Chin. Phys. B

Intrinsic valley-polarized quantum anomalous Hall effect in a two-dimensional germanene/MnI₂ van der Waals heterostructure

Xiao-Jing Dong(董晓晶) and Chang-Wen Zhang(张昌文)

Chin. Phys. B, 2024, 33 (7): 077303. DOI: 10.1088/1674-1056/ad4bbd

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Valley-polarized quantum anomalous Hall effect (VQAHE), combined nontrivial band topology with valleytronics, is of importance for both fundamental sciences and emerging applications. However, the experimental realization of this property is challenging. Here, by using first-principles calculations and modal analysis, we predict a mechanism of producing VQAHE in two-dimensional ferromagnetic van der Waals germanene/MnI$_{2}$ heterostructure. This heterostructure exhibits both valley anomalous Hall effect and VQAHE due to the joint effects of magnetic exchange effect and spin-orbital coupling with the aid of anomalous Hall conductance and chiral edge state. Moreover interestingly, through the electrical modulation of ferroelectric polarization state in In$_{2}$Se$_{3}$, the germanene/MnI$_{2}$/In$_{2}$Se$_{3}$ heterostructure can undergo reversible switching from a semiconductor to a metallic behavior. This work offers a guiding advancement for searching for VQAHE in ferromagnetic van der Waals heterostructures and exploiting energy-efficient devices based on the VQAHE.

Two-fold symmetry of the in-plane resistance in kagome superconductor Cs(V_1-xTa_x)₃Sb₅ with enhanced superconductivity

Zhen Zhao(赵振), Ruwen Wang(王汝文), Yuhang Zhang(张宇航), Ke Zhu(祝轲), Weiqi Yu(余维琪), Yechao Han(韩烨超), Jiali Liu(刘家利), Guojing Hu(胡国静), Hui Guo(郭辉), Xiao Lin(林晓), Xiaoli Dong(董晓莉), Hui Chen(陈辉), Haitao Yang(杨海涛), and Hong-Jun Gao(高鸿钧)

Chin. Phys. B, 2024, 33 (7): 077406. DOI: 10.1088/1674-1056/ad4ffa

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The kagome superconductor CsV$_{3}$Sb$_{5}$ has attracted widespread attention due to its rich correlated electron states including superconductivity, charge density wave (CDW), nematicity, and pair density wave. Notably, the modulation of the intertwined electronic orders by the chemical doping is significant to illuminate the cooperation/competition between multiple phases in kagome superconductors. In this study, we have synthesized a series of tantalum-substituted Cs(V$_{1-x}$Ta$_{x}$)$_{3}$Sb$_{5}$ by a modified self-flux method. Electrical transport measurements reveal that CDW is suppressed gradually and becomes undetectable as the doping content of $ x$ is over 0.07. Concurrently, the superconductivity is enhanced monotonically from $T_{\rm c} \sim 2.8 $ K at $x =0$ to 5.2 K at $x = 0.12$. Intriguingly, in the absence of CDW, Cs(V$_{1-x}$Ta$_{x}$)$_{3}$Sb$_{5}$ ($x = 0.12$) crystals exhibit a pronounced two-fold symmetry of the in-plane angular-dependent magnetoresistance (AMR) in the superconducting state, indicating the anisotropic superconducting properties in the Cs(V$_{1-x}$Ta$_{x}$)$_{3}$Sb$_{5}$. Our findings demonstrate that Cs(V$_{1-x}$Ta$_{x}$)$_{3}$Sb$_{5}$ with the non-trivial band topology is an excellent platform to explore the superconductivity mechanism and intertwined electronic orders in quantum materials.

The n-resolved single-electron capture in slow O⁶⁺-Ne collisions

Shucheng Cui(崔述成), Dadi Xing(邢大地), Xiaolong Zhu(朱小龙), Maogen Su(苏茂根), Yong Gao(高永), Dalong Guo(郭大龙), Dongmei Zhao(赵冬梅), Shaofeng Zhang(张少锋), Yanbiao Fu(符彦飙), and Xinwen Ma(马新文)

Chin. Phys. B, 2024, 33 (7): 073401. DOI: 10.1088/1674-1056/ad39d2

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A study of single-electron capture (SEC) in 18-240 keV O$^{6+}$-Ne collisions has been conducted employing a combination of experimental and theoretical methodologies. Utilizing a reaction microscope, state-selective SEC cross sections and projectile scattering angle distributions were obtained. The translational energy spectra for SEC reveal the prevailing capture into $n=3$ states of the projectile ion, with a minor contribution from $n=4$ states. Notably, as the projectile's energy increases, the relative contribution of SEC $n=4$ states increases while that of SEC $n=3$ states diminishes. Furthermore, we computed state-selective relative cross sections and angular differential cross sections employing the classical molecular Coulomb over-the-barrier model (MCBM) and the multichannel Landau-Zener (MCLZ) model. A discernible discrepancy between the state-selective cross sections from the two theoretical models is apparent for the considered impact energies. However, regarding the angular differential cross sections, an overall agreement was attained between the current experimental results and the theoretical results from the MCLZ model.

Physics package based on intracavity laser cooling ⁸⁷Rb atoms for space cold atom microwave clock

Siminda Deng(邓思敏达), Wei Ren(任伟), Jingfeng Xiang(项静峰), Jianbo Zhao(赵剑波), Lin Li(李琳), Di Zhang(张迪), Jinyin Wan(万金银), Yanling Meng(孟艳玲), Xiaojun Jiang(蒋小军), Tang Li(李唐), Liang Liu(刘亮), and Desheng Lü(吕德胜)

Chin. Phys. B, 2024, 33 (7): 070602. DOI: 10.1088/1674-1056/ad4bc1

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This article proposes a new physics package to enhance the frequency stability of the space cold atom clock with the advantages of a microgravity environment. Clock working processes, including atom cooling, atomic state preparation, microwave interrogation, and transition probability detection, are integrated into the cylindrical microwave cavity to achieve a high-performance and compact physics package for the space cold atom clock. We present the detailed design and ground-test results of the cold atom clock physics package in this article, which demonstrates a frequency stability of $1.2 \times 10^{-12}$ $\tau^{-1/2}$ with a Ramsey linewidth of 12.5 Hz, and a better performance is predicted with a 1 Hz or a narrower Ramsey linewidth in microgravity environment. The miniaturized cold atom clock based on intracavity cooling has great potential for achieving space high-precision time-frequency reference in the future.

Development of 400-μW cryogen-free dilution refrigerators for quantum experiments

Xiang Guan(关翔), Jie Fan(樊洁), Yong-Bo Bian(边勇波), Zhi-Gang Cheng(程智刚), and Zhong-Qing Ji(姬忠庆)

Chin. Phys. B, 2024, 33 (7): 070701. DOI: 10.1088/1674-1056/ad3b87

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We have successfully developed cryogen-free dilution refrigerators with medium cooling power that can be applied to quantum experiments. Breakthroughs have been made in some key technologies and components of heat switches and dilution units. Our prototype has been running continuously and stably for more than 100 hours below 10 mK, with a minimum temperature of 7.6 mK and a cooling power of 450 μW at 100 mK. At the same time, we have also made progress in the application of dilution refrigerators, such as quantum computing, low-temperature detector, and magnet integration. These indicators and test results indicate good prospects for application in physics, astronomy, and quantum information.

FL-Online: An x-ray crystallographic web-server for atomic-scale structure analysis of biomolecule

Bintang Wang(王宾堂), Tongxin Niu(牛彤欣), Haifu Fan(范海福), and Wei Ding(丁玮)

Chin. Phys. B, 2024, 33 (7): 076104. DOI: 10.1088/1674-1056/ad47e5

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FL-Online (http://fanlab.ac.cn) is an out-of-box modern web service featuring a user-friendly interface and simplified parameters, providing academic users with access to a series of online programs for biomolecular crystallography, including SAPI-online, OASIS-online, C-IPCAS-online and a series of upcoming software releases. Meanwhile, it is a highly scalable and maintainable web application framework that provides a powerful and flexible solution for academic web development needs. All the codes are open-source under MIT licenses in GitHub.

Cryo-EM combined with image deconvolution to determine ZIF-8 crystal structure ^Hot! Suggested by editors

Kang Wu(吴抗), Baisong Yang(杨柏松), Wenhua Xue(薛文华), Dapeng Sun(孙大鹏), Binghui Ge(葛炳辉), and Yumei Wang(王玉梅)

Chin. Phys. B, 2024, 33 (7): 076802. DOI: 10.1088/1674-1056/ad48f8

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Metal-organic frameworks (MOFs) are crystalline porous materials with tunable properties, exhibiting great potential in gas adsorption, separation and catalysis.^[1,2]It is challenging to visualize MOFs with transmission electron microscopy (TEM) due to their inherent instability under electron beam irradiation. Here, we employ cryo-electron microscopy (cryo-EM) to capture images of MOF ZIF-8, revealing inverted-space structural information at a resolution of up to about 1.7 Å and enhancing its critical electron dose to around 20 $e^-$/Å$^{2}$. In addition, it is confirmed by electron-beam irradiation experiments that the high voltage could effectively mitigate the radiolysis, and the structure of ZIF-8 is more stable along the [100] direction under electron beam irradiation. Meanwhile, since the high-resolution electron microscope images are modulated by contrast transfer function (CTF) and it is difficult to determine the positions corresponding to the atomic columns directly from the images. We employ image deconvolution to eliminate the impact of CTF and obtain the structural images of ZIF-8. As a result, the heavy atom Zn and the organic imidazole ring within the organic framework can be distinguished from structural images.

Two-dimensional Sb net generated nontrivial topological states in SmAgSb₂ probed by quantum oscillations Suggested by editors

Jian Yuan(袁健), Xian-Biao Shi(石贤彪), Hong Du(杜红), Tian Li(李田), Chuan-Ying Xi(郗传英), Xia Wang(王霞), Wei Xia(夏威), Bao-Tian Wang(王保田), Rui-Dan Zhong(钟瑞丹), and Yan-Feng Guo(郭艳峰)

Chin. Phys. B, 2024, 33 (7): 077102. DOI: 10.1088/1674-1056/ad4bc2

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The REAgSb$_{2}$ ($RE = {\rm rare}$ earth and Y) family has drawn considerable research interest because the two-dimensional Sb net in their crystal structures hosts topological fermions and hence rich topological properties. We report herein the magnetization and magnetotransport measurements of SmAgSb$_{2}$ single crystal, which unveil very large magnetoresistance and high carrier mobility up to $6.2\times 10^{3}%$ and $5.58\times 10^{3}$ cm$^{2}\cdot$V$^{-1}\cdot$s$^{-1}$, respectively. The analysis of both Shubnikov-de Haas and de Haas-van Alphen quantum oscillations indicates nontrivial Berry phases in the paramagnetic state while trivial Berry curvature in the antiferromagnetic state, indicating a topological phase transition induced by the antiferromagnetic order. It is also supported by the first-principles calculations. The results not only provide a new interesting topological material but also offer valuable insights into the correlation between magnetism and nontrivial topological states.

Observation of parabolic electron bands on superconductor LaRu₂As₂ ^Hot! Suggested by editors

Xingtai Zhou(周兴泰), Geng Li(李更), Lulu Pan(潘禄禄), Zichao Chen(陈子超), Meng Li(李萌), Yanhao Shi(时延昊), Haitao Yang(杨海涛), and Hong-Jun Gao(高鸿钧)

Chin. Phys. B, 2024, 33 (7): 077401. DOI: 10.1088/1674-1056/ad4d63

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Ru-based superconductor LaRu$_{2}$As$_{2}$ has been discovered exhibiting the highest critical temperature of $\sim 7.8 $ K among iron-free transition metal pnictides with the ThCr$_{2}$Si$_{2}$-type crystal structure. However, microscopic research on this novel superconducting material is still lacking. Here, we utilize scanning tunneling microscopy/spectroscopy to uncover the superconductivity and surface structure of LaRu$_{2}$As$_{2}$. Two distinct terminating surfaces are identified on the cleaved crystals, namely, the As surface and the La surface. Atomic missing line defects are observed on the La surface. Both surfaces exhibit a superconducting gap of $\sim 1.0 $ meV. By employing quasiparticle interference techniques, we observe standing wave patterns near the line defects on the La atomic plane. These patterns are attributed to quasiparticle scattering from two electron type parabolic bands.

Coevolution of superconductivity and Hall coefficient with anisotropic lattice shrinkage in compressed KCa₂Fe₄As₄F₂ ^Hot! Suggested by editors

Jinyu Han(韩金宇), Wenshan Hong(洪文山), Shu Cai(蔡树), Jinyu Zhao(赵金瑜), Jing Guo(郭静), Yazhou Zhou(周亚洲), Pengyu Wang(王鹏玉), Lixin Cao(曹立新), Huiqian Luo(罗会仟), Shiliang Li(李世亮), Qi Wu(吴奇), and Liling Sun(孙力玲)

Chin. Phys. B, 2024, 33 (7): 077402. DOI: 10.1088/1674-1056/ad4d65

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The stability of superconductivity in superconductors is widely recognized to be determined by various factors, including charge, spin, orbit, lattice, and other related degrees of freedom. Here, we report our findings on the pressure-induced coevolution of superconductivity and Hall coefficient in KCa$_{2}$Fe$_{4}$As$_{4}$F$_{2}$, an iron-based superconductor possessing a hybrid crystal structure combining KFe$_{2}$As$_{2}$ and CaFeAsF. Our investigation, involving high-pressure resistance, Hall effect and x-ray diffraction (XRD) measurements, allows us to observe the connection of the superconductivity and Hall coefficient with the anisotropic lattice shrinkage. We find that its ambient-pressure tetragonal (T) phase presents a collapse starting at around 18 GPa, where the sign of the Hall coefficient ($R_{\rm H}$) changes from positive to negative. Upon further compression, both superconducting transition temperature ($T_{\rm c}$) and $R_{\rm H}$ exhibit a monotonous decrease. At around 41 GPa, the superconductivity is completely suppressed ($T_{\rm c}=0$), where the parameter $a$ begins to decline again and the Hall coefficient remains nearly unchanged. Our experiment results clearly demonstrate that the pressure-induced anisotropic lattice collapse plays a crucial role in tuning the interplay among multiple degrees of freedom in the superconducting system and, correspondingly, the stability of the superconductivity.

Moiré superlattices arising from growth induced by screw dislocations in layered materials ^Hot! Suggested by editors

Fuyu Tian(田伏钰), Muhammad Faizan, Xin He(贺欣), Yuanhui Sun(孙远慧), and Lijun Zhang(张立军)

Chin. Phys. B, 2024, 33 (7): 077403. DOI: 10.1088/1674-1056/ad4cdc

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Moiré superlattices (MSLs) are modulated structures produced from homogeneous or heterogeneous two-dimensional layers stacked with a twist angle and/or lattice mismatch. Enriching the methods for fabricating MSL and realizing the unique emergent properties are key challenges in its investigation. Here we recommend that the spiral dislocation driven growth is another optional method for the preparation of high quality MSL samples. The spiral structure stabilizes the constant out-of-plane lattice distance, causing the variations in electronic and optical properties. Taking SnS$_{2}$ MSL as an example, we find prominent properties including large band gap reduction ($\sim 0.4 $ eV) and enhanced optical activity. First-principles calculations reveal that these unusual properties can be ascribed to the locally enhanced interlayer interaction associated with the Moiré potential modulation. We believe that the spiral dislocation driven growth would be a powerful method to expand the MSL family and broaden their scope of application.

Absence of BCS-BEC crossover in FeSe_0.45Te_0.55 superconductor ^Hot! Suggested by editors

Junjie Jia(贾俊杰), Yadong Gu(谷亚东), Chaohui Yin(殷超辉), Yingjie Shu(束英杰), Yiwen Chen(陈逸雯), Jumin Shi(史聚民), Xing Zhang(张杏), Hao Chen(陈浩), Taimin Miao(苗泰民), Xiaolin Ren(任晓琳), Bo Liang(梁波), Wenpei Zhu(朱文培), Neng Cai(蔡能), Fengfeng Zhang(张丰丰), Shenjin Zhang(张申金), Feng Yang(杨峰), Zhimin Wang(王志敏), Qinjun Peng(彭钦军), Zuyan Xu(许祖彦), Hanqing Mao(毛寒青), Guodong Liu(刘国东), Zhian Ren(任治安), Lin Zhao(赵林), and Xing-Jiang Zhou(周兴江)

Chin. Phys. B, 2024, 33 (7): 077404. DOI: 10.1088/1674-1056/ad51f9

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In iron-based superconductor Fe(Se,Te), a flat band-like feature near the Fermi level was observed around the Brillouin zone center in the superconducting state. It is under debate whether this is the evidence on the presence of the BCS-BEC [Bardeen-Cooper-Schrieffer (BCS), Bose-Einstein condensation (BEC)] crossover in the superconductor. High-resolution laser-based angle-resolved photoemission measurements are carried out on high quality single crystals of FeSe$_{0.45}$Te$_{0.55}$ superconductor to address the issue. By employing different polarization geometries, we have resolved and isolated the d$_{yz}$ band and the topological surface band, making it possible to study their superconducting behaviors separately. The d$_{yz}$ band alone does not form a flat band-like feature in the superconducting state and the measured dispersion can be well described by the BCS picture. We find that the flat band-like feature is formed from the combination of the d$_{yz}$ band and the topological surface state band in the superconducting state. These results reveal the origin of the flat band-like feature and rule out the presence of BCS-BEC crossover in Fe(Se,Te) superconductor.

Critical behavior of quasi-two-dimensional ferromagnet Cr_1.04Te₂ ^Hot! Suggested by editors

Wei Niu(钮伟), Qin-Xin Song(宋沁心), Shi-Qi Chang(常世琦), Min Wang(王敏), Kui Yuan(袁奎), Jia-Cheng Gao(高嘉程), Shuo Wang(王硕), Zhen-Dong Wang(王振东), Kai-Fei Liu(刘凯斐), Ping Liu(刘萍), Yong-Bing Xu(徐永兵), Xiao-Qian Zhang(张晓倩), and Yong Pu(普勇)

Chin. Phys. B, 2024, 33 (7): 077506. DOI: 10.1088/1674-1056/ad4cd8

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The self-intercalation of Cr into pristine two-dimensional (2D) van der Waals ferromagnetic CrTe$_{2}$, which forms chromium tellurides (Cr$_{x}$Te$_{2}$), has garnered interest due to their remarkable magnetic characteristics and the wide variety of chemical compositions available. Here, comprehensive basic characterization and magnetic studies are conducted on quasi-2D ferromagnetic Cr$_{1.04}$Te$_{2}$ crystals. Measurements of the isothermal magnetization curves are conducted around the critical temperature to systematically investigate the critical behavior. Specifically, the critical exponents $\beta = 0.2399$, $\gamma = 0.859$, and $\delta = 4.3498$, as well as the Curie temperature $T_{\rm C} = 249.56$,K, are determined using various methods, including the modified Arrott plots, the Kouvel-Fisher method, the Widom scaling method, and the critical isotherm analysis. These results indicate that the tricritical mean-field model accurately represents the critical behavior of Cr$_{1.04}$Te$_{2}$. A magnetic phase diagram with tricritical phenomenon is thus constructed. Further investigations confirm that the critical exponents obtained conform to the scalar equation near $T_{\rm C}$, indicating their self-consistency and reliability. Our work sheds light on the magnetic properties of quasi-2D Cr$_{1.04}$Te$_{2}$, broadening the scope of the van der Waals crystals for developments of future spintronic devices operable at room temperature.

Disorder-to-order transition induced by spontaneous cooling regulation in robotic active matter Suggested by editors

Shuaixu Hou(侯帅旭), Gao Wang(王高), Xingyu Ma(马星宇), Chuyun Wang(汪楚云), Peng Wang(王鹏), Huaicheng Chen(陈怀城), Liyu Liu(刘雳宇), and Jing Wang(王璟)

Chin. Phys. B, 2024, 33 (7): 078701. DOI: 10.1088/1674-1056/ad4327

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In classical matter systems, typical phase-transition phenomena usually stem from changes in state variables, such as temperature and pressure, induced by external regulations such as heat transfer and volume adjustment. However, in active matter systems, the self-propulsion nature of active particles endows the systems with the ability to induce unique collective-state transitions by spontaneously regulating individual properties to alter the overall states. Based on an innovative robot-swarm experimental system, we demonstrate a field-driven active matter model capable of modulating individual motion behaviors through interaction with a recoverable environmental resource field by the resource perception and consumption. In the simulated model, by gradually reducing the individual resource-conversion coefficient over time, this robotic active matter can spontaneously decrease the overall level of motion, thereby actively achieving a regulation behavior like the cooling-down control. Through simulation calculations, we discover that the spatial structures of this robotic active matter convert from disorder to order during this process, with the resulting ordered structures exhibiting a high self-adaptability on the geometry of the environmental boundaries.

Opinion consensus incorporating higher-order interactions in individual-collective networks

Shun Ye(叶顺), Li-Lan Tu(涂俐兰), Xian-Jia Wang(王先甲), Jia Hu(胡佳), and Yi-Chao Wang(王薏潮)

Chin. Phys. B, 2024, 33 (7): 070201. DOI: 10.1088/1674-1056/ad3b84

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In the current information society, the dissemination mechanisms and evolution laws of individual or collective opinions and their behaviors are the research hot topics in the field of opinion dynamics. First, in this paper, a two-layer network consisting of an individual-opinion layer and a collective-opinion layer is constructed, and a dissemination model of opinions incorporating higher-order interactions (i.e. OIHOI dissemination model) is proposed. Furthermore, the dynamic equations of opinion dissemination for both individuals and groups are presented. Using Lyapunov's first method, two equilibrium points, including the negative consensus point and positive consensus point, and the dynamic equations obtained for opinion dissemination, are analyzed theoretically. In addition, for individual opinions and collective opinions, some conditions for reaching negative consensus and positive consensus as well as the theoretical expression for the dissemination threshold are put forward. Numerical simulations are carried to verify the feasibility and effectiveness of the proposed theoretical results, as well as the influence of the intra-structure, inter-connections, and higher-order interactions on the dissemination and evolution of individual opinions. The main results are as follows. (i) When the intra-structure of the collective-opinion layer meets certain characteristics, then a negative or positive consensus is easier to reach for individuals. (ii) Both negative consensus and positive consensus perform best in mixed type of inter-connections in the two-layer network. (iii) Higher-order interactions can quickly eliminate differences in individual opinions, thereby enabling individuals to reach consensus faster.

An integrable generalization of the Fokas-Lenells equation: Darboux transformation, reduction and explicit soliton solutions Suggested by editors

Jiao Wei(魏姣), Xianguo Geng(耿献国), and Xin Wang(王鑫)

Chin. Phys. B, 2024, 33 (7): 070202. DOI: 10.1088/1674-1056/ad4633

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Under investigation is an integrable generalization of the Fokas-Lenells equation, which can be derived from the negative power flow of a $2\times 2$ matrix spectral problem with three potentials. Based on the gauge transformation of the matrix spectral problem, one kind of Darboux transformation with multi-parameters for the three-component coupled Fokas-Lenells system is constructed. As a reduction, the $N$-fold Darboux transformation for the generalized Fokas-Lenells equation is obtained, from which the $N$-soliton solution in a compact Vandermonde-like determinant form is given. Particularly, the explicit one- and two-soliton solutions are presented and their dynamical behaviors are shown graphically.

Event-based nonfragile state estimation for memristive recurrent neural networks with stochastic cyber-attacks and sensor saturations

Xiao-Guang Shao(邵晓光), Jie Zhang(张捷), and Yan-Juan Lu(鲁延娟)

Chin. Phys. B, 2024, 33 (7): 070203. DOI: 10.1088/1674-1056/ad3dcb

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This paper addresses the issue of nonfragile state estimation for memristive recurrent neural networks with proportional delay and sensor saturations. In practical engineering, numerous unnecessary signals are transmitted to the estimator through the networks, which increases the burden of communication bandwidth. A dynamic event-triggered mechanism, instead of a static event-triggered mechanism, is employed to select useful data. By constructing a meaningful Lyapunov-Krasovskii functional, a delay-dependent criterion is derived in terms of linear matrix inequalities for ensuring the global asymptotic stability of the augmented system. In the end, two numerical simulations are employed to illustrate the feasibility and validity of the proposed theoretical results.

Bipartite consensus problems of Lurie multi-agent systems over signed graphs: A contraction approach

Xiaojiao Zhang(张晓娇) and Xiang Wu(吴祥)

Chin. Phys. B, 2024, 33 (7): 070204. DOI: 10.1088/1674-1056/ad3dca

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This paper examines the bipartite consensus problems for the nonlinear multi-agent systems in Lurie dynamics form with cooperative and competitive communication between different agents. Based on the contraction theory, some new conditions for the nonlinear Lurie multi-agent systems reaching bipartite leaderless consensus and bipartite tracking consensus are presented. Compared with the traditional methods, this approach degrades the dimensions of the conditions, eliminates some restrictions of the system matrix, and extends the range of the nonlinear function. Finally, two numerical examples are provided to illustrate the efficiency of our results.

A viscoelastic nonlinear energy sink with an electromagnetic energy harvester: Narrow-band random response Suggested by editors

Zhi-Jing Liao(廖志晶), Ya-Hui Sun(孙亚辉), and Yang Liu(刘洋)

Chin. Phys. B, 2024, 33 (7): 070205. DOI: 10.1088/1674-1056/ad4632

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Nonlinear energy sink is a passive energy absorption device that surpasses linear dampers, and has gained significant attention in various fields of vibration suppression. This is owing to its capacity to offer high vibration attenuation and robustness across a wide frequency spectrum. Energy harvester is a device employed to convert kinetic energy into usable electric energy. In this paper, we propose an electromagnetic energy harvester enhanced viscoelastic nonlinear energy sink (VNES) to achieve passive vibration suppression and energy harvesting simultaneously. A critical departure from prior studies is the investigation of the stochastic P-bifurcation of the electromechanically coupled VNES system under narrow-band random excitation. Initially, approximate analytical solutions are derived using a combination of a multiple-scale method and a perturbation approach. The substantial agreement between theoretical analysis solutions and numerical solutions obtained from Monte Carlo simulation underscores the method's high degree of validity. Furthermore, the effects of system parameters on system responses are carefully examined. Additionally, we demonstrate that stochastic P-bifurcation can be induced by system parameters, which is further verified by the steady-state density functions of displacement. Lastly, we analyze the impacts of various parameters on the mean square current and the mean output power, which are crucial for selecting suitable parameters to enhance the energy harvesting performance.

Dynamic analysis of major public health emergency transmission considering the dual-layer coupling of community-resident complex networks

Peng Yang(杨鹏), Ruguo Fan(范如国), Yibo Wang(王奕博), and Yingqing Zhang(张应青)

Chin. Phys. B, 2024, 33 (7): 070206. DOI: 10.1088/1674-1056/ad39c7

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We construct a dual-layer coupled complex network of communities and residents to represent the interconnected risk transmission network between communities and the disease transmission network among residents. It characterizes the process of infectious disease transmission among residents between communities through the SE2IHR model considering two types of infectors. By depicting a more fine-grained social structure and combining further simulation experiments, the study validates the crucial role of various prevention and control measures implemented by communities as primary executors in controlling the epidemic. Research shows that the geographical boundaries of communities and the social interaction patterns of residents have a significant impact on the spread of the epidemic, where early detection, isolation and treatment strategies at community level are essential for controlling the spread of the epidemic. In addition, the study explores the collaborative governance model and institutional advantages of communities and residents in epidemic prevention and control.

Detecting the quantum phase transition from the perspective of quantum information in the Aubry-André model

Geng-Biao Wei(韦庚彪), Liu Ye(叶柳), and Dong Wang(王栋)

Chin. Phys. B, 2024, 33 (7): 070301. DOI: 10.1088/1674-1056/ad2f1f

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We investigate the effectiveness of entropic uncertainty, entanglement and steering in discerning quantum phase transitions (QPTs). Specifically, we observe significant fluctuations in entropic uncertainty as the driving parameter traverses the phase transition point. It is observed that the entropic uncertainty, entanglement and quantum steering, based on the electron distribution probability, can serve as indicators for detecting QPTs. Notably, we reveal an intriguing anticorrelation relationship between entropic uncertainty and entanglement in the Aubry-André model. Moreover, we explore the feasibility of detecting a QPT when the period parameter is a rational number. These observations open up new and efficient avenues for probing QPTs.

Verifiable quantum secret sharing scheme based on orthogonal product states

Chen-Ming Bai(白晨明), Lu Liu(刘璐), and Sujuan Zhang(张素娟)

Chin. Phys. B, 2024, 33 (7): 070302. DOI: 10.1088/1674-1056/ad342a

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In the domain of quantum cryptography, the implementation of quantum secret sharing stands as a pivotal element. In this paper, we propose a novel verifiable quantum secret sharing protocol using the $d$-dimensional product state and Lagrange interpolation techniques. This protocol is initiated by the dealer Alice, who initially prepares a quantum product state, selected from a predefined set of orthogonal product states within the $\mathbb{C}^d \otimes \mathbb{C}^d$ framework. Subsequently, the participants execute unitary operations on this product state to recover the underlying secret. Furthermore, we subject the protocol to a rigorous security analysis, considering both eavesdropping attacks and potential dishonesty from the participants. Finally, we conduct a comparative analysis of our protocol against existing schemes. Our scheme exhibits economies of scale by exclusively employing quantum product states, thereby realizing significant cost-efficiency advantages. In terms of access structure, we adopt a $(t,n)$-threshold architecture, a strategic choice that augments the protocol's practicality and suitability for diverse applications. Furthermore, our protocol includes a rigorous integrity verification mechanism to ensure the honesty and reliability of the participants throughout the execution of the protocol.

Improvement and security analysis of multi-ring discrete modulation continuous variable quantum secret sharing scheme

Huan-Yao Jiang(姜欢窈), Min Nie(聂敏), Guang Yang(杨光), Ai-Jing Sun(孙爱晶), Mei-Ling Zhang(张美玲), and Chang-Xing Pei(裴昌幸)

Chin. Phys. B, 2024, 33 (7): 070303. DOI: 10.1088/1674-1056/ad3b81

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In order to avoid the complexity of Gaussian modulation and the problem that the traditional point-to-point communication DM-CVQKD protocol cannot meet the demand for multi-user key sharing at the same time, we propose a multi-ring discrete modulation continuous variable quantum key sharing scheme (MR-DM-CVQSS). In this paper, we primarily compare single-ring and multi-ring M-symbol amplitude and phase-shift keying modulations. We analyze their asymptotic key rates against collective attacks and consider the security key rates under finite-size effects. Leveraging the characteristics of discrete modulation, we improve the quantum secret sharing scheme. Non-dealer participants only require simple phase shifters to complete quantum secret sharing. We also provide the general design of the MR-DM-CVQSS protocol. We conduct a comprehensive analysis of the improved protocol's performance, confirming that the enhancement through multi-ring M-PSK allows for longer-distance quantum key distribution. Additionally, it reduces the deployment complexity of the system, thereby increasing the practical value.

Verifying hierarchical network nonlocality in general quantum networks

Shu-Yuan Yang(杨舒媛), Jin-Chuan Hou(侯晋川), and Kan He(贺衎)

Chin. Phys. B, 2024, 33 (7): 070304. DOI: 10.1088/1674-1056/ad3dd5

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Recently, a class of innovative notions on quantum network nonlocality (QNN), called full quantum network nonlocality (FQNN), have been proposed in Phys. Rev. Lett. 128 010403 (2022). As the generalization of full network nonlocality (FNN), $l$-level quantum network nonlocality ($l$-QNN) was defined in arxiv. 2306.15717 quant-ph (2024). FQNN is a NN that can be generated only from a network with all sources being non-classical. This is beyond the existing standard network nonlocality, which may be generated from a network with only a non-classical source. One of the challenging tasks is to establish corresponding Bell-like inequalities to demonstrate the FQNN or $l$-QNN. Up to now, the inequality criteria for FQNN and $l$-QNN have only been established for star and chain networks. In this paper, we devote ourselves to establishing Bell-like inequalities for networks with more complex structures. Note that star and chain networks are special kinds of tree-shaped networks. We first establish the Bell-like inequalities for verifying $l$-QNN in $k$-forked tree-shaped networks. Such results generalize the existing inequalities for star and chain networks. Furthermore, we find the Bell-like inequality criteria for $l$-QNN for general acyclic and cyclic networks. Finally, we discuss the demonstration of $l$-QNN in the well-known butterfly networks.

Simulations of superconducting quantum gates by digital flux tuner for qubits

Xiao Geng(耿霄), Kaiyong He(何楷泳), Jianshe Liu(刘建设), and Wei Chen(陈炜)

Chin. Phys. B, 2024, 33 (7): 070305. DOI: 10.1088/1674-1056/ad47ab

Abstract ( 61 )

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The interconnection bottleneck caused by limitations of cable number, inner space and cooling power of dilution refrigerators has been an outstanding challenge for building scalable superconducting quantum computers with the increasing number of qubits in quantum processors. To surmount such an obstacle, it is desirable to integrate qubits with quantum-classical interface (QCI) circuits based on rapid single flux quantum (RSFQ) circuits. In this work, a digital flux tuner for qubits (DFTQ) is proposed for manipulating flux of qubits as a crucial part of the interface circuit. A schematic diagram of the DFTQ is presented, consisting of a coarse tuning unit and a fine-tuning unit for providing magnetic flux with different precision to qubits. The method of using DFTQ to provide flux for gate operations is discussed from the optimization of circuit design and input signal. To verify the effectiveness of the method, simulations of a single DFTQ and quantum gates including a $Z$ gate and an iSWAP gate with DFTQs are performed for flux-tunable transmons. The quantum process tomography corresponding to the two gates is also carried out to analyze the sources of gate error. The results of tomography show that the gate fidelities independent of the initial states of the $Z$ gate and the iSWAP gate are 99.935% and 99.676%, respectively. With DFTQs inside, the QCI would be a powerful tool for building large-scale quantum computers.

A wealth distribution model with a non-Maxwellian collision kernel Suggested by editors

Jun Meng(孟俊), Xia Zhou(周霞), and Shaoyong Lai(赖绍永)

Chin. Phys. B, 2024, 33 (7): 070501. DOI: 10.1088/1674-1056/ad3dc6

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A non-Maxwellian collision kernel is employed to study the evolution of wealth distribution in a multi-agent society. The collision kernel divides agents into two different groups under certain conditions. Applying the kinetic theory of rarefied gases, we construct a two-group kinetic model for the evolution of wealth distribution. Under the continuous trading limit, the Fokker-Planck equation is derived and its steady-state solution is obtained. For the non-Maxwellian collision kernel, we find a suitable redistribution operator to match the taxation. Our results illustrate that taxation and redistribution have the property to change the Pareto index.

A color image encryption scheme based on a 2D coupled chaotic system and diagonal scrambling algorithm

Jingming Su(苏静明), Shihui Fang(方士辉), Yan Hong(洪炎), and Yan Wen(温言)

Chin. Phys. B, 2024, 33 (7): 070502. DOI: 10.1088/1674-1056/ad3efa

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A novel color image encryption scheme is developed to enhance the security of encryption without increasing the complexity. Firstly, the plain color image is decomposed into three grayscale plain images, which are converted into the frequency domain coefficient matrices (FDCM) with discrete cosine transform (DCT) operation. After that, a two-dimensional (2D) coupled chaotic system is developed and used to generate one group of embedded matrices and another group of encryption matrices, respectively. The embedded matrices are integrated with the FDCM to fulfill the frequency domain encryption, and then the inverse DCT processing is implemented to recover the spatial domain signal. Eventually, under the function of the encryption matrices and the proposed diagonal scrambling algorithm, the final color ciphertext is obtained. The experimental results show that the proposed method can not only ensure efficient encryption but also satisfy various sizes of image encryption. Besides, it has better performance than other similar techniques in statistical feature analysis, such as key space, key sensitivity, anti-differential attack, information entropy, noise attack, etc.

Bifurcation analysis and control study of improved full-speed differential model in connected vehicle environment

Wen-Huan Ai(艾文欢), Zheng-Qing Lei(雷正清), Dan-Yang Li(李丹洋), Dong-Liang Fang(方栋梁), and Da-Wei Liu(刘大为)

Chin. Phys. B, 2024, 33 (7): 070503. DOI: 10.1088/1674-1056/ad3b80

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In recent years, the traffic congestion problem has become more and more serious, and the research on traffic system control has become a new hot spot. Studying the bifurcation characteristics of traffic flow systems and designing control schemes for unstable pivots can alleviate the traffic congestion problem from a new perspective. In this work, the full-speed differential model considering the vehicle network environment is improved in order to adjust the traffic flow from the perspective of bifurcation control, the existence conditions of Hopf bifurcation and saddle-node bifurcation in the model are proved theoretically, and the stability mutation point for the stability of the transportation system is found. For the unstable bifurcation point, a nonlinear system feedback controller is designed by using Chebyshev polynomial approximation and stochastic feedback control method. The advancement, postponement, and elimination of Hopf bifurcation are achieved without changing the system equilibrium point, and the mutation behavior of the transportation system is controlled so as to alleviate the traffic congestion. The changes in the stability of complex traffic systems are explained through the bifurcation analysis, which can better capture the characteristics of the traffic flow. By adjusting the control parameters in the feedback controllers, the influence of the boundary conditions on the stability of the traffic system is adequately described, and the effects of the unstable focuses and saddle points on the system are suppressed to slow down the traffic flow. In addition, the unstable bifurcation points can be eliminated and the Hopf bifurcation can be controlled to advance, delay, and disappear, so as to realize the control of the stability behavior of the traffic system, which can help to alleviate the traffic congestion and describe the actual traffic phenomena as well.

Proposal for a realtime Einstein-synchronization-defined satellite virtual clock

Chenhao Yan(严晨皓), Xueyi Tang(汤雪逸), Shiguang Wang(王时光), Lijiaoyue Meng(孟李皎悦), Haiyuan Sun(孙海媛), Yibin He(何奕彬), and Lijun Wang(王力军)

Chin. Phys. B, 2024, 33 (7): 070601. DOI: 10.1088/1674-1056/ad3dc9

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Realization of high performance satellite onboard clock is vital for various positioning, navigation, and timing applications. For further improvement of the synchronization-based satellite time and frequency references, we propose a geosynchronous (GEO) satellite virtual clock concept based on ground-satellite synchronization and present a beacon transponder structure for its implementation (scheduled for launch in 2025), which does not require atomic clocks to be mounted on the satellite. Its high performance relies only on minor modifications to the existing transponder structure of GEO satellites. We carefully model the carrier phase link and analyze the factors causing link asymmetry within the special relativity. Considering that performance of such synchronization-based satellite clocks is primarily limited by the link's random phase noise, which cannot be adequately modeled, we design a closed-loop experiment based on commercial GEO satellites for pre-evaluation. This experiment aims at extracting the zero-means random part of the ground-satellite Ku-band carrier phase via a feedback loop. Ultimately, we obtain a 1$\sigma$ value of 0.633 ps (two-way link), following the Gaussian distribution. From this result, we conclude that the proposed real-time Einstein-synchronization-defined satellite virtual clock can achieve picosecond-level replication of onboard time and frequency.

Physical information-enhanced graph neural network for predicting phase separation Suggested by editors

Yaqiang Zhang(张亚强), Xuwen Wang(王煦文), Yanan Wang(王雅楠), and Wen Zheng(郑文)

Chin. Phys. B, 2024, 33 (7): 070702. DOI: 10.1088/1674-1056/ad4328

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Although phase separation is a ubiquitous phenomenon, the interactions between multiple components make it difficult to accurately model and predict. In recent years, machine learning has been widely used in physics simulations. Here, we present a physical information-enhanced graph neural network (PIENet) to simulate and predict the evolution of phase separation. The accuracy of our model in predicting particle positions is improved by 40.3% and 51.77% compared with CNN and SVM respectively. Moreover, we design an order parameter based on local density to measure the evolution of phase separation and analyze the systematic changes with different repulsion coefficients and different Schmidt numbers. The results demonstrate that our model can achieve long-term accurate predictions of order parameters without requiring complex handcrafted features. These results prove that graph neural networks can become new tools and methods for predicting the structure and properties of complex physical systems.

Excitation and ionization of OCS molecules in strong UV and NIR laser fields

Huijun Shi(师慧军), Yang Liu(刘洋), Tian Sun(孙添), Hang Lv(吕航), and Haifeng Xu(徐海峰)

Chin. Phys. B, 2024, 33 (7): 073301. DOI: 10.1088/1674-1056/ad3035

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Rydberg state excitation (RSE) is a highly non-linear physical phenomenon that is induced by the ionization of atoms or molecules in strong femtosecond laser fields. Here we observe that both parent and fragments (S, C, OC) of the tri-atomic molecule carbonyl sulfide (OCS) can survive strong 800 nm or 400 nm laser fields in high Rydberg states. The dependence of parent and fragment RSE yields on laser intensity and ellipticity is investigated in both laser fields, and the results are compared with those for strong-field ionization. Distinctly different tendencies for laser intensity and ellipticity are observed for fragment RSE compared with the corresponding ions. The mechanisms of RSE and strong-field ionization of OCS molecules in different laser fields are discussed based on the experimental results. Our study sheds some light on the strong-field excitation and ionization of molecules irradiated by femtosecond NIR and UV laser fields.

Atomic transport dynamics in crossed optical dipole trap Suggested by editors

Peng Peng(彭鹏), Zhengxi Zhang(张正熙), Yaoyuan Fan(樊耀塬), Guoling Yin(殷国玲), Dekai Mao(毛德凯), Xuzong Chen(陈徐宗), Wei Xiong(熊炜), and Xiaoji Zhou(周小计)

Chin. Phys. B, 2024, 33 (7): 073701. DOI: 10.1088/1674-1056/ad401c

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We study the dynamical evolution of cold atoms in crossed optical dipole trap theoretically and experimentally. The atomic transport process is accompanied by two competitive kinds of physical mechanics, atomic loading and atomic loss. The loading process normally is negligible in the evaporative cooling experiment on the ground, while it is significant in preparation of ultra-cold atoms in the space station. Normally, the atomic loading process is much weaker than the atomic loss process, and the atomic number in the central region of the trap decreases monotonically, as reported in previous research. However, when the atomic loading process is comparable to the atomic loss process, the atomic number in the central region of the trap will initially increase to a maximum value and then slowly decrease, and we have observed the phenomenon first. The increase of atomic number in the central region of the trap shows the presence of the loading process, and this will be significant especially under microgravity conditions. We build a theoretical model to analyze the competitive relationship, which coincides with the experimental results well. Furthermore, we have also given the predicted evolutionary behaviors under different conditions. This research provides a solid foundation for further understanding of the atomic transport process in traps. The analysis of loading process is of significant importance for preparation of ultra-cold atoms in a crossed optical dipole trap under microgravity conditions.

Effect of boundary slip on electroosmotic flow in a curved rectangular microchannel

Yong-Bo Liu(刘勇波)1,2

Chin. Phys. B, 2024, 33 (7): 074101. DOI: 10.1088/1674-1056/ad3340

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The aim of this study is to numerically investigate the impact of boundary slip on electroosmotic flow (EOF) in curved rectangular microchannels. Navier slip boundary conditions were employed at the curved microchannel walls. The electric potential distribution was governed by the Poisson-Boltzmann equation, whereas the velocity distribution was determined by the Navier-Stokes equation. The finite-difference method was employed to solve these two equations. The detailed discussion focuses on the impact of the curvature ratio, electrokinetic width, aspect ratio and slip length on the velocity. The results indicate that the present problem is strongly dependent on these parameters. The results demonstrate that by varying the dimensionless slip length from 0.001 to 0.01 while maintaining a curvature ratio of 0.5 there is a twofold increase in the maximum velocity. Moreover, this increase becomes more pronounced at higher curvature ratios. In addition, the velocity difference between the inner and outer radial regions increases with increasing slip length. Therefore, the incorporation of the slip boundary condition results in an augmented velocity and a more non-uniform velocity distribution. The findings presented here offer valuable insights into the design and optimization of EOF performance in curved hydrophobic microchannels featuring rectangular cross-sections.

Radiation of a TM mode from an open end of a three-layer dielectric capillary

Sergey N. Galyamin and Alexandr M. Altmark

Chin. Phys. B, 2024, 33 (7): 074102. DOI: 10.1088/1674-1056/ad3ef7

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Modern trends in beam-driven radiation sources include the interaction of Cherenkov wakefields in open-ended circular waveguides with complicated dielectric linings, with a three-layer dielectric capillary recently proposed to reduce radiation divergence being a representative example [Opt. Lett. 45 5416 (2020)]. We present a rigorous approach that allows for an analytical description of the electromagnetic processes that occur when the structure is excited by a single waveguide TM mode. In other words, the corresponding canonical waveguide diffraction problem is solved in a rigorous formulation. This is a continuation of our previous papers which considered simpler cases with a homogeneous or two-layer dielectric filling. Here we use the same analytical approach based on the Wiener-Hopf-Fock technique and deal with the more complicated case of a three-layer dielectric lining. Using the obtained rigorous solution, we discuss the possibility of manipulating the far-field radiation pattern using a third layer made of a low permittivity material.

Internal phase control of fiber laser array based on photodetector array Suggested by editors

Kai-Kai Jin(靳凯凯), Jin-Hu Long(龙金虎), Hong-Xiang Chang(常洪祥), Rong-Tao Su(粟荣涛), Jia-Yi Zhang(张嘉怡), Si-Yu Chen(陈思雨), Yan-Xing Ma(马阎星), and Pu Zhou(周朴)

Chin. Phys. B, 2024, 33 (7): 074201. DOI: 10.1088/1674-1056/ad47af

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Coherent beam combining (CBC) of fiber laser array is a promising technique to realize high output power while maintaining near diffraction-limited beam quality. To implement CBC, an appropriate phase control feedback structure should be established to realize phase-locking. In this paper, an innovative internal active phase control CBC fiber laser array based on photodetector array is proposed. The dynamic phase noises of the laser amplifiers are compensated before being emitted into free space. And the static phase difference compensation of emitting laser array is realized by interference measurement based on photodetector array. The principle of the technique is illustrated and corresponding simulations are carried out, and a CBC system with four laser channels is built to verify the technique. When the phase controllers are turned on, the phase deviation of the laser array is less than $\lambda /20$, and $\sim 95$% fringe contrast of the irradiation distribution is obtained. The technique proposed in this paper could provide a reference for the system design of a massive high-power CBC system.

High-visibility ghost imaging with phase-controlled discrete classical light sources Suggested by editors

Xueying Wu(仵雪滢), Yue Zhao(赵岳), and Liming Li(李利明)

Chin. Phys. B, 2024, 33 (7): 074202. DOI: 10.1088/1674-1056/ad4631

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We take phase modulation to create discrete phase-controlled sources and realize the super-bunching effect by a phase-correlated method. From theoretical and numerical simulations, we find the space translation invariance of the bunching effect is a key point for the ghost imaging realization. Experimentally, we create the orderly phase-correlated discrete sources which can realize high-visibility second-order ghost imaging than the result with chaotic sources. Moreover, some factors affecting the visibility of ghost image are discussed in detail.

Multi-functional photonic spin Hall effect sensor controlled by phase transition Suggested by editors

Jie Cheng(程杰), Rui-Zhao Li(李瑞昭), Cheng Cheng(程骋), Ya-Lin Zhang(张亚林), Sheng-Li Liu(刘胜利), and Peng Dong(董鹏)

Chin. Phys. B, 2024, 33 (7): 074203. DOI: 10.1088/1674-1056/ad3b85

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Photonic spin Hall effect (PSHE), as a novel physical effect in light-matter interaction, provides an effective metrological method for characterizing the tiny variation in refractive index (RI). In this work, we propose a multi-functional PSHE sensor based on VO$_{2}$, a material that can reveal the phase transition behavior. By applying thermal control, the mutual transformation into different phase states of VO$_{2}$ can be realized, which contributes to the flexible switching between multiple RI sensing tasks. When VO$_{2}$ is insulating, the ultrasensitive detection of glucose concentrations in human blood is achieved. When VO$_{2}$ is in a mixed phase, the structure can be designed to distinguish between the normal cells and cancer cells through no-label and real-time monitoring. When VO$_{2}$ is metallic, the proposed PSHE sensor can act as an RI indicator for gas analytes. Compared with other multi-functional sensing devices with the complex structures, our design consists of only one analyte and two VO$_{2}$ layers, which is very simple and elegant. Therefore, the proposed VO$_{2}$-based PSHE sensor has outstanding advantages such as small size, high sensitivity, no-label, and real-time detection, providing a new approach for investigating tunable multi-functional sensors.

Dynamically enhanced Autler-Townes splitting by orthogonal XUV fields

Li-Long Wu(吴立龙), Wei-Chao Jiang(姜维超), and Liang-You Peng(彭良友)

Chin. Phys. B, 2024, 33 (7): 074204. DOI: 10.1088/1674-1056/ad3dd3

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Based on numerical solutions of the time-dependent Schrödinger equation, we theoretically investigate the photoelectron spectrum of hydrogen atoms ionized by a pair of ultrashort, intense, and orthogonally polarized laser pulses with a relative time delay in a pump-probe configuration. The pump pulse resonantly excites electrons from the 1s and 2p levels, inducing Rabi oscillations. The resulting dynamically enhanced Autler-Townes (AT) splitting is observed in the photoelectron energy spectrum upon interaction with the second probe pulse. In contrast to the previous parallel-polarization scheme, the proposed orthogonal-polarization configuration enables the resolution of dynamically enhanced AT splitting over a considerably wider range of probe photon energies.

Entangling two levitated charged nanospheres through Coulomb interaction

Guoyao Li(李国耀) and Zhangqi Yin(尹璋琦)

Chin. Phys. B, 2024, 33 (7): 074205. DOI: 10.1088/1674-1056/ad3229

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Limited by the thermal environment, the entanglement of a massive object is extremely difficult to generate. Based on a coherent scattering mechanism, we propose a scheme to generate the entanglement of two optically levitated nanospheres through the Coulomb interaction. Two nanospheres are charged and coupled to each other through the Coulomb interaction. In this manner, the entanglement of two nanospheres is induced either under a weak/strong optomechanical coupling regime or under an ultra-strong optomechanical coupling regime. The charges, radius and distance of the two nanospheres are taken into consideration to enhance the Coulomb interaction, thereby achieving a higher degree of entanglement in the absence of ground-state cooling. The corresponding maximum entanglement can be attained as the dynamics of the system approaches the boundary between the steady and the unsteady regimes. This provides a useful resource for both quantum-enhanced sensing and quantum information processing, as well as a new platform for studying many-body physics.

Continuous wave and active Q-switched operation of Watt-level LED-pumped two-rod Nd,Ce:YAG laser

Jian-Ping Shen(沈建平), Peng Lu(芦鹏), Shao-Cong Xu(徐少聪), Rong-Rong Jiang(江容容), Yang Chen(陈阳), Liang Chen(陈亮), and Feng-Yang Xing(邢凤阳)

Chin. Phys. B, 2024, 33 (7): 074207. DOI: 10.1088/1674-1056/ad34c9

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A high-performance LED-side-pumped two-rod Nd,Ce:YAG laser with continuous-wave (CW) and acousto-optical (A-O) $Q$-switched operation is demonstrated in this work. A symmetrically shaped flat-flat cavity with two identical LED-side-pumped laser modules is employed for power scalability. In the CW regime, the maximum output average power of laser at 1064 nm is 4.41 W, corresponding to a maximum optical conversion efficiency of 5.3% and a slope efficiency is 12.4%. In the active $Q$-switched regime, the pulse energy of laser reaches as high as 0.89 mJ at a repetition rate of 800 Hz with a pulse width of 457.2 ns, the corresponding highest peak output power is 1.94 kW and the $M^{2}$ factor is measured to be about 8.8. To the best of the authors' knowledge, this is the first demonstration and the highest performance of a CW LED-side-pumped two-rod laser Nd,Ce:YAG with Watt-level output reported so far.

Dissipative soliton resonance within different dispersion regimes in a single mode-locked laser Suggested by editors

Zhetao Zhao(赵哲韬), Qinke Shu(舒沁珂), Ziyi Xie(解梓怡), Yuxuan Ren(任俞宣), Ying Zhang(张颖), Bo Yuan(袁博), Chunbo Zhao(赵春勃), Junsong Peng(彭俊松), and Heping Zeng(曾和平)

Chin. Phys. B, 2024, 33 (7): 074208. DOI: 10.1088/1674-1056/ad47b1

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Dissipative soliton resonance (DSR) was previously studied in separated mode-locked fiber lasers within different dispersion regimes including anomalous, near-zero and normal dispersion. Here we propose a method to study DSR in a single mode-locked laser in these different dispersion regimes. This is achieved by virtue of a waveshaper which can control the laser dispersion readily using software, avoiding the usual tedious cutback method. We find that dispersion has a negligible effect on DSR since the pulse duration keeps constant while dispersion is varied. Moreover, we examine the dynamics of DSR on the parameters of the SA including modulation depth and saturation power, and find that the pulse duration can be changed in a large range when the saturation power is decreased. Our numerical simulations could be important to guide relative experimental studies.

Wavelength-interval switchable Brillouin-Raman random fiber laser through Brillouin pump manipulation Suggested by editors

Yang Li(李阳), En-Ming Xu(徐恩明), Rui-Jia Chen(陈睿佳), Yu-Gang Shee, and Zu-Xing Zhang(张祖兴)

Chin. Phys. B, 2024, 33 (7): 074209. DOI: 10.1088/1674-1056/ad3efb

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A wavelength-interval switchable Brillouin-Raman random fiber laser (BRRFL) based on Brillouin pump (BP) manipulation is proposed in this paper. The proposed wavelength-interval switchable BRRFL has a full-open cavity configuration, featuring multiwavelength output with wavelength interval of double Brillouin frequency shifts. Through simultaneously injecting the BP light and its first-order stimulated Brillouin-scattered light into the cavity, the laser output exhibits a wavelength interval of single Brillouin frequency shift. The wavelength-interval switching effect can be manipulated by controlling the power of the first-order stimulated Brillouin scattering light. The experimental results show the multiwavelength output can be switched between double Brillouin frequency shift multiwavelength emission with a broad bandwidth of approximately 60 nm and single Brillouin frequency shift multiwavelength emission of 44 nm. The flexible optically controlled random fiber laser with switchable wavelength interval makes it useful for a wide range of applications and holds significant potential in the field of wavelength-division multiplexing optical communication.

Comprehensive study of the ultrafast photoexcited carrier dynamics in Sb₂Te₃-GeTe superlattices Suggested by editors

Zhijiang Ye(叶之江), Zuanming Jin(金钻明), Yexin Jiang(蒋叶昕), Qi Lu(卢琦), Menghui Jia(贾梦辉), Dong Qian(钱冬), Xiamin Huang(黄夏敏), Zhou Li(李舟), Yan Peng(彭滟), and Yiming Zhu(朱亦鸣)

Chin. Phys. B, 2024, 33 (7): 074210. DOI: 10.1088/1674-1056/ad432a

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Chalcogenide superlattices Sb$_{2}$Te$_{3}$-GeTe is a candidate for interfacial phase-change memory (iPCM) data storage devices. By employing terahertz emission spectroscopy and the transient reflectance spectroscopy together, we investigate the ultrafast photoexcited carrier dynamics and current transients in Sb$_{2}$Te$_{3}$-GeTe superlattices. Sample orientation and excitation polarization dependences of the THz emission confirm that ultrafast thermo-electric, shift and injection currents contribute to the THz generation in Sb$_{2}$Te$_{3}$-GeTe superlattices. By decreasing the thickness and increasing the number of GeTe and Sb$_{2}$Te$_{3}$ layer, the interlayer coupling can be enhanced, which significantly reduces the contribution from circular photo-galvanic effect (CPGE). A photo-induced bleaching in the transient reflectance spectroscopy probed in the range of $\sim 1100 $ nm to $\sim 1400 $ nm further demonstrates a gapped state resulting from the interlayer coupling. These demonstrates play an important role in the development of iPCM-based high-speed optoelectronic devices.

Pipeline thickness estimation using the dispersion of higher-order SH guided waves

Zhengchen Dai(代政辰), Jinxia Liu(刘金霞), Yunfei Long(龙云飞), Jianhai Zhang(张建海), Tribikram Kundu, and Zhiwen Cui(崔志文)

Chin. Phys. B, 2024, 33 (7): 074301. DOI: 10.1088/1674-1056/ad3033

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Thickness measurement plays an important role in the monitoring of pipeline corrosion damage. However, the requirement for prior knowledge of the shear wave velocity in the pipeline material for popular ultrasonic thickness measurement limits its widespread application. This paper proposes a method that utilizes cylindrical shear horizontal (SH) guided waves to estimate pipeline thickness without prior knowledge of shear wave velocity. The inversion formulas are derived from the dispersion of higher-order modes with the high-frequency approximation. The waveform of the example problems is simulated using the real-axis integral method. The data points on the dispersion curves are processed in the frequency domain using the wave-number method. These extracted data are then substituted into the derived formulas. The results verify that employing higher-order SH guided waves for the evaluation of thickness and shear wave velocity yields less than 1% error. This method can be applied to both metallic and non-metallic pipelines, thus opening new possibilities for health monitoring of pipeline structures.

Large-scale particle trapping by acoustic vortices with a continuously variable topological charge

Haofei Zhuang(庄昊霏), Qingyuan Zhang(张清源), Gehao Hu(胡格昊), Qingdong Wang(王青东), and Libin Du(杜立彬)

Chin. Phys. B, 2024, 33 (7): 074302. DOI: 10.1088/1674-1056/ad5aef

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Strengthened directivity with higher-order side lobes can be generated by the transducer with a larger radius at a higher frequency. The multi-annular pressure distributions are displayed in the cross-section of the acoustic vortices (AVs) which are formed by side lobes. In the near field, particles can be trapped in the valley region between the two annuli of the pressure peak, and cannot be moved to the vortex center. In this paper, a trapping method based on a sector transducer array is proposed, which is characterized by the continuously variable topological charge (CVTC). This acoustic field can not only enlarge the range of particle trapping but also improve the aggregation degree of the trapped particles. In the experiments, polyethylene particles with a diameter of 0.2 mm are trapped into the multi-annular valleys by the AV with a fixed topological charge. Nevertheless, by applying the CVTC, particles outside the radius of the AV can cross the pressure peak successfully and move to the vortex center. Theoretical studies are also verified by the experimental particles trapping using the AV with the continuous variation of three topological charges, and suggest the potential application of large-scale particle trapping in biomedical engineering.

Experimental investigation of closed-loop active control to modulate coherent structures by mu-level method

Jian-Xia Bai(白建侠), Zi-Ye Fan(范子椰), Nan Jiang(姜楠), Qiu-Ying Li(李秋营), and Xiao-Bo Zheng(郑小波)

Chin. Phys. B, 2024, 33 (7): 074701. DOI: 10.1088/1674-1056/ad3dc7

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The experimental research on zero-net-mass-flux jet closed-loop active control was conducted in the wind tunnel. The mu-level method successfully detected burst events of the coherent structures. The streamwise velocity signals in the turbulent boundary layer were measured by HWA. The drag reduction rate of 16.7% is obtained comparable to that of the open-loop control and saves 75% of the input energy at the asynchronous 100 V/160 Hz control case, which reflects the advantages of the closed-loop control. The experimental findings indicate that the intensity increases in the near-wall region. The perturbation of the PZT vibrators on the skewness factor is concentrated in the region $y^{+}<60$. The generation of high-speed fluids is depressed and the downward effect of high-speed fluids weakens. The alteration of energy distribution and the discernible impact of modulation between structures of varying scales are observed. The correlation coefficient exhibits a strong positive correlation, which indicates that the large-scale structures produce modulation effect on small-scale ones. The occurrence of burst events is effectively suppressed. The disturbance has the characteristics of stable periodicity, positive and negative symmetry, low intermittency, and high pulsation strength. The conditional phase waveform shows that the fluctuation amplitude increases, indicating amplitude modulation effects on coherent structures.

Effect of distribution shape on the melting transition, local ordering, and dynamics in a model size-polydisperse two-dimensional fluid

Jackson Pame and Lenin S. Shagolsem

Chin. Phys. B, 2024, 33 (7): 074702. DOI: 10.1088/1674-1056/ad39c9

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We study the effect of particle size polydispersity ($\delta$) on the melting transition ($T^*$), local ordering, solid-liquid coexistence phase and dynamics of two-dimensional Lennard-Jones fluids up to moderate polydispersity by means of computer simulations. The particle sizes are drawn at random from the Gaussian (G) and uniform (U) distribution functions. For these systems, we further consider two different kinds of particles, viz., particles having the same mass irrespective of size, and in the other case the mass of the particle scales with its size. It is observed that with increasing polydispersity, the value of $T^\ast$ initially increases due to improved packing efficiency ($\phi$) followed by a decrease and terminates at $\delta\approx 8%$ (U-system) and $14%$ (G-system) with no significant difference for both mass types. The interesting observation is that the particular value at which $\phi$ drops suddenly coincides with the peak of the heat capacity $(C_{P})$ curve, indicating a transition. The quantification of local particle ordering through the hexatic order parameter ($Q_6$), Voronoi construction and pair correlation function reveals that the ordering decreases with increasing $\delta$ and $T$. Furthermore, the solid-liquid coexistence region for the G-system is shown to be comparatively wider in the $T$-$\delta$ plane phase diagram than that for the U system. Finally, the study of dynamics reveals that polydisperse systems relax faster compared to monodisperse systems; however, no significant qualitative differences, depending on the distribution type and mass polydispersity, are observed.

Power transfer efficiency in an air-breathing radio frequency ion thruster Suggested by editors

Gao-Huang Huang(黄高煌), Hong Li(李宏), Fei Gao(高飞), and You-Nian Wang(王友年)

Chin. Phys. B, 2024, 33 (7): 075201. DOI: 10.1088/1674-1056/ad426c

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Due to a series of challenges such as low-orbit maintenance of satellites, the air-breathing electric propulsion has got widespread attention. Commonly, the radio frequency ion thruster is favored by low-orbit missions due to its high specific impulse and efficiency. In this paper, the power transfer efficiency of the radio frequency ion thruster with different gas compositions is studied experimentally, which is obtained by measuring the radio frequency power and current of the antenna coil with and without discharge operation. The results show that increasing the turns of antenna coils can effectively improve the radio frequency power transfer efficiency, which is due to the improvement of $Q$ factor. In pure N$_{2}$ discharge, with the increase of radio frequency power, the radio frequency power transfer efficiency first rises rapidly and then exhibits a less steep increasing trend. The radio frequency power transfer efficiency increases with the increase of gas pressure at relatively high power, while declines rapidly at relatively low power. In N$_{2}$/O$_{2}$ discharge, increasing the N$_{2}$ content at high power can improve the radio frequency power transfer efficiency, but the opposite was observed at low power. In order to give a better understanding of these trends, an analytic solution in limit cases is utilized, and a Langmuir probe was employed to measure the electron density. It is found that the evolution of radio frequency power transfer efficiency can be well explained by the variation of plasma resistance, which is related to the electron density and the effective electron collision frequency.

Effect of Y element on atomic structure, glass forming ability, and magnetic properties of FeBC alloy Suggested by editors

Jin-Hua Xiao(肖晋桦), Da-Wei Ding(丁大伟), Lin Li(李琳), Yi-Tao Sun(孙奕韬), Mao-Zhi Li(李茂枝), and Wei-Hua Wang(汪卫华)

Chin. Phys. B, 2024, 33 (7): 076101. DOI: 10.1088/1674-1056/ad3dd4

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The atomic structure of amorphous alloys plays a crucial role in determining both their glass-forming ability and magnetic properties. In this study, we investigate the influence of adding the Y element on the glass-forming ability and magnetic properties of Fe$_{86-x}$Y$_{x}$B$_{7}$C$_{7}$ ($x=0$, 5, 10 at.%) amorphous alloys via both experiments and ab initio molecular dynamics simulations. Furthermore, we explore the correlation between local atomic structures and properties. Our results demonstrate that an increased Y content in the alloys leads to a higher proportion of icosahedral clusters, which can potentially enhance both glass-forming ability and thermal stability. These findings have been experimentally validated. The analysis of the electron energy density and magnetic moment of the alloy reveals that the addition of Y leads to hybridization between Y-4d and Fe-3d orbitals, resulting in a reduction in ferromagnetic coupling between Fe atoms. This subsequently reduces the magnetic moment of Fe atoms as well as the total magnetic moment of the system, which is consistent with experimental results. The results could help understand the relationship between atomic structure and magnetic property, and providing valuable insights for enhancing the performance of metallic glasses in industrial applications.

First-principles study of structural and electronic properties of multiferroic oxide Mn₃TeO₆ under high pressure Suggested by editors

Xiao-Long Pan(潘小龙), Hao Wang(王豪), Lei Liu(柳雷), Xiang-Rong Chen(陈向荣), and Hua-Yun Geng(耿华运)

Chin. Phys. B, 2024, 33 (7): 076102. DOI: 10.1088/1674-1056/ad3ef6

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Mn$_{3}$TeO$_{6}$ (MTO) has been experimentally found to adopt a $P2_1/n$ structure under high pressure, which exhibits a significantly smaller band gap compared to the atmospheric $R\bar{3}$ phase. In this study, we systematically investigate the magnetism, structural phase transition, and electronic properties of MTO under high pressure through first-principles calculations. Both $R\bar{3}$ and $P2_1/n$ phases of MTO are antiferromagnetic at zero temperature. The $R\bar{3}$ phase transforms to the $P2_1/n$ phase at 7.58 GPa, accompanied by a considerable volume collapse of about 6.47%. Employing the accurate method that combines DFT$+U$ and GW, the calculated band gap of $R\bar{3}$ phase at zero pressure is very close to the experimental values, while that of the $P2_1/n$ phase is significantly overestimated. The main reason for this difference is that the experimental study incorrectly used the Kubelka-Munk plot for the indirect band gap to obtain the band gap of the $P2_1/n$ phase instead of the Kubelka-Munk plot for the direct band gap. Furthermore, our study reveals that the transition from the $R\bar{3}$ phase to the $P2_1/n$ phase is accompanied by a slight reduction in the band gap.

Properties of radiation defects and threshold energy of displacement in zirconium hydride obtained by new deep-learning potential

Xi Wang(王玺), Meng Tang(唐孟), Ming-Xuan Jiang(蒋明璇), Yang-Chun Chen(陈阳春), Zhi-Xiao Liu(刘智骁), and Hui-Qiu Deng(邓辉球)

Chin. Phys. B, 2024, 33 (7): 076103. DOI: 10.1088/1674-1056/ad362b

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Zirconium hydride (ZrH$_{2}$) is an ideal neutron moderator material. However, radiation effect significantly changes its properties, which affect its behavior and the lifespan of the reactor. The threshold energy of displacement is an important quantity of the number of radiation defects produced, which helps us to predict the evolution of radiation defects in ZrH$_{2}$. Molecular dynamics (MD) and ab initio molecular dynamics (AIMD) are two main methods of calculating the threshold energy of displacement$.$ The MD simulations with empirical potentials often cannot accurately depict the transitional states that lattice atoms must surpass to reach an interstitial state. Additionally, the AIMD method is unable to perform large-scale calculation, which poses a computational challenge beyond the simulation range of density functional theory. Machine learning potentials are renowned for their high accuracy and efficiency, making them an increasingly preferred choice for molecular dynamics simulations. In this work, we develop an accurate potential energy model for the ZrH$_{2}$ system by using the deep-potential (DP) method. The DP model has a high degree of agreement with first-principles calculations for the typical defect energy and mechanical properties of the ZrH$_{2}$ system, including the basic bulk properties, formation energy of point defects, as well as diffusion behavior of hydrogen and zirconium. By integrating the DP model with Ziegler-Biersack-Littmark (ZBL) potential, we can predict the threshold energy of displacement of zirconium and hydrogen in $\varepsilon $-ZrH$_{2}$.

Influence of temperature, stress, and grain size on behavior of nano-polycrystalline niobium

Yu-Ping Yan(晏玉平), Liu-Ting Zhang(张柳亭), Li-Pan Zhang(张丽攀), Gang Lu(芦刚), and Zhi-Xin Tu(涂志新)

Chin. Phys. B, 2024, 33 (7): 076201. DOI: 10.1088/1674-1056/ad3b83

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Atomic simulations are executed to investigate the creep responses of nano-polycrystalline (NC) niobium established by using the Voronoi algorithm. The effects of varying temperature, applied stress, and grain size (GS) on creep properties and mechanisms are investigated. Notably, the occurrence of tertiary creep is exclusively observed under conditions where the applied stress exceeds 4.5 GPa and the temperature is higher than 1100 K. This phenomenon can be attributed to the significant acceleration of grain boundary and lattice diffusion, driven by the elevated temperature and stress levels. It is found that the strain rate increases with both temperature and stress increasing. However, an interesting trend is observed in which the strain rate decreases as the grain size increases. The stress and temperature are crucial parameters governing the creep behavior. As these factors intensify, the creep mechanism undergoes a sequential transformation: initially from lattice diffusion under low stress and temperature conditions to a mixed mode combining grain boundaries (GBs) and lattice diffusion at moderate stress and mid temperature levels, and ultimately leading to the failure of power-law controlled creep behavior, inclusive of grain boundary recrystallization under high stress and temperature conditions. This comprehensive analysis provides in more detail an understanding of the intricate creep behavior of nano-polycrystalline niobium and its dependence on various physical parameters.

Structure and dynamical properties during solidification of liquid aluminum induced by cooling and compression

Min Wu(吴旻), Yong-Qi Yang(杨永琪), and Yao Wang(王垚)

Chin. Phys. B, 2024, 33 (7): 076301. DOI: 10.1088/1674-1056/ad39d0

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The structural transformation from a liquid into a crystalline solid is an important subject in condensed matter physics and materials science. In the present study, first-principles molecular dynamics calculations are performed to investigate the structure and properties of aluminum during the solidification which is induced by cooling and compression. In the cooling process and compression process, it is found that the icosahedral short-range order is initially enhanced and then begin to decay, the face-centered cubic short-range order eventually becomes dominant before it transforms into a crystalline solid.

Density of excess modes below the first phonon mode in four-dimensional glasses Suggested by editors

Lijin Wang(王利近), Ding Xu(胥鼎), and Shiyun Zhang(张世允)

Chin. Phys. B, 2024, 33 (7): 076401. DOI: 10.1088/1674-1056/ad3dd1

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Glasses are known to possess low-frequency excess modes beyond the Debye prediction. For decades, it has been assumed that evolution of low-frequency density of excess modes $D(\omega)$ with frequency $\omega$ follows a power-law scaling: $D(\omega)\sim \omega^{\gamma}$. However, it remains debated on the value of $\gamma$ at low frequencies below the first phonon-like mode in finite-size glasses. Early simulation studies reported $\gamma=4$ at low frequencies in two- (2D), three- (3D), and four-dimensional (4D) glasses, whereas recent observations in 2D and 3D glasses suggested $\gamma=3.5$ in a lower-frequency regime. It is uncertain whether the low-frequency scaling of $D(\omega)\sim \omega^{3.5}$ could be generalized to 4D glasses. Here, we conduct numerical simulation studies of excess modes at frequencies below the first phonon-like mode in 4D model glasses. It is found that the system size dependence of $D(\omega)$ below the first phonon-like mode varies with spatial dimensions: $D(\omega)$ increases in 2D glasses but decreases in 3D and 4D glasses as the system size increases. Furthermore, we demonstrate that the $\omega^{3.5}$ scaling, rather than the $\omega^{4}$ scaling, works in the lowest-frequency regime accessed in 4D glasses, regardless of interaction potentials and system sizes examined. Therefore, our findings in 4D glasses, combined with previous results in 2D and 3D glasses, suggest a common low-frequency scaling of $D(\omega)\sim \omega^{3.5}$ below the first phonon-like mode across different spatial dimensions, which would inspire further theoretical studies.

Evolution of helium bubbles in FeCoNiCr-based high-entropy alloys containing $ \gamma '$ nanoprecipitates

Ting Feng(冯婷), Sheng-Ming Jiang(蒋胜明), Xiao-Tian Hu(胡潇天), Zi-Jun Zhang(张子骏), Zi-Jing Huang(黄子敬), Shi-Gang Dong(董士刚), and Jian Zhang(张建)

Chin. Phys. B, 2024, 33 (7): 076501. DOI: 10.1088/1674-1056/ad342f

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A series of high-entropy alloys (HEAs) containing nanoprecipitates of varying sizes is successfully prepared by a non-consuming vacuum arc melting method. In order to study the irradiation evolution of helium bubbles in the FeCoNiCr-based HEAs with $\gamma'$ precipitates, these samples are irradiated by 100-keV helium ions with a fluence of 5$\times10^{20 }$ ions/m$^{2}$ at 293 K and 673 K, respectively. And the samples irradiated at room temperature are annealed at different temperatures to examine the diffusion behavior of helium bubbles. Transmission electron microscope (TEM) is employed to characterize the structural morphology of precipitated nanoparticles and the evolution of helium bubbles. Experimental results reveal that nanosized, spherical, dispersed, coherent, and ordered L1$_{2}$-type Ni$_{3}$Ti $\gamma'$ precipitations are introduced into FeCoNiCr(Ni$_{3}$Ti)$_{0.1}$ HEAs by means of ageing treatments at temperatures between 1073 K and 1123 K. Under the ageing treatment conditions adopted in this work, $\gamma'$ nanoparticles are precipitated in FeCoNiCr(Ni$_{3}$Ti)$_{0.1}$ HEAs, with average diameters of 15.80 nm, 37.09 nm, and 62.50 nm, respectively. The average sizes of helium bubbles observed in samples after 673-K irradiation are 1.46 nm, 1.65 nm, and 1.58 nm, respectively. The improvement in the irradiation resistance of FeCoNiCr(Ni$_{3}$Ti)$_{0.1}$ HEAs is evidenced by the diminution in bubbles size. Furthermore, the FeCoNiCr(Ni$_{3}$Ti)$_{0.1}$ HEAs containing $\gamma'$ precipitates of 15.8 nm exhibits the minimum size and density of helium bubbles, which can be ascribed to the considerable helium trapping effects of heterogeneous coherent phase boundaries. Subsequently, annealing experiments conducted after 293-K irradiation indicate that HEAs containing precipitated phases exhibits smaller apparent activation energy ($E_{\rm a}$) for helium bubbles, resulting in larger helium bubble size. This study provides guidance for improving the irradiation resistance of L1$_{2}$-strengthened high-entropy alloy.

Quantum dynamics within curved thin layers with deviation Suggested by editors

Run Cheng(程润), Hao Zhao(赵浩), Cui-Bai Luo(罗翠柏), Xuan Zhou(周璇), Bi-Li Wang(王必利), Yan-Biao Li(李延标), and Jun Wang(王骏)

Chin. Phys. B, 2024, 33 (7): 076801. DOI: 10.1088/1674-1056/ad3dd2

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Combining the deviation between thin layers' adjacent surfaces with the confining potential method applied to the quantum curved systems, we derive the effective Schrödinger equation describing the particle constrained within a curved layer, accompanied by a general geometric potential $V_{\rm gq}$ composed of a compression-corrected geometric potential $V_{\rm gq}^{*}$ and a novel potential $V_{\rm gq}^{**}$ brought by the deviation. Applying this analysis to the cylindrical layer emerges two types of deviation-induced geometric potential, resulting from the the cases of slant deviation and tangent deviation, respectively, which strongly renormalizes the purely geometric potential and contribute to the energy spectrum based on a very substantial deepening of bound states they offer.

Optimal parameter space for stabilizing the ferroelectric phase of Hf_0.5Zr_0.5O₂ thin films under strain and electric fields Suggested by editors

Lvjin Wang(王侣锦), Cong Wang(王聪), Linwei Zhou(周霖蔚), Xieyu Zhou(周谐宇), Yuhao Pan(潘宇浩), Xing Wu(吴幸), and Wei Ji(季威)

Chin. Phys. B, 2024, 33 (7): 076803. DOI: 10.1088/1674-1056/ad498b

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Hafnia-based ferroelectric materials, like Hf$_{0.5}$Zr$_{0.5}$O$_{2}$ (HZO), have received tremendous attention owing to their potentials for building ultra-thin ferroelectric devices. The orthorhombic(O)-phase of HZO is ferroelectric but metastable in its bulk form under ambient conditions, which poses a considerable challenge to maintaining the operation performance of HZO-based ferroelectric devices. Here, we theoretically addressed this issue that provides parameter spaces for stabilizing the O-phase of HZO thin-films under various conditions. Three mechanisms were found to be capable of lowering the relative energy of the O-phase, namely, more significant surface-bulk portion of (111) surfaces, compressive $c$-axis strain, and positive electric fields. Considering these mechanisms, we plotted two ternary phase diagrams for HZO thin-films where the strain was applied along the in-plane uniaxial and biaxial, respectively. These diagrams indicate the O-phase could be stabilized by solely shrinking the film-thickness below 12.26 nm, ascribed to its lower surface energies. All these results shed considerable light on designing more robust and higher-performance ferroelectric devices.

Effect of lattice distortion on spin admixture and quantum transport in organic devices with spin-orbit coupling

Ying Wang(王莹), Dan Li(李丹), Xinying Sun(孙新英), Huiqing Zhang(张惠晴), Han Ma(马晗), Huixin Li(李慧欣), Junfeng Ren(任俊峰), Chuankui Wang(王传奎), and Guichao Hu(胡贵超)

Chin. Phys. B, 2024, 33 (7): 077101. DOI: 10.1088/1674-1056/ad35ae

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With an extended Su-Schrieffer-Heeger model and Green's function method, the spin-orbit coupling (SOC) effects on spin admixture of electronic states and quantum transport in organic devices are investigated. The role of lattice distortion induced by the strong electron-lattice interaction in organics is clarified in contrast with a uniform chain. The results demonstrate an enhanced SOC effect on the spin admixture of frontier eigenstates by the lattice distortion at a larger SOC, which is explained by the perturbation theory. The quantum transport under the SOC is calculated for both nonmagnetic and ferromagnetic electrodes. A more notable SOC effect on total transmission and current is observed for ferromagnetic electrodes, where spin filtering induced by spin-flipped transmission and suppression of magnetoresistance are obtained. Unlike the spin admixture, a stronger SOC effect on transmission exists for the uniform chain rather than the organic lattices with distortion. The reason is attributed to the modified spin-polarized conducting states in the electrodes by lattice configuration, and hence the spin-flip transmission, instead of the spin admixture of eigenstates. This work is helpful to understand the SOC effect in organic spin valves in the presence of lattice distortion.

Electronic transport evolution across the successive structural transitions in Ni_50-xFe_xTi₅₀ shape memory alloys

Ping He(何萍), Jinying Yang(杨金颖), Qiusa Ren(任秋飒), Binbin Wang(王彬彬), Guangheng Wu(吴光恒), and Enke Liu(刘恩克)

Chin. Phys. B, 2024, 33 (7): 077201. DOI: 10.1088/1674-1056/ad39d3

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TiNi-based shape memory alloys have been extensively investigated due to their significant applications, but a comprehensive understanding of the evolution of electronic structure and electrical transport in a system with martensitic transformations (MT) is still lacking. In this work, we focused on the electronic transport behavior of three phases in Ni$_{50-x}$Fe$_{x}$Ti$_{50}$ across the MT. A phase diagram of Ni$_{50-x}$Fe$_{x}$Ti$_{50}$ was established based on x-ray diffraction, calorimetric, magnetic, and electrical measurements. To reveal the driving force of MT, phonon softening was revealed using first-principles calculations. Notably, the transverse and longitudinal transport behavior changed significantly across the phase transition, which can be attributed to the reconstruction of electronic structures. This work promotes the understanding of phase transitions and demonstrates the sensitivity of electron transport to phase transition.

Effect of the mixing of s-wave and chiral p-wave pairings on electrical shot noise properties of normal metal/superconductor tunnel junctions Suggested by editors

Yu-Chen Hu(胡雨辰) and Liang-Bin Hu(胡梁宾)

Chin. Phys. B, 2024, 33 (7): 077202. DOI: 10.1088/1674-1056/ad498a

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We study theoretically the electrical shot noise properties of tunnel junctions between a normal metal and a superconductor with the mixture of singlet s-wave and chiral triplet p-wave pairing due to broken inversion symmetry. We investigate how the shot noise properties vary as the relative amplitude between the two parity components in the pairing potential is changed. It is demonstrated that some characteristics of the electrical shot noise properties of such tunnel junctions may depend sensitively on the relative amplitude between the two parity components in the pairing potential, and some significant changes may occur in the electrical shot noise properties when the relative amplitude between the two parity components is varied from the singlet s-wave pairing dominated regime to the chiral triplet p-wave pairing dominated regime. In the chiral triplet p-wave pairing dominated regime, the ratio of noise power to electric current is close to $2e$ both in the in-gap and in the out-gap region. In the singlet s-wave pairing dominated regime, the value of this ratio is close to $4e$ in the inner gap region but may reduce to about $2e$ in the outer gap region as the relative amplitude of the chiral triplet pairing component is increased. The variations of the differential shot noise with the bias voltage also exhibit some significantly different features in different regimes. Such different features can serve as useful diagnostic tools for the determination of the relative magnitude of the two parity components in the pairing potential.

Nonlinear Seebeck and Peltier effects in a Majorana nanowire coupled to leads

Feng Chi(迟锋), Jia Liu(刘佳), Zhenguo Fu(付振国), Liming Liu(刘黎明), and Zichuan Yi(易子川)

Chin. Phys. B, 2024, 33 (7): 077301. DOI: 10.1088/1674-1056/ad3f99

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We theoretically study nonlinear thermoelectric transport through a topological superconductor nanowire hosting Majorana bound states (MBSs) at its two ends, a system named as Majorana nanowire (MNW). We consider that the MNW is coupled to the left and right normal metallic leads subjected to either bias voltage or temperature gradient. We focus our attention on the sign change of nonlinear Seebeck and Peltier coefficients induced by mechanisms related to the MBSs, by which the possible existence of MBSs might be proved. Our results show that for a fixed temperature difference between the two leads, the sign of the nonlinear Seebeck coefficient (thermopower) can be reversed by changing the overlap amplitude between the MBSs or the system equilibrium temperature, which are similar to the cases in linear response regime. By optimizing the MBS-MBS interaction amplitude and system equilibrium temperature, we find that the temperature difference may also induce sign change of the nonlinear thermopower. For zero temperature difference and finite bias voltage, both the sign and magnitude of nonlinear Peltier coefficient can be adjusted by changing the bias voltage or overlap amplitude between the MBSs. In the presence of both bias voltage and temperature difference, we show that the electrical current at zero Fermi level and the states induced by overlap between the MBSs keep unchanged, regardless of the amplitude of temperature difference. We also find that the direction of the heat current driven by bias voltage may be changed by weak temperature difference.

Magnetic and electrical transport properties in GdAlSi and SmAlGe Suggested by editors

Jing Gong(巩静), Huan Wang(王欢), Xiao-Ping Ma(马小平), Xiang-Yu Zeng(曾祥雨), Jun-Fa Lin(林浚发), Kun Han(韩坤), Yi-Ting Wang(王乙婷), and Tian-Long Xia(夏天龙)

Chin. Phys. B, 2024, 33 (7): 077302. DOI: 10.1088/1674-1056/ad41ba

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We conduct a detailed examination of the magnetic and electrical transport properties in GdAlSi and SmAlGe crystals, which possess a LaPtSi-type structure (space group $I$4$_{1}md$). The magnetic susceptibility data unambiguously reveal magnetic ordering below a characteristic transition temperature ($T_{\rm N}$). For GdAlSi, a hysteresis loop is observed in the magnetization and magnetoresistance curves within the $ab$ plane when the magnetic field is applied below $T_{\rm N}$, which is around 32 K. Notable specific heat anomalies are detected at 32 K for GdAlSi and 6 K for SmAlGe, confirming the occurrence of magnetic transitions. In addition, the extracted magnetic entropy at high temperatures is consistent with the theoretical value of $R$ln($2{J}+1$) for $J=7/2$ in Gd$^{3+}$ and $J=5/2$ in Sm$^{3+}$, respectively. SmAlGe also exhibits Schottky-like specific heat contributions. Additionally, both GdAlSi and SmAlGe exhibit positive magnetoresistance and a normal Hall effect.

Negligible normal fluid in superconducting state of heavily overdoped Bi₂Sr₂CaCu₂O_8+δ detected by ultra-low temperature angle-resolved photoemission spectroscopy Suggested by editors

Chaohui Yin(殷超辉), Qinghong Wang(汪清泓), Yuyang Xie(解于洋), Yiwen Chen(陈逸雯), Junhao Liu(刘俊豪), Jiangang Yang(杨鉴刚), Junjie Jia(贾俊杰), Xing Zhang(张杏), Wenkai Lv(吕文凯), Hongtao Yan(闫宏涛), Hongtao Rong(戎洪涛), Shenjin Zhang(张申金), Zhimin Wang(王志敏), Nan Zong(宗楠), Lijuan Liu(刘丽娟), Rukang Li(李如康), Xiaoyang Wang(王晓洋), Fengfeng Zhang(张丰丰), Feng Yang(杨峰), Qinjun Peng(彭钦军), Zuyan Xu(许祖彦), Guodong Liu(刘国东), Hanqing Mao(毛寒青), Lin Zhao(赵林), Xintong Li(李昕彤), and Xingjiang Zhou(周兴江)

Chin. Phys. B, 2024, 33 (7): 077405. DOI: 10.1088/1674-1056/ad51f8

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In high temperature cuprate superconductors, it was found that the superfluid density decreases with the increase of hole doping. One natural question is whether there exists normal fluid in the superconducting state in the overdoped region. In this paper, we have carried out high-resolution ultra-low temperature laser-based angle-resolved photoemission measurements on a heavily overdoped Bi2212 sample with a $T_\mathrm{c}$ of 48K. We find that this heavily overdoped Bi2212 remains in the strong coupling regime with $2 \varDelta_0 / (k_{\mathrm{B}} T_{\mathrm{c}})=5.8$. The single-particle scattering rate is very small along the nodal direction ($\sim$5meV) and increases as the momentum moves from the nodal to the antinodal regions. A hard superconducting gap opening is observed near the antinodal region with the spectral weight at the Fermi level fully suppressed to zero. The normal fluid is found to be negligibly small in the superconducting state of this heavily overdoped Bi2212. These results provide key information to understand the high $T_\mathrm{c}$ mechanism in the cuprate superconductors.

Crystal growth, magnetic and electrical transport properties of the kagome magnet RCr₆Ge₆ (R=Gd-Tm)

Xingyu Yang(杨星宇), Qingqi Zeng(曾庆祺), Miao He(何苗), Xitong Xu(许锡童), Haifeng Du(杜海峰), and Zhe Qu(屈哲)

Chin. Phys. B, 2024, 33 (7): 077501. DOI: 10.1088/1674-1056/ad3dcf

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Kagome magnets have attracted considerable research attention due to the interplay between topology, magnetism and electronic correlations. In this study we report single-crystal synthesis of a series of the kagome magnets $R$Cr$_{6}$Ge$_{6}$ ($R={\rm Gd}$-Tm) that possess defect-free Cr kagome lattices and systematically study their magnetic and electrical transport properties. The transition from a canted ferrimagnetic to a paramagnetic state in GdCr$_{6}$Ge$_{6}$, TbCr$_{6}$Ge$_{6}$, DyCr$_{6}$Ge$_{6}$, HoCr$_{6}$Ge$_{6}$, ErCr$_{6}$Ge$_{6}$ and TmCr$_{6}$Ge$_{6}$ occurs at 11.3 K, 10.8 K, 4.3 K, 2.5 K, 3.3 K and below 2 K, respectively, due to $R$-$R$ interactions within the compounds. Magnetization measurements reveal highly anisotropic magnetism with canted magnetic moments in these compounds. In electrical transport, both negative and positive magnetoresistances at different magnetic fields and temperatures have been observed due to the competition between different scattering mechanisms. This work enriches our understanding of the Cr-based kagome magnets and paves the way to search for possible topological responses in this family.

Theoretical characterization of the temperature-dependent saturation magnetization of magnetic metallic materials

Jin-Long Wu(吴金龙), Pan Dong(董攀), Yi He(贺屹), Yan-Li Ma(马艳丽), Zi-Yuan Li(李梓源), Qin-Yuan Yao(姚沁远), Jun Qiu(邱俊), Jian-Zuo Ma(麻建坐), and Wei-Guo Li(李卫国)

Chin. Phys. B, 2024, 33 (7): 077502. DOI: 10.1088/1674-1056/ad39d1

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Based on the force-heat equivalence energy density principle, a theoretical model for magnetic metallic materials is developed, which characterizes the temperature-dependent magnetic anisotropy energy by considering the equivalent relationship between magnetic anisotropy energy and heat energy; then the relationship between the magnetic anisotropy constant and saturation magnetization is considered. Finally, we formulate a temperature-dependent model for saturation magnetization, revealing the inherent relationship between temperature and saturation magnetization. Our model predicts the saturation magnetization for nine different magnetic metallic materials at different temperatures, exhibiting satisfactory agreement with experimental data. Additionally, the experimental data used as reference points are at or near room temperature. Compared to other phenomenological theoretical models, this model is considerably more accessible than the data required at 0 K. The index included in our model is set to a constant value, which is equal to $10/3$ for materials other than Fe, Co, and Ni. For transition metals (Fe, Co, and Ni in this paper), the index is 6 in the range of 0 K to 0.65$T_{\rm cr}$ ($T_{\rm cr}$ is the critical temperature), and 3 in the range of 0.65$T_{\rm cr}$ to $T_{\rm cr}$, unlike other models where the adjustable parameters vary according to each material. In addition, our model provides a new way to design and evaluate magnetic metallic materials with superior magnetic properties over a wide range of temperatures.

RKKY interaction in helical higher-order topological insulators Suggested by editors

Sha Jin(金莎), Jian Li(李健), Qing-Xu Li(李清旭), and Jia-Ji Zhu(朱家骥)

Chin. Phys. B, 2024, 33 (7): 077503. DOI: 10.1088/1674-1056/ad3ef9

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We theoretically investigate the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction in helical higher-order topological insulators (HOTIs), revealing distinct behaviors mediated by hinge and Dirac-type bulk carriers. Our findings show that hinge-mediated interactions consist of Heisenberg, Ising, and Dzyaloshinskii-Moriya (DM) terms, exhibiting a decay with impurity spacing $z$ and oscillations with Fermi energy $\varepsilon_{\scriptscriptstyle{\rm F}}$. These interactions demonstrate ferromagnetic behaviors for the Heisenberg and Ising terms and alternating behavior for the DM term. In contrast, bulk-mediated interactions include Heisenberg, twisted Ising, and DM terms, with a conventional cubic oscillating decay. This study highlights the nuanced interplay between hinge and bulk RKKY interactions in HOTIs, offering insights into designs of next-generation quantum devices based on HOTIs.

Tailoring-compensated ferrimagnetic state and anomalous Hall effect in quaternary Mn-Ru-V-Ga Heusler compounds

Jin-Jing Liang(梁瑾静), Xue-Kui Xi(郗学奎), Wen-Hong Wang(王文洪), and Yong-Chang Lau(刘永昌)

Chin. Phys. B, 2024, 33 (7): 077504. DOI: 10.1088/1674-1056/ad34c8

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Cubic Mn$_{2}$Ru$_{x}$Ga Heusler compound is a typical example of compensated ferrimagnet with attractive potential for high-density, ultrafast, and low-power spintronic applications. In the form of epitaxial thin films, Mn$_{2}$Ru$_{x}$Ga exhibits high spin polarization and high tunability of compensation temperature by freely changing the Ru content $x$ in a broad range ($0.3 < x < 1.0$). Herein Mn-Ru-Ga-based polycrystalline bulk buttons prepared by arc melting are systematically studied and it is found that in equilibrium bulk form, the cubic structure is unstable when $x < 0.75$. To overcome this limitation, Mn-Ru-Ga is alloyed with a fourth element V. By adjusting the content of V in the Mn$_{2}$Ru$_{0.75}$V$_{y}$Ga and Mn$_{2.25-y}$Ru$_{0.75}$V$_{y}$Ga quaternary systems, the magnetic compensation temperature is tuned. Compensation is achieved near 300 K which is confirmed by both the magnetic measurement and anomalous Hall effect measurement. The analyses of the anomalous Hall effect scaling in quaternary Mn-Ru-V-Ga alloy reveal the dominant role of skew scattering, notably that contributed caused by the thermally excited phonons, in contrast to the dominant intrinsic mechanism found in many other 3d ferromagnets and Heusler compounds. It is further shown that the Ga antisites and V content can simultaneously control the residual resistivity ratio (RRR) as well as the relative contribution of phonon and defect to the anomalous Hall effect $a''/a'$ in Mn-Ru-V-Ga, resulting in a scaling relation $a''/a' \propto $ RRR$^{1.8}$.

Shape-influenced non-reciprocal transport of magnetic skyrmions in nanoscale channel

Jie-Yao Chen(陈杰尧), Jia Luo(罗佳), Geng-Xin Hu(胡更新), Jun-Lin Wang(王君林), Guan-Qi Li(李冠祺), Zhen-Dong Chen(陈振东), Xian-Yang Lu(陆显扬), Guo-Ping Zhao(赵国平), Yuan Liu(刘远), Jing Wu(吴竞), and Yong-Bing Xu(徐永兵)

Chin. Phys. B, 2024, 33 (7): 077505. DOI: 10.1088/1674-1056/ad34c7

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Skyrmions, with their vortex-like structures and inherent topological protection, play a pivotal role in developing innovative low-power memory and logic devices. The efficient generation and control of skyrmions in geometrically confined systems are crucial for the development of skyrmion-based spintronic devices. In this study, we focus on investigating the non-reciprocal transport behavior of skyrmions and their interactions with boundaries of various shapes. The shape of the notch structure in the nanotrack significantly affects the dynamic behavior of magnetic skyrmions. Through micromagnetic simulation, the non-reciprocal transport properties of skyrmions in nanowires with different notch structures are investigated in this work.

Subpicosecond laser ablation behavior of a magnesium target and crater evolution: Molecular dynamics study and experimental validation

Guolong Jiang(江国龙) and Xia Zhou(周霞)

Chin. Phys. B, 2024, 33 (7): 077901. DOI: 10.1088/1674-1056/ad3ef8

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The micro-ablation processes and morphological evolution of ablative craters on single-crystal magnesium under subpicosecond laser irradiation are investigated using molecular dynamics (MD) simulations and experiments. The simulation results exhibit that the main failure mode of single-crystal Mg film irradiated by a low fluence and long pulse width laser is the ejection of surface atoms, which has laser-induced high stress. However, under high fluence and short pulse width laser irradiation, the main damage mechanism is nucleation fracture caused by stress wave reflection and superposition at the bottom of the film. In addition, Mg$[0\,0\,0\,1]$ has higher pressure sensitivity and is more prone to ablation than Mg$[1\,0\,\overline 1 \,0]$. The evolution equation of crater depth is established using multi-pulse laser ablation simulation and verified by experiments. The results show that, under multiple pulsed laser irradiation, not only does the crater depth increase linearly with the pulse number, but also the quadratic term and constant term of the fitted crater profile curve increase linearly.

Mutation in a non-force-bearing region of protein L influences force-dependent unfolding behavior Suggested by editors

Huanjie Jiang(蒋环杰), Yanwei Wang(王艳伟), Jiayuan Chen(陈家媛), Dan Hu(胡丹), Hai Pan(潘海), Zilong Guo(郭子龙), and Hu Chen(陈虎)

Chin. Phys. B, 2024, 33 (7): 078201. DOI: 10.1088/1674-1056/ad3dcd

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Single-molecule magnetic tweezers (MTs) have revealed multiple transition barriers along the unfolding pathway of several two-state proteins, such as GB1 and Csp. In this study, we utilized MTs to measure the force-dependent folding and unfolding rates of both protein L (PLWT) and its Y47W mutant (PLY47W) where the mutation point is not at the force-bearing $\beta$-strands. The measurements were conducted within a force range of 3-120 pN. Notably, the unfolding rates of both PLWT and PWY47W exhibit distinct force sensitivities below 50 pN and above 60 pN, implying a two-barrier free energy landscape. Both PLWT and PLY47W share the same force-dependent folding rate and the same transition barriers, but the unfolding rate of PLY47W is faster than that of PLWT. Our finding demonstrates that the residue outside of the force-bearing region will also affect the force-induced unfolding dynamics.

Unveiling the in-plane anisotropic dielectric waveguide modes in α-MoO₃ flakes Suggested by editors

Ying Liao(廖莹) and Jianing Chen(陈佳宁)

Chin. Phys. B, 2024, 33 (7): 078401. DOI: 10.1088/1674-1056/ad3dd7

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The unique in-plane and out-of-plane anisotropy of $\alpha $-MoO$_{3}$ has attracted considerable interest with regard to potential optoelectronic applications. However, most research has focused on the mid-infrared spectrum, leaving its properties and applications in the visible and near-infrared light spectrum less explored. This study advances the understanding of waveguiding properties of $\alpha $-MoO$_{3}$ by near-field imaging of the waveguide modes along the [100] and [001] directions of $\alpha $-MoO$_{3}$ flakes at 633 nm and 785 nm. We investigate the effects of flake thickness and documented the modes' dispersion relationships, which is crucial for tailoring the optical responses of $\alpha $-MoO$_{3}$ in device applications. Our findings enhance the field of research into $\alpha $-MoO$_{3}$, highlighting its utility in fabricating next-generation optoelectronic devices due to its unique optically anisotropic waveguide.

Single event effects evaluation on convolution neural network in Xilinx 28 nm system on chip

Xu Zhao(赵旭), Xuecheng Du(杜雪成), Xu Xiong(熊旭), Chao Ma(马超), Weitao Yang(杨卫涛), Bo Zheng(郑波), and Chao Zhou(周超)

Chin. Phys. B, 2024, 33 (7): 078501. DOI: 10.1088/1674-1056/ad3b82

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Convolutional neural networks (CNNs) exhibit excellent performance in the areas of image recognition and object detection, which can enhance the intelligence level of spacecraft. However, in aerospace, energetic particles, such as heavy ions, protons, and alpha particles, can induce single event effects (SEEs) that lead CNNs to malfunction and can significantly impact the reliability of a CNN system. In this paper, the MNIST CNN system was constructed based on a 28 nm system-on-chip (SoC), and then an alpha particle irradiation experiment and fault injection were applied to evaluate the SEE of the CNN system. Various types of soft errors in the CNN system have been detected, and the SEE cross sections have been calculated. Furthermore, the mechanisms behind some soft errors have been explained. This research will provide technical support for the design of radiation-resistant artificial intelligence chips.

Model-driven CT reconstruction algorithm for nano-resolution x-ray phase contrast imaging Suggested by editors

Yuhang Tan(谭雨航), Xuebao Cai(蔡学宝), Jiecheng Yang(杨杰成), Ting Su(苏婷), Hairong Zheng(郑海荣), Dong Liang(梁栋), Peiping Zhu(朱佩平), and Yongshuai Ge(葛永帅)

Chin. Phys. B, 2024, 33 (7): 078702. DOI: 10.1088/1674-1056/ad3dcc

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The low-density imaging performance of a zone plate-based nano-resolution hard x-ray computed tomography (CT) system can be significantly improved by incorporating a grating-based Lau interferometer. Due to the diffraction, however, the acquired nano-resolution phase signal may suffer splitting problem, which impedes the direct reconstruction of phase contrast CT (nPCT) images. To overcome, a new model-driven nPCT image reconstruction algorithm is developed in this study. In it, the diffraction procedure is mathematically modeled into a matrix ${\bm B}$, from which the projections without signal splitting can be generated invertedly. Furthermore, a penalized weighted least-square model with total variation (PWLS-TV) is employed to denoise these projections, from which nPCT images with high accuracy are directly reconstructed. Numerical experiments demonstrate that this new algorithm is able to work with phase projections having any splitting distances. Moreover, results also reveal that nPCT images of higher signal-to-noise-ratio (SNR) could be reconstructed from projections having larger splitting distances. In summary, a novel model-driven nPCT image reconstruction algorithm with high accuracy and robustness is verified for the Lau interferometer-based hard x-ray nano-resolution phase contrast imaging.

WT-FCTGN: A wavelet-enhanced fully connected time-gated neural network for complex noisy traffic flow modeling

Zhifang Liao(廖志芳), Ke Sun(孙轲), Wenlong Liu(刘文龙), Zhiwu Yu(余志武), Chengguang Liu(刘承光), and Yucheng Song(宋禹成)

Chin. Phys. B, 2024, 33 (7): 078901. DOI: 10.1088/1674-1056/ad3349

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Accurate forecasting of traffic flow provides a powerful traffic decision-making basis for an intelligent transportation system. However, the traffic data's complexity and fluctuation, as well as the noise produced during collecting information and summarizing original data of traffic flow, cause large errors in the traffic flow forecasting results. This article suggests a solution to the above mentioned issues and proposes a fully connected time-gated neural network based on wavelet reconstruction (WT-FCTGN). To eliminate the potential noise and strengthen the potential traffic trend in the data, we adopt the methods of wavelet reconstruction and periodic data introduction to preprocess the data. The model introduces fully connected time-series blocks to model all the information including time sequence information and fluctuation information in the flow of traffic, and establishes the time gate block to comprehend the periodic characteristics of the flow of traffic and predict its flow. The performance of the WT-FCTGN model is validated on the public PeMS data set. The experimental results show that the WT-FCTGN model has higher accuracy, and its mean absolute error (MAE), mean absolute percentage error (MAPE) and root mean square error (RMSE) are obviously lower than those of the other algorithms. The robust experimental results prove that the WT-FCTGN model has good anti-noise ability.

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