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 Select Measuring Loschmidt echo via Floquet engineering in superconducting circuits Shou-Kuan Zhao(赵寿宽), Zi-Yong Ge(葛自勇), Zhong-Cheng Xiang(相忠诚), Guang-Ming Xue(薛光明), Hai-Sheng Yan(严海生), Zi-Ting Wang(王子婷), Zhan Wang(王战), Hui-Kai Xu(徐晖凯), Fei-Fan Su(宿非凡), Zhao-Hua Yang(杨钊华), He Zhang(张贺), Yu-Ran Zhang(张煜然), Xue-Yi Guo(郭学仪), Kai Xu(许凯), Ye Tian(田野), Hai-Feng Yu(于海峰), Dong-Ning Zheng(郑东宁), Heng Fan(范桁), and Shi-Ping Zhao(赵士平) Chin. Phys. B, 2022, 31 (3): 030307.   DOI: 10.1088/1674-1056/ac40f8 Abstract （499）   HTML （1）    PDF （1107KB）（496）       The Loschmidt echo is a useful diagnostic for the perfection of quantum time-reversal process and the sensitivity of quantum evolution to small perturbations. The main challenge for measuring the Loschmidt echo is the time reversal of a quantum evolution. In this work, we demonstrate the measurement of the Loschmidt echo in a superconducting 10-qubit system using Floquet engineering and discuss the imperfection of an initial Bell-state recovery arising from the next-nearest-neighbor (NNN) coupling present in the qubit device. Our results show that the Loschmidt echo is very sensitive to small perturbations during quantum-state evolution, in contrast to the quantities like qubit population that is often considered in the time-reversal experiment. These properties may be employed for the investigation of multiqubit system concerning many-body decoherence and entanglement, etc., especially when devices with reduced or vanishing NNN coupling are used.
 Select Direct visualization of structural defects in 2D semiconductors Yutuo Guo(郭玉拓), Qinqin Wang(王琴琴), Xiaomei Li(李晓梅), Zheng Wei(魏争), Lu Li(李璐), Yalin Peng(彭雅琳), Wei Yang(杨威), Rong Yang(杨蓉), Dongxia Shi(时东霞), Xuedong Bai(白雪冬), Luojun Du(杜罗军), and Guangyu Zhang(张广宇) Chin. Phys. B, 2022, 31 (7): 076105.   DOI: 10.1088/1674-1056/ac6738 Abstract （493）   HTML （34）    PDF （4731KB）（394）       Direct visualization of the structural defects in two-dimensional (2D) semiconductors at a large scale plays a significant role in understanding their electrical/optical/magnetic properties, but is challenging. Although traditional atomic resolution imaging techniques, such as transmission electron microscopy and scanning tunneling microscopy, can directly image the structural defects, they provide only local-scale information and require complex setups. Here, we develop a simple, non-invasive wet etching method to directly visualize the structural defects in 2D semiconductors at a large scale, including both point defects and grain boundaries. Utilizing this method, we extract successfully the defects density in several different types of monolayer molybdenum disulfide samples, providing key insights into the device functions. Furthermore, the etching method we developed is anisotropic and tunable, opening up opportunities to obtain exotic edge states on demand.
 Select Solving quantum rotor model with different Monte Carlo techniques Weilun Jiang(姜伟伦), Gaopei Pan(潘高培), Yuzhi Liu(刘毓智), and Zi-Yang Meng(孟子杨) Chin. Phys. B, 2022, 31 (4): 040504.   DOI: 10.1088/1674-1056/ac4f52 Abstract （486）   HTML （4）    PDF （1004KB）（379）       We systematically test the performance of several Monte Carlo update schemes for the (2+1)d XY phase transition of quantum rotor model. By comparing the local Metropolis (LM), LM plus over-relaxation (OR), Wolff-cluster (WC), hybrid Monte Carlo (HM), hybrid Monte Carlo with Fourier acceleration (FA) schemes, it is clear that among the five different update schemes, at the quantum critical point, the WC and FA schemes acquire the smallest autocorrelation time and cost the least amount of CPU hours in achieving the same level of relative error, and FA enjoys a further advantage of easily implementable for more complicated interactions such as the long-range ones. These results bestow one with the necessary knowledge of extending the quantum rotor model, which plays the role of ferromagnetic/antiferromagnetic critical bosons or Z2 topological order, to more realistic and yet challenging models such as Fermi surface Yukawa-coupled to quantum rotor models.
 Select Gauss quadrature based finite temperature Lanczos method Jian Li(李健) and Hai-Qing Lin(林海青) Chin. Phys. B, 2022, 31 (5): 050203.   DOI: 10.1088/1674-1056/ac5986 Abstract （382）   HTML （4）    PDF （782KB）（359）       The finite temperature Lanczos method (FTLM), which is an exact diagonalization method intensively used in quantum many-body calculations, is formulated in the framework of orthogonal polynomials and Gauss quadrature. The main idea is to reduce finite temperature static and dynamic quantities into weighted summations related to one- and two-dimensional Gauss quadratures. Then lower order Gauss quadrature, which is generated from Lanczos iteration, can be applied to approximate the initial weighted summation. This framework fills the conceptual gap between FTLM and kernel polynomial method, and makes it easy to apply orthogonal polynomial techniques in the FTLM calculation.
 Select Electronic structure and spin–orbit coupling in ternary transition metal chalcogenides Cu2TlX2 (X = Se, Te) Na Qin(秦娜), Xian Du(杜宪), Yangyang Lv(吕洋洋), Lu Kang(康璐), Zhongxu Yin(尹中旭), Jingsong Zhou(周景松), Xu Gu(顾旭), Qinqin Zhang(张琴琴), Runzhe Xu(许润哲), Wenxuan Zhao(赵文轩), Yidian Li(李义典), Shuhua Yao(姚淑华), Yanfeng Chen(陈延峰), Zhongkai Liu(柳仲楷), Lexian Yang(杨乐仙), and Yulin Chen(陈宇林) Chin. Phys. B, 2022, 31 (3): 037101.   DOI: 10.1088/1674-1056/ac3ecd Abstract （382）   HTML （4）    PDF （5919KB）（342）       Ternary transition metal chalcogenides provide a rich platform to search and study intriguing electronic properties. Using angle-resolved photoemission spectroscopy and ab initio calculation, we investigate the electronic structure of Cu$_{2}$Tl$X_{2}$ ($X=\text{Se, Te}$), ternary transition metal chalcogenides with quasi-two-dimensional crystal structure. The band dispersions near the Fermi level are mainly contributed by the Te/Se p orbitals. According to our ab-initio calculation, the electronic structure changes from a semiconductor with indirect band gap in Cu$_{2}$TlSe$_{2}$ to a semimetal in Cu$_{2}$TlTe$_{2}$, suggesting a band-gap tunability with the composition of Se and Te. By comparing ARPES experimental data with the calculated results, we identify strong modulation of the band structure by spin-orbit coupling in the compounds. Our results provide a ternary platform to study and engineer the electronic properties of transition metal chalcogenides related to large spin-orbit coupling.
 Select Intrinsic V vacancy and large magnetoresistance in V1-δSb2 single crystal Yong Zhang(张勇), Xinliang Huang(黄新亮), Jinglei Zhang(张警蕾), Wenshuai Gao(高文帅), Xiangde Zhu(朱相德), and Li Pi(皮雳) Chin. Phys. B, 2022, 31 (3): 037102.   DOI: 10.1088/1674-1056/ac3070 Abstract （266）   HTML （1）    PDF （2105KB）（323）       The binary pnictide semimetals have attracted considerable attention due to their fantastic physical properties that include topological effects, negative magnetoresistance, Weyl fermions, and large non-saturation magnetoresistance. In this paper, we have successfully grown the high-quality V1-δSb2 single crystals by Sb flux method and investigated their electronic transport properties. A large positive magnetoresistance that reaches 477% under a magnetic field of 12 T at T = 1.8 K was observed. Notably, the magnetoresistance showed a cusp-like feature at the low magnetic fields and such feature weakened gradually as the temperature increased, which indicated the presence of a weak antilocalization effect (WAL). In addition, based upon the experimental and theoretical band structure calculations, V1-δSb2 is a research candidate for a flat band.
 Select Monolayer MoS2 of high mobility grown on SiO2 substrate by two-step chemical vapor deposition Jia-Jun Ma(马佳俊), Kang Wu(吴康), Zhen-Yu Wang(王振宇), Rui-Song Ma(马瑞松), Li-Hong Bao(鲍丽宏), Qing Dai(戴庆), Jin-Dong Ren(任金东), and Hong-Jun Gao(高鸿钧) Chin. Phys. B, 2022, 31 (8): 088105.   DOI: 10.1088/1674-1056/ac6737 Abstract （352）   HTML （17）    PDF （1277KB）（310）       We report a novel two-step ambient pressure chemical vapor deposition (CVD) pathway to grow high-quality MoS2 monolayer on the SiO2 substrate with large crystal size up to 110 μm. The large specific surface area of the pre-synthesized MoO3 flakes on the mica substrate compared to MoO3 powder could dramatically reduce the consumption of the Mo source. The electronic information inferred from the four-probe scanning tunneling microscope (4P-STM) image explains the threshold voltage variations and the n-type behavior observed in the two-terminal transport measurements. Furthermore, the direct van der Pauw transport also confirms its relatively high carrier mobility. Our study provides a reliable method to synthesize high-quality MoS2 monolayer, which is confirmed by the direct 4P-STM measurement results. Such methodology is a key step toward the large-scale growth of transition metal dichalcogenides (TMDs) on the SiO2 substrate and is essential to further development of the TMDs-related integrated devices.
 Select Quantum algorithm for neighborhood preserving embedding Shi-Jie Pan(潘世杰), Lin-Chun Wan(万林春), Hai-Ling Liu(刘海玲), Yu-Sen Wu(吴宇森), Su-Juan Qin(秦素娟), Qiao-Yan Wen(温巧燕), and Fei Gao(高飞) Chin. Phys. B, 2022, 31 (6): 060304.   DOI: 10.1088/1674-1056/ac523a Abstract （390）   HTML （13）    PDF （911KB）（293）       Neighborhood preserving embedding (NPE) is an important linear dimensionality reduction technique that aims at preserving the local manifold structure. NPE contains three steps, i.e., finding the nearest neighbors of each data point, constructing the weight matrix, and obtaining the transformation matrix. Liang et al. proposed a variational quantum algorithm (VQA) for NPE [Phys. Rev. A 101 032323 (2020)]. The algorithm consists of three quantum sub-algorithms, corresponding to the three steps of NPE, and was expected to have an exponential speedup on the dimensionality n. However, the algorithm has two disadvantages: (i) It is not known how to efficiently obtain the input of the third sub-algorithm from the output of the second one. (ii) Its complexity cannot be rigorously analyzed because the third sub-algorithm in it is a VQA. In this paper, we propose a complete quantum algorithm for NPE, in which we redesign the three sub-algorithms and give a rigorous complexity analysis. It is shown that our algorithm can achieve a polynomial speedup on the number of data points m and an exponential speedup on the dimensionality n under certain conditions over the classical NPE algorithm, and achieve a significant speedup compared to Liang et al.'s algorithm even without considering the complexity of the VQA.
 Select Development of series SQUID array with on-chip filter for TES detector Wentao Wu(伍文涛), Zhirong Lin(林志荣), Zhi Ni(倪志), Peizhan Li(李佩展), Tiantian Liang(梁恬恬), Guofeng Zhang(张国峰), Yongliang Wang(王永良), Liliang Ying(应利良), Wei Peng(彭炜), Wen Zhang(张文), Shengcai Shi(史生才), Lixing You(尤立星), and Zhen Wang(王镇) Chin. Phys. B, 2022, 31 (2): 028504.   DOI: 10.1088/1674-1056/ac2b91 Abstract （357）   HTML （3）    PDF （3471KB）（283）       A cold preamplifier based on superconducting quantum interference devices (SQUIDs) is currently the preferred readout technology for the low-noise transition edge sensor (TES). In this work, we have designed and fabricated a series SQUID array (SSA) amplifier for the TES detector readout circuit. In this SSA amplifier, each SQUID cell is composed of a first-order gradiometer formed using two equally large square washers, and an on-chip low pass filter (LPF) as a radio-frequency (RF) choke has been developed to reduce the Josephson oscillation interference between individual SQUID cells. In addition, a highly symmetric layout has been designed carefully to provide a fully consistent embedded electromagnetic environment and achieve coherent flux operation. The measured results show smooth V-Φ characteristics and a swing voltage that increases linearly with increasing SQUID cell number N. A white flux noise level as low as 0.28 μΦ0/Hz1/2 is achieved at 0.1 K, corresponding to a low current noise level of 7 pA/Hz1/2. We analyze the measured noise contribution at mK-scale temperatures and find that the dominant noise derives from a combination of the SSA intrinsic noise and the equivalent current noise of the room temperature electronics.
 Select Solutions and memory effect of fractional-order chaotic system: A review Shaobo He(贺少波), Huihai Wang(王会海), and Kehui Sun(孙克辉) Chin. Phys. B, 2022, 31 (6): 060501.   DOI: 10.1088/1674-1056/ac43ae Abstract （137）   HTML （5）    PDF （13449KB）（282）       Fractional calculus is a 300 years topic, which has been introduced to real physics systems modeling and engineering applications. In the last few decades, fractional-order nonlinear chaotic systems have been widely investigated. Firstly, the most used methods to solve fractional-order chaotic systems are reviewed. Characteristics and memory effect in those method are summarized. Then we discuss the memory effect in the fractional-order chaotic systems through the fractional-order calculus and numerical solution algorithms. It shows that the integer-order derivative has full memory effect, while the fractional-order derivative has nonideal memory effect due to the kernel function. Memory loss and short memory are discussed. Finally, applications of the fractional-order chaotic systems regarding the memory effects are investigated. The work summarized in this manuscript provides reference value for the applied scientists and engineering community of fractional-order nonlinear chaotic systems.
 Select Pressure-induced phase transitions in the ZrXY (X= Si, Ge, Sn;Y= S, Se, Te) family compounds Qun Chen(陈群), Juefei Wu(吴珏霏), Tong Chen(陈统), Xiaomeng Wang(王晓梦), Chi Ding(丁弛), Tianheng Huang(黄天衡), Qing Lu(鲁清), and Jian Sun(孙建) Chin. Phys. B, 2022, 31 (5): 056201.   DOI: 10.1088/1674-1056/ac5989 Abstract （250）   HTML （3）    PDF （6039KB）（252）       Pressure is an effective and clean way to modify the electronic structures of materials, cause structural phase transitions and even induce the emergence of superconductivity. Here, we predicted several new phases of the ZrXY family at high pressures using the crystal structures search method together with first-principle calculations. In particular, the ZrGeS compound undergoes an isosymmetric phase transition from P4/nmm-I to P4/nmm-II at approximately 82 GPa. Electronic band structures show that all the high-pressure phases are metallic. Among these new structures, P4/nmm-II ZrGeS and P4/mmm ZrGeSe can be quenched to ambient pressure with superconducting critical temperatures of approximately 8.1 K and 8.0 K, respectively. Our study provides a way to tune the structure, electronic properties, and superconducting behavior of topological materials through pressure.
 Select Slight Co-doping tuned magnetic and electric properties on cubic BaFeO3 single crystal Shijun Qin(覃湜俊), Bowen Zhou(周博文), Zhehong Liu(刘哲宏), Xubin Ye(叶旭斌), Xueqiang Zhang(张雪强), Zhao Pan(潘昭), and Youwen Long(龙有文) Chin. Phys. B, 2022, 31 (9): 097503.   DOI: 10.1088/1674-1056/ac7549 Abstract （289）   HTML （19）    PDF （2095KB）（251）       The single crystal of cubic perovskite BaFeO$_{3}$ shows multiple magnetic transitions and external stimulus sensitive magnetism. In this paper, a 5%-Co-doped BaFeO$_{3}$ (i.e. BaFe$_{0.95}$Co$_{0.05}$O$_{3})$ single crystal was grown by combining floating zone methods with high-pressure techniques. Such a slight Co doping has little effect on crystal structure, but significantly changes the magnetism from the parent antiferromagnetic ground state to a ferromagnetic one with the Curie temperature $T_{\rm C} \approx 120$ K. Compared with the parent BaFeO$_{3}$ at the induced ferromagnetic state, the saturated magnetic moment of the doped BaFe$_{0.95}$Co$_{0.05}$O$_{3}$ increases by about 10% and reaches 3.64 $\mu_{\rm B}$/f.u. Resistivity and specific heat measurements show that the ferromagnetic ordering favors metallic-like electrical transport behavior for BaFe$_{0.95}$Co$_{0.05}$O$_{3}$. The present work indicates that Co-doping is an effective method to tune the magnetic and electric properties for the cubic perovskite phase of BaFeO$_{3}$.
 Select Bright 547-dimensional Hilbert-space entangled resource in 28-pair modes biphoton frequency comb from a reconfigurable silicon microring resonator Qilin Zheng(郑骑林), Jiacheng Liu(刘嘉成), Chao Wu(吴超), Shichuan Xue(薛诗川), Pingyu Zhu(朱枰谕), Yang Wang(王洋), Xinyao Yu(于馨瑶), Miaomiao Yu(余苗苗), Mingtang Deng(邓明堂), Junjie Wu(吴俊杰), and Ping Xu(徐平) Chin. Phys. B, 2022, 31 (2): 024206.   DOI: 10.1088/1674-1056/ac3507 Abstract （337）   HTML （9）    PDF （1893KB）（237）       High-dimensional entanglement provides valuable resources for quantum technologies, including quantum communication, quantum optical coherence tomography, and quantum computing. Obtaining a high brightness and dimensional entanglement source has significant value. Here we utilize a tunable asymmetric Mach-Zehnder interferometer coupled silicon microring resonator with 100 GHz free spectral range to achieve this goal. With the strategy of the tunable coupler, the dynamical and extensive tuning range of quality factors of the microring can be obtained, and then the biphoton pair generation rate can be optimized. By selecting and characterizing 28 pairs from a more than 30-pair modes biphoton frequency comb, we obtain a Schmidt number of at least 23.4 and on-chip pair generation rate of 19.9 MHz/mW2 under a low on-chip pump power, which corresponds to 547 dimensions Hilbert space in frequency freedom. These results will prompt the wide applications of quantum frequency comb and boost the further large density and scalable on-chip quantum information processing.
 Select High-precision nuclear magnetic resonance probe suitable for in situ studies of high-temperature metallic melts Ao Li(李傲), Wei Xu(许巍), Xiao Chen(陈霄), Bing-Nan Yao(姚冰楠), Jun-Tao Huo(霍军涛), Jun-Qiang Wang(王军强), and Run-Wei Li(李润伟) Chin. Phys. B, 2022, 31 (4): 040706.   DOI: 10.1088/1674-1056/ac4a70 Abstract （195）   HTML （3）    PDF （1503KB）（229）       High-temperature nuclear magnetic resonance (NMR) has proven to be very useful for detecting the temperature-induced structural evolution and dynamics in melts. However, the sensitivity and precision of high-temperature NMR probes are limited. Here we report a sensitive and stable high-temperature NMR probe based on laser-heating, suitable for in situ studies of metallic melts, which can work stably at the temperature of up to 2000 K. In our design, a well-designed optical path and the use of a water-cooled copper radio-frequency (RF) coil significantly optimize the signal-to-noise ratio (S/NR) at high temperatures. Additionally, a precise temperature controlling system with an error of less than ±1 K has been designed. After temperature calibration, the temperature measurement error is controlled within ±2 K. As a performance testing, 27Al NMR spectra are measured in Zr-based metallic glass-forming liquid in situ. Results show that the S/NR reaches 45 within 90 s even when the sample's temperature is up to 1500 K and that the isothermal signal drift is better than 0.001 ppm per hour. This high-temperature NMR probe can be used to clarify some highly debated issues about metallic liquids, such as glass transition and liquid-liquid transition.
 Select Non-invasive and low-artifact in vivo brain imaging by using a scanning acoustic-photoacoustic dual mode microscopy Wentian Chen(陈文天), Chao Tao(陶超), Zizhong Hu(胡仔仲), Songtao Yuan(袁松涛), Qinghuai Liu(刘庆淮), and Xiaojun Liu(刘晓峻) Chin. Phys. B, 2022, 31 (4): 044304.   DOI: 10.1088/1674-1056/ac4a6f Abstract （303）   HTML （0）    PDF （2890KB）（217）       Photoacoustic imaging is a potential candidate for in vivo brain imaging, whereas, its imaging performance could be degraded by inhomogeneous multi-layered media, consisted of scalp and skull. In this work, we propose a low-artifact photoacoustic microscopy (LAPAM) scheme, which combines conventional acoustic-resolution photoacoustic microscopy with scanning acoustic microscopy to suppress the reflection artifacts induced by multi-layers. Based on similar propagation characteristics of photoacoustic signals and ultrasonic echoes, the ultrasonic echoes can be employed as the filters to suppress the reflection artifacts to obtain low-artifact photoacoustic images. Phantom experiment is used to validate the effectiveness of this method. Furthermore, LAPAM is applied for in-vivo imaging mouse brain without removing the scalp and the skull. Experimental results show that the proposed method successfully achieves the low-artifact brain image, which demonstrates the practical applicability of LAPAM. This work might improve the photoacoustic imaging quality in many biomedical applications which involve tissues with complex acoustic properties, such as brain imaging through scalp and skull.
 Select Experimental realization of two-dimensional single-layer ultracold gases of 87Rb in an accordion lattice Liangwei Wang(王良伟), Kai Wen(文凯), Fangde Liu(刘方德), Yunda Li(李云达), Pengjun Wang(王鹏军), Lianghui Huang(黄良辉), Liangchao Chen(陈良超), Wei Han(韩伟), Zengming Meng(孟增明), and Jing Zhang(张靖) Chin. Phys. B, 2022, 31 (10): 103401.   DOI: 10.1088/1674-1056/ac873c Abstract （252）   HTML （17）    PDF （1293KB）（210）       We experimentally realize two-dimensional (2D) single-layer ultracold gases of 87Rb by dynamically tuning the periodicity of a standing wave, known as accordion lattice. In order to load 87Rb Bose—Einstein condensate into single dark fringe node of the blue detuning optical lattice, we reduce the lattice periodicity from 26.7 μ to 3.5 μ with the help of an acousto-optic deflector (AOD) to compress the three-dimensional BEC adiabatically into a flat and uniform quasi-2D single-layer. We describe the experimental procedure of the atoms loading into the accordion lattice in detail and present the characteristics of the quasi-2D ultracold gases. This setup provides an important platform for studying in- and out-of equilibrium physics, phase transition and 2D topological matter.
 Select The 50 nm-thick yttrium iron garnet films with perpendicular magnetic anisotropy Shuyao Chen(陈姝瑶), Yunfei Xie(谢云飞), Yucong Yang(杨玉聪), Dong Gao(高栋), Donghua Liu(刘冬华), Lin Qin(秦林), Wei Yan(严巍), Bi Tan(谭碧), Qiuli Chen(陈秋丽), Tao Gong(龚涛), En Li(李恩), Lei Bi(毕磊), Tao Liu(刘涛), and Longjiang Deng(邓龙江) Chin. Phys. B, 2022, 31 (4): 048503.   DOI: 10.1088/1674-1056/ac4cc4 Abstract （320）   HTML （0）    PDF （1413KB）（208）       Yttrium iron garnet (YIG) films possessing both perpendicular magnetic anisotropy (PMA) and low damping would serve as ideal candidates for high-speed energy-efficient spintronic and magnonic devices. However, it is still challenging to achieve PMA in YIG films thicker than 20 nm, which is a major bottleneck for their development. In this work, we demonstrate that this problem can be solved by using substrates with moderate lattice mismatch with YIG so as to suppress the excessive strain-induced stress release as increasing the YIG thickness. After carefully optimizing the growth and annealing conditions, we have achieved out-of-plane spontaneous magnetization in YIG films grown on sGGG substrates, even when they are as thick as 50 nm. Furthermore, ferromagnetic resonance and spin pumping induced inverse spin Hall effect measurements further verify the good spin transparency at the surface of our YIG films.
 Select Asymmetric Fraunhofer pattern in Josephson junctions from heterodimensional superlattice V5S8 Juewen Fan(范珏雯), Bingyan Jiang(江丙炎), Jiaji Zhao(赵嘉佶), Ran Bi(毕然), Jiadong Zhou(周家东), Zheng Liu(刘政), Guang Yang(杨光), Jie Shen(沈洁), Fanming Qu(屈凡明), Li Lu(吕力), Ning Kang(康宁), and Xiaosong Wu(吴孝松) Chin. Phys. B, 2022, 31 (5): 057402.   DOI: 10.1088/1674-1056/ac5d30 Abstract （315）   HTML （5）    PDF （1074KB）（187）       Introduction of spin-orbit coupling (SOC) in a Josephson junction (JJ) gives rise to unusual Josephson effects. We investigate JJs based on a newly discovered heterodimensional superlattice V5S8 with a special form of SOC. The unique homointerface of our JJs enables elimination of extrinsic effects due to interfaces and disorder. We observe asymmetric Fraunhofer patterns with respect to both the perpendicular magnetic field and the current. The asymmetry is influenced by an in-plane magnetic field. Analysis of the pattern points to a nontrivial spatial distribution of the Josephson current that is intrinsic to the SOC in V5S8.
 Select Fast prediction of aerodynamic noise induced by the flow around a cylinder based on deep neural network Hai-Yang Meng(孟海洋), Zi-Xiang Xu(徐自翔), Jing Yang(杨京), Bin Liang(梁彬), and Jian-Chun Cheng(程建春) Chin. Phys. B, 2022, 31 (6): 064305.   DOI: 10.1088/1674-1056/ac5e98 Abstract （194）   HTML （5）    PDF （1086KB）（173）       Accurate and fast prediction of aerodynamic noise has always been a research hotspot in fluid mechanics and aeroacoustics. The conventional prediction methods based on numerical simulation often demand huge computational resources, which are difficult to balance between accuracy and efficiency. Here, we present a data-driven deep neural network (DNN) method to realize fast aerodynamic noise prediction while maintaining accuracy. The proposed deep learning method can predict the spatial distributions of aerodynamic noise information under different working conditions. Based on the large eddy simulation turbulence model and the Ffowcs Williams-Hawkings acoustic analogy theory, a dataset composed of 1216 samples is established. With reference to the deep learning method, a DNN framework is proposed to map the relationship between spatial coordinates, inlet velocity and overall sound pressure level. The root-mean-square-errors of prediction are below 0.82 dB in the test dataset, and the directivity of aerodynamic noise predicted by the DNN framework are basically consistent with the numerical simulation. This work paves a novel way for fast prediction of aerodynamic noise with high accuracy and has application potential in acoustic field prediction.
 Select Filling up complex spectral regions through non-Hermitian disordered chains Hui Jiang and Ching Hua Lee Chin. Phys. B, 2022, 31 (5): 050307.   DOI: 10.1088/1674-1056/ac4a73 Abstract （163）   HTML （11）    PDF （9183KB）（164）       Eigenspectra that fill regions in the complex plane have been intriguing to many, inspiring research from random matrix theory to esoteric semi-infinite bounded non-Hermitian lattices. In this work, we propose a simple and robust ansatz for constructing models whose eigenspectra fill up generic prescribed regions. Our approach utilizes specially designed non-Hermitian random couplings that allow the co-existence of eigenstates with a continuum of localization lengths, mathematically emulating the effects of semi-infinite boundaries. While some of these couplings are necessarily long-ranged, they are still far more local than what is possible with known random matrix ensembles. Our ansatz can be feasibly implemented in physical platforms such as classical and quantum circuits, and harbors very high tolerance to imperfections due to its stochastic nature.
ISSN 1674-1056   CN 11-5639/O4