/Fe is well consistent with the multi-layer permeation theory. In PDP and GDP experiments, hydrogen through GaInSn/Fe satisfies the diffusion-limited regime. In addition, the permeation flux of PDP is greater than that of GDP. The increase of hydrogen plasma density hardly causes the hydrogen PDP flux to change within the test scope of this work, which is due to the dissolution saturation. These findings provide guidance for a comprehensive and systematic understanding of hydrogen isotope recycling, permeation, and retention in plasma-facing components under actual conditions.

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Drift characteristics and the multi-field coupling stress mechanism of the pantograph-catenary arc under low air pressure Zhilei Xu(许之磊), Guoqiang Gao(高国强), Pengyu Qian(钱鹏宇), Song Xiao(肖嵩), Wenfu Wei(魏文赋), Zefeng Yang(杨泽锋), Keliang Dong(董克亮), Yaguang Ma(马亚光), and Guangning Wu(吴广宁) Chin. Phys. B, 2023, 32 (4):  045202.  DOI: 10.1088/1674-1056/ac9360 Abstract ( 326 )   HTML ( 1 )   PDF (1483KB) ( 137 )   The fault caused by a pantograph-catenary arc is the main factor that threatens the stability of high-speed railway energy transmission. Pantograph-catenary arc vertical drift is more severe than the case under normal pressure, as it is easy to develop the rigid busbar, which may lead to the flashover occurring around the support insulators. We establish a pantograph-catenary arc experiment and diagnosis platform to simulate low pressure and strong airflow environment. Meanwhile, the variation law of arc drift height with time under different air pressures and airflow velocities is analyzed. Moreover, arc drift characteristics and influencing factors are explored. The physical process of the arc column drifting to the rigid busbar with the jumping mechanism of the arc root on the rigid busbar is summarized. In order to further explore the mechanism of the above physical process, a multi-field stress coupling model is built, as the multi-stress variation law of arc is quantitatively evaluated. The dynamic action mechanism of multi-field stress on arc drifting characteristics is explored, as the physical mechanism of arc drifting under low pressure is theoretically explained. The research results provide theoretical support for arc suppression in high-altitude areas.

CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

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Effect of temperature on heavy ion-induced single event transient on 16-nm FinFET inverter chains Li Cai(蔡莉), Ya-Qing Chi(池雅庆), Bing Ye(叶兵), Yu-Zhu Liu(刘郁竹), Ze He(贺泽), Hai-Bin Wang(王海滨), Qian Sun(孙乾), Rui-Qi Sun(孙瑞琪), Shuai Gao(高帅), Pei-Pei Hu(胡培培), Xiao-Yu Yan(闫晓宇), Zong-Zhen Li(李宗臻), and Jie Liu(刘杰) Chin. Phys. B, 2023, 32 (4):  046101.  DOI: 10.1088/1674-1056/ac8e9c Abstract ( 278 )   HTML ( 4 )   PDF (1700KB) ( 150 )   The variations of single event transient (SET) pulse width of high-LET heavy ion irradiation in 16-nm-thick bulk silicon fin field-effect transistor (FinFET) inverter chains with different driven strengths are measured at different temperatures. Three-dimensional (3D) technology computer-aided design simulations are carried out to study the SET pulse width and saturation current varying with temperature. Experimental and simulation results indicate that the increase in temperature will enhance the parasitic bipolar effect of bulk FinFET technology, resulting in the increase of SET pulse width. On the other hand, the increase of inverter driven strength will change the layout topology, which has a complex influence on the SET temperature effects of FinFET inverter chains. The experimental and simulation results show that the device with the strongest driven strength has the least dependence on temperature.

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Analytical determination of non-local parameter value to investigate the axial buckling of nanoshells affected by the passing nanofluids and their velocities considering various modified cylindrical shell theories Soheil Oveissi, Aazam Ghassemi, Mehdi Salehi, S. Ali Eftekhari, and Saeed Ziaei-Rad Chin. Phys. B, 2023, 32 (4):  046201.  DOI: 10.1088/1674-1056/ac9cba Abstract ( 274 )   HTML ( 2 )   PDF (1101KB) ( 24 )   We analytically determine the nonlocal parameter value to achieve a more accurate axial-buckling response of carbon nanoshells conveying nanofluids. To this end, the four plates/shells' classical theories of Love, Flügge, Donnell, and Sanders are generalized using Eringen's nonlocal elasticity theory. By combining these theories in cylindrical coordinates, a modified motion equation is presented to investigate the buckling behavior of the nanofluid-nanostructure-interaction problem. Herein, in addition to the small-scale effect of the structure and the passing fluid on the critical buckling strain, we discuss the effects of nanoflow velocity, fluid density (nano-liquid/nano-gas), half-wave numbers, aspect ratio, and nanoshell flexural rigidity. The analytical approach is used to discretize and solve the obtained relations to study the mentioned cases.

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Pressure-induced structural transition and low-temperature recovery of sodium pentazolate Zitong Zhao(赵梓彤), Ran Liu(刘然), Linlin Guo(郭琳琳), Shuang Liu(刘爽), Minghong Sui(隋明宏), Bo Liu(刘波), Zhen Yao(姚震), Peng Wang(王鹏), and Bingbing Liu(刘冰冰) Chin. Phys. B, 2023, 32 (4):  046202.  DOI: 10.1088/1674-1056/acb917 Abstract ( 338 )   HTML ( 1 )   PDF (2398KB) ( 124 )   Pentazolate compounds have attracted extensive attention as high energy density materials. The synthesis and recovery of pentazolate compounds is of great importance for their potential applications. Here, we report the synthesis of $Pmn$2$_{1}$-NaN$_{5}$ and $Pm$-Na$_{2}$N$_{5}$ through compressing and laser heating pure NaN$_{3}$ at $\sim 60 $ GPa. Upon decompression, the pressure-induced structural transition from $Pmn$2$_{1}$-NaN$_{5}$ into $Cm$-NaN$_{5}$ is observed in the pressure range of 14-23 GPa for the first time. The cyclo-N$_{5}^{-}$ can be traced down to 4.7 GPa at room temperature and recovered to ambient pressure under low temperature condition (up to 160 K). The $Pm$-Na$_{2}$N$_{5}$ is suggested to decompose into the $P$4/$mmm$-NaN$_{2}$ at 23 GPa, and be stable at ambient conditions. This work provides insight into the high-pressure behaviors of pentazolate compounds and an alternative way to stabilize energetic polynitrogen compounds.

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Mechanical enhancement and weakening in Mo6S6 nanowire by twisting Ke Xu(徐克), Yanwen Lin(林演文), Qiao Shi(石桥), Yuequn Fu(付越群), Yi Yang(杨毅), Zhisen Zhang(张志森), and Jianyang Wu(吴建洋) Chin. Phys. B, 2023, 32 (4):  046204.  DOI: 10.1088/1674-1056/aca7e7 Abstract ( 298 )   HTML ( 4 )   PDF (1272KB) ( 110 )   The torsional, bending and tensile mechanical properties of Mo6S6 nanowire are examined by molecular dynamics (MD) simulations with a first-principles-based reactive force field (ReaxFF). It is found that Mo6S6 nanowire shows unique mechanical properties such as high torsional and bending flexibility, high Young's modulus and strength, and negative Poisson's ratio. The Mo6S6 nanowire can be strengthened or weakened via twisting, depending on the twist angle. The Mo6S6 nanowire with a slight twist angle shows brittle failure, whereas it with a large twist angle exhibits ductile failure and necking behavior. Twisted Mo6S6 nanowires show a crossover in the negative Poisson's ratio at critical strains, that is, Poisson's ratio first decreases but then increases, with a minimum value down to around -0.8 at the strain of 0.01 as the twist angle is 21.0 °/nm. The negative Poisson's ratio and the crossover are explained by the bond transform that makes zero angles to the wire cross-section.

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Effects of phonon bandgap on phonon-phonon scattering in ultrahigh thermal conductivity θ-phase TaN Hot! Chao Wu(吴超) and Chenhan Liu(刘晨晗) Chin. Phys. B, 2023, 32 (4):  046502.  DOI: 10.1088/1674-1056/acb201 Abstract ( 362 )   HTML ( 13 )   PDF (2411KB) ( 302 )   Phonon bandgap typically has a significant effect on phonon-phonon scattering process. In this work, the effects of mass modified phonon bandgap in θ -phase TaN are systemically investigated by the means of first-principles calculations with linearized Boltzmann transport equation. Through detailed calculations, we find that phonon bandgap has a significant effect on three-phonon process while exhibits a much weaker effect on four-phonon process. The reason for the ultrahigh thermal conductivity of θ -phase TaN is the long lifetime of phonons including both three-phonon and four-phonon processes, which originates from the weak phonon anharmonicity and large phonon bandgap-induced small phonon-phonon scattering phase space. This work advances the understanding of phonon bandgap effects on phonon transport.

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Study of metal-ceramic WC/Cu nano-wear behavior and strengthening mechanism Min Zheng(郑敏), Jie Chen(陈杰), Zong-Xiao Zhu(朱宗孝), Ding-Feng Qu(曲定峰), Wei-Hua Chen(陈卫华), Zhuo Wu(吴卓), Lin-Jun Wang(王林军), and Xue-Zhong Ma(马学忠) Chin. Phys. B, 2023, 32 (4):  046801.  DOI: 10.1088/1674-1056/ac8ea0 Abstract ( 237 )   HTML ( 0 )   PDF (3632KB) ( 204 )   In view of the inherent poor tribological properties of copper, the reinforcement of copper matrix composites with WC particles presents a promising research area with significant industrial influence. Therefore, in the present study, a molecular dynamics approach is used to simulate the process of repeated friction of diamond grinding balls on WC/Cu composites, and the friction force, friction coefficient, abrasion depth, wear rate, abrasion morphology, von-Mises stress, internal defects, workpiece energy, and performance comparison of different layer thicknesses are systematically investigated in the multiple friction process. It is found that the fluctuation amplitude of friction force, friction coefficient, and abrasion depth are smaller and the fluctuation frequency is larger during the initial friction, whereas near the WC phase, there appears extreme values of the above parameters and the von-Mises stress is highly concentrated while the workpiece energy contonues to increase. In the case of the repeated friction, with the increase of friction times, the friction force, friction coefficient, and abrasion depth fluctuation amplitude increase, the fluctuation frequency decreases, the workpiece energy reaches an extreme value near the WC phase, and a large number of dislocations plug, therefore, the region is strengthened. As the distance between the grinding ball and the WC phase decreases, the more obvious the strengthening effect, the stronger the ability of workpiece to resist the wear will be.

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Strain compensated type II superlattices grown by molecular beam epitaxy Chao Ning(宁超), Tian Yu(于天), Rui-Xuan Sun(孙瑞轩), Shu-Man Liu(刘舒曼), Xiao-Ling Ye(叶小玲), Ning Zhuo(卓宁), Li-Jun Wang(王利军), Jun-Qi Liu(刘俊岐), Jin-Chuan Zhang(张锦川), Shen-Qiang Zhai(翟慎强), and Feng-Qi Liu(刘峰奇) Chin. Phys. B, 2023, 32 (4):  046802.  DOI: 10.1088/1674-1056/ac7cd4 Abstract ( 333 )   HTML ( 0 )   PDF (1536KB) ( 166 )   We investigate a strain compensation method for the growth of complex interband cascade laser structures. For thick InAs/AlSb superlattice clad layers, the sublayer thicknesses were adjusted so that the tensile strain energy in the InAs sublayer was equal to the compressive strain energy in the AlSb sublayer. For the four-constituent active region, as the compressive strain in the Ga0.65In0.35Sb alloy layer was large, a tensile strain was incorporated in the chirped InAs/AlSb superlattice region for strain compensation to the Ga0.65In0.35Sb alloy. A laser structure of thickness 6 μm was grown on the GaSb substrate by molecular beam epitaxy. The wafer exhibited good surface morphology and high crystalline quality.

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Polarization Raman spectra of graphene nanoribbons Wangwei Xu(许望伟), Shijie Sun(孙诗杰), Muzi Yang(杨慕紫), Zhenliang Hao(郝振亮), Lei Gao(高蕾), Jianchen Lu(卢建臣), Jiasen Zhu(朱嘉森), Jian Chen(陈建), and Jinming Cai(蔡金明) Chin. Phys. B, 2023, 32 (4):  046803.  DOI: 10.1088/1674-1056/ac80b3 Abstract ( 293 )   HTML ( 4 )   PDF (1684KB) ( 183 )   The on-surface synthesis method allows the fabrication of atomically precise narrow graphene nanoribbons (GNRs), which bears great potential in electronic applications. Here, we synthesize armchair graphene nanoribbons (AGNRs) and chevron-type graphene nanoribbons (CGNRs) array on a vicinal Au(11 11 12) surface using 10,10'-dibromo-9,9'-bianthracene (DBBA) and 6,12-dibromochrysene (DBCh) as precursors, respectively. This process creates spatially well-aligned GNRs, as characterized by scanning tunneling microscopy. AGNRs show strong Raman linear polarizability for application in optical modulation devices. Different from the distinct polarization of AGNRs, only weak polarization exists in CGNRs polarized Raman spectrum, which suggests that the presence of the zigzag boundary in the nanoribbon attenuates the polarization rate as an important factor affecting the polarization. We analyze the Raman activation mode of CGNRs using the peak polarization to expand the application of the polarization Raman spectroscopy in nanoarray analysis.

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

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Predicting novel atomic structure of the lowest-energy FenP13-n (n=0-13) clusters: A new parameter for characterizing chemical stability Yuanqi Jiang(蒋元祺) and Ping Peng(彭平) Chin. Phys. B, 2023, 32 (4):  047102.  DOI: 10.1088/1674-1056/acae75 Abstract ( 290 )   HTML ( 3 )   PDF (1294KB) ( 132 )   A series of novel atomic structure of lowest-energy Fe$_{n}$P$_{13-n}$ ($n=0$-13) clusters via density functional theory (DFT) calculations and an unbiased structure search using Crystal structure AnaLYsis by Particle Swarm Optimization (CALYPSO) code. Our research results show that the global minimum geometry structure of neutral Fe$_{13-n}$P$_{n}$ ($n=0$-6) clusters tend to form cage structures but the lowest-energy Fe$_{13-n}$P$_{n}$ ($n=7$-13) clusters are gradually evolution from a cage structure to a chain shape geometric structure. Their geometric structure should responsible for the raise of binding energy from Fe$_{7}$P$_{6}$ to P$_{13}$ clusters rather than chemical components. This is completely different from a linear relation of the binding energy with chemical components in our previous research for Cu$_{n}$Zr$_{13-n}$ ($n=3$-10) clusters (J. Mol. Liq. 343 117603 (2021)). Hence, in order to characterize the global chemical stability of target cluster, we proposed a new parameter (${\rm jyq}=\eta /\chi $) that the chemical hardness of isolated cluster is used to be divided by its electronegativity. One of the biggest advantages of this parameter is successful coupling the ability of a resistance to redistribution of electrons and the ability to attract electrons from other system (such as atom, molecular or metallic clusters). Moreover, it is found that the P$_{13}$ cluster shows typical insulator characteristics but the Fe$_{12}$P$_{1}$ shows typical conductor characteristics, which phenomena can be attributed to the remarkable delocalized and localized electrons in Fe$_{12}$P$_{1}$ and P$_{13}$, respectively. In terms of nearly-free-electron mode, we also found that the number of electrons on Femi level ($N(E_{\rm F})$) are obviously tended to toward a lower value when Fe was replaced gradually with P from Fe$_{13}$ to P$_{13}$, and a non-magnetic can be observed in Fe$_{13}$, Fe$_{2}$P$_{11}$, Fe$_{1}$P$_{12}$, and P$_{13}$ that mainly because their perfect symmetrical between spin-up and spin-down of density of states of electrons.

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Exploration of growth conditions of TaAs Weyl semimetal thin film using pulsed laser deposition Shien Li(李世恩), Zefeng Lin(林泽丰), Wei Hu(胡卫), Dayu Yan(闫大禹), Fucong Chen(陈赋聪), Xinbo Bai(柏欣博), Beiyi Zhu(朱北沂), Jie Yuan(袁洁), Youguo Shi(石友国), Kui Jin(金魁), Hongming Weng(翁红明), and Haizhong Guo(郭海中) Chin. Phys. B, 2023, 32 (4):  047103.  DOI: 10.1088/1674-1056/acb913 Abstract ( 306 )   HTML ( 0 )   PDF (2033KB) ( 156 )   TaAs, the first experimentally discovered Weyl semimetal material, has attracted a lot of attention due to its high carrier mobility, high anisotropy, nonmagnetic properties and strong interaction with light. These make it an ideal candidate for the study of Weyl fermions and applications in quantum computation, thermoelectric devices, and photodetection. For further basic physics studies and potential applications, large-size and high-quality TaAs films are urgently needed. However, it is difficult to grow As-stoichiometry TaAs films due to the volatilization of As during the growth. To solve this problem, we attempted to grow TaAs films on different substrates using targets with different As stoichiometric ratios via pulsed laser deposition (PLD). In this work, we found that partial As ions of the GaAs substrate are likely to diffuse into the TaAs films during growth, which was preliminarily confirmed by structural characterization, surface topography and composition analysis. As a result, the As content in the TaAs film was improved and the TaAs phase was achieved. Our work presents an effective method for the fabrication of TaAs films using PLD, enabling possible use of the Weyl semimetal film for functional devices.

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Demonstrate chiral spin currents with nontrivial interactions in superconducting quantum circuit Xiang-Min Yu(喻祥敏), Xiang Deng(邓翔), Jian-Wen Xu(徐建文), Wen Zheng(郑文), Dong Lan(兰栋), Jie Zhao(赵杰), Xinsheng Tan(谭新生), Shao-Xiong Li(李邵雄), and Yang Yu(于扬) Chin. Phys. B, 2023, 32 (4):  047104.  DOI: 10.1088/1674-1056/acac17 Abstract ( 328 )   HTML ( 1 )   PDF (1032KB) ( 173 )   Quantum many-body systems in which time-reversal symmetry is broken give rise to a wealth of exotic phases, and thus constitute one of the frontiers of modern condensed matter physics. Quantum simulation allows us to better understand many-body systems with huge Hilbert space, where classical simulation is usually inefficient. With superconducting quantum circuit as a platform for quantum simulation, we realize synthetic Abelian gauge fields by using microwave drive and tunable coupling in loop configurations to break the time-reversal symmetry of the system. Based on high-precision manipulation and readout of circuit-QED architecture, we demonstrate the chiral ground spin current of a time-reversal symmetry broken system with nontrivial interactions. Our work is a significant attempt to simulate quantum many-body systems with time-reversal symmetry breaking in multi-qubit superconducting processors.

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Anisotropy of 2H-NbSe2 in the superconducting and charge density wave states Chi Zhang(张驰), Shan Qiao(乔山), Hong Xiao(肖宏), and Tao Hu(胡涛) Chin. Phys. B, 2023, 32 (4):  047201.  DOI: 10.1088/1674-1056/ac8343 Abstract ( 230 )   HTML ( 0 )   PDF (899KB) ( 118 )   Anisotropy is an important feature of layered materials, and a large anisotropy is usually related to the two-dimensional characteristics. We investigated the anisotropy of the layered transition metal dicalcogenide 2H-NbSe$_2$ in the superconducting and charge density wave (CDW) states using magnetotransport measurements. In the superconducting state, the normalized $H_{\rm c2}^{||c}/H_{\rm p}$ is independent of the thickness of 2H-NbSe$_2$, while $H_{\rm c2}^{||ab}/H_{\rm p}$ increases significantly with decreasing thickness, where $H_{\rm p}$ is the Pauli limiting magnetic field and $H_{\rm c2}^{||c}$ and $H_{\rm c2}^{||ab}$ are the upper critical fields in the $c$ and $ab$ directions, respectively. It is found that the superconducting anisotropy parameter $\gamma_{H_{\rm c2}}=H_{\rm c2}^{||ab}/H_{\rm c2}^{||c}$ increases with reduction in the thickness of 2H-NbSe$_2$. In the CDW state, the angular ($\theta$) dependence of magnetoresistance, $R(H,\theta)$ scales with $H(\cos^2\theta+\gamma_{\rm CDW}^{-2}\sin^2\theta)^{1/2}$, which decreases with increasing temperature and disappears at about 40 K. It is found that the CDW anisotropy parameter $\gamma_{\rm CDW}$ is much larger than the effective mass anisotropy but does not change a lot for ultrathin and bulk samples. Our results suggest the existence of three-dimensional superconductivity and quasi-two dimensional CDWs in bulk 2H-NbSe$_2$.

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Advancing thermoelectrics by suppressing deep-level defects in Pb-doped AgCrSe2 alloys Yadong Wang(王亚东), Fujie Zhang(张富界), Xuri Rao(饶旭日), Haoran Feng(冯皓然), Liwei Lin(林黎蔚), Ding Ren(任丁), Bo Liu(刘波), and Ran Ang(昂然) Chin. Phys. B, 2023, 32 (4):  047202.  DOI: 10.1088/1674-1056/acb765 Abstract ( 300 )   HTML ( 0 )   PDF (2317KB) ( 152 )   AgCrSe$_{2}$-based compounds have attracted much attention as an environmentally friendly thermoelectric material in recent years due to the intriguing liquid-like properties. However, the ultra-low carrier concentration and the high Ag$_{\rm Cr}$ deep-level defects limit the overall thermoelectric performance. Here, we successfully introduced Pb into Ag-deficient Ag$_{0.97}$CrSe$_{2}$ alloys to tune the carrier concentration across a broad temperature range. The Pb$^{2+}$ as an acceptor dopant preferentially occupies Cr sites, boosting the hole carrier concentration to 1.77$\times 10^{19}$ cm$^{-3}$ at room temperature. Furthermore, the Pb strongly inhibits the creation of intrinsic Ag$_{\rm Cr}$ defects, weakens the increased thermal excited ionization with the increasing temperature and slowed the rising trend of the carrier concentration. The designed carrier concentration matches the theoretically predicted optimized one over the entire temperature range, leading to a remarkable enhancement in power factor, especially the maximum power factor of $\sim 500 $μW$\cdot $m$^{-1}\cdot $K$^{-2}$ at 750 K is superior to most previous results. Additionally, the abundant point defects promote phonon scattering, thus reducing the lattice thermal conductivity. As a result, the maximum figure of merit $zT$ ($\sim 0.51$ at 750 K) is achieved in Ag$_{0.97}$Cr$_{0.995}$Pb$_{0.005}$Se$_{2}$. This work confirms the feasibility of manipulating deep-level defects to achieve temperature-dependent optimal carrier concentration and provides a valuable guidance for other thermoelectric materials.

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A self-powered ultraviolet photodetector based on a Ga2O3/Bi2WO6 heterojunction with low noise and stable photoresponse Li-Li Yang(杨莉莉), Yu-Si Peng(彭宇思), Zeng Liu(刘增), Mao-Lin Zhang(张茂林),Yu-Feng Guo(郭宇锋), Yong Yang(杨勇), and Wei-Hua Tang(唐为华) Chin. Phys. B, 2023, 32 (4):  047301.  DOI: 10.1088/1674-1056/ac7865 Abstract ( 215 )   HTML ( 0 )   PDF (1115KB) ( 251 )   A self-powered solar-blind ultraviolet (UV) photodetector (PD) was successfully constructed on a Ga$_{2}$O$_{3}$/Bi$_{2}$WO$_{6}$ heterojunction, which was fabricated by spin-coating the hydrothermally grown Bi$_{2}$WO$_{6}$ onto MOCVD-grown Ga$_{2}$O$_{3}$ film. The results show that a typical type-I heterojunction is formed at the interface of the Ga$_{2}$O$_{3}$ film and clustered Bi$_{2}$WO$_{6}$, which demonstrates a distinct photovoltaic effect with an open-circuit voltage of 0.18 V under the irradiation of 254 nm UV light. Moreover, the Ga$_{2}$O$_{3}$/Bi$_{2}$WO$_{6}$ PD displays excellent photodetection performance with an ultra-low dark current of $\sim 6 $ fA, and a high light-to-dark current ratio (PDCR) of $3.5\times 10^{4}$ in self-powered mode (0 V), as well as a best responsivity result of 2.21 mA/W in power supply mode (5 V). Furthermore, the PD possesses a stable and fast response speed under different light intensities and voltages. At zero voltage, the PD exhibits a fast rise time of 132 ms and 162 ms, as well as a quick decay time of 69 ms and 522 ms, respectively. In general, the newly attempted Ga$_{2}$O$_{3}$/Bi$_{2}$WO$_{6}$ heterojunction may become a potential candidate for the realization of self-powered and high-performance UV photodetectors.

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Cascade excitation of vortex motion and reentrant superconductivity in flexible Nb thin films Liping Zhang(张丽萍), Zuyu Xu(徐祖雨), Xiaojie Li(黎晓杰), Xu Zhang(张旭), Mingyang Qin(秦明阳), Ruozhou Zhang(张若舟), Juan Xu(徐娟), Wenxin Cheng(程文欣), Jie Yuan(袁洁), Huabing Wang(王华兵), Alejandro V. Silhanek, Beiyi Zhu(朱北沂), Jun Miao(苗君), and Kui Jin(金魁) Chin. Phys. B, 2023, 32 (4):  047302.  DOI: 10.1088/1674-1056/acac16 Abstract ( 293 )   HTML ( 0 )   PDF (2675KB) ( 126 )   High quality Nb films were successfully prepared on both flexible polyimide (PI) and rigid Al2O3 substrates and their transport properties were systematically studied at various applied currents, external magnetic fields, and sample orientations. It is found that a curved Nb/PI film exhibits quite different superconducting transition and vortex dynamics compared to the flat Nb/Al2O3 film. For the curved Nb/PI film, smooth superconducting transitions were obtained at low currents, while unexpected cascade structures were revealed in the ρ(T) curves at high currents. We attribute this phenomenon to the gradient distribution of vortex density together with a variation of superconductivity along the curved film. In addition, reentrant superconductivity was induced in the curved Nb/PI thin film by properly choosing the measurement conditions. We attribute this effect to the vortex pinning from both in-plane vortices and out-of-plane vortices. This work reveals the complex transport properties of curved superconducting thin films, providing important insights for further theoretical investigations and practical developments of flexible superconductors.

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Focused-ion-beam assisted technique for achieving high pressure by uniaxial-pressure devices Di Liu(刘迪), Xingyu Wang(王兴玉), Zezhong Li(李泽众), Xiaoyan Ma(马肖燕), and Shiliang Li(李世亮) Chin. Phys. B, 2023, 32 (4):  047401.  DOI: 10.1088/1674-1056/acac1a Abstract ( 301 )   HTML ( 3 )   PDF (2127KB) ( 126 )   Uniaxial pressure or strain can introduce a symmetry-breaking distortion on the lattice and may alter the ground states of a material. Compared to hydrostatic pressure, a unique feature of the uniaxial-pressure measurements is that a tensile force can be applied and thus a "negative" pressure can be achieved. In doing so, both ends of the sample are usually glued on the frame of the uniaxial-pressure device. The maximum force that can be applied onto the sample is sometimes limited by the shear strength of the glue, the quality of the interface between the sample and the glue, etc. Here we use focused ion beam to reduce the width of the middle part of the sample, which can significantly increase the effective pressure applied on the sample. By applying this technique to a home-made piezobender-based uniaxial-pressure device, we can easily increase the effective pressure by one or two orders of magnitude as shown by the change of the superconducting transition temperature of an iron-based superconductor. Our method thus provides a possible way to increase the upper limit of the pressure for the uniaxial-pressure devices.

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Algebraic equation of motion approach for solving the Anderson model Hou-Min Du(杜厚旻) and Yu-Liang Liu(刘玉良) Chin. Phys. B, 2023, 32 (4):  047501.  DOI: 10.1088/1674-1056/ac8cdb Abstract ( 308 )   HTML ( 0 )   PDF (533KB) ( 112 )   Based on the algebraic equation of motion (AEOM) approach, we have studied the single-impurity Anderson model by analytically solving the AEOM of the f-electron one-particle Green function in the Kondo limit. The related spectral function satisfies the sum rule and shows that there is a well-known three-peak structure at zero temperature. In the low energy limit, we obtain the analytical formula of the Kondo temperature that is the same as the exact solution in form except for a prefactor. We also show that the shape of the Kondo resonance is the Lorentzian form and the corresponding weight is proportional to the spin-flip correlation function.

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Doping-enhanced robustness of anomaly-related magnetoresistance in WTe2±α flakes Jianchao Meng(孟建超), Xinxiang Chen(陈鑫祥), Tingna Shao(邵婷娜), Mingrui Liu(刘明睿), Weimin Jiang(姜伟民), Zitao Zhang(张子涛), Changmin Xiong(熊昌民), Ruifen Dou(窦瑞芬), and Jiacai Nie(聂家财) Chin. Phys. B, 2023, 32 (4):  047502.  DOI: 10.1088/1674-1056/acb423 Abstract ( 360 )   HTML ( 3 )   PDF (807KB) ( 162 )   We study systematically the negative magnetoresistance ($MR$) effect in WTe$_{2\pm \alpha }$ flakes with different thicknesses and doping concentrations. The negative $MR$ is sensitive to the relative orientation between electrical-/magnetic-field and crystallographic orientation of WTe$_{2\pm \alpha }$. The analysis proves that the negative $MR$ originates from chiral anomaly and is anisotropic. Maximum entropy mobility spectrum is used to analyze the electron and hole concentrations in the flake samples. It is found that the negative $MR$ observed in WTe$_{2\pm \alpha }$ flakes with low doping concentration is small, and the high doping concentration is large. The doping-induced disorder obviously inhibits the positive $MR$, so the negative $MR$ can be more easily observed. In a word, we introduce disorder to suppress positive $MR$ by doping, and successfully obtain the negative $MR$ in WTe$_{2\pm \alpha }$ flakes with different thicknesses and doping concentrations, which indicates that the chiral anomaly effect in WTe$_{2}$ is robust.

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Abnormal magnetic behavior of prussian blue analogs modified with multi-walled carbon nanotubes Jia-Jun Mo(莫家俊), Pu-Yue Xia(夏溥越), Ji-Yu Shen(沈纪宇), Hai-Wen Chen(陈海文), Ze-Yi Lu(陆泽一), Shi-Yu Xu(徐诗语), Qing-Hang Zhang(张庆航), Yan-Fang Xia(夏艳芳), and Min Liu(刘敏) Chin. Phys. B, 2023, 32 (4):  047503.  DOI: 10.1088/1674-1056/ac946b Abstract ( 292 )   HTML ( 4 )   PDF (2355KB) ( 110 )   This work examines the origin of the abnormal magnetism exhibited by CuMnFe-PBAs modified with multi-walled carbon nanotubes (MWCNTs). The system of CuMnFe-PBAs@MWCNTs coexists with both large and small clusters. CuMnFe-PBAs clusters have an average particle size of 28 nm, and some of the smaller particles are adsorbed on the surface of MWCNTs. Surprisingly, the magnitude of magnetization increases linearly with decreasing temperature. When above the Curie temperature, the magnitude of magnetization is significantly greater than that of PBAs without being modified. This phenomenon can be attributed to magnetostatic interactions between ultra-fine magnetic nanoparticles adsorbed on the surface of MWCNTs. Using the Monte Carlo method, we simulated the magnetostatic interaction of cylindrical adsorbed particles, and the simulation results are almost identical to those observed experimentally. The results indicate that 0.089 CuMnFe-PBAs clusters per 1 nm2 can be adsorbed onto the surface area of MWCNTs. We demonstrate that MWCNTs adsorbing magnetic particles exhibit magnetic behavior, and suggest a method for producing ultrafine materials. It also introduces a new method of calculating the adsorption efficiency of carbon nanotubes, offering theoretical guidance for future research on nanomaterials with enhanced adsorption efficiency.

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Micromagnetic study of magnetization reversal in inhomogeneous permanent magnets Zhi Yang(杨质), Yuanyuan Chen(陈源源), Weiqiang Liu(刘卫强), Yuqing Li(李玉卿), Liying Cong(丛利颖), Qiong Wu(吴琼), Hongguo Zhang(张红国), Qingmei Lu(路清梅), Dongtao Zhang(张东涛), and Ming Yue(岳明) Chin. Phys. B, 2023, 32 (4):  047504.  DOI: 10.1088/1674-1056/ac9359 Abstract ( 291 )   HTML ( 0 )   PDF (863KB) ( 169 )   Macroscopic magnetic properties of magnets strongly depend on the magnetization process and the microstructure of the magnets. Complex materials such as hard-soft exchange-coupled magnets or just real technical materials with impurities and inhomogeneities exhibit complex magnetization behavior. Here we investigate the effects of size, volume fraction, and surroundings of inhomogeneities on the magnetic properties of an inhomogeneous magnetic material via micromagnetic simulations. The underlying magnetization reversal and coercivity mechanisms are revealed. Three different demagnetization characteristics corresponding to the exchange coupling phase, semi-coupled phase, and decoupled phase are found, depending on the size of inhomogeneities. In addition, the increase in the size of inhomogeneities leads to a transition of the coercivity mechanism from nucleation to pinning. This work could be useful for optimizing the magnetic properties of both exchange-coupled nanomagnets and inhomogeneous single-phase magnets.

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Domain size and charge defects affecting the polarization switching of antiferroelectric domains Jinghao Zhu(朱静浩), Zhen Liu(刘震), Boyi Zhong(钟柏仪), Yaojin Wang(汪尧进), and Baixiang Xu(胥柏香) Chin. Phys. B, 2023, 32 (4):  047701.  DOI: 10.1088/1674-1056/aca39e Abstract ( 349 )   HTML ( 4 )   PDF (3017KB) ( 197 )   The switching behavior of antiferroelectric domain structures under the applied electric field is not fully understood. In this work, by using the phase field simulation, we have studied the polarization switching property of antiferroelectric domains. Our results indicate that the ferroelectric domains nucleate preferably at the boundaries of the antiferroelectric domains, and antiferroelectrics with larger initial domain sizes possess a higher coercive electric field as demonstrated by hysteresis loops. Moreover, we introduce charge defects into the sample and numerically investigate their influence. It is also shown that charge defects can induce local ferroelectric domains, which could suppress the saturation polarization and narrow the enclosed area of the hysteresis loop. Our results give insights into understanding the antiferroelectric phase transformation and optimizing the energy storage property in experiments.

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SiC gate-controlled bipolar field effect composite transistor with polysilicon region for improving on-state current Baoxing Duan(段宝兴), Kaishun Luo(罗开顺), and Yintang Yang(杨银堂) Chin. Phys. B, 2023, 32 (4):  047702.  DOI: 10.1088/1674-1056/ac80ab Abstract ( 329 )   HTML ( 3 )   PDF (719KB) ( 73 )   A novel silicon carbide gate-controlled bipolar field effect composite transistor with polysilicon region (SiC GCBTP) is proposed. Different from the traditional electrode connection mode of SiC vertical diffused MOS (VDMOS), the P$+$ region of P-well is connected with the gate in SiC GCBTP, and the polysilicon region is added between the P$+$ region and the gate. By this method, additional minority carriers can be injected into the drift region at on-state, and the distribution of minority carriers in the drift region will be optimized, so the on-state current is increased. In terms of static characteristics, it has the same high breakdown voltage (811 V) as SiC VDMOS whose length of drift is 5.5 μm. The on-state current of SiC GCBTP is $2.47\times 10^{-3}$ A/μm ($V_{\rm G}=10$ V, $V_{\rm D}=10$ V) which is 5.7 times of that of SiC IGBT and 36.4 times of that of SiC VDMOS. In terms of dynamic characteristics, the turn-on time of SiC GCBTP is only 0.425 ns. And the turn-off time of SiC GCBTP is similar to that of SIC insulated gate bipolar transistor (IGBT), which is 114.72 ns.

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Effects of O2 adsorption on secondary electron emission properties Zhao-Lun Yang(杨兆伦), Jing Yang(杨晶), Yun He(何鋆), Tian-Cun Hu(胡天存), Xin-Bo Wang(王新波), Na Zhang(张娜), Ze-Yu Chen(陈泽煜), Guang-Hui Miao(苗光辉), Yu-Ting Zhang(张雨婷), and Wan-Zhao Cui(崔万照) Chin. Phys. B, 2023, 32 (4):  047901.  DOI: 10.1088/1674-1056/ac904b Abstract ( 300 )   HTML ( 1 )   PDF (981KB) ( 96 )   The surface adsorption of gas molecules is a key factor limiting the secondary electron yield (SEY) of a material in many areas of applied physics. The influence of O2 adsorption on the SEY of metallic Ag is investigated in this work. To account for the particle distribution, we propose a BET theory based on multilayer O2 physisorption model. Furthermore, based on the phenomenological model of secondary electron (SE) emission and by taking into account the different scattering processes between electrons and particles in the adsorbed layer, we develop a numerical model of SEY in the adsorbed state using Monte Carlo simulations. The relationships among O2 adsorption, adsorption layer thickness, and SEY variation characteristics are then examined through a series of experiments. After 12-h exposure to O2, the clean samples increases 12%-19% of the maximum value of SEY and 2.3 nm in thickness of the adsorbed layer. Experimental results are also compared with the results from the MC model to determine whether the model is accurate.

INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY

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Resonant perfect absorption of molybdenum disulfide beyond the bandgap Hao Yu(于昊), Ying Xie(谢颖), Jiahui Wei(魏佳辉), Peiqing Zhang(张培晴),Zhiying Cui(崔志英), and Haohai Yu(于浩海) Chin. Phys. B, 2023, 32 (4):  048101.  DOI: 10.1088/1674-1056/ac80ad Abstract ( 312 )   HTML ( 2 )   PDF (1068KB) ( 127 )   Light absorption and radiation are fundamental processes in optical science and engineering. Materials with perfect absorption properties play an important role in numerous optical applications. Following the meteoric rise of MoS2 material, global opportunities and challenges coexist due to its extremely weak light-matter interaction capability beyond its energy band. In this work, we designed a kind of sandwich resonance structure and investigated MoS2 as a perfect absorber in the infrared spectrum that should be transparent according to the optical band theory. The infrared absorption properties of W or Au/MoS2/Au models at 800 nm-2400 nm were systematic simulated. By optimizing the structural parameters, the resonant wavelength of perfect absorption can be modulated from 830 nm to 1700 nm with angle insensitivity and polar independence. Moreover, we discovered that the bandwidth of absorption exceeding 50% of the W-top model reaches 500 nm, while that of the Au-top model is less than 100 nm, indicating that the top metal material has a great influence on the resonance absorption spectrum. Our work provides a practical route for enhancing and manipulating the light-matter interactions of low-dimensional materials beyond their own band gaps, which will be critical in the future design and implementation of optoelectronic devices and systems.

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Secondary electron emission and photoemission from a negative electron affinity semiconductor with large mean escape depth of excited electrons Ai-Gen Xie(谢爱根), Hong-Jie Dong(董红杰), and Yi-Fan Liu(刘亦凡) Chin. Phys. B, 2023, 32 (4):  048102.  DOI: 10.1088/1674-1056/ac7dbd Abstract ( 284 )   HTML ( 1 )   PDF (750KB) ( 101 )   The formulae for parameters of a negative electron affinity semiconductor (NEAS) with large mean escape depth of secondary electrons $\lambda $ (NEASLD) are deduced. The methods for obtaining parameters such as $\lambda $, $B$, $E_{\rm pom}$ and the maximum $\delta $ and $\delta $ at 100.0 ${\rm keV} \ge E_{\rm po} \ge 1.0 $ keV of a NEASLD with the deduced formulae are presented ($B$ is the probability that an internal secondary electron escapes into the vacuum upon reaching the emission surface of the emitter, $\delta $ is the secondary electron yield, $ E_{\rm po}$ is the incident energy of primary electrons and $E_{\rm pom}$ is the $E_{\rm po}$ corresponding to the maximum $\delta $). The parameters obtained here are analyzed, and it can be concluded that several parameters of NEASLDs obtained by the methods presented here agree with those obtained by other authors. The relation between the secondary electron emission and photoemission from a NEAS with large mean escape depth of excited electrons is investigated, and it is concluded that the presented method of obtaining $\lambda $ is more accurate than that of obtaining the corresponding parameter for a NEAS with large $\lambda_{\rm ph}$ ($\lambda_{\rm ph}$ being the mean escape depth of photoelectrons), and that the presented method of calculating $B$ at $E_{\rm po} > 10.0 $ keV is more widely applicable for obtaining the corresponding parameters for a NEAS with large $\lambda_{\rm ph}$.

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Lightweight broadband microwave absorbing metamaterial with CB-ABS composites fabricated by 3D printing Meng-Zhou Chen(陈孟州), Liu-Ying Wang(汪刘应), Gu Liu(刘顾), Chao-Qun Ge(葛超群), Di-Chen Li(李涤尘), and Qing-Xuan Liang(梁庆宣) Chin. Phys. B, 2023, 32 (4):  048103.  DOI: 10.1088/1674-1056/ac935c Abstract ( 296 )   HTML ( 0 )   PDF (2399KB) ( 97 )   The self-similarity, high geometric symmetry and spatial utilization properties of fractal structures provide new methods for the development of absorbing metamaterials. In this paper, the microwave absorption properties of the gradient dendritic fractal metamaterial structure (GDFMs) based on carbon black and acrylonitrile-butadiene-styrene composites were investigated. The optimal metamaterial structure has an effective absorption in the frequency range of 4.5-40 GHz. The rotational-symmetry GDFMs leads to the polarization independence, and the GDFMs exhibits a wide-angle absorption performance for both TE and TM waves. It is expected that the proposed GDFMs has good application prospects in electromagnetic wave absorption.

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Tailoring of thermal expansion and phase transition temperature of ZrW2O8 with phosphorus and enhancement of negative thermal expansion of ZrW1.5P0.5O7.75 Chenjun Zhang(张晨骏), Xiaoke He(何小可), Zhiyu Min(闵志宇), and Baozhong Li(李保忠) Chin. Phys. B, 2023, 32 (4):  048201.  DOI: 10.1088/1674-1056/ac9364 Abstract ( 318 )   HTML ( 1 )   PDF (2343KB) ( 59 )   ZrW$_{2}$O$_{8}$ is a typical isotropic negative thermal expansion material with cubic structure. However, quenching preparation, pressure phase transition and metastable structure influence its practical applications. Adopting P to part-substitute W for ZrW$_{2-x}$P$_{x}$O$_{8-0.5x}$ has decreased the sintering temperature and avoided the quenching process. When $x=0.1$, ZrW$_{1.9}$P$_{0.1}$O$_{7.95}$ with a stable cubic structure can be obtained at 1150 $^\circ$C. The thermal expansion coefficient is tailored with the P content, and phase transition temperature is lowered. When $x=0.5$, thermal expansion coefficient attains $-13.6\times10^{-6}$ $^{\circ}$C$^{-1}$, ZrW$_{1.5}$P$_{0.5}$O$_{7.75}$ exhibits enhance negative thermal expansion property. The difference of electronegativity leads to the decrease of phase transition temperature with the increase of P content. The different radii of ions lead to new structure of materials when P substitutes more. The results suggest that the P atom plays the stabilization role in the crystal structure of ZrW$_{2-x}$P$_{x}$O$_{8-0.5x}$.

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Dynamic electrostatic-discharge path investigation relied on different impact energies in metal-oxide-semiconductor circuits Tian-Tian Xie(谢田田), Jun Wang(王俊), Fei-Bo Du(杜飞波), Yang Yu(郁扬), Yan-Fei Cai(蔡燕飞), Er-Yuan Feng(冯二媛), Fei Hou(侯飞), and Zhi-Wei Liu(刘志伟) Chin. Phys. B, 2023, 32 (4):  048501.  DOI: 10.1088/1674-1056/ac9607 Abstract ( 307 )   HTML ( 1 )   PDF (2725KB) ( 228 )   Gate-grounded n-channel metal-oxide-semiconductor (GGNMOS) devices have been widely implemented as power clamps to protect semiconductor devices from electrostatic discharge stress owing to their simple construction, easy triggering, and low power dissipation. We present a novel I-V characterization of the GGNMOS used as the power clamp in complementary metal-oxide-semiconductor circuits as a result of switching the ESD paths under different impact energies. This special effect could cause an unexpected latch-up or pre-failure phenomenon in some applications with relatively large capacitances from power supply to power ground, and thus should be urgently analyzed and resolved. Transmission-line-pulse, human-body-modal, and light-emission tests were performed to explore the root cause.

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Thickness effect on solar-blind photoelectric properties of ultrathin β-Ga2O3 films prepared by atomic layer deposition Shao-Qing Wang(王少青), Ni-Ni Cheng(程妮妮), Hai-An Wang(王海安), Yi-Fan Jia(贾一凡), Qin Lu(陆芹), Jing Ning(宁静), Yue Hao(郝跃), Xiang-Tai Liu(刘祥泰), and Hai-Feng Chen(陈海峰) Chin. Phys. B, 2023, 32 (4):  048502.  DOI: 10.1088/1674-1056/ac8ce9 Abstract ( 307 )   HTML ( 0 )   PDF (2214KB) ( 201 )   The $\beta $-Ga$_{2}$O$_{3}$ films with different thicknesses are prepared by an atomic layer deposition system. The influence of film thickness on the crystal quality is obvious, indicating that the thicker films perform better crystal quality, which is verified from x-ray diffraction (XRD) and scanning electron microscope (SEM) results. The Ga$_{2}$O$_{3}$-based solar blind photodetectors with different thicknesses are fabricated and studied. The experimental results show that the responsivity of the photodetectors increases exponentially with the increase of the film thickness. The photodetectors with inter-fingered structure based on 900 growth cycles $\beta $-Ga$_{2}$O$_{3}$ active layers (corresponding film thickness of 58 nm) exhibit the best performances including a low dark current of 134 fA, photo-to-dark current ratio of 1.5$\times10^{7}$, photoresponsivity of 1.56 A/W, detectivity of 2.77$\times10^{14}$ Jones, and external quantum efficiency of 764.49% at a bias voltage of 10 V under 254-nm DUV illumination. The photoresponse rejection ratio ($R_{254}/R_{365}$) is up to $1.86\times 10^{5}$. In addition, we find that the photoelectric characteristics also depend on the finger spacing of the MSM structure. As the finger spacing decreases from 50 μm to 10 μm, the photoresponsivity, detectivity, and external quantum efficiency increase significantly.

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A 4H-SiC trench IGBT with controllable hole-extracting path for low loss Lijuan Wu(吴丽娟), Heng Liu(刘恒), Xuanting Song(宋宣廷), Xing Chen(陈星), Jinsheng Zeng(曾金胜), Tao Qiu(邱滔), and Banghui Zhang(张帮会) Chin. Phys. B, 2023, 32 (4):  048503.  DOI: 10.1088/1674-1056/ac8722 Abstract ( 369 )   HTML ( 9 )   PDF (1713KB) ( 187 )   A novel 4H-SiC trench insulated gate bipolar transistor (IGBT) with a controllable hole-extracting (CHE) path is proposed and investigated in this paper. The CHE path is controlled by metal semiconductor gate (MES gate) and metal oxide semiconductor gate (MOS gate) in the p-shield region. The grounded p-shield region can significantly suppress the high electric field around gate oxide in SiC devices, but it weakens the conductivity modulation in the SiC trench IGBT by rapidly sweeping out holes. This effect can be eliminated by introducing the CHE path. The CHE path is pinched off by the high gate bias voltage at on-state to maintain high conductivity modulation and obtain a comparatively low on-state voltage ($V_{\rm ON}$). During the turn-off transient, the CHE path is formed, which contributes to a decreased turn-off loss ($E_{\rm OFF}$). Based on numerical simulation, the $E_{\rm OFF}$ of the proposed IGBT is reduced by 89% compared with the conventional IGBT at the same $V_{\rm ON}$ and the $V_{\rm ON}$ of the proposed IGBT is reduced by 50% compared to the grounded p-shield IGBT at the same $E_{\rm OFF}$. In addition, the average power reduction for the proposed device can be 51.0% to 81.7% and 58.2% to 72.1% with its counterparts at a wide frequency range of 500 Hz to 10 kHz, revealing a great improvement of frequency characteristics.

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Ta thickness effect on field-free switching and spin-orbit torque efficiency in a ferromagnetically coupled Co/Ta/CoFeB trilayer Zhongshu Feng(冯重舒), Changqiu Yu(于长秋), Haixia Huang(黄海侠), Haodong Fan(樊浩东),Mingzhang Wei(卫鸣璋), Birui Wu(吴必瑞), Menghao Jin(金蒙豪), Yanshan Zhuang(庄燕山),Ziji Shao(邵子霁), Hai Li(李海), Jiahong Wen(温嘉红), Jian Zhang(张鉴), Xuefeng Zhang(张雪峰),Ningning Wang(王宁宁), Sai Mu(穆赛), and Tiejun Zhou(周铁军) Chin. Phys. B, 2023, 32 (4):  048504.  DOI: 10.1088/1674-1056/aca7e9 Abstract ( 330 )   HTML ( 3 )   PDF (1352KB) ( 174 )   Current induced spin-orbit torque (SOT) switching of magnetization is a promising technology for nonvolatile spintronic memory and logic applications. In this work, we systematically investigated the effect of Ta thickness on the magnetic properties, field-free switching and SOT efficiency in a ferromagnetically coupled Co/Ta/CoFeB trilayer with perpendicular magnetic anisotropy. We found that both the anisotropy field and coercivity increase with increasing Ta thickness from 0.15 nm to 0.4 nm. With further increase of Ta thickness to 0.5 nm, two-step switching is observed, indicating that the two magnetic layers are magnetically decoupled. Measurements of pulse-current induced magnetization switching and harmonic Hall voltages show that the critical switching current density increases while the field-free switching ratio and SOT efficiency decrease with increasing Ta thickness. Both the enhanced spin memory loss and reduced interlayer exchange coupling might be responsible for the βDL decrease as the Ta spacer thickness increases. The studied structure with the incorporation of a CoFeB layer is able to realize field-free switching in the strong ferromagnetic coupling region, which may contribute to the further development of magnetic tunnel junctions for better memory applications.

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Optimal impurity distribution model and experimental verification of variation of lateral doping termination Min Ren(任敏), Chang-Yu Ye(叶昶宇), Jian-Yu Zhou(周建宇), Xin Zhang(张新), Fang Zheng(郑芳), Rong-Yao Ma(马荣耀), Ze-Hong Li(李泽宏), and Bo Zhang(张波) Chin. Phys. B, 2023, 32 (4):  048505.  DOI: 10.1088/1674-1056/acbd29 Abstract ( 317 )   HTML ( 4 )   PDF (1710KB) ( 178 )   Based on the charge balance principle, an optimal impurity distribution variation of lateral doping termination (OID-VLD) and its ion-injection mask design method are proposed and verified. The comparative simulations and experiments show that OID-VLD can achieve better blocking ability and reliability than the traditional VLD (T-VLD). Vertical double diffusion MOSFET (VDMOS) with OID-VLD achieved breakdown voltage (BV) of 1684 V and passed the 168 hours 100 ℃-110 ℃-120 ℃-125 ℃ high-temperature reverse bias (HTRB) test, while VDMOS with T-VLD obtained BV of 1636 V and failed in the 20 hours 120 ℃ HTRB test.

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Effects of electric field on vibrational resonances in Hindmarsh-Rose neuronal systems for signal detection Xiaoxia Li(李晓霞), Xiaopeng Xue(薛小鹏), Dongjie Liu(刘栋杰), Tianyi Yu(余天意), Qianqian He(何倩倩), and Guizhi Xu(徐桂芝) Chin. Phys. B, 2023, 32 (4):  048701.  DOI: 10.1088/1674-1056/ac9cc0 Abstract ( 283 )   HTML ( 0 )   PDF (2998KB) ( 129 )   Changes in the concentration of charged ions in neurons can generate induced electric fields, which can further modulate cell membrane potential. In this paper, Fourier coefficients are used to investigate the effect of electric field on vibrational resonance for signal detection in a single neuron model and a bidirectionally coupled neuron model, respectively. The study found that the internal electric field weakens vibrational resonance by changing two factors, membrane potential and phase-locked mode, while the periodic external electric field of an appropriate frequency significantly enhances the vibrational resonance, suggesting that the external electric field may play a constructive role in the detection of weak signals in the brain and neuronal systems. Furthermore, when the coupling of two neurons is considered, the effect of the electric field on the vibrational resonance is similar to that of a single neuron. The paper also illustrates the effect of electric field coupling on vibrational resonance. This study may provide a new theoretical basis for understanding information encoding and transmission in neurons.

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Integrated system of traditional THz time-domain spectroscopy and asynchronous optical sampling Jing Ding(丁晶), Qing-Hao Meng(孟庆昊), Yan Shen(沈妍), Chen-Xin Ding(丁晨鑫), Bo Su(苏波), Hai-Lin Cui(崔海林), and Cun-Lin Zhang(张存林) Chin. Phys. B, 2023, 32 (4):  048702.  DOI: 10.1088/1674-1056/ac90b2 Abstract ( 314 )   HTML ( 0 )   PDF (1586KB) ( 82 )   Terahertz time-domain spectroscopy (THz-TDS) system, as a new means of spectral analysis and detection, plays an increasingly pivotal role in basic scientific research. However, owing to the long scanning time of the traditional THz-TDS system and the complex control of the asynchronous optical scanning (ASOPS) system, which requires frequent calibration, we combine traditional THz-TDS and ASOPS systems to form a composite system and propose an all-fiber trigger signal generation method based on the time overlapping interference signal generated by the collinear motion of two laser pulses. Finally, the time-domain and frequency-domain spectra are obtained by using two independent systems in the integrated systems. It is found that the full width at half maximum (FWHM) of the time-domain spectra and the spectral width of the frequency-domain spectra are almost the same, but the sampling speed of the ASOPS system is significantly faster than that of the traditional THz-TDS system, which conduces to the study of the transient characteristics of substances.

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Transverse manipulation of particles using Bessel beam of tunable size generated by cross-phase modulation Xiang-Lai Qiao(乔响来), Xue-Mei Cheng(程雪梅), Qian Zhang(张倩), Wen-Ding Zhang(张文定), Zhao-Yu Ren(任兆玉), and Jin-Tao Bai(白晋涛) Chin. Phys. B, 2023, 32 (4):  048703.  DOI: 10.1088/1674-1056/ac8925 Abstract ( 235 )   HTML ( 0 )   PDF (1325KB) ( 265 )   We report on a method to achieve multiple microscopic particles being trapped and manipulated transversely by using a size-tunable Bessel beam generated by cross-phase modulation (XPM) based on the thermal nonlinear optical effect. The results demonstrate that multiple polystyrene particles can be stably trapped simultaneously, and the number of the trapped particles can be controlled by varying the trapping beam power. In addition, the trapped particles can be manipulated laterally with micron-level precision by changing the size of J0 Bessel beam. This work provides a simple but efficient way to trap and manipulate multiple particles simultaneously, which would have potential applications in many fields such as cell sorting and transportation.

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Electron beam pumping improves the conversion efficiency of low-frequency photons radiated by perovskite quantum dots Peng Du(杜鹏), Yining Mu(母一宁), Hang Ren(任航), Idelfonso Tafur Monroy, Yan-Zheng Li(李彦正), Hai-Bo Fan(樊海波), Shuai Wang(王帅), Makram Ibrahim, and Dong Liang(梁栋) Chin. Phys. B, 2023, 32 (4):  048704.  DOI: 10.1088/1674-1056/ac8348 Abstract ( 330 )   HTML ( 1 )   PDF (6067KB) ( 111 )   This research argues that using an electron beam with high kinetic energy to pump perovskite quantum dots can significantly boost the efficiency of the low-frequency photon radiation conversion. Firstly, we measure the random lasing threshold and luminescence threshold of CsPbX3 films pumped by an electron beam. Then, we simulate the spatial distribution of the electron beams in CsPbX3 films. Combined with the above data, a low-frequency photon radiation conversion model based on the electron pumped perovskite quantum dots is presented. This could be a way to create a terahertz source with a high-power output or to multiply the terahertz power.

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Pedestrian evacuation simulation in multi-exit case: An emotion and group dual-driven method Yong-Xing Li(李永行), Xiao-Xia Yang(杨晓霞), Meng Meng(孟梦), Xin Gu(顾欣), and Ling-Peng Kong(孔令鹏) Chin. Phys. B, 2023, 32 (4):  048901.  DOI: 10.1088/1674-1056/ac9609 Abstract ( 316 )   HTML ( 0 )   PDF (774KB) ( 73 )   This paper analyzes the characteristics of emotion state and group behavior in the evacuation process. During the emergency evacuation, emotion state and group behavior are interacting with each other, and indivisible. The emotion spread model with the effect of group behavior, and the leader-follower model with the effect of emotion state are proposed. On this basis, exit choice strategies with the effect of emotion state and group behavior are proposed. Fusing emotion spread model, leader-follower model, and exit choice strategies into a cellular automata (CA)-based pedestrian simulation model, we simulate the evacuation process in a multi-exit case. Simulation results indicate that panic emotion and group behavior are two negative influence factors for pedestrian evacuation. Compared with panic emotion or group behavior only, pedestrian evacuation efficiency with the effects of both is lower.