Chin. Phys. B

Customizing topological phases in the twisted bilayer superconductors with even-parity pairings

Conghao Lin(林丛豪), Chuanshuai Huang(黄传帅), and Xiancong Lu(卢仙聪)

Chin. Phys. B, 2023, 32 (8): 087401. DOI: 10.1088/1674-1056/acd3e3

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We investigate the topological properties of twisted bilayer superconductors with different even-parity pairings in each layer. In the presence of spin-orbit coupling, the Hamiltonian is mapped into an effective odd-parity superconductor. Based on this, we deduce the topological properties by examining the relative configuration between Fermi surface and Dirac pairing node. We show that mixed Rashba and Dresselhaus spin-orbit coupling and anisotropic hopping terms, which break the C₄ symmetry of the Fermi surface, can induce first-order topological superconductors with non-zero bulk Chern number. This provides a versatile way to control the topological phases of bilayer superconductors by adjusting the twisted angle and chemical potential. We demonstrate our results using a typical twisted angle of 53.13°, at which the translation symmetry is restored and the Chern number and edge state are calculated using the Moiré momentum.

Improving physical properties of poly(vinyl alcohol)/montmorillonite nanocomposite hydrogels via the Hofmeister effect

Rongrong Guo(郭蓉蓉), Deshuai Yu(余德帅), Yifan Huang(黄一帆), Sen Wang(王森), Cong Fu(付聪), Shuihong Zhu(朱水洪), Jia Yi(易佳), Hanqi Wang(王涵淇), and Youhui Lin(林友辉)

Chin. Phys. B, 2023, 32 (8): 088103. DOI: 10.1088/1674-1056/acdfc2

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Hydrogel is a kind of three-dimensional crosslinked polymer material with high moisture content. However, due to the network defects of polymer gels, traditional hydrogels are usually brittle and fragile, which limits their practical applications. Herein, we present a Hofmeister effect-aided facile strategy to prepare high-performance poly(vinyl alcohol)/montmorillonite nanocomposite hydrogels. Layered montmorillonite nanosheets can not only serve as crosslinking agents to enhance the mechanical properties of the hydrogel but also promote the ion conduction. More importantly, based on the Hofmeister effect, the presence of (NH₄)₂SO₄ can endow nanocomposite hydrogels with excellent mechanical properties by affecting PVA chains' aggregation state and crystallinity. As a result, the as-prepared nanocomposite hydrogels possess unique physical properties, including robust mechanical and electrical properties. The as-prepared hydrogels can be further assembled into a high-performance flexible sensor, which can sensitively detect large-scale and small-scale human activities. The simple design concept of this work is believed to provide a new prospect for developing robust nanocomposite hydrogels and flexible devices in the future.

Pressure-driven membrane inflation through nanopores on the cell wall

Qi Zhong(钟祺), Chen-Xu Wu(吴晨旭), and Rui Ma(马锐)

Chin. Phys. B, 2023, 32 (8): 088704. DOI: 10.1088/1674-1056/acd7cc

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Walled cells, such as in plants and fungi, compose an important part of the model systems in biology. The cell wall primarily prevents the cell from over-expansion when exposed to water, and is a porous material distributed with nanosized pores on it. In this paper, we study the deformation of a membrane patch by an osmotic pressure through a nanopore on the cell wall. We find that there exists a critical pore size or a critical pressure beyond which the membrane cannot stand against the pressure and would inflate out through the pore and further expand. The critical pore size scales linearly with the membrane tension and quadratically with the spontaneous curvature. The critical pressure is inversely proportional to the pore radius. Our results also show that the fluid membrane expansion by pressure is mechanically different from the solid balloon expansion, and predict that the bending rigidity of the membrane in walled cells should be much larger than that of the mammalian cells so as to prevent membrane inflation through the pores on the cell wall.

Mutual neutralization in low-energy collisions of Na⁺ + H^- ions

Kun Wang(王堃), Chuan Dong(董川), Yizhi Qu(屈一至), Yong Wu(吴勇), Xiaohe Lin(林晓贺), and Robert J. Buenker

Chin. Phys. B, 2023, 32 (8): 083103. DOI: 10.1088/1674-1056/acd624

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The low-energy mutual neutralization (MN) reactions Na⁺ + H^- →Na(nl) + H have been studied by employing the full quantum-mechanical molecular-orbital close-coupling (QMOCC) method over a wide energy range of 10^-3-10³ eV/u. Total and state-selective cross sections have been investigated and compared with the available theoretical and experimental data, and the state-selective rate coefficients for the temperature range of 100-10000 K have been obtained. In the present work, all the necessary highly excited states are included, and the influences of rotational couplings and 10 active electrons are considered. It is found that in the energy below 10 eV/u, the Na(4s) state is the most dominant exit state with a contribution of approximately 78% to the branch fraction, which is in best agreement with the experimental data. For energies above 10 eV/u, the MN total cross section is larger than those obtained in other theoretical calculations and shows a slow decreasing trend because the main exit states change, when the energy is above 100 eV/u, the dominant exit state becomes the Na(3p) state, while the Na(4s) state becomes the third most important exit state. The datasets presented in this paper, including the potential energy curve, the radial and rotational couplings, the total and state-selective cross sections, are openly available at https://doi.org/10.57760/sciencedb.j00113.00112.

A simple semiempirical model for the static polarizability of ions

Alexander S Sharipov and Boris I Loukhovitski

Chin. Phys. B, 2023, 32 (8): 083301. DOI: 10.1088/1674-1056/acd2b2

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A concise analytical model for the static dipole polarizability of ionized atoms and molecules is created for the first time. As input, it requires, alongside the polarizability of neutral counterpart of a given ion, only the charge and elemental composition. This physically motivated semiempirical model is based on a number of established regularities in polarizability of charged monatomic and polyatomic compounds. In order to adjust it, the results of quantum chemistry calculations and gas-phase measurements available for a broad range of ionized multielectron species are employed. To counteract the appreciable bias in the literature data toward polarizability of monoatomic ions, for some molecular ions of general concern the results of the authors' own density functional theory calculations are additionally invoked. A total of 541 data points are used to optimize the model. It is demonstrated that the model we suggested has reasonable (given the substantial uncertainties of the reference data) accuracy in predicting the static isotropic polarizability of arbitrarily charged ions of any size and atomic composition. The resulting polarizability estimates are found to achieve a coefficient of determination of 0.93 for the assembled data set. The created analytic tool is universally applicable and might be advantageous for some applications where there is an urgent need for rapid low-cost evaluation of the static gas-phase polarizability of ionized atoms and molecules. This is especially relevant to constructing the complex models of nonequilibrium chemical kinetics aimed at precisely describing the observable refractive index (dielectric permittivity) of plasma flows. The data sets that support the findings of this study are openly available in Science Data Bank at https://doi.org/10.57760/sciencedb.07526.

A low-noise X-band microwave source with digital automatic frequency control for electron paramagnetic resonance spectroscopy

Yu He(贺羽), Runqi Kang(康润琪), Zhifu Shi(石致富), and Xing Rong(荣星)

Chin. Phys. B, 2023, 32 (8): 087601. DOI: 10.1088/1674-1056/accf7e

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We report a new design of microwave source for X-band electron paramagnetic resonance spectrometer. The microwave source is equipped with a digital automatic frequency control circuit. The parameters of the digital automatic frequency control circuit can be flexibly configured for different experimental conditions, such as the input powers or the quality factors of the resonator. The configurability makes the microwave source universally compatible and greatly extends its application. To demonstrate the ability of adapting to various experimental conditions, the microwave source is tested by varying the input powers and the quality factors of the resonator. A satisfactory phase noise as low as -135 dBc/Hz at 100-kHz offset from the center frequency is achieved, due to the use of a phase-locked dielectric resonator oscillator and a direct digital synthesizer. Continuous-wave electron paramagnetic resonance experiments are conducted to examine the performance of the microwave source. The outstanding performance shows a prospect of wide applications of the microwave source in numerous fields of science.

The growth and expansive applications of amorphous Ga₂O₃

Zhao-Ying Xi(奚昭颖), Li-Li Yang(杨莉莉), Lin-Cong Shu(舒林聪), Mao-Lin Zhang(张茂林), Shan Li(李山), Li Shi(史丽), Zeng Liu(刘增), Yu-Feng Guo(郭宇锋), and Wei-Hua Tang(唐为华)

Chin. Phys. B, 2023, 32 (8): 088502. DOI: 10.1088/1674-1056/accf81

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As a promising ultra-wide bandgap semiconductor material, gallium oxide (Ga₂O₃) is attracting extensive attention of researchers due to its feasible growth process, appropriate bandgap of 4.4 eV-5.3 eV allowing for deep-ultraviolet (deep-UV) detection, good physical and chemical stability, high breakdown field strength and electron mobility, etc. Different from the strict processes for controllable crystalline Ga₂O₃ (usually refer to as stable monoclinic β-Ga₂O₃), amorphous Ga₂O₃ (a-Ga₂O₃) film can be prepared uniformly at low temperature on a large-area deposition substrate, suggesting great advantages such as low manufacturing cost and excellent flexibility, dispensing with high-temperature and high vacuum techniques. Thus, a-Ga₂O₃ extremely facilitates important applications in various applied fields. Therefore, in this concise review, we summarize several major deposition methods for a-Ga₂O₃ films, of which the characteristics are discussed. Additionally, potential methods to optimize the film properties are proposed by right of the inspiration from some recent studies. Subsequently, the applications of a-Ga₂O₃ thin films, e.g., in photodetectors, resistive random access memories (RRAMs) and gas sensors, are represented with a fruitful discussion of their structures and operating mechanisms.

Degenerate polarization entangled photon source based on a single Ti-diffusion lithium niobate waveguide in a polarization Sagnac interferometer Suggested by editors

Yu Sun(孙宇), Chang-Wei Sun(孙昌伟), Wei Zhou(周唯), Ran Yang(杨然), Jia-Chen Duan(端家晨), Yan-Xiao Gong(龚彦晓), Ping Xu(徐平), and Shi-Ning Zhu(祝世宁)

Chin. Phys. B, 2023, 32 (8): 080308. DOI: 10.1088/1674-1056/acd8b3

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Combining a Ti-diffusion periodically poled lithium niobate (PPLN) waveguide with a Sagnac interferometer, two opposite directions type-II spontaneous parametric down conversions (SPDC) occur coherently and yield a high brightness, high stability polarization entanglement source. The source produces degenerate photon pairs at 1540.4 nm with a brightness of B = (1.36±0.03)×10⁶ pairs/(s· nm·mW). We perform quantum state tomography to reconstruct the density matrix of the output state and obtain a fidelity of F=0.983±0.001. The high brightness and phase stability of our waveguide source enable a wide range of quantum information experiments operating at a low pump power as well as hold the advantage in mass production which can promote the practical applications of quantum technologies.

Theoretical investigation of F-P cavity mode manipulation by single gold nanoparticles Suggested by editors

Xusheng Shi(史旭升), Zhiqiang Luo(罗志强), Zhi-Yuan Li(李志远), and Huakang Yu(虞华康)

Chin. Phys. B, 2023, 32 (8): 084204. DOI: 10.1088/1674-1056/acd2c1

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The ability to manipulate microlaser is highly desirable towards high-performance optoelectronic devices. Here we demonstrate feasible mode manipulation of Fabry-Pérot type microlasers of a perovskite nanowire via incorporation of single gold nanoparticles. The influences of resonant wavelength, quality factor and emission directions are successively investigated using a two-dimensional finite-difference time-domain method. It is found that blueshift of resonant wavelength could be achieved together with either promoted or degraded quality factor of the microlaser via single Au NPs with varied sizes. Unidirectional emission could also be realized which is favorable for on-chip integration. Our results provide useful reference for feasible manipulation of light-matter interactions and mode selection.

Atomistic simulations of graphene origami: Dynamics and kinetics ^Hot!

Panpan Zhang(张盼盼), Haihong Jia(贾海洪), Yan-Fang Zhang(张艳芳), and Shixuan Du(杜世萱)

Chin. Phys. B, 2023, 32 (8): 087107. DOI: 10.1088/1674-1056/acd527

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Origami offers two-dimensional (2D) materials with great potential for applications in flexible electronics, sensors, and smart devices. However, the dynamic process, which is crucial to construct origami, is too fast to be characterized by using state-of-the-art experimental techniques. Here, to understand the dynamics and kinetics at the atomic level, we explore the edge effects, structural and energy evolution during the origami process of an elliptical graphene nano-island (GNI) on a highly ordered pyrolytic graphite (HOPG) substrate by employing steered molecular dynamics simulations. The results reveal that a sharper armchair edge is much easier to be lifted up and realize origami than a blunt zigzag edge. The potential energy of the GNI increases at the lifting-up stage, reaches the maximum at the beginning of the bending stage, decreases with the formation of van der Waals overlap, and finally reaches an energy minimum at a half-folded configuration. The unfolding barriers of elliptical GNIs with different lengths of major axis show that the major axis should be larger than 242 Å to achieve a stable single-folded structure at room temperature. These findings pave the way for pursuing other 2D material origami and preparing origami-based nanodevices.

Single crystal growth and electronic structure of Rh-doped Sr₃Ir₂O₇ ^Hot!

Bingqian Wang(王冰倩), Shuting Peng(彭舒婷), Zhipeng Ou(欧志鹏), Yuchen Wang(王宇晨), Muhammad Waqas, Yang Luo(罗洋), Zhiyuan Wei(魏志远), Linwei Huai(淮琳崴), Jianchang Shen(沈建昌), Yu Miao(缪宇), Xiupeng Sun(孙秀鹏), Yuewei Yin(殷月伟), and Junfeng He(何俊峰)

Chin. Phys. B, 2023, 32 (8): 087108. DOI: 10.1088/1674-1056/acd7d5

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Ruddlesden-Popper iridate Sr₃Ir₂O₇ is a spin-orbit coupled Mott insulator. Hole doped Sr₃Ir₂O₇ provides an ideal platform to study the exotic quantum phenomena that occur near the metal-insulator transition (MIT) region. Rh substitution of Ir is an effective method to induce hole doping into Sr₃Ir₂O₇. However, the highest doping level reported in Sr₃(Ir_1-xRh_x)₂O₇ single crystals was only around 3%, which is far from the MIT region. In this paper, we report the successful growth of single crystals of Sr₃(Ir_1-xRh_x)₂O₇ with a doping level of ～ 9%. The samples have been fully characterized, demonstrating the high quality of the single crystals. Transport measurements have been carried out, confirming the tendency of MIT in these samples. The electronic structure has also been examined by angle-resolved photoemission spectroscopy (ARPES) measurements. Our results establish a platform to investigate the heavily hole doped Sr₃Ir₂O₇ compound, which also provide new insights into the MIT with hole doping in this material system.

Chiral current regulation and detection of Berry phase in triangular triple quantum dots ^Hot!

Yue Qi(齐月), Yi-Ming Liu(刘一铭), Yuan-Dong Wang(王援东), Jian-Hua Wei(魏建华), and Zhen-Gang Zhu(朱振刚)

Chin. Phys. B, 2023, 32 (8): 087304. DOI: 10.1088/1674-1056/acd36c

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Based on the hierarchical equations of motion (HEOM) calculation, we theoretically investigate the corresponding control of a triangular triple-quantum-dots (TTQD) ring which is connected to two reservoirs. We initially demonstrate by adding bias voltage and further adjusting the coupling strength between quantum dots, the chiral current induced by bias will go through a transformation of clockwise to counterclockwise direction and an unprecedented effective Hall angle will be triggered. The transformation is very rapid, with a corresponding characteristic time of 80-200 ps. In addition, by adding a magnetic flux to compensate for the chiral current in the original system, we elucidate the relationship between the applied magnetic flux and the Berry phase, which can realize direct measurement of the chiral current and reveal the magnetoelectric coupling relationship.

Electric modulation of anisotropic magnetoresistance in Pt/HfO_2-x/NiO_y/Ni heterojunctions ^Hot!

Xiaoyu Ye(叶晓羽), Xiaojian Zhu(朱小健), Huali Yang(杨华礼), Jipeng Duan(段吉鹏), Cui Sun(孙翠), and Run-Wei Li(李润伟)

Chin. Phys. B, 2023, 32 (8): 087305. DOI: 10.1088/1674-1056/acd2b6

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Electric field control of magnetism through nanoionics has attracted tremendous attention owing to its high efficiency and low power consumption. In solid-state dielectrics, an electric field drives the redistribution of ions to create one-dimensional magnetic conductive nanostructures, enabling the realization of intriguing magnetoresistance (MR) effects. Here, we explored the electric-controlled nickel and oxygen ion migration in Pt/HfO_2-x/NiO_y/Ni heterojunctions for MR modulation. By adjusting the voltage polarity and amplitude, the magnetic conductive filaments with mixed nickel and oxygen vacancy are constructed. This results in the reduction of device resistance by ～ 10³ folds, and leads to an intriguing partial asymmetric MR effect. We show that the difference of the device resistance under positive and negative saturation magnetic fields exhibits good linear dependence on the magnetic field angle, which can be used for magnetic field direction detection. Our study suggests the potential of electrically controlled ion migration in creating novel magnetic nanostructures for sensor applications.

Nonlinear current response and electric quantum oscillations in the Dirac semimetal Cd₃As₂ ^Hot!

Hao-Nan Cui(崔浩楠), Ze-Nan Wu(吴泽南), Jian-Kun Wang(王建坤), Guang-Yu Zhu(祝光宇), Jia-Jie Yang(杨佳洁), Wen-Zhuang Zheng(郑文壮), Zhi-Min Liao(廖志敏), Shuo Wang(王硕), Ben-Chuan Lin(林本川), and Dapeng Yu(俞大鹏)

Chin. Phys. B, 2023, 32 (8): 087306. DOI: 10.1088/1674-1056/acd9c5

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Chiral anomaly is a distinct quantum anomaly associated with chiral fermions in Dirac or Weyl semimetals. The use of negative magnetoresistance (negative MR) as a signature for this anomaly remains contentious, as trivial mechanisms such as current jetting and weak localization can also induce negative MR. In this study, we report a novel nonlinear behavior of the chiral anomaly in the longitudinal direction, which we observed by applying parallel current and magnetic field to the Dirac semimetal Cd₃As₂. This nonlinear characteristic peaks at an intermediate magnetic field of approximately 5 T, displaying a resistance-increasing property concomitant with strengthening of the current source. Through angle-dependence experiments, we were able to rule out trivial factors, such as thermal effects, geometric artifacts, and anisotropy. Furthermore, additional electric quantum oscillations were observed when the direct current (DC) was applied as high as 300 μA. Such an unusual phenomenon is ascribed to the formation of quantized levels due to Bloch oscillation in the high DC regime, suggesting that an oscillatory density distribution may arise as the electric field increases. The non-Ohmic electric quantum oscillations open a new avenue for exploring chiral anomaly and other nontrivial topological properties, which is also one of the salient features of nonequilibrium steady states in condensed matter physics.

Ultrafast antiferromagnet rearrangement in Co/IrMn/CoGd trilayers ^Hot!

Zongxia Guo(郭宗夏), Gregory Malinowski, Pierre Vallobra, Yi Peng(彭懿), Yong Xu(许涌), Stéphane Mangin, Weisheng Zhao(赵巍胜), Michel Hehn, and Boyu Zhang(张博宇)

Chin. Phys. B, 2023, 32 (8): 087507. DOI: 10.1088/1674-1056/acda83

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Antiferromagnets offer great potential for high-speed data processing applications, as they can expend spintronic devices from a static storage and gigahertz frequency range to the terahertz range. However, their zero net magnetization makes them difficult to manipulate and detect. In recent years, there has been a lot of attention given to the ultrafast manipulation of magnetic order using ultra-short single laser pulses, but it remains unknown whether a similar scenario can be observed in antiferromagnets. In this work, we demonstrate the manipulation of antiferromagnets with a single femtosecond laser pulse in perpendicular exchange-biased Co/IrMn/CoGd trilayers. We study the dual exchange bias interlayer interaction in quasi-static conditions and competition in ultrafast antiferromagnet rearrangement. Our results show that, compared to conventional ferromagnetic/antiferromagnetic systems, the IrMn antiferromagnet can be ultrafast and efficiently manipulated by the coupled CoGd ferrimagnetic layer, which paves the way for potential energy-efficient spintronic devices.

Prediction of a monolayer spin-spiral semiconductor: CoO with a honeycomb lattice Suggested by editors

Jie Zhang(张杰), Shunuo Song(宋姝诺), Yan-Fang Zhang(张艳芳),Yu-Yang Zhang(张余洋), Sokrates T. Pantelides, and Shixuan Du(杜世萱)

Chin. Phys. B, 2023, 32 (8): 087508. DOI: 10.1088/1674-1056/acd923

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The recent successful fabrication of two-dimensional (2D) CoO with nanometer-thickness motivates us to investigate monolayer CoO due to possible magnetic properties induced by Co atoms. Here, we employ first-principles calculations to show that monolayer CoO is a 2D spin-spiral semiconductor with a honeycomb lattice. The calculated phonon dispersion reveals the monolayer's dynamical stability. Monolayer CoO exhibits a type-I spin-spiral magnetic ground state. The spin-spiral state and the direct bandgap character are both robust under biaxial compressive strain (-5%) to tensile strain (5%). The bandgap varies only slightly under either compressive or tensile strain up to 5%. These results suggest a potential for applications in spintronic devices and offer a new platform to explore magnetism in the 2D limit.

F-μ bond length and μSR depolarization spectrum calculation for fluoride using two-component density functional theory ^Hot!

Zhikang Pan(潘智康), Li Deng(邓力), Ziwen Pan(潘子文), Yue Yuan(原钺), Hongjun Zhang(张宏俊), and Bangjiao Ye(叶邦角)

Chin. Phys. B, 2023, 32 (8): 087602. DOI: 10.1088/1674-1056/acd109

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First-principles calculation of muons in ionic fluorides has been proposed recently. However, there is a considerable difference between the obtained F-μ bond length and the experimental data obtained by muon spin relaxation (μSR). Considering that the difference may be caused by ignoring the quantum effect of muons, we use two-component density functional theory (TCDFT) to consider the quantized muon and recalculate the bond length and the μSR depolarization spectrum. After testing several muon-electron correlation, we show that TCDFT can give better results than the commonly used "DFT+μ".

Synthesis and electrochemical performance of La₂CuO₄ as a promising coating material for high voltage Li-rich layered oxide cathodes Suggested by editors

Fuliang Guo(郭福亮), Jiaze Lu(卢嘉泽), Meihua Su(苏美华), Yue Chen(陈约), Jieyun Zheng(郑杰允), Liang Yin(尹良), and Hong Li(李泓)

Chin. Phys. B, 2023, 32 (8): 088201. DOI: 10.1088/1674-1056/acd2bc

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The structural transformations, oxygen releasing and side reactions with electrolytes on the surface are considered as the main causes of the performance degradation of Li-rich layered oxides (LROs) cathodes in Li-ion batteries. Thus, stabilizing the surfaces of LROs is the key to realize their practical application in high energy density Li-ion batteries. Surface coating is regarded as one of the most effective strategies for high voltage cathodes. The ideal coating materials should prevent cathodes from electrolyte corrosion and possess both electronic and Li-ionic conductivities simultaneously. However, commonly reported coating materials are unable to balance these functions well. Herein, a new type of coating material, La₂CuO₄ was introduced to mitigate the surface issues of LROs for the first time, due to its superb electronic conductivity (26-35 mS·cm^-1) and lithium-ionic diffusion coefficient (10^-12-10^-13 cm²·s^-1). After coating with the La₂CuO₄, the capacity retention of Li_1.2Ni_0.54Co_0.13Mn_0.13O₂ cathode was increased to 85.9% (compared to 79.3% of uncoated cathode) after 150 cycles in the voltage range of 2.0-4.8 V. In addition, only negligible degradations on the deliverable capacity and rate capability were observed.

Bio-inspired environmental adaptability of swarm active matter Suggested by editors

Yangkai Jin(金阳凯), Gao Wang(王高), Daming Yuan(袁大明), Peilong Wang(王培龙), Jing Wang(王璟), Huaicheng Chen(陈怀城), Liyu Liu(刘雳宇), and Xingjie Zan(昝兴杰)

Chin. Phys. B, 2023, 32 (8): 088703. DOI: 10.1088/1674-1056/acd688

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How biologically active matters survive adaptively in complex and changeable environments is a common concern of scientists. Genetics, evolution and natural selection are vital factors in the process of biological evolution and are also the key to survival in harsh environments. However, it is challenging to intuitively and accurately reproduce such long-term adaptive survival processes in the laboratory. Although simulation experiments are intuitive and efficient, they lack fidelity. Therefore, we propose to use swarm robots to study the adaptive process of active matter swarms in complex and changeable environments. Based on a self-built virtual environmental platform and a robot swarm that can interact with the environment, we introduce the concept of genes into the robot system, giving each robot unique digital genes, and design robot breeding methods and rules for gene mutations. Our previous work [Proc. Natl. Acad. Sci. USA 119 e2120019119 (2022)] has demonstrated the effectiveness of this system. In this work, by analyzing the relationship between the genetic traits of the population and the characteristics of environmental resources, and comparing different experimental conditions, we verified in both robot experiments and corresponding simulation experiments that agents with genetic inheritance can survive for a long time under the action of natural selection in periodically changing environments. We also confirmed that in the robot system, both breeding and mutation are essential factors. These findings can help answer the practical scientific question of how individuals and swarms can successfully adapt to complex, dynamic, and unpredictable actual environments.

Inference of interactions between players based on asynchronously updated evolutionary game data

Hong-Li Zeng(曾红丽), Bo Jing(景浡), Yu-Hao Wang(王于豪), and Shao-Meng Qin(秦绍萌)

Chin. Phys. B, 2023, 32 (8): 080201. DOI: 10.1088/1674-1056/acc7fd

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The interactions between players of the prisoner's dilemma game are inferred using observed game data. All participants play the game with their counterparts and gain corresponding rewards during each round of the game. The strategies of each player are updated asynchronously during the game. Two inference methods of the interactions between players are derived with naïve mean-field (nMF) approximation and maximum log-likelihood estimation (MLE), respectively. Two methods are tested numerically also for fully connected asymmetric Sherrington-Kirkpatrick models, varying the data length, asymmetric degree, payoff, and system noise (coupling strength). We find that the mean square error of reconstruction for the MLE method is inversely proportional to the data length and typically half (benefit from the extra information of update times) of that by nMF. Both methods are robust to the asymmetric degree but work better for large payoffs. Compared with MLE, nMF is more sensitive to the strength of couplings and prefers weak couplings.

High-fidelity topological quantum state transfersin a cavity-magnon system Suggested by editors

Xi-Xi Bao(包茜茜), Gang-Feng Guo(郭刚峰), Xu Yang(杨煦), and Lei Tan(谭磊)

Chin. Phys. B, 2023, 32 (8): 080301. DOI: 10.1088/1674-1056/acc3f6

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We propose a scheme for realizing high-fidelity topological state transfer via the topological edge states in a one-dimensional cavity-magnon system. It is found that the cavity-magnon system can be mapped analytically into the generalized Su-Schrieffer-Heeger model with tunable cavity-magnon coupling. It is shown that the edge state can be served as a quantum channel to realize the photonic and magnonic state transfers by adjusting the coupling strength between adjacent cavity modes. Further, our scheme can realize the quantum state transfer between photonic state and magnonic state by changing the cavity-magnon coupling strength. With the numerical simulation, we quantitatively show that the photonic, magnonic and magnon-to-photon state transfers can be achieved with high fidelity in the cavity-magnon system. Spectacularly, three different types of quantum state transfer schemes can be even transformed into each other in a controllable fashion. The Su-Schrieffer-Heeger model based on the cavity-magnon system provides us a tunable platform to engineer the transport of photon and magnon, which may have potential applications in topological quantum processing.

Quantum interferometric power and non-Markovianity in the decoherence channels Suggested by editors

Shaojie Xiong(熊少杰), Zhe Sun(孙哲), and Xiaoguang Wang(王晓光)

Chin. Phys. B, 2023, 32 (8): 080302. DOI: 10.1088/1674-1056/accb4e

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In quantum open systems, non-Markovianity is an important phenomenon that allows a backflow of information from the environment to the system. In this work, we investigate the non-Markovianity problems in two different types of channels, where the system-environment interactions are treated with and without the rotating-wave approximation (RWA). We employ the quantum interferometric power (QIP) to quantify the non-Markovian dynamics, which is the minimal quantum Fisher information obtained by the local unitary evolution in a bipartite system. By the hierarchy equation method, we calculate the dynamical evolution of the QIP in the non-RWA case. The results show that the dynamical behavior under the non-RWA is significantly different from that under the RWA in both weak and strong coupling. Moreover, in the non-RWA case, we also find the nonmonotonic behavior of the non-Markovianity measure with the variation of coupling strength, which is caused by the competition between the rotating-wave terms and the counterrotating-wave terms. As a result, we highlight the importance of the counterrotating-wave terms for the influence of non-Markovianity.

An efficient multiparty quantum secret sharing scheme using a single qudit

Wenwen Hu(胡文文), Bangshu Xiong(熊邦书), and Rigui Zhou(周日贵)

Chin. Phys. B, 2023, 32 (8): 080303. DOI: 10.1088/1674-1056/aca391

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The aim of quantum secret sharing, as one of most promising components of quantum cryptograph, is one-to-multiparty secret communication based on the principles of quantum mechanics. In this paper, an efficient multiparty quantum secret sharing protocol in a high-dimensional quantum system using a single qudit is proposed. Each participant's shadow is encoded on a single qudit via a measuring basis encryption method, which avoids the waste of qudits caused by basis reconciliation. Security analysis indicates that the proposed protocol is immune to general attacks, such as the measure-resend attack, entangle-and-measure attack and Trojan horse attack. Compared to former protocols, the proposed protocol only needs to perform the single-qudit measurement operation, and can share the predetermined dits instead of random bits or dits.

Exact solution of slow quench dynamics and nonadiabatic characterization of topological phases Suggested by editors

Rui Wu(邬睿), Panpan Fang(房盼攀), Chen Sun(孙辰), and Fuxiang Li(李福祥)

Chin. Phys. B, 2023, 32 (8): 080304. DOI: 10.1088/1674-1056/acd0a5

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Previous studies have shown that the bulk topology of single-particle systems can be captured by the band inversion surface or by the spin inversion surface emerging on the time-averaged spin polarization. Most of the studies, however, are based on the single-particle picture even though the systems are fermionic and multi-bands. Here, we study the slow quench dynamics of topological systems with all the valence bands fully occupied, and show that the concepts of band inversion surface and spin inversion surface are still valid. More importantly, the many-particle nonadiabatic quench dynamics is shown to be reduced to a new and nontrivial three-level Landau-Zener model. This nontrivial three-level Landau-Zener problem is then solved analytically by applying the integrability condition and symmetry considerations, and thus adds a new member to the few models that are exactly solvable. Based on the analytical results, the topological spin texture revealed by the time-averaged spin polarization can be applied to characterize the bulk topology and thus provides a direct comparison for future experiments.

Variational quantum simulation of the quantum critical regime

Zhi-Quan Shi(石志全), Xu-Dan Xie(谢旭丹), and Dan-Bo Zhang(张旦波)

Chin. Phys. B, 2023, 32 (8): 080305. DOI: 10.1088/1674-1056/accb43

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The quantum critical regime marks a zone in the phase diagram where quantum fluctuation around the critical point plays a significant role at finite temperatures. While it is of great physical interest, simulation of the quantum critical regime can be difficult on a classical computer due to its intrinsic complexity. Herein, we propose a variational approach, which minimizes the variational free energy, to simulate and locate the quantum critical regime on a quantum computer. The variational quantum algorithm adopts an ansatz by performing an unitary operator on a product of a single-qubit mixed state, in which the entropy can be analytically obtained from the initial state, and thus the free energy can be accessed conveniently. With numeral simulation, using the one-dimensional Kitaev model as a demonstration we show that the quantum critical regime can be identified by accurately evaluating the temperature crossover line. Moreover, the dependencies of both the correlation length and the phase coherence time with temperature are evaluated for the thermal states. Our work suggests a practical way as well as a first step for investigating quantum critical systems at finite temperatures on quantum devices with few qubits.

Improved statistical fluctuation analysis for two decoy-states phase-matching quantum key distribution

Jiang-Ping Zhou(周江平), Yuan-Yuan Zhou(周媛媛), Xue-Jun Zhou(周学军), and Xuan Bao(暴轩)

Chin. Phys. B, 2023, 32 (8): 080306. DOI: 10.1088/1674-1056/acbdea

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Phase-matching quantum key distribution is a promising scheme for remote quantum key distribution, breaking through the traditional linear key-rate bound. In practical applications, finite data size can cause significant system performance to deteriorate when data size is below 10¹⁰. In this work, an improved statistical fluctuation analysis method is applied for the first time to two decoy-states phase-matching quantum key distribution, offering a new insight and potential solutions for improving the key generation rate and the maximum transmission distance while maintaining security. Moreover, we also compare the influence of the proposed improved statistical fluctuation analysis method on system performance with those of the Gaussian approximation and Chernoff-Hoeffding boundary methods on system performance. The simulation results show that the proposed scheme significantly improves the key generation rate and maximum transmission distance in comparison with the Chernoff-Hoeffding approach, and approach the results obtained when the Gaussian approximation is employed. At the same time, the proposed scheme retains the same security level as the Chernoff-Hoeffding method, and is even more secure than the Gaussian approximation.

Algorithm for evaluating distance-based entanglement measures Suggested by editors

Yixuan Hu(胡奕轩), Ye-Chao Liu(刘烨超), and Jiangwei Shang(尚江伟)

Chin. Phys. B, 2023, 32 (8): 080307. DOI: 10.1088/1674-1056/acd5c5

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Quantifying entanglement in quantum systems is an important yet challenging task due to its NP-hard nature. In this work, we propose an efficient algorithm for evaluating distance-based entanglement measures. Our approach builds on Gilbert's algorithm for convex optimization, providing a reliable upper bound on the entanglement of a given arbitrary state. We demonstrate the effectiveness of our algorithm by applying it to various examples, such as calculating the squared Bures metric of entanglement as well as the relative entropy of entanglement for GHZ states, W states, Horodecki states, and chessboard states. These results demonstrate that our algorithm is a versatile and accurate tool that can quickly provide reliable upper bounds for entanglement measures.

Shadow thermodynamics of AdS black hole with the nonlinear electrodynamics term

He-Bin Zheng(郑何斌), Ping-Hui Mou(牟平辉), Yun-Xian Chen(陈芸仙), and Guo-Ping Li(李国平)

Chin. Phys. B, 2023, 32 (8): 080401. DOI: 10.1088/1674-1056/acc806

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We creatively employ the shadow radius to study the thermodynamics of a charged AdS black hole with a nonlinear electrodynamics (NLED) term. First, the connection between the shadow radius and event horizon is constructed with the aid of the geodesic analysis. It turns out that the black hole shadow radius shows a positive correlation as a function of the event horizon radius. Then in the shadow context, we find that the black hole temperature and heat capacity can be presented by the shadow radius. Further analysis shows that the shadow radius can work similarly to the event horizon in revealing black hole phase transition process. In this sense, we construct the thermal profile of the charged AdS black hole with inclusion of the NLED effect. In the P<P_c case, it is found that the N-type trend of the temperature given by the shadow radius is always consistent with that obtained by using the event horizon. Thus, we can conclude for the charged AdS black hole that the phase transition process can be intuitively presented as the thermal profile in the shadow context. Finally, the effects of NLED are carefully analyzed.

On numerical stationary distribution of overdamped Langevin equation in harmonic system

De-Zhang Li(李德彰) and Xiao-Bao Yang(杨小宝)

Chin. Phys. B, 2023, 32 (8): 080501. DOI: 10.1088/1674-1056/acc05c

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Efficient numerical algorithm for stochastic differential equation has been an important object in the research of statistical physics and mathematics for a long time. In this work we study the highly accurate numerical algorithm for the overdamped Langevin equation. In particular, our interest is in the behaviour of the numerical schemes for solving the overdamped Langevin equation in the harmonic system. Based on the large friction limit of the underdamped Langevin dynamic scheme, three algorithms for overdamped Langevin equation are obtained. We derive the explicit expression of the stationary distribution of each algorithm by analysing the discrete time trajectory for both one-dimensional case and multi-dimensional case. The accuracy of the stationary distribution of each algorithm is illustrated by comparing with the exact Boltzmann distribution. Our results demonstrate that the "BAOA-limit" algorithm generates an accurate distribution of the harmonic system in a canonical ensemble, within a stable range of time interval. The other algorithms do not produce the exact distribution of the harmonic system.

Phase behavior and percolation in an equilibrium system of symmetrically interacting Janus disks on the triangular lattice

Xixian Zhang(张希贤) and Hao Hu(胡皓)

Chin. Phys. B, 2023, 32 (8): 080502. DOI: 10.1088/1674-1056/acc7fe

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A Janus particle has two distinct areas on its surface. Denoting the two areas as P (patch) and N (nonpatch), when two particles come close to each other, the strength of the PP interaction is usually different from that of the NN interaction. Recently the interplay between a rotational-symmetry-breaking continuous phase transition and percolation has been explored for an equilibrium system of asymmetrically interacting (i.e., attractive PP interaction, zero NN and PN interactions) Janus disks on the triangular lattice. By Monte Carlo simulation and finite-size scaling analysis, in this work we study an equilibrium system of symmetrically interacting (i.e., attractive PP and NN interactions with the same strength, zero PN interaction) Janus disks on the same lattice. By definition, the phase diagram in the T-θ plane is symmetric for systems with patch sizes θ below and above 90°. We determine the phase diagram and compare it with that of the asymmetric system. Similar to the latter system, for 60° < θ < 90°, a rotational-symmetry-breaking continuous phase transition and an anisotropic percolation transition are found in the symmetric system, though the transition points in the two systems are quite different. Phase crossover curves are found to be different, e.g., a continuous varying crossover line extends between θ=0° and 90° for the symmetric model; and in the range 0° < θ ≤ 30°, along the crossover lines of the two models, the trends of 1/T vs. θ are opposite in the two systems. We understand the latter by analytically solving the models with two particles in 0° < θ ≤ 30°. These results are helpful for understanding close-packed systems of Janus disks with more complex interactions.

Dynamical analysis, geometric control and digital hardware implementation of a complex-valued laser system with a locally active memristor Suggested by editors

Yi-Qun Li(李逸群), Jian Liu(刘坚), Chun-Biao Li(李春彪), Zhi-Feng Hao(郝志峰), and Xiao-Tong Zhang(张晓彤)

Chin. Phys. B, 2023, 32 (8): 080503. DOI: 10.1088/1674-1056/acd68b

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In order to make the peak and offset of the signal meet the requirements of artificial equipment, dynamical analysis and geometric control of the laser system have become indispensable. In this paper, a locally active memristor with non-volatile memory is introduced into a complex-valued Lorenz laser system. By using numerical measures, complex dynamical behaviors of the memristive laser system are uncovered. It appears the alternating appearance of quasi-periodic and chaotic oscillations. The mechanism of transformation from a quasi-periodic pattern to a chaotic one is revealed from the perspective of Hamilton energy. Interestingly, initial-values-oriented extreme multi-stability patterns are found, where the coexisting attractors have the same Lyapunov exponents. In addition, the introduction of a memristor greatly improves the complexity of the laser system. Moreover, to control the amplitude and offset of the chaotic signal, two kinds of geometric control methods including amplitude control and rotation control are designed. The results show that these two geometric control methods have revised the size and position of the chaotic signal without changing the chaotic dynamics. Finally, a digital hardware device is developed and the experiment outputs agree fairly well with those of the numerical simulations.

Parameter estimation method for a linear frequency modulation signal with a Duffing oscillator based on frequency periodicity

Ningzhe Zhang(张宁哲), Xiaopeng Yan(闫晓鹏), Minghui Lv(吕明慧), Xiumei Chen(陈秀梅), and Dingkun Huang(黄鼎琨)

Chin. Phys. B, 2023, 32 (8): 080701. DOI: 10.1088/1674-1056/aca206

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In view of the complexity of existing linear frequency modulation (LFM) signal parameter estimation methods and the poor antinoise performance and estimation accuracy under a low signal-to-noise ratio (SNR), a parameter estimation method for LFM signals with a Duffing oscillator based on frequency periodicity is proposed in this paper. This method utilizes the characteristic that the output signal of the Duffing oscillator excited by the LFM signal changes periodically with frequency, and the modulation period of the LFM signal is estimated by autocorrelation processing of the output signal of the Duffing oscillator. On this basis, the corresponding relationship between the reference frequency of the frequency-aligned Duffing oscillator and the frequency range of the LFM signal is analyzed by the periodic power spectrum method, and the frequency information of the LFM signal is determined. Simulation results show that this method can achieve high-accuracy parameter estimation for LFM signals at an SNR of -25 dB.

Glancing incidence x-ray fluorescence spectrometry based on a single-bounce parabolic capillary

Shangkun Shao(邵尚坤), Huiquan Li(李惠泉), Tianyu Yuan(袁天语), Xuepeng Sun(孙学鹏), Lu Hua(华路), Zhiguo Liu(刘志国), and Tianxi Sun(孙天希)

Chin. Phys. B, 2023, 32 (8): 080702. DOI: 10.1088/1674-1056/ac9b38

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Glancing incidence x-ray fluorescence spectrometry using a single-bounce parabolic capillary is proposed for the analysis of layered samples. The divergence of the x-ray beam was 0.33 mrad. In this paper, we used this instrumental setup to analyze a Si single crystal and a 50 nm HfO₂ single-layer film deposited on a Si substrate.

Loading uniform Ag₃PO₄ nanoparticles on three-dimensional peony-like WO₃ for good stability and excellent selectivity towards NH₃ at room temperature

Xingyan Shao(邵星炎), Fuchao Jia(贾福超), Tingting Liu(刘婷婷), Jiancheng Liu(刘健诚), Xiaomei Wang(王小梅), Guangchao Yin(尹广超), Na Lv(吕娜), Tong Zhou(周通), Ramachandran Rajan, and Bo Liu(刘波)

Chin. Phys. B, 2023, 32 (8): 080703. DOI: 10.1088/1674-1056/ac98a0

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A heterojunction structure design is a very good method for improving the properties of semiconductors in many research fields. This method is employed in the present study to promote the gas-sensing performance of Ag₃PO₄ nanocomposites at room temperature (25 ℃). A nanocomposite of Ag₃PO₄ nanoparticles and three-dimensional peony-like WO₃ (WO₃/Ag₃PO₄) was successfully prepared by the precipitation method. The crystalline phases were analyzed by x-ray diffraction and the microstructure was characterized by scanning electron microscopy and transmission electron microscopy. The chemical bonding states were analyzed by x-ray photoelectron spectroscopy. The gas-sensing performance of WO₃/Ag₃PO₄ sensors was systematically explored at room temperature. The composite sensors possessed a higher response and lower detection limit (1 ppm) to NH₃ than those made of a single type of material; this is ascribed to the synergistic effect achieved by the heterojunction structure. Among the different composite sensors tested, gas sensor A5W5 (Ag₃PO₄:WO₃ mass ratio of 5:5) displayed the highest response to NH₃ at room temperature. Interestingly, the A5W5 gas sensor exhibited relatively good stability and excellent selectivity to NH₃. The A5W5 sensor also displayed a relatively good response under high humidity. The gas-sensing mechanism of the WO₃/Ag₃PO₄ sensors is explained in detail. Taken together, the as-prepared sensor is highly efficient at detecting NH₃ and could be suitable for practical applications. In addition, this study also provides a new method for developing Ag₃PO₄-based sensors in the gas-sensing field.

High-order Hamiltonian obtained by Foldy-Wouthuysen transformation up to the order of mα⁸

Tong Chen(陈彤), Xuesong Mei(梅雪松), Wanping Zhou(周挽平), and Haoxue Qiao(乔豪学)

Chin. Phys. B, 2023, 32 (8): 083101. DOI: 10.1088/1674-1056/ac9e98

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Complete relativistic corrections of an effective Hamiltonian for a single-particle system in an external electromagnetic field and their unitary equivalent form up to the order of mα⁸ are obtained. The derivation is based on two approaches applying Foldy-Wouthuysen (FW) transformation to the Dirac Hamiltonian for a particle in an external electromagnetic field. The results are consistent with the previous work at the mα⁶ and mα⁸ order correction [Phys. Rev. A 71 012503 (2005); Phys. Rev. A 100 012513 (2019)]. We also further consider the effect of anomalous magnetic moments, namely, the Dirac-Pauli equation, and obtain FW-Hamiltonians at the same order. The results obtained can be used for the subsequent calculation of relativistic and radiation effects in simple atomic and molecular systems.

L-shell x-ray fluorescence relative intensities for elements with 62 ≤ Z ≤ 83 at 18 keV and 23 keV by synchrotron radiation

M Alqadi, S AL-Humaidi, H Alkhateeb, and F Alzoubi

Chin. Phys. B, 2023, 32 (8): 083201. DOI: 10.1088/1674-1056/accb46

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The relative intensities of L-subshell x-ray fluorescence (XRF) for elements with atomic numbers 62 ≤ Z ≤ 83 were measured at two excitation energies, 18 keV and 23 keV, using a synchrotron radiation source at a beamline of the Synchrotron Light Center for Experimental Science and Applications in the Middle East (SESAME), Jordan. The experimentally measured results of the relative intensities were compared with the calculated results using the subshell fluorescence yield and the Coster-Kronig transition probabilities recommended by Campbell and the values based on the Dirac-Hartree-Slater model by Puri. The experimental and theoretical results are in agreement. In this work, L XRF relative intensities for the elements Sm, Gd, Tb, Er, Ta, W, Re, Hg, Pb and Bi at energies of 18 keV and 23 keV were measured.

Facilitation of controllable excitation in Rydberg atomic ensembles Suggested by editors

Han Wang(王涵) and Jing Qian(钱静)

Chin. Phys. B, 2023, 32 (8): 083302. DOI: 10.1088/1674-1056/acd0a6

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Strongly-interacting Rydberg atomic ensembles have shown intense collective excitation effects due to the inclusion of single Rydberg excitation shared by multiple atoms in the ensemble. In this paper we investigate a counter-intuitive Rydberg excitation facilitation with a strongly-interacting atomic ensemble in the strong probe-field regime, which is enabled by the role of a control atom nearby. Differing from the case of a single ensemble, we show that, the control atom's excitation adds to a second two-photon transition onto the doubly-excited Rydberg state, arising an excitation facilitation for the ensemble atoms. Our numerical studies depending on the method of quantum Monte Carlo wave function, exhibit the observation constraints of this excitation facilitation effect under practical experimental conditions. The results obtained can provide a flexible control for the excitation of Rydberg atomic ensembles and participate further uses in developing mesoscopic Rydberg gates for multiqubit quantum computation.

A novel power-combination method using a time-reversal pulse-compression technique

Xi-Cheng Lu(陆希成), Jin Tian(田锦), Rong-Wei Zhang(张荣威), Hai-Bo Wang(汪海波), and Yang Qiu(邱扬)

Chin. Phys. B, 2023, 32 (8): 084101. DOI: 10.1088/1674-1056/acaa2a

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The electromagnetic time-reversal (TR) technique has the characteristics of spatiotemporal focusing in a time-reversal cavity (TRC), which can be used for pulse compression, thus forming an electromagnetic pulse with high peak power. A time-reversed pulse-compression method in a single channel has high pulse compression gain. However, single channel pulse compression can only generate limited gain. This paper proposes a novel TR power-combination method in a multichannel TRC to obtain higher peak power based on TR pulse-compression theory. First, the TR power-combination model is given, and the crosstalk properties of the associated channel and the influence of the reversal performance are studied. Then, the power-combination performances for the TR pulse compression, such as combined signal to noise ratio (SNR) and combined compression gain, are analyzed by numerical simulation and experimental methods. The results show that the proposed method has obvious advantages over pulse-compression methods using a single channel cavity, and is more convenient for power combination.

Design of an optically-transparent ultra-broadband microwave absorber

Mian Gao(高冕), Qiang Chen(陈强), Yue-Jun Zheng(郑月军), Fang Yuan(袁方), Zhan-Shan Sun(孙占山), and Yun-Qi Fu(付云起)

Chin. Phys. B, 2023, 32 (8): 084102. DOI: 10.1088/1674-1056/ac9a39

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The optical window of low-observable platform needs to be compatible with ultra-broadband absorption, hence an optically-transparent absorber with ultra-broadband absorption is designed and analyzed in this paper. The transparent materials indium-tin-oxide (ITO) film and polymethylmethacrylate (PMMA) are selected as the lossy layer and the supporting dielectric layer, respectively. The optically-transparent ultra-broadband absorber (OT-UBA) is composed of three layers of ITO square patterns, three layers of PMMA dielectric and a uniform ITO plane. The ITO square patterns can realize arbitrary equivalent series of RC (resistor and capacitor) circuit, so that three layers of ITO square patterns together with the ITO plane can achieve ultra-broadband absorption based on the equivalent circuit optimization. Measured results shows that the 90%-absorption bandwidth covers 2-17 GHz while the light transmittance achieves 59.6% with a total thickness of only 12.9 mm.

Effect of photovoltaic panel electric field on the wind speed required for dust removal from the panels Suggested by editors

Xingcai Li(李兴财), Juan Wang(王娟), Yinge Liu(刘滢格), and Xin Ma(马鑫)

Chin. Phys. B, 2023, 32 (8): 084103. DOI: 10.1088/1674-1056/acd5c1

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Methods to remove dust deposits by high-speed airflow have significant potential applications, with optimal design of flow velocity being the core technology. In this paper, we discuss the wind speed required for particle removal from photovoltaic (PV) panels by compressed air by analyzing the force exerted on the dust deposited on inclined photovoltaic panels, which also included different electrification mechanisms of dust while it is in contact with the PV panel. The results show that the effect of the particle charging mechanism in the electric field generated by the PV panel is greatly smaller than the effect of the Van der Waals force and gravity, but the effect of the particle charged by the contact electrification mechanism in the electrostatic field is very pronounced. The wind speed required for dust removal from the PV panel increases linearly with the PV panel electric field, so we suggest that the nighttime, when the PV electric field is relatively small, would be more appropriate time for dust removal. The above results are of great scientific importance for accurately grasping the dust distribution law and for achieving scientific removal of dust on PV panels.

Real-time and high-transmission middle-infrared optical imaging system based on a pixel-wise metasurface micro-polarization array

Lifeng Ma(马丽凤), Shan Du(杜杉), Jun Chang(常军), Weilin Chen(陈蔚霖), Chuhan Wu(武楚晗), Xinxin Shi(石鑫鑫), Yi Huang(黄翼), Yue Zhong(钟乐), and Quanquan Mu(穆全全)

Chin. Phys. B, 2023, 32 (8): 084201. DOI: 10.1088/1674-1056/acaa25

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Real-time polarization medium-wave infrared (MIR) optical imaging systems enable the acquisition of infrared and polarization information for a target. At present, real-time polarization MIR devices face the following problems: poor real-time performance, low transmission and high requirements for fabrication and integration. Herein, we aim to improve the performance of real-time polarization imaging systems in the MIR waveband and solve the above-mentioned defects. Therefore, we propose a MIR polarization imaging system to achieve real-time polarization-modulated imaging with high transmission as well as improved performance based on a pixel-wise metasurface micro-polarization array (PMMPA). The PMMPA element comprises several linear polarization (LP) filters with different polarization angles. The optimization results demonstrate that the transmittance of the center field of view for the LP filters is up to 77% at a wavelength of 4.0 μ and an extinction ratio of 88 dB. In addition, a near-diffraction-limited real-time MIR imaging optical system is designed with a field of view of 5° and an F-number of 2. The simulation results show that an MIR polarization imaging system with excellent real-time performance and high transmission is achieved by using the optimized PMMPA element. Therefore, the method is compatible with the available optical system design technologies and provides a way to realize real-time polarization imaging in MIR wavebands.

Microwave absorption and bandwidth study of Y₂Co₁₇ rare earth soft magnetic alloy with easy-plane anisotropy Suggested by editors

Yun-Guo Ma(马云国), Liang Qiao(乔亮), Zu-Ying Zheng(郑祖应), Hong-Bo Hao(郝宏波), Hao Wang(王浩), Zhe Sun(孙哲), Cheng-Fa Tu(涂成发), Tao Wang(王涛), Zheng Yang(杨正), and Fa-Shen Li(李发伸)

Chin. Phys. B, 2023, 32 (8): 084202. DOI: 10.1088/1674-1056/aca148

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The easy-plane anisotropy of the Y₂Co₁₇ rare earth soft magnetic alloy has high saturation magnetization and operating frequency, and good impedance matching. Therefore, it is expected to become a kind of high-performance microwave absorbing material. In this paper, Y₂Co₁₇ alloy was prepared by a reduction-diffusion method, and its micropowder was prepared as polyurethane (PU) based composite absorbing materials (Y₂Co₁₇/PU composites). The microwave properties of composites with different volume fractions were calculated. The composites showed outstanding absorption characteristics in the range of 20-30 vol%, and the minimum reflection loss (RL) was less than -50 dB. When the volume fraction was 25%, the effective absorption bandwidth could cover the X-band at a thickness of 1.5 mm, and the Ku-band at a thickness of 1.08 mm. The absorption mechanism was analyzed by the interface reflection model. The RL absorption peak bandwidth mechanism was discussed by using the amplitude relation and calculating the effective absorption bandwidth at different thicknesses. The effective absorption bandwidth values were in good agreement with the theoretical expectation.

Nonlinear perturbation of a high-order exceptional point: Skin discrete breathers and the hierarchical power-law scaling

Hui Jiang(江慧), Enhong Cheng(成恩宏), Ziyu Zhou(周子榆), and Li-Jun Lang(郎利君)

Chin. Phys. B, 2023, 32 (8): 084203. DOI: 10.1088/1674-1056/accb47

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We study the nonlinear perturbation of a high-order exceptional point (EP) of the order equal to the system site number L in a Hatano-Nelson model with unidirectional hopping and Kerr nonlinearity. Notably, we find a class of discrete breathers that aggregate to one boundary, here named as skin discrete breathers (SDBs). The nonlinear spectrum of these SDBs shows a hierarchical power-law scaling near the EP. Specifically, the response of nonlinear energy to the perturbation is given by E_m ∝ Γ^α_m, where α_m=3^m-1 is the power with m=1,...,L labeling the nonlinear energy bands. This is in sharp contrast to the L-th root of a linear perturbation in general. These SDBs decay in a double-exponential manner, unlike the edge states or skin modes in linear systems, which decay exponentially. Furthermore, these SDBs can survive over the full range of nonlinearity strength and are continuously connected to the self-trapped states in the limit of large nonlinearity. They are also stable, as confirmed by a defined nonlinear fidelity of an adiabatic evolution from the stability analysis. As nonreciprocal nonlinear models may be experimentally realized in various platforms, such as the classical platform of optical waveguides, where Kerr nonlinearity is naturally present, and the quantum platform of optical lattices with Bose-Einstein condensates, our analytical results may inspire further exploration of the interplay between nonlinearity and non-Hermiticity, particularly on high-order EPs, and benchmark the relevant simulations.

Influences of double diffusion upon radiative flow of thin film Maxwell fluid through a stretching channel

Arshad Khan, Ishtiaq Ali, Musawa Yahya Almusawa, Taza Gul, and Wajdi Alghamdi

Chin. Phys. B, 2023, 32 (8): 084401. DOI: 10.1088/1674-1056/acc059

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This work explores the influence of double diffusion over thermally radiative flow of thin film hybrid nanofluid and irreversibility generation through a stretching channel. The nanoparticles of silver and alumina have mixed in the Maxwell fluid (base fluid). Magnetic field influence has been employed to channel in normal direction. Equations that are going to administer the fluid flow have been converted to dimension-free notations by using appropriate variables. Homotopy analysis method is used for the solution of the resultant equations. In this investigation it has pointed out that motion of fluid has declined with growth in magnetic effects, thin film thickness, and unsteadiness factor. Temperature of fluid has grown up with upsurge in Brownian motion, radiation factor, and thermophoresis effects, while it has declined with greater values of thermal Maxwell factor and thickness factor of the thin film. Concentration distribution has grown up with higher values of thermophoresis effects and has declined for augmentation in Brownian motion.

Simulations of hot electron transport in radiation-ablated plasma Suggested by editors

Bin Zhao(赵斌), Tao Tao(陶弢), Rui Yan(闫锐), and Jian Zheng(郑坚)

Chin. Phys. B, 2023, 32 (8): 085201. DOI: 10.1088/1674-1056/acc0f3

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The transport of hot electrons in inertial confinement fusion (ICF) is integrated issue due to the coupling of hydrodynamic evolution and many physical processes. A hot electron transport code is developed and coupled with the radiation hydrodynamic code MULTI1D in this study. Using the code, the slowing-down process and ablation process of the hot electron beam are simulated. The ablation pressure scaling law of hot electron beam is confirmed in our simulations. The hot electron transport is simulated in the radiation-ablated plasmas relevant to indirect-drive ICF, where the spatial profile of hot electron energy deposition is presented around the shock compressed region. It is shown that the hot electron can prominently increase the total ablation pressure in the early phase of radiation-ablated plasma. So, our study suggests that a potential-driven symmetric mechanism may occur under the irradiation of asymmetric hot electron beam. The possible degradation from the hot electron transport and preheating is also discussed.

Efficient hydrophilicity improvement of titanium surface by plasma jet in micro-hollow cathode discharge geometry Suggested by editors

Peng-Ying Jia(贾鹏英), Han-Xiao Jia(贾焓潇), Jun-Xia Ran(冉俊霞), Kai-Yue Wu(吴凯玥), Jia-Cun Wu(武珈存), Xue-Xia Pang(庞学霞), and Xue-Chen Li(李雪辰)

Chin. Phys. B, 2023, 32 (8): 085202. DOI: 10.1088/1674-1056/acbde9

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Surface hydrophilicity improvement of titanium (Ti) is of great significance for the applications of the important biomaterial. In this study, efficient hydrophilicity on the Ti surface is improved by an air plasma jet generated by a micro-hollow cathode discharge (MHCD) geometry. Elementary discharge aspects of the plasma jet and surface characteristics of the Ti surface are investigated by varying dissipated power (P_d). The results show that the plasma jet can operate in a pulsed mode or a continuous mode, depending on P_d. The plume length increases with P_d and air flow rate increasing. By optical emission spectroscopy, plasma parameters as a function of P_d are investigated. After plasma treatment, water contact angel (WCA) of the Ti sample decreases to a minimum value of 15° with P_d increasing. In addition, the surface topography, roughness, and content of chemical composition are investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM), and x-ray photoelectron spectroscopy (XPS) with P_d increasing. The results show that Ti-O bond and O-H group on the Ti surface are beneficial to the improvement of the hydrophilicity of Ti surface.

Pressure-induced phase transition and electronic structure evolution in layered semimetal HfTe₂ Suggested by editors

Mei-Guang Zhang(张美光), Lei Chen(陈磊), Long Feng(冯龙), Huan-Huan Tuo(拓换换), Yun Zhang(张云), Qun Wei(魏群), and Pei-Fang Li(李培芳)

Chin. Phys. B, 2023, 32 (8): 086101. DOI: 10.1088/1674-1056/acd2bf

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Motivated by the recent experimental work, the pressure-induced structural transition of well-known two-dimensional (2D) 1T-HfTe₂ was investigated up to 50 GPa through the advanced CALYPSO structure search technique combined with the first-principles calculations. Our calculations suggested that the 1T-HfTe₂ will first transform to C2/m phase at 3.6 GPa with a volume reduction of 7.6% and then to P$\bar{{6}}$2m phase at 9.6 GPa with a volume collapse of 4.6%. The occurrences of 3D C2/m and P$\bar{{6}}$2m phases mainly originated from the enhanced Te-Te interlayer coupling and the drastic distortions of Hf-Te polyhedrons in P$\bar{{3}}$m1 phase under compression. Concomitantly, the coordination number of Hf atoms increased from six in P$\bar{{3}}$m1 to eight in C2/m and eventually to nine in P$\bar{{6}}$2m at elevated pressure. The metallic and semimetallic nature of C2/m and P$\bar{{6}}$2m phases were characterized, and the evidence of the reinforced covalent interactions of Te-Hf and Te-Te orbitals in these two novel high-pressure phases were manifested by the atom-projected electronic DOS and Bader charge.

Initial-state dependence of phase behaviors in a dense active system

Lu Chen(陈璐), Bokai Zhang(张博凯), and Z. C. Tu(涂展春)

Chin. Phys. B, 2023, 32 (8): 086401. DOI: 10.1088/1674-1056/acca09

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There are rich emergent phase behaviors in non-equilibrium active systems. Flocking and clustering are two representative dynamic phases. The relationship between both the phases is still unclear. Herein, we numerically investigate the evolution of flocking and clustering in a system consisting of self-propelled particles with active reorientation. We consider the interplay between flocking and clustering phases with different initial configurations, and observe a domain in steady state order parameter phase diagrams sensitive to the choice of initial configurations. Specifically, by tuning the initial degree of polar ordering, either a more ordered flocking or a disordered clustering state can be observed in the steady state. These results enlighten us to manipulate emergent behaviors and collective motions of an active system, and are qualitatively different from the emergence of a new bi-stable regime observed in aligned active particles due to an explicit attraction [New J. Phys. 14 073033 (2012)].

Quantum tunneling in the surface diffusion of single hydrogen atoms on Cu(001) Suggested by editors

Xiaofan Yu(于小凡), Yangwu Tong(童洋武), and Yong Yang(杨勇)

Chin. Phys. B, 2023, 32 (8): 086801. DOI: 10.1088/1674-1056/acd2b4

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The adsorption and diffusion of hydrogen atoms on Cu(001) are studied using first-principles calculations. By taking into account the contribution of zero-point energy (ZPE), the originally identical barriers are shown to be different for H and D, which are respectively calculated to be ～ 158 meV and ～ 139 meV in height. Using the transfer matrix method (TMM), we are able to calculate the accurate probability of transmission across the barriers. The crucial role of quantum tunneling is clearly demonstrated at low-temperature region. By introducing a temperature-dependent attempting frequency prefactor, the rate constants and diffusion coefficients are calculated. The results are in agreement with the experimental measurements at temperatures from ～ 50 K to 80 K.

Modulation of CO adsorption on 4,12,2-graphyne by Fe atom doping and applied electric field

Yu Dong(董煜), Zhi-Gang Shao(邵志刚), Cang-Long Wang(王苍龙), and Lei Yang(杨磊)

Chin. Phys. B, 2023, 32 (8): 087101. DOI: 10.1088/1674-1056/acc935

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Adsorption characteristics of CO adsorbed on pristine 4,12,2-graphyne (4,12,2-G) and Fe-doped 4,12,2-graphyne (Fe-4,12,2-G) are studied by first-principles calculations. It is shown that CO is only physically adsorbed on pristine 4,12,2-G. Fe atoms can be doped into 4,12,2-G stably and lead to band gap opening. After doping, the interaction between Fe-4,12,2-G and CO is significantly enhanced and chemisorption occurs. The maximum adsorption energy reaches -1.606 eV. Meanwhile, the charge transfer between them increases from 0.009e to 0.196e. Moreover, the electric field can effectively regulate the adsorption ability of the Fe-4,12,2-G system, which is expected to achieve the capture and release of CO. Our study is helpful to promote applications of two-dimensional carbon materials in gas sensing and to provide new ideas for reversible CO sensor research.

Helicity-dependent photoconductance of the edge states in the topological insulator Bi₂Te₃ Suggested by editors

Yuchao Zhou(周宇超), Jinling Yu(俞金玲), Yonghai Chen(陈涌海), Yunfeng Lai(赖云锋), and Shuying Cheng(程树英)

Chin. Phys. B, 2023, 32 (8): 087102. DOI: 10.1088/1674-1056/acc3fb

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The helicity-dependent photoconductance of the edge states in three-dimensional topological insulator Bi₂Te₃ films is investigated. It is revealed that the helicity-dependent photoconductivity current on the left edge of the Bi₂Te₃ film shows an opposite sign with that on the right edge. In addition, the helicity-dependent photoconductivity current increases linearly with the applied longitudinal electric field, and it reverses the sign with the reversal of the electric field. As the thickness of the Bi₂Te₃ film increases, the helicity-dependent photoconductivity current also increases. Theoretical analysis suggests that the helicity-dependent photo-conductivity current may come from the intrinsic spin orbit coupling (SOC) or the SOC introduced by the chiral impurities or defects.

Rashba spin-orbit coupling induced rectified currents in monolayer graphene with exchange field and sublattice potential

Liang Chen(陈亮), Feng Li(李峰), and Xiao-Ming Ding(丁晓明)

Chin. Phys. B, 2023, 32 (8): 087103. DOI: 10.1088/1674-1056/acc932

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We investigate the effect of Rashba spin-orbit coupling (RSOC) on photoconductivities of rectified currents in monolayer graphene with exchange field and sublattice potential. The system shows that the photoconductivities of resonant shift and injection current contributions are nonzero, while the photoconductivities of non-resonant shift current contribution are zero. We find that the RSOC induces a warping term, which leads to the nonzero rectified currents. Moreover, the photoconductivities of resonant injection (shift) current contribution are (not) related to the relaxation rate. The similar behavior can be found in other Dirac materials, and our findings provide a way to tune the nonlinear transport properties of Dirac materials.

Highly anisotropic Dirac fermion and spin transportproperties in Cu-graphane

Chao Wu(吴超), Lichuan Zhang(张礼川), Lin Xia(夏霖), Dong Hao(郝东), Shiqi Li(李仕琪), Lizhi Zhang(张礼智), Yuee Xie(谢月娥), and Yuanping Chen(陈元平)

Chin. Phys. B, 2023, 32 (8): 087104. DOI: 10.1088/1674-1056/accff1

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Inspired by the successful synthesis of hHv-graphane [Nano Lett. 15 903 (2015)], a new two-dimensional (2D) Janus material Cu-graphane is proposed based on the first-principles calculations. Without the spin-orbit coupling (SOC) effect, Cu-graphane is a Dirac semimetal with a highly anisotropic Dirac cone, whose Fermi velocity ranges from 0.12×10⁵ m/s to 2.9×10⁵ m/s. The Dirac cone near the Fermi level can be well described with an extended 2D Dirac model Hamiltonian. In the presence of the SOC effect, band splitting is observed around the Fermi level, and a large intrinsic spin Hall conductivity (ISHC) with a maximum value of 346 (ħ/e) S/cm is predicted. Moreover, the spin Hall transport can be regulated by slightly adjusting the Fermi energy, e.g., grid voltage or chemical doping. Our work not only proposes a new 2D Janus material with a highly anisotropic Dirac cone and a large ISHC, but also reveals that a large ISHC may exist in some Dirac systems.

Electronic structure of cuprate-nickelate infinite-layer heterostructure Suggested by editors

Dachuan Chen(陈大川), Paul Worm, Liang Si(司良), Chunxiao Zhang(张春小), Fenglin Deng(邓凤麟), Peiheng Jiang(蒋沛恒), and Zhicheng Zhong(钟志诚)

Chin. Phys. B, 2023, 32 (8): 087105. DOI: 10.1088/1674-1056/acd368

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The discovery of superconductivity in Sr/Ca-doped infinite-layer nickelates Nd(La)NiO₂ thin films inspired extensive experimental and theoretical research. However, research on the possibilities of enhanced critical temperature by interface heterostructure is still lacking. Due to the similarities of the crystal structure and band structure of infinite-layer nickelate LaNiO₂ and cuprate CaCuO₂, we investigate the crystal, electronic and magnetic properties of LaNiO₂:CaCuO₂ heterostructure using density functional theory and dynamical mean-field theory. Our theoretical results demonstrate that, even a very weak inter-layer z-direction bond is formed, an intrinsic charge transfer between Cu-3d_x²-y² and Ni-3d_x²-y² orbitals is obtained. The weak interlayer hopping between Cu and Ni leaves a parallel band contributed by Ni/Cu-3d_x²-y² orbitals near the Fermi energy. Such an infinite-layer heterostructure with negligible interlayer interaction and robust charge transfer opens a new way for interface engineering and nickelate superconductors.

Saturation thickness of stacked SiO₂ in atomic-layer-deposited Al₂O₃ gate on 4H-SiC Suggested by editors

Zewei Shao(邵泽伟), Hongyi Xu(徐弘毅), Hengyu Wang(王珩宇), Na Ren(任娜), and Kuang Sheng(盛况)

Chin. Phys. B, 2023, 32 (8): 087106. DOI: 10.1088/1674-1056/acd5c3

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High-k materials as an alternative dielectric layer for SiC power devices have the potential to reduce interfacial state defects and improve MOS channel conduction capability. Besides, under identical conditions of gate oxide thickness and gate voltage, the high-k dielectric enables a greater charge accumulation in the channel region, resulting in a larger number of free electrons available for conduction. However, the lower energy band gap of high-k materials leads to significant leakage currents at the interface with SiC, which greatly affects device reliability. By inserting a layer of SiO₂ between the high-k material and SiC, the interfacial barrier can be effectively widened and hence the leakage current will be reduced. In this study, the optimal thickness of the intercalated SiO₂ was determined by investigating and analyzing the gate dielectric breakdown voltage and interfacial defects of a dielectric stack composed of atomic-layer-deposited Al₂O₃ layer and thermally nitride SiO₂. Current-voltage and high-frequency capacitance-voltage measurements were performed on metal-oxide-semiconductor test structures with 35 nm thick Al₂O₃ stacked on 1 nm, 2 nm, 3 nm, 6 nm, or 9 nm thick nitride SiO₂. Measurement results indicated that the current conducted through the oxides was affected by the thickness of the nitride oxide and the applied electric field. Finally, a saturation thickness of stacked SiO₂ that contributed to dielectric breakdown and interfacial band offsets was identified. The findings in this paper provide a guideline for the SiC gate dielectric stack design with the breakdown strength and the interfacial state defects considered.

Proton irradiation-induced dynamic characteristics on high performance GaN/AlGaN/GaN Schottky barrier diodes

Tao Zhang(张涛), Ruo-Han Li(李若晗), Kai Su(苏凯), Hua-Ke Su(苏华科), Yue-Guang Lv(吕跃广), Sheng-Rui Xu(许晟瑞), Jin-Cheng Zhang(张进成), and Yue Hao(郝跃)

Chin. Phys. B, 2023, 32 (8): 087301. DOI: 10.1088/1674-1056/acbded

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Dynamic characteristics of the single-crystal GaN-passivated lateral AlGaN/GaN Schottky barrier diodes (SBDs) treated with proton irradiation are investigated. Radiation-induced changes including idealized Schottky interface and slightly degraded on-resistance (R_ON) are observed under 10-MeV proton irradiation at a fluence of 10¹⁴ cm^-2. Because of the existing negative polarization charges induced at GaN/AlGaN interface, the dynamic ON-resistance (R_ON,dyn) shows negligible degradation after a 1000-s-long forward current stress of 50 mA to devices with and without being irradiated by protons. Furthermore, the normalized R_ON,dyn increases by only 14% that of the initial case after a 100-s-long bias of -600 V has been applied to the irradiated devices. The high-performance lateral AlGaN/GaN SBDs with tungsten as anode metal and in-situ single-crystal GaN as passivation layer show a great potential application in the harsh radiation environment of space.

Coherent manipulation of a tunable hybrid qubit via microwave control Suggested by editors

Si-Si Gu(顾思思), Bao-Chuan Wang(王保传), Hai-Ou Li(李海欧), Gang Cao(曹刚), and Guo-Ping Guo(郭国平)

Chin. Phys. B, 2023, 32 (8): 087302. DOI: 10.1088/1674-1056/acd0a7

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Hybrid qubits enable the hybridization of charge and spin degrees of freedom, which provides a way to realize both a relatively long coherence time and rapid qubit manipulation. Here, we use microwave driving to demonstrate the coherent operation of a tunable hybrid qubit, including X-rotation, Z-rotation, and rotation around an arbitrary axis in the X-Y panel of the Bloch sphere. Moreover, the coherence properties of the qubit and its tunability are studied. The measured coherence time of the X-rotation reaches ～ 14.3 ns. While for the Z-rotation, the maximum decoherence time is ～ 5.8 ns due to the larger sensitivity to noise. By employing the Hahn echo sequence to mitigate the influence of the low-frequency noise, we have improved the qubit coherence time from ～ 5.8 ns to ～ 15.0 ns. Our results contribute to a further understanding of the hybrid qubit and a step towards achieving high-fidelity qubit gates in the hybrid qubit.

InSe-Te van der Waals heterostructures for current rectification and photodetection Suggested by editors

Hao Wang(王昊), Guo-Yu Xian(冼国裕), Li Liu(刘丽), Xuan-Ye Liu(刘轩冶), Hui Guo(郭辉), Li-Hong Bao(鲍丽宏), Hai-Tao Yang(杨海涛), and Hong-Jun Gao(高鸿钧)

Chin. Phys. B, 2023, 32 (8): 087303. DOI: 10.1088/1674-1056/acd2b1

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As the basis of modern electronics and optoelectronics, high-performance, multi-functional p-n junctions have manifested and occupied an important position. However, the performance of the silicon-based p-n junctions declines gradually as the thickness approaches to few nanometers. The heterojunction constructed by two-dimensional (2D) materials can significantly improve the device performance compared with traditional technologies. Here, we report the InSe-Te type-II van der Waals heterostructures with rectification ratio up to 1.56×10⁷ at drain-source voltage of ±2 V. The p-n junction exhibits a photovoltaic and photoelectric effect under different laser wavelengths and densities and has high photoresponsivity and detectivity under low irradiated light power. Moreover, the heterojunction has stable photo/dark current states and good photoelectric switching characteristics. Such high-performance heterostructured device based on 2D materials provides a new way for futural electronic and optoelectronic devices.

Critical behavior in the itinerant ferromagnet SmMn₂Ge₂

Qingyi Hou(侯清漪), Meng Song(宋猛), Xitong Xu(许锡童), Yihao Wang(王宜豪), Chao Dong(董超), Yinfa Feng(冯寅发), Miao He(何苗), Yonglai Liu(刘永来), Liang Cao(曹亮), Junfeng Wang(王俊峰), Zhe Qu(屈哲), and Yimin Xiong(熊奕敏)

Chin. Phys. B, 2023, 32 (8): 087501. DOI: 10.1088/1674-1056/accb49

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Transition metal and rare earth intermetallics have been a fertile playground for research of various quantum states. We report detailed magnetic studies on SmMn₂Ge₂, an anisotropic itinerant magnet with multiple magnetic phases. The critical behavior of the ferromagnetic phase transition is investigated by employing the modified Arrott plot with the Kouvel-Fisher method. The critical temperature TC is determined to be around 342.7 K with critical exponents of β =0.417 and γ=1.122, and the interaction function is found to be J(r)～ r^-4.68, suggesting the coexistence of long-range and short-range magnetic interactions. Our results contribute to the understanding of complex magnetism in SmMn₂Ge₂, which may provide fundamental guidance in future spintronic applications.

Out-of-plane weak ferromagnetism at room temperaturein lattice-distortion non-collinear antiferromagnet of single-crystal Mn₃Sn

Bo-Xi Zhang(张博熙), Ping Song(宋平), Shan-Shan Deng(邓珊珊), Li Lou(娄理), and Sen Yao(姚森)

Chin. Phys. B, 2023, 32 (8): 087502. DOI: 10.1088/1674-1056/acca0b

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Out-of-plane weak ferromagnetic (OWFM) spin arrangements with topological properties can realize a series of interesting physical properties. However, this spin structure tends to exist at low temperatures. The OWFM structure can also be induced at room temperature by hydrostatic pressure, whereas this isotropic approach tends to form helical AFM structures. We report the OWFM spin arrangement in single crystal Mn₃Sn by an anisotropic strategy of high-stressconstrained compression deformation at room temperature. Both experimental and theoretical simulation results show that the alignment of the OWFM spin structure is due to the distortion of the atomic scale caused by the strain energy during deformation. The OWFM spin arrangement can significantly change the magnetic property of Mn₃Sn. As a result, the remanent magnetization M_r for the deformed sample (0.056 μ_B/f.u.) is about eleven times that for the pre-deformed sample (0.005 μ_B/f.u.), and the coercivity (H_c) increases from 0 kOe (pre-deformed sample) to 6.02 kOe (deformed sample). Our findings provide a way to generate the OWFM spin structure at room temperature and may give fresh ideas for creating antiferromagnetic materials with excellent physical properties.

Hysteresis loss free soft magnetic ferrites based on Larmor precession

Shuang-Jiu Feng(冯双久), Xin-Li Zhao(赵幸丽), Shou-Jin Zhu(朱守金),Qing-Rong Lv(吕庆荣), Xu-Cai Kan(阚绪材), and Xian-Song Liu(刘先松)

Chin. Phys. B, 2023, 32 (8): 087503. DOI: 10.1088/1674-1056/acbdec

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A big enough transverse magnetic field applied to soft magnetic ferrite toroid can magnetize the ferrite to a saturation level in transverse direction and almost completely suppresses magnetic domain structures in the ferrite, the response to the longitudinal alternating electromagnetic field changes from the original domain wall displacements and spin rotations to the precession of magnetization around the transverse field, and the hysteresis loss disappears in the ferrites. Both theoretical and experimental results indicate that the permeability and magnetic loss in the ferrite can be controlled by adjusting the transverse magnetic field. A higher Q value with relatively low permeability can be achieved by increasing the transverse field, which ensures that the ferrite can be operated at high frequencies, with magnetic loss being very low.

Low-temperature ferromagnetism in tensile-strained LaCoO_2.5 thin film Suggested by editors

Yang-Yang Fan(范洋洋), Jing Wang(王晶), Feng-Xia Hu(胡凤霞), Bao-He Li(李宝河), Ai-Cong Geng(耿爱丛), Zhuo Yin(殷卓), Cheng Zhang(张丞), Hou-Bo Zhou(周厚博), Meng-Qin Wang(王梦琴), Zi-Bing Yu(尉紫冰), and Bao-Gen Shen(沈保根)

Chin. Phys. B, 2023, 32 (8): 087504. DOI: 10.1088/1674-1056/acafdc

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The origin of ferromagnetism in epitaxial strained LaCoO_3-x films has long been controversial. Here, we investigated the magnetic behavior of a series of oxygen vacancy-ordered LaCoO_3-x films on different substrates. Obvious ferromagnetism was observed in perovskite LaCoO₃/LSAT (LSAT = (LaAlO₃)_0.3(SrAlTaO₆)_0.7) and LaCoO₃/SrTiO₃ films, while LaCoO₃/LaAlO₃ films showed weak ferromagnetic behavior. Meanwhile, LaCoO_2.67 films exhibited antiferromagnetic behavior. An unexpected low-temperature ferromagnetic phenomenon with a Curie temperature of ～ 83 K and a saturation magnetization of ～ 1.2 μ_B/Co was discovered in 15 nm thick LaCoO_2.5/LSAT thin films, which is probably related to the change in the interface CoO₆ octahedron rotation pattern. Meanwhile, the observed ferromagnetism gradually disappeared as the thickness of the film increased, indicating a relaxation of tensile strain. Analysis suggests that the rotation and rhombohedral distortion of the CoO₆ octahedron weakened the crystal field splitting and promoted the generation of the ordered high-spin state of Co²⁺. Thus the super-exchange effect between Co²⁺ (high spin state), Co²⁺ (low spin state) and Co²⁺(high spin state) produced a low-temperature ferromagnetic behavior. However, compressive-strained LaCoO_2.5 film on a LaAlO₃ substrate showed normal anti-ferromagnetic behavior. These results demonstrate that both oxygen vacancies and tensile strain are correlated with the emergent magnetic properties in epitaxial LaCoO_3-x films and provide a new perspective to regulate the magnetic properties of transition oxide thin films.

Unusual magnetic relaxation in a single-molecule magnet with toroidal magnetic moments Suggested by editors

Dan Su(苏丹), Yi-Quan Zhang(张义权), En-Ke Liu(刘恩克), and Yang Sun(孙阳)

Chin. Phys. B, 2023, 32 (8): 087505. DOI: 10.1088/1674-1056/acd622

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We report the synthesis and characterization of a single-molecule magnet composed of triangular clusters of dysprosium ions. The structural study shows that the symmetry changes from one polar point group (mm2) at room temperature to another polar point group (m) at low temperature. Magnetic studies and theory calculations illustrate that the vortex distribution of magnetic dipoles in the triangular dysprosium clusters forms a toroidal magnetic moment. Interestingly, the analysis of AC magnetic susceptibility reveals the coexistence of three distinct magnetic relaxation processes, corresponding to the Raman, Orbach, and QTM relaxation pathways, respectively. The sum of three modified Debye functions is successfully used to describe the multiple relaxation behavior.

Magnetic and electronic properties of bulk and two-dimensional FeBi₂Te₄: A first-principles study Suggested by editors

Qianqian Wang(王倩倩), Jianzhou Zhao(赵建洲), Weikang Wu(吴维康), Yinning Zhou(周胤宁), Qile Li, Mark T. Edmonds, and Shengyuan A. Yang(杨声远)

Chin. Phys. B, 2023, 32 (8): 087506. DOI: 10.1088/1674-1056/acd522

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Layered magnetic materials, such as MnBi₂Te₄, have drawn much attention owing to their potential for realizing two-dimensional (2D) magnetism and possible topological states. Recently, FeBi₂Te₄, which is isostructural to MnBi₂Te₄, has been synthesized in experiments, but its detailed magnetic ordering and band topology have not been clearly understood yet. Here, based on first-principles calculations, we investigate the magnetic and electronic properties of FeBi₂Te₄ in bulk and 2D forms. We show that different from MnBi₂Te₄, the magnetic ground states of bulk, single-layer, and bilayer FeBi₂Te₄ all favor a 120° noncollinear antiferromagnetic ordering, and they are topologically trivial narrow-gap semiconductors. For the bilayer case, we find that a quantum anomalous Hall effect with a unit Chern number is realized in the ferromagnetic state, which may be achieved in experiment by an external magnetic field or by magnetic proximity coupling. Our work clarifies the physical properties of the new material system of FeBi₂Te₄ and reveals it as a potential platform for studying magnetic frustration down to 2D limit as well as quantum anomalous Hall effect.

Charge trapping effect at the interface of ferroelectric/interlayer in the ferroelectric field effect transistor gate stack Suggested by editors

Xiaoqing Sun(孙晓清), Hao Xu(徐昊), Junshuai Chai(柴俊帅), Xiaolei Wang(王晓磊), and Wenwu Wang(王文武)

Chin. Phys. B, 2023, 32 (8): 087701. DOI: 10.1088/1674-1056/acd524

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We study the charge trapping phenomenon that restricts the endurance of n-type ferroelectric field-effect transistors (FeFETs) with metal/ferroelectric/interlayer/Si (MFIS) gate stack structure. In order to explore the physical mechanism of the endurance failure caused by the charge trapping effect, we first establish a model to simulate the electron trapping behavior in n-type Si FeFET. The model is based on the quantum mechanical electron tunneling theory. And then, we use the pulsed I_d-V_g method to measure the threshold voltage shift between the rising edges and falling edges of the FeFET. Our model fits the experimental data well. By fitting the model with the experimental data, we get the following conclusions. (i) During the positive operation pulse, electrons in the Si substrate are mainly trapped at the interface between the ferroelectric (FE) layer and interlayer (IL) of the FeFET gate stack by inelastic trap-assisted tunneling. (ii) Based on our model, we can get the number of electrons trapped into the gate stack during the positive operation pulse. (iii) The model can be used to evaluate trap parameters, which will help us to further understand the fatigue mechanism of FeFET.

Anomalous photoluminescence enhancement and resonance charge transfer in type-II 2D lateral heterostructures Suggested by editors

Chun-Yan Zhao(赵春艳), Sha-Sha Li(李莎莎), and Yong Yan(闫勇)

Chin. Phys. B, 2023, 32 (8): 087801. DOI: 10.1088/1674-1056/acc1d1

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Type-II band alignment can realize the efficient charge transfer and separation at the semiconductor heterointerface, which results in photoluminescence (PL) quenching. Recently, several researches demonstrated great enhancement of localized PL at the interface of type-II two-dimensional (2D) heterostructure. However, the dominant physical mechanism of this enhanced PL emission has not been well understood. In this work, we symmetrically study the exciton dynamics of type-II lateral heterostructures of monolayer MoS₂ and WS₂ at room temperatures. The strong PL enhancement along the one-dimensional (1D) heterointerface is associated with the trion emission of the WS₂ shell, while a dramatic PL quenching of neutral exciton is observed on the MoS₂ core. The enhanced quantum yield of WS₂ trion emission can be explained by charge-transfer-enhanced photoexcited carrier dynamics, which is facilitated by resonance hole transfer from MoS₂ side to WS₂ side. This work sheds light on the 1D exciton photophysics in lateral heterostructures, which has the potential to lead to new concepts and applications of optoelectronic device.

Magneto-optical Kerr and Faraday effects in bilayer antiferromagnetic insulators

Wan-Qing Zhu(朱婉情) and Wen-Yu Shan(单文语)

Chin. Phys. B, 2023, 32 (8): 087802. DOI: 10.1088/1674-1056/acd68a

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Control and detection of antiferromagnetic topological materials are challenging since the total magnetization vanishes. Here we investigate the magneto-optical Kerr and Faraday effects in bilayer antiferromagnetic insulator MnBi₂Te₄. We find that by breaking the combined mirror symmetries with either perpendicular electric field or external magnetic moment, Kerr and Faraday effects occur. Under perpendicular electric field, antiferromagnetic topological insulators (AFMTI) show sharp peaks at the interband transition threshold, whereas trivial insulators show small adjacent positive and negative peaks. Gate voltage and Fermi energy can be tuned to reveal the differences between AFMTI and trivial insulators. We find that AFMTI with large antiferromagnetic order can be proposed as a pure magneto-optical rotator due to sizable Kerr (Faraday) angles and vanishing ellipticity. Under external magnetic moment, AFMTI and trivial insulators are significantly different in the magnitude of Kerr and Faraday angles and ellipticity. For the qualitative behaviors, AFMTI shows distinct features of Kerr and Faraday angles when the spin configurations of the system change. These phenomena provide new possibilities to optically detect and manipulate the layered topological antiferromagnets.

High performance trench diamond junction barrier Schottky diode with a sidewall-enhanced structure

Ying Zhu(朱盈), Wang Lin(林旺), Dong-Shuai Li(李东帅), Liu-An Li(李柳暗), Xian-Yi Lv(吕宪义), Qi-Liang Wang(王启亮), and Guang-Tian Zou(邹广田)

Chin. Phys. B, 2023, 32 (8): 088101. DOI: 10.1088/1674-1056/acc2ae

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The trench diamond junction barrier Schottky (JBS) diode with a sidewall enhanced structure is designed by Silvaco simulation. Comparing with the conventional trench JBS diode, Schottky contact areas are introduced on the sidewall of the trench beside the top cathode. The sidewall Schottky contact weakens the junction field-effect transistor effect between the trenches to realize a low on-resistance and a high Baliga's figure of merit (FOM) value. In addition, the existence of the n-type diamond helps to suppress the electric field crowding effect and enhance the reverse breakdown voltage. With the optimal parameters of device structure, a high Baliga's FOM value of 2.28 GW/cm² is designed. Therefore, the proposed sidewall-enhanced trench JBS diode is a promising component for the applications in diamond power electronics.

Effects of Cu and Co additions on the crystallization and magnetic properties of FeNbB alloy Suggested by editors

Wan-Qiu Yu(于万秋), Bo Tian(田博), Ping-Li Zhang(张平丽), Jia-Hui Wang(王佳慧), and Zhong Hua(华中)

Chin. Phys. B, 2023, 32 (8): 088102. DOI: 10.1088/1674-1056/acd525

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The nanocrystalline-forming element Cu and magnetic element Co are commonly used as additive elements to tune the structure and improve the properties of alloys. In this study, four kinds of amorphous alloys, Fe₇₂Nb₁₂B₁₆, Fe₇₂Nb₁₂B₁₅Cu₁, Fe₃₆Co₃₆Nb₁₂B₁₆, and Fe₃₆Co₃₆Nb₁₂B₁₅Cu₁, were prepared by melt-spinning and annealed at various temperatures to investigate the effects of Cu and Co additions, individually and in combination, on the crystallization and magnetic properties of Fe₇₂Nb₁₂B₁₆ alloy. The four kinds of alloys exhibited different crystallization behaviors with different primary crystallization phases observed. For the Fe₇₂Nb₁₂B₁₆ alloy, only the α-Mn-type metastable phase formed after annealing. The addition of 1 at.% Cu and 36 at.% Co led to the observation of the α-Mn-type and β-Mn-type metastable phases, respectively, and a reduction in the crystallization volume fraction in the metastable phase. The Fe₃₆Co₃₆Nb₁₂B₁₅Cu₁ alloy only exhibited α-Fe(Co) phase as a primary phase, and the addition of both Cu and Co completely inhibited the precipitation of the metastable phase. Cu clusters were found in energy dispersive spectroscopy elemental maps. Compared with other alloys, Fe₃₆Co₃₆Nb₁₂B₁₅Cu₁ alloy with both Cu and Co exhibited a lower coercivity (H_c) below 973 K.

On the origin of carrier localization in AlInAsSb digital alloy Suggested by editors

Wen-Guang Zhou(周文广), Dong-Wei Jiang(蒋洞微), Xiang-Jun Shang(尚向军), Dong-Hai Wu(吴东海), Fa-Ran Chang(常发冉), Jun-Kai Jiang(蒋俊锴), Nong Li(李农), Fang-Qi Lin(林芳祁), Wei-Qiang Chen(陈伟强), Hong-Yue Hao(郝宏玥), Xue-Lu Liu(刘雪璐), Ping-Heng Tan(谭平恒), Guo-Wei Wang(王国伟), Ying-Qiang Xu(徐应强), and Zhi-Chuan Niu(牛智川)

Chin. Phys. B, 2023, 32 (8): 088501. DOI: 10.1088/1674-1056/accf7b

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We compared the photoluminescence (PL) properties of AlInAsSb digital alloy samples with different periods grown on GaSb (001) substrates by molecular beam epitaxy. Temperature-dependent S-shape behavior is observed and explained using a thermally activated redistribution model within a Gaussian distribution of localized states. There are two different mechanisms for the origin of the PL intensity quenching for the AlInAsSb digital alloy. The high-temperature activation energy E₁ is positively correlated with the interface thickness, whereas the low-temperature activation energy E₂ is negatively correlated with the interface thickness. A quantitative high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) study shows that the interface quality improves as the interface thickness increases. Our results confirm that E₁ comes from carrier trapping at a state in the InSb interface layer, while E₂ originates from the exciton binding energy due to the roughness of the AlAs interface layer.

Paradoxical roles of inhibitory autapse and excitatory synapse in formation of counterintuitive anticipated synchronization

Xue-Li Ding(丁学利), Hua-Guang Gu(古华光), Yu-Ye Li(李玉叶), and Yan-Bing Jia(贾雁兵)

Chin. Phys. B, 2023, 32 (8): 088701. DOI: 10.1088/1674-1056/acc450

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Different from the common delayed synchronization (DS) in which response appears after stimulation, anticipated synchronization (AS) in unidirectionally coupled neurons denotes a counterintuitive phenomenon in which response of the receiver neuron appears before stimulation of the sender neuron, showing an interesting function of brain to anticipate the future. The dynamical mechanism for the AS remains unclear due to complex dynamics of inhibitory and excitatory modulations. In this article, the paradoxical roles of excitatory synapse and inhibitory autapse in the formation of AS are acquired. Firstly, in addition to the common roles such that inhibitory modulation delays and excitatory modulation advances spike, paradoxical roles of excitatory stimulation to delay spike via type-Ⅱ phase response and of inhibitory autapse to advance spike are obtained in suitable parameter regions, extending the dynamics and functions of the excitatory and inhibitory modulations. Secondly, AS is related to the paradoxical roles of the excitatory and inhibitory modulations, presenting deep understandings to the AS. Inhibitory autapse induces spike of the receiver neuron advanced to appear before that of the sender neuron at first, and then excitatory synapse plays a delay role to prevent the spike further advanced, resulting in the AS as the advance and delay effects realize a dynamic balance. Lastly, inhibitory autapse with strong advance, middle advance, and weak advance and delay effects induce phase drift (spike of the receiver neuron advances continuously), AS, and DS, respectively, presenting comprehensive relationships between AS and other behaviors. The results present potential measures to modulate AS related to brain function.

Exploring unbinding mechanism of drugs from SERT via molecular dynamics simulation and its implication in antidepressants Suggested by editors

Xin-Guan Tan(谭新官), Xue-Feng Liu(刘雪峰), Ming-Hui Pang(庞铭慧), Yu-Qing Wang(王雨晴), and Yun-Jie Zhao(赵蕴杰)

Chin. Phys. B, 2023, 32 (8): 088702. DOI: 10.1088/1674-1056/acd687

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The human serotonin transporter (SERT) terminates neurotransmission by removing serotonin from the synaptic cleft, which is an essential process that plays an important role in depression. In addition to natural substrate serotonin, SERT is also the target of the abused drug cocaine and, clinically used antidepressants, escitalopram, and paroxetine. To date, few studies have attempted to investigate the unbinding mechanism underlying the orthosteric and allosteric modulation of SERT. In this article, the conserved property of the orthosteric and allosteric sites (S1 and S2) of SERT was revealed by combining the high resolutions of x-ray crystal structures and molecular dynamics (MD) simulations. The residues Tyr95 and Ser438 located within the S1 site, and Arg104 located within the S2 site in SERT illustrate conserved interactions (hydrogen bonds and hydrophobic interactions), as responses to selective serotonin reuptake inhibitors. Van der Waals interactions were keys to designing effective drugs inhibiting SERT and further, electrostatic interactions highlighted escitalopram as a potent antidepressant. We found that cocaine, escitalopram, and paroxetine, whether the S1 site or the S2 site, were more competitive. According to this potential of mean force (PMF) simulations, the new insights reveal the principles of competitive inhibitors that lengths of trails from central SERT to an opening were ～ 18 Å for serotonin and ～ 22 Å for the above-mentioned three drugs. Furthermore, the distance between the natural substrate serotonin and cocaine (or escitalopram) at the allosteric site was ～ 3 Å. Thus, it can be inferred that the potent antidepressants tended to bind at deeper positions of the S1 or the S2 site of SERT in comparison to the substrate. Continuing exploring the processes of unbinding four ligands against the two target pockets of SERT, this study observed a broad pathway in which serotonin, cocaine, escitalopram (at the S1 site), and paroxetine all were pulled out to an opening between MT1b and MT6a, which may be helpful to understand the dissociation mechanism of antidepressants.

A kinetic description of the impact of agent competence and psychological factors on investment decision-making

Chunhua Hu(胡春华) and Hongjing Chen(陈弘婧)

Chin. Phys. B, 2023, 32 (8): 088901. DOI: 10.1088/1674-1056/accb4a

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The kinetic theory is employed to analyze influence of agent competence and psychological factors on investment decision-making. We assume that the wealth held by agents in the financial market is non-negative, and agents set their own investment strategies. The herding behavior is considered when analyzing the impact of an agent's psychological factors on investment decision-making. A nonlinear Boltzmann model containing herding behavior, agent competence and irrational behavior is employed to investigate investment decision-making. To characterize the agent's irrational behavior, we utilize a value function which includes current and ideal-investment decisions to describe the agent's irrational behavior. Employing the asymptotic procedure, we obtain the Fokker-Planck equation from the Boltzmann equation. Numerical results and the stationary solution of the obtained Fokker-Planck equation illustrate how herding behavior, agent competence, psychological factors, and irrational behavior affect investment decision-making, i.e., herding behavior has both advantages and disadvantages for investment decision-making, and the agent's competence to invest helps the agent to increase income and to reduce loss.

Erratum to “Relativistic solutions for diatomic molecules subject to pseudoharmonic oscillator in arbitrary dimensions”

Sami Ortakaya

Chin. Phys. B, 2023, 32 (8): 089901. DOI: 10.1088/1674-1056/ace356

Abstract ( 146 )

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Klein-Gordon equation with pseudoharmonic oscillator has been corrected through physical acceptable solutions. In a way, we correct the energy spectra related to its behavior versus potential parameter D_e.

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