Chin. Phys. B

A thermal conductivity switch via the reversible 2H-1T' phase transition in monolayer MoTe₂

Dingbo Zhang(张定波), Weijun Ren(任卫君), Ke Wang(王珂), Shuai Chen(陈帅),Lifa Zhang(张力发), Yuxiang Ni(倪宇翔), and Gang Zhang(张刚)

Chin. Phys. B, 2023, 32 (5): 050505. DOI: 10.1088/1674-1056/acbaf0

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The two-dimensional (2D) material-based thermal switch is attracting attention due to its novel applications, such as energy conversion and thermal management, in nanoscale devices. In this paper, we observed that the reversible 2H-1T' phase transition in MoTe₂ is associated with about a fourfold/tenfold change in thermal conductivity along the X/Y direction by using first-principles calculations. This phenomenon can be profoundly understood by comparing the Mo-Te bonding strength between the two phases. The 2H-MoTe₂ has one stronger bonding type, while 1T'-MoTe₂ has three weaker types of bonds, suggesting bonding inhomogeneity in 1T'-MoTe₂. Meanwhile, the bonding inhomogeneity can induce more scattering of vibration modes. The weaker bonding indicates a softer structure, resulting in lower phonon group velocity, a shorter phonon relaxation lifetime and larger Grüneisen constants. The impact caused by the 2H to 1T' phase transition in MoTe₂ hinders the propagation of phonons, thereby reducing thermal conductivity. Our study describes the possibility for the provision of the MoTe₂-based controllable and reversible thermal switch device.

Thermal transport properties of two-dimensional boron dichalcogenides from a first-principles and machine learning approach

Zhanjun Qiu(邱占均), Yanxiao Hu(胡晏箫), Ding Li(李顶), Tao Hu(胡涛), Hong Xiao(肖红),Chunbao Feng(冯春宝), and Dengfeng Li(李登峰)

Chin. Phys. B, 2023, 32 (5): 054402. DOI: 10.1088/1674-1056/acb9e6

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The investigation of thermal transport is crucial to the thermal management of modern electronic devices. To obtain the thermal conductivity through solution of the Boltzmann transport equation, calculation of the anharmonic interatomic force constants has a high computational cost based on the current method of single-point density functional theory force calculation. The recent suggested machine learning interatomic potentials (MLIPs) method can avoid these huge computational demands. In this work, we study the thermal conductivity of two-dimensional MoS$_{2}$-like hexagonal boron dichalcogenides (H-B$_{2}{VI}_{2}$; ${VI} = {\rm S}$, Se, Te) with a combination of MLIPs and the phonon Boltzmann transport equation. The room-temperature thermal conductivity of H-B$_{2}$S$_{2}$ can reach up to 336 W$\cdot $m$^{-1}\cdot $K$^{-1}$, obviously larger than that of H-B$_{2}$Se$_{2}$ and H-B$_{2}$Te$_{2}$. This is mainly due to the difference in phonon group velocity. By substituting the different chalcogen elements in the second sublayer, H-B$_{2}{VI}{VI}^\prime $ have lower thermal conductivity than H-B$_{2}{VI}_{2}$. The room-temperature thermal conductivity of B$_{2}$STe is only 11% of that of H-B$_{2}$S$_{2}$. This can be explained by comparing phonon group velocity and phonon relaxation time. The MLIP method is proved to be an efficient method for studying the thermal conductivity of materials, and H-B$_{2}$S$_{2}$-based nanodevices have excellent thermal conduction.

Impeded thermal transport in aperiodic BN/C nanotube superlattices due to phonon Anderson localization

Luyi Sun(孙路易), Fangyuan Zhai(翟方园), Zengqiang Cao(曹增强), Xiaoyu Huang(黄晓宇), Chunsheng Guo(郭春生), Hongyan Wang(王红艳), and Yuxiang Ni(倪宇翔)

Chin. Phys. B, 2023, 32 (5): 056301. DOI: 10.1088/1674-1056/acb9e7

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Anderson localization of phonons is a kind of phonon wave effect, which has been proved to occur in many structures with disorders. In this work, we introduced aperiodicity to boron nitride/carbon nanotube superlattices (BN/C NT SLs), and used molecular dynamics to calculate the thermal conductivity and the phonon transmission spectrum of the models. The existence of phonon Anderson localization was proved in this quasi one-dimensional structure by analyzing the phonon transmission spectra. Moreover, we introduced interfacial mixing to the aperiodic BN/C NT SLs and found that the coexistence of the two disorder entities (aperiodicity and interfacial mixing) can further decrease the thermal conductivity. In addition, we also showed that anharmonicity can destroy phonon localization at high temperatures. This work provides a reference for designing thermoelectric materials with low thermal conductivity by taking advantage of phonon localization.

Lattice thermal conductivity switching via structural phase transition in ferromagnetic VI₃

Chao Wu(吴超) and Chenhan Liu(刘晨晗)

Chin. Phys. B, 2023, 32 (5): 056502. DOI: 10.1088/1674-1056/acb764

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The realization of reversible thermal conductivity through ferromagnetic ordering can improve the heat management and energy efficiency in magnetic materials-based devices. VI$_{3}$, as a new layered ferromagnetic semiconductor, exhibits a structural phase transition from monoclinic ($C2/m$) to rhombohedral ($R\bar{3}$) phase as temperature decreases, making it a suitable platform to investigate thermal switching in magnetic phase transition materials. This work reveals that the thermal switching ratio of VI$_{3}$ can reach 3.9 along the $a$-axis. Mechanical properties analysis indicates that the $C2/m$ structure is stiffer than the $R\bar{3}$ one, causing the larger phonon velocity in $C2/m$ phase. Moreover, due to the fewer phonon branches in $C2/m$ phase, the number of phonon-phonon scattering channels in $C2/m$ phase is smaller compared to that of $R\bar{3}$ phase. Both the larger phonon velocity and the longer phonon lifetime lead to larger lattice thermal conductivity in $C2/m$ phase. This study uncovers the mechanical and thermal properties of VI$_{3}$, which provides useful guides for designing magnetic materials-based devices such as thermal switch.

Reconstruction and stability of Fe₃O₄(001) surface: An investigation based on particle swarm optimization and machine learning

Hongsheng Liu(柳洪盛), Yuanyuan Zhao(赵圆圆), Shi Qiu(邱实), Jijun Zhao(赵纪军), and Junfeng Gao(高峻峰)

Chin. Phys. B, 2023, 32 (5): 056802. DOI: 10.1088/1674-1056/acb9e4

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Magnetite nanoparticles show promising applications in drug delivery, catalysis, and spintronics. The surface of magnetite plays an important role in these applications. Therefore, it is critical to understand the surface structure of Fe₃O₄ at atomic scale. Here, using a combination of first-principles calculations, particle swarm optimization (PSO) method and machine learning, we investigate the possible reconstruction and stability of Fe₃O₄(001) surface. The results show that besides the subsurface cation vacancy (SCV) reconstruction, an A layer with Fe vacancy (A-layer-V_Fe) reconstruction of the (001) surface also shows very low surface energy especially at oxygen poor condition. Molecular dynamics simulation based on the iron-oxygen interaction potential function fitted by machine learning further confirms the thermodynamic stability of the A-layer-V_Fe reconstruction. Our results are also instructive for the study of surface reconstruction of other metal oxides.

Machine learning of the Γ-point gap and flat bands of twisted bilayer graphene at arbitrary angles

Xiaoyi Ma(马宵怡), Yufeng Luo(罗宇峰), Mengke Li(李梦可), Wenyan Jiao(焦文艳), Hongmei Yuan(袁红梅), Huijun Liu(刘惠军), and Ying Fang(方颖)

Chin. Phys. B, 2023, 32 (5): 057306. DOI: 10.1088/1674-1056/acb2c3

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The novel electronic properties of bilayer graphene can be fine-tuned via twisting, which may induce flat bands around the Fermi level with nontrivial topology. In general, the band structure of such twisted bilayer graphene (TBG) can be theoretically obtained by using first-principles calculations, tight-binding method, or continuum model, which are either computationally demanding or parameters dependent. In this work, by using the sure independence screening sparsifying operator method, we propose a physically interpretable three-dimensional (3D) descriptor which can be utilized to readily obtain the Γ-point gap of TBG at arbitrary twist angles and different interlayer spacings. The strong predictive power of the descriptor is demonstrated by a high Pearson coefficient of 99% for both the training and testing data. To go further, we adopt the neural network algorithm to accurately probe the flat bands of TBG at various twist angles, which can accelerate the study of strong correlation physics associated with such a fundamental characteristic, especially for those systems with a larger number of atoms in the unit cell.

Designing radiative cooling metamaterials for passive thermal management by particle swarm optimization

Shenshen Yan(闫申申), Yan Liu(刘岩), Zi Wang(王子), Xiaohua Lan(兰晓华), Yi Wang(汪毅), and Jie Ren(任捷)

Chin. Phys. B, 2023, 32 (5): 057802. DOI: 10.1088/1674-1056/acc061

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The passive radiative cooling technology shows a great potential application on reducing the enormous global energy consumption. The multilayer metamaterials could enhance the radiative cooling performance. However, it is a challenge to design the radiative cooler. In this work, based on the particle swarm optimization (PSO) evolutionary algorithm, we develop an intelligent workflow in designing photonic radiative cooling metamaterials. Specifically, we design two 10-layer ${\rm SiO_2}$ radiative coolers doped by cylindrical ${\rm MgF_2}$ or air impurities, possessing high emissivity within the selective (8-13 μm) and broadband (8-25 μm) atmospheric transparency windows, respectively. Our two kinds of coolers demonstrate power density as high as 119 W/m$^2$ and 132 W/m$^2$ at the room temperature (300 K). Our scheme does not rely on the usage of special materials, forming high-performing metamaterials with conventional poor-performing components. This significant improvement of the emission spectra proves the effectiveness of our inverse design algorithm in boosting the discovery of high-performing functional metamaterials.

Stress effect on lattice thermal conductivity of anode material NiNb₂O₆ for lithium-ion batteries

Ao Chen(陈奥), Hua Tong(童话), Cheng-Wei Wu(吴成伟), Guofeng Xie(谢国锋), Zhong-Xiang Xie(谢忠祥), Chang-Qing Xiang(向长青), and Wu-Xing Zhou(周五星)

Chin. Phys. B, 2023, 32 (5): 058201. DOI: 10.1088/1674-1056/acaa2d

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The thermal transport properties of NiNb$_{2}$O$_{6}$ as anode material for lithium-ion battery and the effect of strain were studied by machine learning interatomic potential combined with Boltzmann transport equation. The results show that the lattice thermal conductivity of NiNb$_{2}$O$_{6}$ along the three crystal directions [100], [010], and [001] are 0.947 W$\cdot$m$^{-1}\cdot$K$^{-1}$, 0.727 W$\cdot$m$^{-1}\cdot$K$^{-1}$, and 0.465 W$\cdot$m$^{-1}\cdot$K$^{-1}$, respectively, indicating the anisotropy of the lattice thermal conductivity of NiNb$_{2}$O$_{6}$. This anisotropy of the lattice thermal conductivity stems from the significant difference of phonon group velocities in different crystal directions of NiNb$_{2}$O$_{6}$. When the tensile strain is applied along the [001] crystal direction, the lattice thermal conductivity in all three directions decreases. However, when the compressive strain is applied, the lattice thermal conductivity in the [100] and [010] crystal directions is increased, while the lattice thermal conductivity in the [001] crystal direction is abnormally reduced due to the significant inhibition of compressive strain on the group velocity. These indicate that the anisotropy of thermal conductivity of NiNb$_{2}$O$_{6}$ can be enhanced by the compressive strain, and reduced by the tensile strain.

Theoretical study of electron-impact broadening for highly charged Ar XV ion lines

Chao Wu(吴超), Xiang Gao(高翔), Yu-Hao Zhu(朱宇豪), Xiao-Ying Han(韩小英), Bin Duan(段斌),Ju Meng(孟举), Song-Bin Zhang(张松斌), Jun Yan(颜君), Yong Wu(吴勇), and Jian-Guo Wang(王建国)

Chin. Phys. B, 2023, 32 (5): 053101. DOI: 10.1088/1674-1056/acb769

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Spectral line widths produced by collisions between charged particles and emitters are of special interest for precise plasma spectroscopy. The highly charged Ar XV ion is demonstrated to have strong intrashell electron interactions, which manifest as an atomic system with many resonance structures, due to the quasi-degeneracy of orbital energies. In this paper we use the relativistic R-matrix method to investigate the electron-impact broadening of highly charged Ar XV ion spectral lines under the impact approximation. It is found that the results considering resonance structures are significantly different from those of the distorted wave approach. Furthermore, we propose a new empirical formula with a correction term to take into account the effect of resonances for electron-impact widths over a relatively wide range of plasma conditions. The corresponding fitting parameters of the new empirical formula for all 47 calculated transitions are also given with an estimated accuracy within 1%, which should be convenient for practical applications. The dataset that supported the findings of this study is available in Science Data Bank, with the link https://doi.org/10.57760/sciencedb.j00113.00101.

Asymmetry parameters in single ionization of He, Ne by XUV pulses

Jian-Ting Lei(雷建廷), Xuan Yu(余璇), Guo-Qiang Shi(史国强), Chen-Yu Tao(陶琛玉), Shao-Hua Sun(孙少华), Shun-Cheng Yan(闫顺成), Xin-Wen Ma(马新文), Jing-Jie Ding(丁晶洁), and Shao-Feng Zhang(张少锋)

Chin. Phys. B, 2023, 32 (5): 053205. DOI: 10.1088/1674-1056/aca6d9

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Fully differential cross-sections of single ionization of He and Ne atoms are studied by linearly polarized extreme ultraviolet (XUV) photons in the energy range of 22.1 eV-43.7 eV, using a reaction microscope. Photoelectron angular distributions and the $\beta $ asymmetry parameters for He 1s$^{2}$ electrons prove the reliability of our experiment, and the $\beta $ asymmetry parameters extracted from the angular distributions of Ne 2p$^{6}$ electrons are obtained. By comparing with different theoretical calculations, it is found that the contribution of the electron correlation effect in Ne 2p$^{6}$ single ionization becomes increasingly important as the incident photon energy increases, while the relativistic effect is relatively low in the whole incident energy range. Our experimental $\beta $ asymmetry parameters may serve as a significant reference to test the most elaborated theories in the field. The datasets presented in this paper, including the photoelectron angular distributions and $\beta $ asymmetry parameters, are openly available at https://doi.org/10.57760/sciencedb.j00113.00073.

Optical spectroscopy of CrO and electronic states of the Cr group metal monoxides

Lei Zhang(张磊), Yao Yu(于尧), Xinwen Ma(马新文), and Jie Yang(杨杰)

Chin. Phys. B, 2023, 32 (5): 053301. DOI: 10.1088/1674-1056/acb763

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All of the experimentally known electronic states of the Cr group metal monoxides (CrO, MoO, and WO) have been presented in the paper. The optical spectra of the CrO molecule have been investigated in the gas phase through a combination of the laser-induced fluorescence (LIF) excitation and single-vibronic-level (SVL) emission spectroscopy in the supersonic expansion. The rotational constants of the vibronic electronic states, including ${\rm X}\,{}^{5}\Pi_{-1}$ ($v'' = 0$-3), ${\rm B}\,{}^{5}\Pi _{-1}$ ($v^\prime =0$-10), and ${\rm B}\,{}^{5}\Pi_{1}$ ($v^\prime = 1$, 5), and the vibrational constants of the spin-orbit components ${\rm X}\,{}^{5}\Pi _{-1,0,1}$ have been obtained. The molecular constants of the MoO and WO molecules have been summarized by reviewing the previous spectroscopic studies, and a comprehensive energy level diagram of the Cr group metal monoxides has been constructed. By comparing the electronic configurations, bond lengths, and vibrational frequencies of all the transition metal monoxides in the ground electronic state, the significance of the relativistic effect in the bonding of the 5d transition metal monoxides has been discussed. The related spectroscopic data of the CrO molecule are available at https://doi.org/10.57760/sciencedb.j00113.00085.

Evaluating thermal expansion in fluorides and oxides: Machine learning predictions with connectivity descriptors

Yilin Zhang(张轶霖), Huimin Mu(穆慧敏), Yuxin Cai(蔡雨欣), Xiaoyu Wang(王啸宇), Kun Zhou(周琨), Fuyu Tian(田伏钰), Yuhao Fu(付钰豪), and Lijun Zhang(张立军)

Chin. Phys. B, 2023, 32 (5): 056302. DOI: 10.1088/1674-1056/accdca

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Open framework structures (e.g., ScF₃, Sc₂W₃O₁₂, etc.) exhibit significant potential for thermal expansion tailoring owing to their high atomic vibrational degrees of freedom and diverse connectivity between polyhedral units, displaying positive/negative thermal expansion (PTE/NTE) coefficients at a certain temperature. Despite the proposal of several physical mechanisms to explain the origin of NTE, an accurate mapping relationship between the structural-compositional properties and thermal expansion behavior is still lacking. This deficiency impedes the rapid evaluation of thermal expansion properties and hinders the design and development of such materials. We developed an algorithm for identifying and characterizing the connection patterns of structural units in open-framework structures and constructed a descriptor set for the thermal expansion properties of this system, which is composed of connectivity and elemental information. Our developed descriptor, aided by machine learning (ML) algorithms, can effectively learn the thermal expansion behavior in small sample datasets collected from literature-reported experimental data (246 samples). The trained model can accurately distinguish the thermal expansion behavior (PTE/NTE), achieving an accuracy of 92%. Additionally, our model predicted six new thermodynamically stable NTE materials, which were validated through first-principles calculations. Our results demonstrate that developing effective descriptors closely related to thermal expansion properties enables ML models to make accurate predictions even on small sample datasets, providing a new perspective for understanding the relationship between connectivity and thermal expansion properties in the open framework structure. The datasets that were used to support these results are available on Science Data Bank, accessible via the link https://doi.org/10.57760/sciencedb.j00113.00100.

Measurement of remanent magnetic moment using a torsion pendulum with single frequency modulation method

Min-Na Qiao(乔敏娜), Lu-Hua Liu(刘鲁华), Bo-Song Cai(蔡柏松), Ya-Ting Zhang(张雅婷),Qing-Lan Wang(王晴岚), Jia-Hao Xu(徐家豪), and Qi Liu(刘祺)

Chin. Phys. B, 2023, 32 (5): 050702. DOI: 10.1088/1674-1056/acae73

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In TianQin spaceborne gravitational-wave detectors, the stringent requirements on the magnetic cleanliness of the test masses demand the high resolution ground-based characterization measurement of their magnetic properties. Here we present a single frequency modulation method based on a torsion pendulum to measure the remanent magnetic moment $m_{\rm r}$ of $1.1$ kg dummy copper test mass, and the measurement result is $(6.45\pm0.04(\rm{stat})\pm0.07(\rm{syst}))\times10^{-8} \rm{A\cdot m^2}$. The measurement precision of the $m_{\rm r}$ is about $0.9 \rm{nA\cdot m^2}$, well below the present measurement requirement of TianQin. The method is particularly useful for measuring extremely low magnetic properties of the materials for use in the construction of space-borne gravitational wave detection and other precision scientific apparatus.

Three-dimensional color particle image velocimetry based on a cross-correlation and optical flow method

Liang Shan(单良), Jun-Zhe Xiong(熊俊哲), Fei-Yang Shi(施飞杨), Bo Hong(洪波), Juan Jian(简娟), Hong-Hui Zhan(詹虹晖), and Ming Kong(孔明)

Chin. Phys. B, 2023, 32 (5): 054702. DOI: 10.1088/1674-1056/acb1ff

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Rainbow particle image velocimetry (PIV) can restore the three-dimensional velocity field of particles with a single camera; however, it requires a relatively long time to complete the reconstruction. This paper proposes a hybrid algorithm that combines the fast Fourier transform (FFT) based co-correlation algorithm and the Horn-Schunck (HS) optical flow pyramid iterative algorithm to increase the reconstruction speed. The Rankine vortex simulation experiment was performed, in which the particle velocity field was reconstructed using the proposed algorithm and the rainbow PIV method. The average endpoint error and average angular error of the proposed algorithm were roughly the same as those of the rainbow PIV algorithm; nevertheless, the reconstruction time was 20% shorter. Furthermore, the effect of velocity magnitude and particle density on the reconstruction results was analyzed. In the end, the performance of the proposed algorithm was verified using real experimental single-vortex and double-vortex datasets, from which a similar particle velocity field was obtained compared with the rainbow PIV algorithm. The results show that the reconstruction speed of the proposed hybrid algorithm is approximately 25% faster than that of the rainbow PIV algorithm.

Application of silicon carbide temperature monitors in 49-2 swimming-pool test reactor

Guang-Sheng Ning(宁广胜), Li-Min Zhang(张利民), Wei-Hua Zhong(钟巍华), Sheng-Hong Wang(王绳鸿), Xin-Yu Liu(刘心语), Ding-Ping Wang(汪定平), An-Ping He(何安平), Jian Liu(刘健), and Chang-Yi Zhang(张长义)

Chin. Phys. B, 2023, 32 (5): 056102. DOI: 10.1088/1674-1056/acb41c

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High purity SiC crystal was used as a passive monitor to measure neutron irradiation temperature in the 49-2 research reactor. The SiC monitors were irradiated with fast neutrons at elevated temperatures to 3.2×10²⁰ n/cm². The isochronal and isothermal annealing behaviors of the irradiated SiC were investigated by x-ray diffraction and four-point probe techniques. Invisible point defects and defect clusters are found to be the dominating defect types in the neutron-irradiated SiC. The amount of defect recovery in SiC reaches a maximum value after isothermal annealing for 30 min. Based on the annealing temperature dependences of both lattice swelling and material resistivity, the irradiation temperature of the SiC monitors is determined to be ～ 410 ℃, which is much higher than the thermocouple temperature of 275 ℃ recorded during neutron irradiation. The possible reasons for the difference are carefully discussed.

A spin-based magnetic scanning microscope for in-situ strain tuning of soft matter

Zhe Ding(丁哲), Yumeng Sun(孙豫蒙), Mengqi Wang(王孟祺), Pei Yu(余佩), Ningchong Zheng(郑宁冲), Yipeng Zang(臧一鹏), Pengfei Wang(王鹏飞), Ya Wang(王亚), Yuefeng Nie(聂越峰), Fazhan Shi(石发展), and Jiangfeng Du(杜江峰)

Chin. Phys. B, 2023, 32 (5): 057504. DOI: 10.1088/1674-1056/acbaee

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We present a magnetic scanning microscope equipped with a nitrogen-vacancy (NV) center scanning probe that has the ability to mechanically tune the strain of soft matter in-situ. The construction of the microscope and a continuous strain-tuning sample holder are discussed. An optically detected magnetic resonance protocol utilized in the imaging is described. In order to show the reliability of this microscope, the strain conduction is estimated with finite element simulation, and x-ray diffraction is required for calibration when freestanding crystal films are under consideration. A magnetic imaging result is displayed to demonstrate the nano-scale imaging capability. The microscope presented in this work is helpful in studying strain-coupled magnetic physics such as magnetic phase transition under strain and strain-tuned cycloidal orientation tilting.

Thermoelectric generators and their applications: Progress, challenges, and future prospects

Nassima Radouane

Chin. Phys. B, 2023, 32 (5): 057307. DOI: 10.1088/1674-1056/aca5fd

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Our community currently deals with issues such as rising electricity costs, pollution, and global warming. Scientists work to improve energy harvesting-based power generators in order to reduce their impacts. The Seebeck effect has been used to illustrate the capacity of thermoelectric generators (TEGs) to directly convert thermal energy to electrical energy. They are also ecologically beneficial since they do not include chemical products, function quietly because they lack mechanical structures and/or moving components, and may be built using different fabrication technologies such as three-dimentional (3D) printing, silicon technology, and screen printing, etc. TEGs are also position-independent and have a long operational lifetime. TEGs can be integrated into bulk and flexible devices. This review gives further investigation of TEGs, beginning with a full discussion of their operating principle, kinds, materials utilized, figure of merit, and improvement approaches, which include various thermoelectric material arrangements and utilised technologies. This paper also discusses the use of TEGs in a variety of disciplines such as automobile and biomedical.

Enhanced phase sensitive amplification towards improving noise immunity ^Hot!

Hui Guo(郭辉), Zhi Li(李治), Hengxin Sun(孙恒信), Kui Liu(刘奎), and Jiangrui Gao(郜江瑞)

Chin. Phys. B, 2023, 32 (5): 054204. DOI: 10.1088/1674-1056/acbdeb

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Quantum states are essential resource for quantum-enhanced applications. Loss incurred in the distribution channel, however, dissipates the high signal-to-noise ratio advantage enjoyed by the squeezed state. Here, we first demonstrate noise immunity enhancement by using phase-sensitive amplifier (PSA) with measurement-based noiseless linear amplifier (MB-NLA). We explore the signal transfer capability with the amplifier in a noisy channel. The MB-NLA enhanced PSA has obvious suppression effect on channel noises, especially it has improvement for the noise contaminated signal. Better performance can be achieved by flexibly adjusting amplifier parameters. With the amplifier, it is promising to overcome the entanglement-distribution loss and show its superiority in squeezing based quantum sensing.

Stability of the topological quantum critical point between multi-Weyl semimetal and band insulator ^Hot!

Zhao-Kun Yang(杨兆昆), Jing-Rong Wang(王景荣), and Guo-Zhu Liu(刘国柱)

Chin. Phys. B, 2023, 32 (5): 056401. DOI: 10.1088/1674-1056/acbaf2

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One could tune a topological double-Weyl semimetal or a topological triple-Weyl semimetal to become a topologically trivial insulator by opening a band gap. This kind of quantum phase transition is characterized by the change of certain topological invariant. A new gapless semimetallic state emerges at each topological quantum critical point. Here we perform a renormalization group analysis to investigate the stability of such critical points against perturbations induced by random scalar potential and random vector potential. We find that the quantum critical point between double-Weyl semimetal and band insulator is unstable and can be easily turned into a compressible diffusive metal by any type of weak disorder. The quantum critical point between triple-Weyl semimetal and band insulator flows to a stable strong-coupling fixed point if the system contains a random vector potential merely along the z-axis, but becomes a compressible diffusive metal when other types of disorders exist.

Visualizing interface states in In₂Se₃–WSe₂ monolayer lateral heterostructures ^Hot!

Da Huo(霍达), Yusong Bai(白玉松), Xiaoyu Lin(林笑宇), Jinghao Deng(邓京昊), Zemin Pan(潘泽敏), Chao Zhu(朱超), Chuansheng Liu(刘传胜), and Chendong Zhang(张晨栋)

Chin. Phys. B, 2023, 32 (5): 056803. DOI: 10.1088/1674-1056/acbaef

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Recent findings of two-dimensional (2D) ferroelectric (FE) materials provide more possibilities for the development of 2D FE heterostructure electronic devices based on van der Waals materials and the application of FE devices under the limit of atomic layer thickness. In this paper, we report the in-situ fabrication and probing of electronic structures of In$_{2}$Se$_{3}$-WSe$_{2}$ lateral heterostructures, compared with most vertical FE heterostructures at present. Through molecular beam epitaxy, we fabricated lateral heterostructures with monolayer WSe$_{2}$ (three atomic layers) and monolayer In$_{2}$Se$_{3}$ (five atomic layers). Type-II band alignment was found to exist in either the lateral heterostructure composed of anti-FE $\beta '$-In$_{2}$Se$_{3}$ and WSe$_{2}$ or the lateral heterostructure composed of FE $\beta^*$-In$_{2}$Se$_{3}$ and WSe$_{2}$, and the band offsets could be modulated by ferroelectric polarization. More interestingly, interface states in both lateral heterostructures acted as narrow gap quantum wires, and the band gap of the interface state in the $\beta^*$-In$_{2}$Se$_{3}$-WSe$_{2}$ heterostructure was smaller than that in the $\beta '$-In$_{2}$Se$_{3}$ heterostructure. The fabrication of 2D FE heterostructure and the modulation of interface state provide a new platform for the development of FE devices.

Prediction of LiCrTe₂ monolayer as a half-metallic ferromagnet with a high Curie temperature ^Hot!

Li-Man Xiao(肖丽蔓), Huan-Cheng Yang(杨焕成), and Zhong-Yi Lu(卢仲毅)

Chin. Phys. B, 2023, 32 (5): 057505. DOI: 10.1088/1674-1056/acbe2e

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By using first-principles electronic structure calculations, we predict a new two-dimensional half-metallic ferromagnet (2DHMF) with distorted square structure, i.e., the LiCrTe₂ monolayer. The results show that the LiCrTe₂ monolayer is dynamically, thermally, and mechanically stable, and takes a large in-plane magnetic anisotropy, a wide spin gap, a large magnetization, and a very high Curie temperature. Under a biaxial strain ranging from -5% to +5%, the ferromagnetism, half-metallicity, and high Curie temperature are maintained well. Both tensile and compressive strains can significantly increase the magnitude of the magnetocrystalline anisotropy energy (MAE) and a transition from in-plane easy-x(y)-axis to out-of-plane easy-z-axis occurs when the compressive strain exceeds 1%. Our systematic study of the LiCrTe₂ monolayer enables its promising applications in spintronics.

Spin reorientation in easy-plane kagome ferromagnet Li₉Cr₃(P₂O₇)₃(PO₄)₂ ^Hot!

Yuanhao Dong(董元浩), Ying Fu(付盈), Yixuan Liu(刘以轩), Zhanyang Hao(郝占阳), Le Wang(王乐), Cai Liu(刘才), Ke Deng(邓可), and Jiawei Mei(梅佳伟)

Chin. Phys. B, 2023, 32 (5): 057506. DOI: 10.1088/1674-1056/acc2b3

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We report the successful growth and characterization of Li$_9$Cr$_3$(P$_2$O$_7$)$_3$(PO$_4$)$_2$ single crystal, and investigate its magnetic properties under external magnetic fields via magnetization and heat capacity measurements. Our study reveals that Li$_9$Cr$_3$(P$_2$O$_7$)$_3$(PO$_4$)$_2$ is an easy-plane kagome ferromagnet with $S=3/2$, as evidenced by the Curie-Weiss temperature of 6 K which implies a ferromagnetic exchange coupling in the material. Under zero magnetic field, Li$_9$Cr$_3$(P$_2$O$_7$)$_3$(PO$_4$)$_2$ undergoes a magnetic transition at $T_{\rm C} = 2.7$ K from a paramagnetic state to a ferromagnetically ordered state with the magnetic moment lying in the kagome plane. By applying a $c$-axis directional magnetic field to rotate the spin alignment from the kagome plane to the $c$-axis, we observe a reduction in the magnetic transition temperature as the field is increased. We construct a magnetic phase diagram as a function of temperature and magnetic field applied parallel to the $c$-axis of Li$_9$Cr$_3$(P$_2$O$_7$)$_3$(PO$_4$)$_2$ and find that the phase boundary is linear over a certain temperature range. Regarding that theoretically, the field-induced phase transition of the spin reorientation in the easy-plane ferromagnet can be viewed as the ferromagnetic magnon Bose-Einstein condensation (BEC), the phase boundary scaling of field-induced ($B \parallel c$) magnetic transition in Li$_9$Cr$_3$(P$_2$O$_7$)$_3$(PO$_4$)$_2$ can be described as the quasi-2D magnon BEC, which has been observed in other ferromagnetic materials such as K$_2$CuF$_4$.

One ε-Ga₂O₃-based solar-blind Schottky photodetector emphasizing high photocurrent gain and photocurrent-intensity linearity Suggested by editors

Yue-Hua An(安跃华), Zhen-Sen Gao(高震森), Yu Guo(郭雨), Shao-Hui Zhang(张少辉), Zeng Liu(刘增), and Wei-Hua Tang(唐为华)

Chin. Phys. B, 2023, 32 (5): 058502. DOI: 10.1088/1674-1056/acb75b

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The $\varepsilon $-Ga$_{2}$O$_{3}$ thin film was grown on sapphire substrate by using metalorganic chemical vapor deposition (MOCVD) method, and then was used to fabricate a deep-ultraviolet (DUV) photodetector (PD). The $\varepsilon $-Ga$_{2}$O$_{3}$ thin film shown good crystal quality and decent surface morphology. Irradiated by a 254-nm DUV light, the photodetector displayed good optoelectronic performance and high wavelength selectivity, such as photoresponsivity ($R$) of 175.69 A/W, detectivity ($D^{\ast }$) of $2.46\times 10^{15}$ Jones, external quantum efficiency (EQE) of $8.6\times 10^{4}{\%}$ and good photocurrent-intensity linearity, suggesting decent DUV photosensing performance. At 5 V and under illumination with light intensity of 800 μW/cm$^{2}$, the photocurrent gain is as high as 859 owing to the recycling gain mechanism and delayed carrier recombination; and the photocurrent gain decreases as the incident light intensity increases because of the recombination of photogenerated carriers by the large photon flux.

Mutation detection and fast identification of switching system based on data-driven method Suggested by editors

Zhonghua Zhang(张钟化), Wei Xu(徐伟), and Yi Song(宋怡)

Chin. Phys. B, 2023, 32 (5): 050201. DOI: 10.1088/1674-1056/acb9f5

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In the engineering field, switching systems have been extensively studied, where sudden changes of parameter value and structural form have a significant impact on the operational performance of the system. Therefore, it is important to predict the behavior of the switching system, which includes the accurate detection of mutation points and rapid reidentification of the model. However, few efforts have been contributed to accurately locating the mutation points. In this paper, we propose a new measure of mutation detection — the threshold-based switching index by analogy with the Lyapunov exponent. We give the algorithm for selecting the optimal threshold, which greatly reduces the additional data collection and the relative error of mutation detection. In the system identification part, considering the small data amount available and noise in the data, the abrupt sparse Bayesian regression (abrupt-SBR) method is proposed. This method captures the model changes by updating the previously identified model, which requires less data and is more robust to noise than identifying the new model from scratch. With two representative dynamical systems, we illustrate the application and effectiveness of the proposed methods. Our research contributes to the accurate prediction and possible control of switching system behavior.

Weak signal detection method based on novel composite multistable stochastic resonance

Shangbin Jiao(焦尚彬), Rui Gao(高蕊), Qiongjie Xue(薛琼婕), and Jiaqiang Shi(史佳强)

Chin. Phys. B, 2023, 32 (5): 050202. DOI: 10.1088/1674-1056/aca4bd

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The weak signal detection method based on stochastic resonance is usually used to extract and identify the weak characteristic signal submerged in strong noise by using the noise energy transfer mechanism. We propose a novel composite multistable stochastic-resonance (NCMSR) model combining the Gaussian potential model and an improved bistable model. Compared with the traditional multistable stochastic resonance method, all the parameters in the novel model have no symmetry, the output signal-to-noise ratio can be optimized and the output amplitude can be improved by adjusting the system parameters. The model retains the advantages of continuity and constraint of the Gaussian potential model and the advantages of the improved bistable model without output saturation, the NCMSR model has a higher utilization of noise. Taking the output signal-to-noise ratio as the index, weak periodic signal is detected based on the NCMSR model in Gaussian noise and α noise environment respectively, and the detection effect is good. The application of NCMSR to the actual detection of bearing fault signals can realize the fault detection of bearing inner race and outer race. The outstanding advantages of this method in weak signal detection are verified, which provides a theoretical basis for industrial practical applications.

Effect of magnetic nanoparticles on magnetic field homogeneity

Si-Lin Guo(郭斯琳), Wen-Tong Yi(易文通), and Zhuang-Zhuang Li(李壮壮)

Chin. Phys. B, 2023, 32 (5): 050203. DOI: 10.1088/1674-1056/acaa26

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The mechanism of magnetic nanoparticles (MNPs) affecting magnetic field uniformity is studied in this work. The spatial distribution of MNPs in liquid is simulated based on Monte Carlo method. The induced field of the single MNP is combined with the magnetic field distribution of magnetofluid. In the simulation, magnetic field uniformity is described by a statistical distribution. As the chemical shift (CS) and full width at half maximum (FWHM) of magnetic resonance (MR) spectrum can reflect the uniformity of magnetic field, the simulation is verified by spectrum experiment. Simulation and measurement results prove that the CS and FWHM of the MR spectrum are basically positively correlated with the concentration of MNPs and negatively correlated with the temperature. The research results can explain how MNPs play a role in MR by affecting the uniform magnetic field, which is of great significance in improving the temperature measurement accuracy of magnetic nanothermometers and the spatial resolution of magnetic particle imaging.

Superposition formulas of multi-solution to a reduced (3+1)-dimensional nonlinear evolution equation

Hangbing Shao(邵杭兵) and Bilige Sudao(苏道毕力格)

Chin. Phys. B, 2023, 32 (5): 050204. DOI: 10.1088/1674-1056/acae7d

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We gave the localized solutions, the interaction solutions and the mixed solutions to a reduced (3+1)-dimensional nonlinear evolution equation. These solutions were characterized by superposition formulas of positive quadratic functions, the exponential and hyperbolic functions. According to the known lump solution in the outset, we obtained the superposition formulas of positive quadratic functions by plausible reasoning. Next, we constructed the interaction solutions between the localized solutions and the exponential function solutions with the similar theory. These two kinds of solutions contained superposition formulas of positive quadratic functions, which were turned into general ternary quadratic functions, the coefficients of which were all rational operation of vector inner product. Then we obtained linear superposition formulas of exponential and hyperbolic function solutions. Finally, for aforementioned various solutions, their dynamic properties were showed by choosing specific values for parameters. From concrete plots, we observed wave characteristics of three kinds of solutions. Especially, we could observe distinct generation and separation situations when the localized wave and the stripe wave interacted at different time points.

Resonant interactions among two-dimensional nonlinear localized waves and lump molecules for the (2+1)-dimensional elliptic Toda equation

Fuzhong Pang(庞福忠), Hasi Gegen(葛根哈斯), and Xuemei Zhao(赵雪梅)

Chin. Phys. B, 2023, 32 (5): 050205. DOI: 10.1088/1674-1056/acb2c2

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The (2+1)-dimensional elliptic Toda equation is a high-dimensional generalization of the Toda lattice and a semi-discrete Kadomtsev-Petviashvili I equation. This paper focuses on investigating the resonant interactions between two breathers, a breather/lump and line solitons as well as lump molecules for the (2+1)-dimensional elliptic Toda equation. Based on the N-soliton solution, we obtain the hybrid solutions consisting of line solitons, breathers and lumps. Through the asymptotic analysis of these hybrid solutions, we derive the phase shifts of the breather, lump and line solitons before and after the interaction between a breather/lump and line solitons. By making the phase shifts infinite, we obtain the resonant solution of two breathers and the resonant solutions of a breather/lump and line solitons. Through the asymptotic analysis of these resonant solutions, we demonstrate that the resonant interactions exhibit the fusion, fission, time-localized breather and rogue lump phenomena. Utilizing the velocity resonance method, we obtain lump-soliton, lump-breather, lump-soliton-breather and lump-breather-breather molecules. The above works have not been reported in the (2+1)-dimensional discrete nonlinear wave equations.

Rigorous solution to second harmonic generation considering transmission and reflection of light at air-crystal interface

Ya-Ting Qiu(邱雅婷), Li-Hong Hong(洪丽红), and Zhi-Yuan Li(李志远)

Chin. Phys. B, 2023, 32 (5): 050301. DOI: 10.1088/1674-1056/ac9fc5

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Considering the transmission and reflection of TE-polarized pump light at the air-crystal interface, the second harmonic generation (SHG) in a lithium niobate (LN) crystal is investigated theoretically and systematically in this work. In previous studies, the theoretical analyses of reflection and transmission of incident wave in the process of nonlinear frequency conversion were not considered in LN crystal on account of the complicated calculations. First, we establish a physical picture describing that a beam of light in TE mode transports in the LN crystal considering transmission and reflection at the crystal surface and generates nonlinear second-order optical polarization in crystal. Then we analytically derive the reflection coefficient and transmission coefficient of pump light by using the dispersion relationships and electromagnetic boundary conditions. We construct the nonlinear coupled wave equations, derive and present the small signal approximation solution and the general large signal solution exactly. Under the transmission model and reflection model, we find that the conversion efficiency of the second-harmonic wave is obviously dependent on transmission coefficient and other general physical quantities such as the length of LN crystal and the amplitude of pump light. Our analytical theory and formulation can act as an accurate tool for the quantitative evaluation of the SHG energy conversion efficiency in an LN crystal under practical situations, and it can practically be used to treat other more complicated and general nonlinear optics problems.

Bounds on positive operator-valued measure based coherence of superposition Suggested by editors

Meng-Li Guo(郭梦丽), Jin-Min Liang(梁津敏), Bo Li(李波), Shao-Ming Fei(费少明), and Zhi-Xi Wang(王志玺)

Chin. Phys. B, 2023, 32 (5): 050302. DOI: 10.1088/1674-1056/acb9f1

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Quantum coherence is a fundamental feature of quantum physics and plays a significant role in quantum information processing. By generalizing the resource theory of coherence from von Neumann measurements to positive operator-valued measures (POVMs), POVM-based coherence measures have been proposed with respect to the relative entropy of coherence, the l₁ norm of coherence, the robustness of coherence and the Tsallis relative entropy of coherence. We derive analytically the lower and upper bounds on these POVM-based coherence of an arbitrary given superposed pure state in terms of the POVM-based coherence of the states in superposition. Our results can be used to estimate range of quantum coherence of superposed states. Detailed examples are presented to verify our analytical bounds.

Quantum color image scaling based on bilinear interpolation

Chao Gao(高超), Ri-Gui Zhou(周日贵), and Xin Li(李鑫)

Chin. Phys. B, 2023, 32 (5): 050303. DOI: 10.1088/1674-1056/ac8f35

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As a part of quantum image processing, quantum image scaling is a significant technology for the development of quantum computation. At present, most of the quantum image scaling schemes are based on grayscale images, with relatively little processing for color images. This paper proposes a quantum color image scaling scheme based on bilinear interpolation, which realizes the $2^{n_{1}}\times 2^{n_{2}}$ quantum color image scaling. Firstly, the improved novel quantum representation of color digital images (INCQI) is employed to represent a $2^{n_{1}}\times 2^{n_{2}}$ quantum color image, and the bilinear interpolation method for calculating pixel values of the interpolated image is presented. Then the quantum color image scaling-up and scaling-down circuits are designed by utilizing a series of quantum modules, and the complexity of the circuits is analyzed. Finally, the experimental simulation results of MATLAB based on the classical computer are given. The ultimate results demonstrate that the complexities of the scaling-up and scaling-down schemes are quadratic and linear, respectively, which are much lower than the cubic function and exponential function of other bilinear interpolation schemes.

One-shot detection limits of time-alignment two-photon illumination radar

Wen-Long Gao(高文珑), Lu-Ping Xu(许录平), Hua Zhang(张华), Bo Yan(阎博), Peng-Xian Li(李芃鲜), and Gui-Ting Hu(胡桂廷)

Chin. Phys. B, 2023, 32 (5): 050304. DOI: 10.1088/1674-1056/ac9fc3

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Quantum radar has recently gained increasing importance in a number of military applications. The estimation accuracy of one-shot quantum illumination events is significant in target detection. However, the accuracy is inevitably deteriorated by measurement noises. The traditional one-shot illumination emits a single photon towards a certain area which thermal noise exists in the path to, and the states of the received photons are hard to distinguish in the following processing. Therefore, a new optical probe source is proposed in this work. The independent detecting unit in the enhanced illumination is comprised of two photons aligned in time by using Hong-Ou-Mandel (HOM) interferometer. Further, one-shot detection in a general discrete model is realized and it proves a significant promotion in accuracy. The expansion of useful parts in parameter space and the lower minimal error probability for hypothesis testing have been mathematically demonstrated. The accuracy of one-shot detection can be effectively improved by the proposed scheme implying that it possesses great potential applications in quantum illumination and imaging.

Effect of weak randomness flaws on security evaluation of practical quantum key distribution with distinguishable decoy states

Yu Zhou(周雨), Hong-Wei Li(李宏伟), Chun Zhou(周淳), Yang Wang(汪洋), Yi-Fei Lu(陆宜飞),Mu-Sheng Jiang(江木生), Xiao-Xu Zhang(张晓旭), and Wan-Su Bao(鲍皖苏)

Chin. Phys. B, 2023, 32 (5): 050305. DOI: 10.1088/1674-1056/ac8730

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Quantum key distribution provides an unconditional secure key sharing method in theory, but the imperfect factors of practical devices will bring security vulnerabilities. In this paper, we characterize the imperfections of the sender and analyze the possible attack strategies of Eve. Firstly, we present a quantized model for distinguishability of decoy states caused by intensity modulation. Besides, considering that Eve may control the preparation of states through hidden variables, we evaluate the security of preparation in practical quantum key distribution (QKD) scheme based on the weak-randomness model. Finally, we analyze the influence of the distinguishability of decoy state to secure key rate, for Eve may conduct the beam splitting attack and control the channel attenuation of different parts. Through the simulation, it can be seen that the secure key rate is sensitive to the distinguishability of decoy state and weak randomness, especially when Eve can control the channel attenuation.

Quantum state protection from finite-temperature thermal noise with application to controlled quantum teleportation Suggested by editors

Chi Wang(王驰), Sajede Harraz, Jiao-Yang Zhang(张骄阳), and Shuang Cong(丛爽)

Chin. Phys. B, 2023, 32 (5): 050306. DOI: 10.1088/1674-1056/acbd2a

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We propose a quantum state protection scheme via quantum feedforward control combined with environment-assisted measurement to protect arbitrary unknown initial states from the finite-temperature thermal noise (FTTN). The main strategy is to transfer the quantum system to a noise-robust state by weak measurement and feedforward control before the noise channel. Then we apply the environment-assisted measurement on the noise channel to select our desired damped states that are invertible to the initial state. After the noise channel, the reversal operations are applied to restore the initial state. We consider the protection of a single-qubit system, derive the analytical expressions of the success probability and the fidelity, and analyze the influence of key parameters on the performance of the proposed scheme. Unlike previous studies, there is no trade-off between the fidelity and the success probability in the proposed scheme; hence one could maximize them separately. Simulation results show that the proposed scheme can greatly improve the fidelity of the quantum state with a certain success probability. Moreover, the proposed scheme is successfully applied to improving the fidelity of controlled quantum teleportation through two independent FTTN channels from the perspective of protecting the shared entanglement.

On the complete weight distributions of quantum error-correcting codes

Chao Du(杜超), Zhi Ma(马智), and Maosheng Xiong(熊茂胜)

Chin. Phys. B, 2023, 32 (5): 050307. DOI: 10.1088/1674-1056/acac09

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In a recent paper, Hu et al. defined the complete weight distributions of quantum codes and proved the MacWilliams identities, and as applications they showed how such weight distributions may be used to obtain the singleton-type and hamming-type bounds for asymmetric quantum codes. In this paper we extend their study much further and obtain several new results concerning the complete weight distributions of quantum codes and applications. In particular, we provide a new proof of the MacWilliams identities of the complete weight distributions of quantum codes. We obtain new information about the weight distributions of quantum MDS codes and the double weight distribution of asymmetric quantum MDS codes. We get new identities involving the complete weight distributions of two different quantum codes. We estimate the complete weight distributions of quantum codes under special conditions and show that quantum BCH codes by the Hermitian construction from primitive, narrow-sense BCH codes satisfy these conditions and hence these estimate applies.

Phase-matching quantum key distribution with imperfect sources

Xiao-Xu Zhang(张晓旭), Yi-Fei Lu(陆宜飞), Yang Wang(汪洋), Mu-Sheng Jiang(江木生), Hong-Wei Li(李宏伟), Chun Zhou(周淳), Yu Zhou(周雨), and Wan-Su Bao(鲍皖苏)

Chin. Phys. B, 2023, 32 (5): 050308. DOI: 10.1088/1674-1056/ac9b03

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The huge discrepancies between actual devices and theoretical assumptions severely threaten the security of quantum key distribution. Recently, a general new framework called the reference technique has attracted wide attention in defending against the imperfect sources of quantum key distribution. Here, the state preparation flaws, the side channels of mode dependencies, the Trojan horse attacks, and the pulse classical correlations are studied by using the reference technique on the phase-matching protocol. Our simulation results highlight the importance of the actual secure parameters choice for transmitters, which is necessary to achieve secure communication. Increasing the single actual secure parameter will reduce the secure key rate. However, as long as the parameters are set properly, the secure key rate is still high. Considering the influences of multiple actual secure parameters will significantly reduce the secure key rate. These actual secure parameters must be considered when scientists calibrate transmitters. This work is an important step towards the practical and secure implementation of phase-matching protocol. In the future, it is essential to study the main parameters, find out their maximum and general values, classify the multiple parameters as the same parameter, and give countermeasures.

Developing improved measures of non-Gaussianity and Gaussianity for quantum states based on normalized Hilbert-Schmidt distance

Shaohua Xiang(向少华), Shanshan Li(李珊珊), and Xianwu Mi(米贤武)

Chin. Phys. B, 2023, 32 (5): 050309. DOI: 10.1088/1674-1056/acb0bd

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Non-Gaussianity of quantum states is a very important source for quantum information technology and can be quantified by using the known squared Hilbert-Schmidt distance recently introduced by Genoni et al. (Phys. Rev. A 78 042327 (2007)). It is, however, shown that such a measure has many imperfects such as the lack of the swapping symmetry and the ineffectiveness evaluation of even Schrödinger-cat-like states with small amplitudes. To deal with these difficulties, we propose an improved measure of non-Gaussianity for quantum states and discuss its properties in detail. We then exploit this improved measure to evaluate the non-Gaussianities of some relevant single-mode non-Gaussian states and multi-mode non-Gaussian entangled states. These results show that our measure is reliable. We also introduce a modified measure for Gaussianity following Mandilara and Cerf (Phys. Rev. A 86 030102(R) (2012)) and establish a conservation relation of non-Gaussianity and Gaussianity of a quantum state.

Improved quantum key agreement protocol with authentication

Ji-Hong Guo(郭继红), Ming-Qiang Bai(柏明强), Xiao-Yan Lei(雷小燕), Jia-Xin Xie(谢佳欣), and Zhi-Wen Mo(莫智文)

Chin. Phys. B, 2023, 32 (5): 050310. DOI: 10.1088/1674-1056/ac9b31

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In order to make the quantum key agreement process immune to participant attacks, it is necessary to introduce the authentication in the communication process. A quantum key agreement protocol with identity authentication that exploits the measurement correlation of six-particle entangled states is proposed. In contrast to some recently proposed quantum key agreement protocols with authentication, this protocol requires neither a semi-trusted third party nor additional private keys in the authentication process. The entire process of authentication and key agreement can be achieved using only n six-particle entangled states, which saves communication costs and reduces the complexity of the authentication process. Finally, security analysis shows that this scheme is resistant to some important attacks.

Nonadiabatic geometric phase in a doubly driven two-level system

Weixin Liu(刘伟新), Tao Wang(汪涛), and Weidong Li(李卫东)

Chin. Phys. B, 2023, 32 (5): 050311. DOI: 10.1088/1674-1056/ac89e3

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We study theoretically the nonadiabatic geometric phase of a doubly driven two-level system with an additional relative phase between the two driving modes introduced in. It is shown that the time evolution of the system strongly depends on this relative phase. The condition for the system returning to its initial state after a single period is given by the means of the Landau-Zener-Stückelberg-Majorana destructive interference. The nonadiabatic geometric phase accompanying a cyclic evolution is shown to be related to the Stokes phase as well as this relative phase. By controlling the relative phase, the geometric phase can characterize two distinct phases in the adiabatic limit.

Model considering panic emotion and personality traits for crowd evacuation

Hua-Kai Sun(孙华锴) and Chang-Kun Chen(陈长坤)

Chin. Phys. B, 2023, 32 (5): 050401. DOI: 10.1088/1674-1056/ac9e94

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Panic is a common emotion when pedestrians are in danger during the actual evacuation, which can affect pedestrians a lot and may lead to fatalities as people are crushed or trampled. However, the systematic studies and quantitative analysis of evacuation panic, such as panic behaviors, panic evolution, and the stress responses of pedestrians with different personality traits to panic emotion are still rare. Here, combined with the theories of OCEAN (openness, conscientiousness, extroversion, agreeableness, neuroticism) model and SIS (susceptible, infected, susceptible) model, an extended cellular automata model is established by the floor field method in order to investigate the dynamics of panic emotion in the crowd and dynamics of pedestrians affected by emotion. In the model, pedestrians are divided into stable pedestrians and sensitive pedestrians according to their different personality traits in response to emotion, and their emotional state can be normal or panic. Besides, emotion contagion, emotion decay, and the influence of emotion on pedestrian movement decision-making are also considered. The simulation results show that evacuation efficiency will be reduced, for panic pedestrians may act maladaptive behaviors, thereby making the crowd more chaotic. The results further suggest that improving pedestrian psychological ability and raising the standard of management can effectively increase evacuation efficiency. And it is necessary to reduce the panic level of group as soon as possible at the beginning of evacuation. We hope this research could provide a new method to analyze crowd evacuation in panic situations.

Detecting physical laws from data of stochastic dynamical systems perturbed by non-Gaussian α-stable Lévy noise

Linghongzhi Lu(陆凌弘志), Yang Li(李扬), and Xianbin Liu(刘先斌)

Chin. Phys. B, 2023, 32 (5): 050501. DOI: 10.1088/1674-1056/aca7ee

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Massive data from observations, experiments and simulations of dynamical models in scientific and engineering fields make it desirable for data-driven methods to extract basic laws of these models. We present a novel method to identify such high dimensional stochastic dynamical systems that are perturbed by a non-Gaussian α-stable Lévy noise. More explicitly, firstly a machine learning framework to solve the sparse regression problem is established to grasp the drift terms through one of nonlocal Kramers-Moyal formulas. Then the jump measure and intensity of the noise are disposed by the relationship with statistical characteristics of the process. Three examples are then given to demonstrate the feasibility. This approach proposes an effective way to understand the complex phenomena of systems under non-Gaussian fluctuations and illuminates some insights into the exploration for further typical dynamical indicators such as the maximum likelihood transition path or mean exit time of these stochastic systems.

Dynamical analysis for the sustained harvesting of microorganisms using flocculants in a random environment

Rong Liu(刘蓉) and Wanbiao Ma(马万彪)

Chin. Phys. B, 2023, 32 (5): 050502. DOI: 10.1088/1674-1056/ac9367

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The use of flocculants to collect/extract microorganisms is of great practical significance for the development of the application of microorganisms. In this paper, a high-dimensional nonlinear stochastic differential equation model is constructed to describe the continuous culture of microorganisms with multiple nutrients and the flocculation process of microorganisms. The study of the dynamics of this model can provide feasible control strategies for the collection/extraction of microorganisms. The main theoretical results are sufficient conditions for the permanence and extinction of the stochastic differential equation model, which are also extensions of some results in the existing literatures. In addition, through numerical simulations, we vividly demonstrate the statistical characteristics of the stochastic differential equation model.

Breather and its interaction with rogue wave of the coupled modified nonlinear Schrödinger equation

Ming Wang(王明), Tao Xu(徐涛), Guoliang He(何国亮), and Yu Tian(田雨)

Chin. Phys. B, 2023, 32 (5): 050503. DOI: 10.1088/1674-1056/ac833d

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We investigate the coupled modified nonlinear Schrödinger equation. Breather solutions are constructed through the traditional Darboux transformation with nonzero plane-wave solutions. To obtain the higher-order localized wave solution, the N-fold generalized Darboux transformation is given. Under the condition that the characteristic equation admits a double-root, we present the expression of the first-order interactional solution. Then we graphically analyze the dynamics of the breather and rogue wave. Due to the simultaneous existence of nonlinear and self-steepening terms in the equation, different profiles in two components for the breathers are presented.

Study on conversion of microstates in breast cell ensemble at the gene level based on the eigen-microstate method Suggested by editors

Su-Hua Zhang(张素花), Xue-Zhi Niu(牛雪芝), Xu-Zhao Wang(王徐朝), Chang Qu(屈畅), Hai-Long An(安海龙), Tong-Jun Zhao(赵同军), and Yong Zhan(展永)

Chin. Phys. B, 2023, 32 (5): 050504. DOI: 10.1088/1674-1056/acb9f8

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Breast cancer is a malignant disease that seriously threatens women's health. Studying the mechanism of cancer occurrence and development is an urgent problem to be solved. In this paper, the eigen-microstate method was used to study conversion of normal breast cells into breast cancer cells and the reason. The main conclusions are as follows: the microstates of normal breast cell and breast cancer cell are different. There is a state conversion when a normal breast cell transforms into a breast cancer cell. The main reason for this state conversion is the combined effect of tumor suppressor genes and oncogenes. By analyzing the function of key genes, it was found that these genes do play an important role in the development of breast cancer. The findings contribute to understanding the mechanism by which breast cancer occurs and progresses, and key genes can serve as potential biomarkers or target genes for breast cancer treatment.

Sympathetic electromagnetically induced transparency ground state cooling of a ⁴⁰Ca⁺–²⁷Al⁺ pair in an ²⁷Al⁺ clock

Chenglong Sun(孙成龙), Kaifeng Cui(崔凯枫), Sijia Chao(晁思嘉), Yuanfei Wei(魏远飞), Jinbo Yuan(袁金波), Jian Cao(曹健), Hualin Shu(舒华林), and Xueren Huang(黄学人)

Chin. Phys. B, 2023, 32 (5): 050601. DOI: 10.1088/1674-1056/aca39d

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We report on electromagnetically induced transparency cooling of ⁴⁰Ca⁺ to sympathetically cool the three-dimensional secular modes of motion in a ⁴⁰Ca⁺-²⁷Al⁺ two-ion pair near the ground state. We observe simultaneous ground state cooling across all radial modes and axial modes of a ⁴⁰Ca⁺-²⁷Al⁺ ion pair, occupying a broader cooling range in frequency space over 3 MHz. The cooling time is observed to be less than 1 ms. The mean phonon number and heating rates of all motional modes are measured. This study is not only an important step for reducing the secular motion time-dilation shift uncertainty and uptime ratio of ²⁷Al⁺ optical clock, but also essential for high-fidelity quantum simulations and quantum information processors using trapped ions.

Construction of multi-walled carbon nanotubes/ZnSnO₃ heterostructures for enhanced acetone sensing performance

Liyong Du(杜丽勇) and Heming Sun(孙鹤鸣)

Chin. Phys. B, 2023, 32 (5): 050701. DOI: 10.1088/1674-1056/ac89da

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Carbon nanotubes (CNTs) have attracted many researcher's attention in gas sensing field because of their excellent physical and chemical properties. Herein, multi-walled carbon nanotubes (MWCNTs)/ZnSnO₃ heterostructures have been obtained by a simple hydrothermal method without additional annealing process. The structural and composition information are characterized by x-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and x-ray photoelectron spectroscopy (XPS). The acetone sensing properties of pure MWCNTs, ZnSnO₃ and MWCNTs/ZnSnO₃ heterostructures are systematically investigated, respectively. The results show that MWCNTs/ZnSnO₃ heterostructures have better sensing properties compared with pure MWCNTs and ZnSnO₃ sample. Specifically, MWCNTs/ZnSnO₃ heterostructures exhibit not only high responses of 24.1 and rapid response/recovery speed of 1 s/9 s to 100 ppm acetone, but also relatively good repeatability and long-term stability. The enhanced sensing performance is analyzed in detail. In addition, this work provides the experimental and theory basis for synthesis of high-performance MWCNT-based chemical sensors.

A miniaturized spin-exchange relaxation-free atomic magnetometer based on uniform light field

Jiajie Li(李佳洁), Xiujie Fang(房秀杰), Renjie Li(李任杰), Baodong Chen(陈宝栋), Yueyang Zhai(翟跃阳), and Ying Liu(刘颖)

Chin. Phys. B, 2023, 32 (5): 053201. DOI: 10.1088/1674-1056/aca7f2

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We experimentally study the dynamic characteristics of a miniaturized spin-exchange relaxation-free (SERF) magnetometer based on uniform light field. The ceramic ferrule is used to expand the Gaussian beam to improve light intensity uniformity, while the volume of the sensor is also reduced. This scheme makes the magnetometer have better sensitivity when the detected light intensity is less than 3.16 mW/cm² at 120 ℃. When the temperature rises to 150 ℃ the sensitivity under the action of uniform light field is 18.5 fT/Hz^1/2. The bandwidth of the sensor remains at the original level and meets application needs. The proposed structure improves transverse polarization uniformity within the miniaturized sensor, which is ideal for the magnetoencephalography and magnetocardiography imaging systems.

Theoretical study of the enhancement of saturable absorption of Kr under x-ray free-electron laser

Jiaxin Ye(叶佳鑫), Yixuan Yang(杨怡璇), Chen Yang(杨晨), and Gang Jiang(蒋刚)

Chin. Phys. B, 2023, 32 (5): 053202. DOI: 10.1088/1674-1056/ac8cdd

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The generation of hollow atoms will reduce the probability of light absorption and provide a high-quality diffraction image in the experiment. In this paper, we calculated the ionization rate of the Kr atom under x-ray free-electron laser (XFEL) using Hartree-Fock-Slater model and simulated the ionization model of Kr atom using Monte-Carlo method to determine the response of the hollow atom of Kr atom to the XFEL photon energy. Calculating the correlation between the total photoionization cross-section of the ground state of Kr atom and the photon energy, we determined three particular photon energies of 1.75 keV, 1.90 keV, and 14.30 keV. The dynamics simulation under the experimental condition's 17.50 keV photon energy was achieved by implementing the Monte-Carlo method and calibrating the photon flux modeling parameters. Consequently, our calculated data are more consistent with experimental phenomena than previous theoretical studies. The saturable absorption of Kr at 1.75 keV, 1.90 keV, 14.30 keV, and 17.50 keV energies was further investigated by using the optimized photon flux model theory. We compared the statistics on main ionization paths under those four specific photon energies and calculated the population changes of various Kr hollow atoms with different configurations. The results demonstrate that the population of hollow atoms produced at the critical ionization photon energy is high. Furthermore, the change of population with respect to position is smooth, which shows a significant difference between the generation mode of ions with low and high photon energies. The result is important for the study of medium- and high-Z element hollow atoms, which has substantial implications for the study of hollow atoms with medium and high charge states, as well as for the scaling of photon energy of free electron lasers.

Atom-based power-frequency electric field measurement using the radio-frequency-modulated Rydberg spectroscopy

Weixin Liu(刘伟新), Linjie Zhang(张临杰), and Tao Wang(汪涛)

Chin. Phys. B, 2023, 32 (5): 053203. DOI: 10.1088/1674-1056/aca6db

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The radio-frequency modulated electromagnetically induced transparency (EIT) in a ladder three-level system with Rydberg state is studied. Under the influence of a fast radio-frequency field, the EIT peak splits into a series of sidebands. When attaching a power-frequency electric field directly to the fast radio-frequency field, the odd-order sidebands of the Rydberg-EIT oscillate sensitively with the power-frequency field. The oscillation frequency is equal to twice the power frequency; the oscillation amplitude is monotonically increasing with the amplitude of the power-frequency field when the change of Stark-shift is smaller than the radio frequency. Our work paves the way for measurement of power-frequency electric field based on Rydberg atoms.

Numerical studies of isotopic selective photoionization of ytterbium in a three-step ionization scheme

Xiao-Yong Lu(卢肖勇) and Li-De Wang(王立德)

Chin. Phys. B, 2023, 32 (5): 053204. DOI: 10.1088/1674-1056/ac9b2f

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Selective photoionization of ytterbium isotope is studied numerically based on a three-step photoionization scheme, 4${\rm f}^{14}$6${\rm s}^{2 1}$S$_{0 }$ (0 cm$^{-1}$) $ \to $ 4${\rm f}^{14}$6${\rm s}$6p$\ {}^{3}$P$_{1 }$ (17992.008 cm$^{-1}$) $ \to $ (4${\rm f}^{13}$6${\rm s}^{2}$6p) (7/2, 3/2)$_{2}$ (35196.98 cm$^{-1}$) $ \to $ auto-ionization state (52353 cm$^{-1}$) $ \to $ Yb$^{+}$, by the density matrix theory with the consideration of atomic hyperfine structures and magnetic sublevels. To examine the physical model, the numerical isotopic abundance of ytterbium is compared with that from mass spectroscopy experiment, showing that they are in good agreement with each other. The excitation process and ionization process of ytterbium, especially for odd isotopes, are discussed and analyzed in detail on this basis. The effects of frequency detuning, power densities, spectral bandwidths, polarization of two excitation lasers, and atomic Doppler broadening on the total ionization yield and isotopic abundance are investigated numerically and the optimal excitation conditions for $^{176}$Yb enrichment are identified semi-quantitatively.

Magic wavelengths for 6s_1/2 → 5d_3/2,5/2 transitions of Yb⁺ ions Suggested by editors

Ting Chen(陈婷), Lei Wu(吴磊), Ru-Kui Zhang(张儒奎), Yong-Bo Tang(唐永波), Jun Jiang(蒋军), and Chen-Zhong Dong(董晨钟)

Chin. Phys. B, 2023, 32 (5): 053206. DOI: 10.1088/1674-1056/acbc6c

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The wave functions, energy levels and matrix elements of Yb$^{+}$ ions are calculated using the relativistic configuration interaction plus core polarization (RCICP) method. The static and dynamic electric dipole polarizabilities of the ground state and low-lying excited states are determined. Then, the magic wavelengths of the magnetic sublevel 6${\rm s}_{1/2,\, m=1/2} \to 5{\rm d}_{3/2,\, m=\pm 3/2,\,\pm 1/2}$ and 6${\rm s}_{1/2,\, m=1/2}\to 5{\rm d}_{5/2,\, m=\pm 5/2,\, \pm 3/2,\, \pm 1/2}$ transitions in the linearly, right-handed, and left-handed polarized light are further determined. The dependence of the magic wavelengths upon the angle between the direction of magnetic field and the direction of laser polarization is analyzed.

Particle-in-cell simulations of low-β magnetic reconnection driven by laser interaction with a capacitor-coil target Suggested by editors

Xiaoxia Yuan(原晓霞), Cangtao Zhou(周沧涛), Hua Zhang(张华), Ran Li(李然), Yongli Ping(平永利), and Jiayong Zhong(仲佳勇)

Chin. Phys. B, 2023, 32 (5): 054101. DOI: 10.1088/1674-1056/acb911

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The dynamics of low-β magnetic reconnection (MR) driven by laser interaction with a capacitor-coil target are reexamined by simulations in this paper. We compare two cases MR and non-MR (also referred as AP-case and P-case standing for the anti-parallel and parallel magnetic field lines, respectively) to distinguish the different characteristics between them. We find that only in the AP-case the reconnection electric field shows up around the X line and the electron jet is directed toward the X line. The quadruple magnetic fields exist in both cases, however, they distribute in the current sheet area in the AP-case, and out of the squeezing area in the P-case, because electrons are demagnetized in the electron diffusion region in the MR process, which is absent in the P-case. The electron acceleration is dominant by the Fermi-like mechanism before the MR process, and by the reconnection electric field when the MR occurs. A power-law electron energy spectrum with an index of 1.8 is found in the AP-case. This work proves the significant potential of this experimental platform to be applied in the studies of low-β astronomy phenomena.

Size effect on light propagation modulation near band edges in one-dimensional periodic structures

Yang Tang(唐洋), Jiajun Wang(王佳俊), Xingqi Zhao(赵星棋), Tongyu Li(李同宇), and Lei Shi(石磊)

Chin. Phys. B, 2023, 32 (5): 054201. DOI: 10.1088/1674-1056/acac0d

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Periodic photonic structures can provide rich modulation in propagation of light due to well-defined band structures. Especially near band edges, light localization and the effect of near-zero refractive index have attracted wide attention. However, the practically fabricated structures can only have finite size, i.e., limited numbers of periods, leading to changes of the light propagation modulation compared with infinite structures. Here, we study the size effect on light localization and near-zero refractive-index propagation near band edges in one-dimensional periodic structures. Near edges of the band gap, as the structure's size shrinks, the broadening of the band gap and the weakening of the light localization are discovered. When the size is small, an added layer on the surface will perform large modulation in the group velocity. Near the degenerate point with Dirac-like dispersion, the zero-refractive-index effects like the zero-phase difference and near-unity transmittance retain as the size changes, while absolute group velocity fluctuates when the size shrinks.

Synthesis, magnetic and electromagnetic wave absorption properties of planar anisotrop Y₂Co₁₇@SiO₂ rare earth soft magnetic composites Suggested by editors

Liang Qiao(乔亮), Cheng-Fa Tu(涂成发), Wei Wu(吴伟), Wen-Biao Wang(王文彪), Sheng-Yu Yang(杨晟宇), Sun Zhe(孙哲), Peng Wu(吴鹏), Jin-Bo Yang(杨金波), Chang-Sheng Wang(王常生), Tao Wang(王涛), and Fa-Shen Li(李发伸)

Chin. Phys. B, 2023, 32 (5): 054202. DOI: 10.1088/1674-1056/aca7f1

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Intermetallic complexes of rare-earth and 3d transition metals with core-shell structures are commonly employed as microwave absorbing materials due to their high saturation magnetizations and natural resonance in GHz. Hence, we synthesized Y₂Co₁₇ alloy via the co-precipitation reduction-diffusion technique, then coated the Y₂Co₁₇ magnetic powders with SiO₂ to create Y₂Co₁₇@SiO₂ core-shell structures. The formation of Y₂Co₁₇@SiO₂/polyurethane (PU) at various volume fractions and their magnetic, electromagnetic properties were investigated using x-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, and vector network analyzer. The microwave absorption characteristics of Y₂Co₁₇@SiO₂/PU were also investigated at various volume fractions. We not only investigate the zero-reflection conditions of the samples with different volume fractions, but also show that every absorber has a strong reflection loss value (RL ≤ -65.00 dB) and excellent microwave absorption properties with an average RL of Y₂Co ₁₇@SiO₂/PU being below -10 dB at 8 GHz-18 GHz under different thicknesses, showing that the enhancement of microwave absorption performance arises from the balance between permeability and permittivity of absorber.

Adjusting amplitude of the stored optical solitons by inter-dot tunneling coupling in triple quantum dot molecules

Yin Wang(王胤), Si-Jie Zhou(周驷杰), Yong-He Deng(邓永和), and Qiao Chen(陈桥)

Chin. Phys. B, 2023, 32 (5): 054203. DOI: 10.1088/1674-1056/ac8f3d

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We study the propagation properties of a probe field in an aligned asymmetric triple quantum dot molecule with both sides inter-dot tunneling coupling effect. It is shown that the probe field can form optical soliton due to the destructive quantum interference induced by the quantum inter-dot tunneling coupling effect. Interestingly, these optical solitons can be stored and retrieved by adjusting single or double inter-dot tunneling coupling effect, different from that light memory in the ultra-cold atom system. Furthermore, we also find that the amplitude of the stored optical soliton can be adjusted by the strength of the single or double inter-dot tunneling coupling. It is possible to improve the stability and the fidelity of the optical information in the process of the storage and retrieval in semiconductor quantum dots devices.

Tunable magnomechanically induced transparency and fast-slow light in a hybrid cavity magnomechanical system

Qinghong Liao(廖庆洪), Kun Peng(彭坤), and Haiyan Qiu(邱海燕)

Chin. Phys. B, 2023, 32 (5): 054205. DOI: 10.1088/1674-1056/acaf2b

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We theoretically explore the tunability of magnomechanically induced transparency (MMIT) phenomenon and fast-slow light effect in a hybrid cavity magnomechanical system in which a high-quality yttrium iron garnet (YIG) sphere and an atomic ensemble are placed inside a microwave cavity. In the probe output spectrum, we can observe magnon-induced transparency (MIT) and MMIT due to the photon-magnon and phonon-magnon couplings. We further investigate the effect of atomic ensemble on the absorption spectrum. The results show that better transparency can be obtained by choosing appropriate atomic ensemble parameters. We give an explicit explanation for the mechanism of the Fano resonance phenomenon. Moreover, we discuss phenomena of slow-light propagation. The maximum group delay increases significantly with the increasing atom-cavity coupling strength, and the conversion between slow light and fast light can also be achieved by adjusting the atom-cavity coupling strength. These results may have potential applications for quantum information processing and high precision measurements.

High efficiency of Brillouin scattering behavior in single-mode Ge-As-Se-Te fibers at 2 μm

Yue Fu(付悦), Shi-Xun Dai(戴世勋), Lu-Lu Xu(徐路路), Yao-Jun Fang(方耀俊), Ying-Ying Wang(王莹莹), Kai Jiao(焦凯), and Xun-Si Wang(王训四)

Chin. Phys. B, 2023, 32 (5): 054206. DOI: 10.1088/1674-1056/ac9a3a

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The Brillouin characteristics of step-index Ge-As-Se-Te (GAST) fibers at 2 μm are designed and simulated on the basis of optical and acoustic properties. The refractive indexes of Ge$_{20}$As$_{20}$Se$_{45}$Te$_{15}$ glass and Ge$_{20}$As$_{20}$Se$_{43}$Te$_{17}$ glass serving as fiber core and cladding are 3.20 and 3.18 at 2 μm, and their acoustic velocities are 2200 m/s and 2300 m/s, respectively. Numerical results indicate that the stimulated Brillouin scattering (SBS) efficiency is 248 m$^{-1}\cdot$W$^{-1}$, and the Brillouin threshold power is 66 mW when the core diameter of the 2-m-long GAST fiber is 4 μm at 2-μm wavelength. The optic-acoustic coupling factor, the Brillouin frequency shift, and the Brillouin gain coefficient are 0.98, 7.02 GHz, and 3.81$\times10^{-9}$ m/W, respectively. The SBS effect of GAST fibers simulated for the first time provides a new promising approach to selecting gain medium based on 2-μm-wavelength fiber laser.

Four-stage cascaded variable optical attenuator with large attenuation range for quantum key distribution

Qing-Hai Liu(刘清海), Pan Pan(潘盼), Jin You(游金), Jia-Shun Zhang(张家顺), Ya Wang(汪亚),Yu-Ting Wang(王玉婷), Liang-Liang Wang(王亮亮), Jun-Ming An(安俊明),Da-Jian Cui(崔大健), Lang Zhou(周浪), and Wei Chen(陈伟)

Chin. Phys. B, 2023, 32 (5): 054207. DOI: 10.1088/1674-1056/ac8af6

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A four-stage cascaded variable optical attenuator (VOA) with a large attenuation range is presented. The VOA is based on a Mach-Zehnder interferometer (MZI) and fabricated in a silica-based planar lightwave circuit (PLC) platform. The thermo-optic effect is used to achieve intensity modulation. The measured maximum attenuation of the four-stage cascaded VOA is 88.38 dB. The chip is also tested in a quantum key distribution (QKD) system to generate signal and decoy states. The mean photon number after attenuation of the four-stage cascaded VOA is less than 0.1, which can meet the requirement of QKD.

Molecular fluorescence significantly enhanced by gold nanoparticles@zeolitic imidazolate framework-8

Yuyi Zhang(张钰伊), Yajie Bian(卞亚杰), Wei Zhang(张炜), Yiting Liu(刘易婷), Xiaolei Zhang(张晓磊),Mengdi Chen(陈梦迪), Bingwen Hu(胡炳文), and Qingyuan Jin(金庆原)

Chin. Phys. B, 2023, 32 (5): 054208. DOI: 10.1088/1674-1056/ac81aa

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Noble metal nanoparticles exhibit unique surface plasmon resonance dependent optical properties. On this basis, gold nanoparticles (AuNPs) encapsulated in metal-organic frameworks (MOFs) can form AuNPs@MOFs composites to modulate the optical properties of fluorescent molecules, which is less reported. In this paper, based on the fluorescence enhancement effect of AuNPs on 2-(2-hydroxyphenyl)-1H-benzimidazole (HPBI) molecules, zeolitic imidazolate framework-8 (ZIF-8) crystals with structural stability were introduced. AuNPs@ZIF-8 exhibited a significantly pronounced fluorescence enhancement of the HPBI molecules. In addition, by comparing the fluorescence characteristics of the HPBI molecules adsorbed on AuNPs@ZIF-8 and those captured in AuNPs@ZIF-8, we found that the ZIF-8 can act as a spacer layer with highly effective near-field enhancement. All our preliminary results shed light on future research on the composite structures of noble metal particles and MOFs for fluorescent probes and sensing applications.

Simultaneous measurements of refractive index and temperature based on a no-core fiber coated with Ag and PDMS films

Yuxin Li(李宇昕), Hailiang Chen(陈海良), Yingyue Zhang(张赢月), Qiang Chen(陈强), Biao Wu(武彪),Xiaoya Fan(樊晓亚), Yingchao Liu(刘英超), and Mingjian Ma(马明建)

Chin. Phys. B, 2023, 32 (5): 054209. DOI: 10.1088/1674-1056/ac8f36

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A compact surface plasmon resonance (SPR) fiber optic sensor, being utilized to simultaneously measure refractive index (RI) and temperature, is proposed and experimentally demonstrated in this paper. One part of a no-core fiber (NCF) was coated with a silver (Ag) film, and the other part was coated with a silver/polydimethylsiloxane (Ag/PDMS) composite film to stimulate the SPR effect. Due to the two heterogeneous films, two dips appeared in the transmission spectrum and were used to achieve the dual-parameter measurements. The experimental results showed that the RI sensitivity reached 2121.43 nm/RIU and 0 nm/RIU, while the temperature sensitivity reached -0.32 nm/℃ and -2.21 nm/℃ for the two dips, respectively. Based on the obtained transfer matrix, the measurements of RI and temperature could be demodulated. This designed sensor showed the merits of simple structure, easy to implement, and high sensitivity, demonstrating application prospects in dual-parameter monitoring.

Optically pumped wavelength-tunable lasing from a GaN beam cavity with an integrated Joule heater pivoted on Si Suggested by editors

Feifei Qin(秦飞飞), Yang Sun(孙阳), Ying Yang(杨颖), Xin Li(李欣), Xu Wang(王旭), Junfeng Lu(卢俊峰), Yongjin Wang(王永进), and Gangyi Zhu(朱刚毅)

Chin. Phys. B, 2023, 32 (5): 054210. DOI: 10.1088/1674-1056/acc05e

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Dynamically tunable laser sources are highly promising for realizing visionary concepts of integrated photonic circuits and other applications. In this paper, a GaN-based laser with an integrated PN junction heater on Si is fabricated. The photoluminescence properties of the GaN beam cavity are controlled by temperature, and the Joule heater provides electrically driven regulation of temperature. These two features of the cavity make it possible to realize convenient tuning of the lasing properties. The multi-functional GaN beam cavity achieves optically pumped lasing with a single mode near 362.4 nm with a high Q-factor of 1394. The temperature of this device increases by 0-5 ℃ under the Joule heating effect. Then, electrical control of the lasing mode is demonstrated. The lasing resonant peak shows a continuous redshift of about 0.5 nm and the device also exhibits dynamic switching of its lasing mode. The lasing modulation can be ascribed to temperature-induced reduction of the bandgap. Our work may be of benefit for external optical modulation in future chip-based optoelectronic devices.

Three-dimensional acoustic propagation model for shallow waters based on an indirect boundary element method

Edmundo F. Lavia, Juan D. Gonzalez, and Silvia Blanc

Chin. Phys. B, 2023, 32 (5): 054301. DOI: 10.1088/1674-1056/ac90b1

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This work has a two-fold purpose. On the one hand, the theoretical formulation of a three-dimensional (3D) acoustic propagation model for shallow waters with a constant sound speed is presented, based on the boundary element method (BEM), which uses a half-space Green function instead of the more conventional free-space Green function. On the other hand, a numerical implementation is illustrated to explore the formulation in simple idealized cases, controlled by a few parameters, which provides necessary tests for the accuracy and performance of the model. The half-space Green's function, which has been previously used in scattering and diffraction, adds terms to the usual expressions of the integral operators without altering their continuity properties. Verifications against the wavenumber integration solution of the Pekeris waveguide suggest that the model allows an adequate prediction for the acoustic field. Likewise, numerical experiments in relation to the necessary mesh size for the description of the water-marine sediment interface lead to the conclusion that a transmission loss prediction with acceptable accuracy can be obtained with the use of a limited mesh around the desired evaluation region.

Analysis of influencing factors of excitation parameters for magnetoacoustic tomography with current injection

Su Li(李粟), Guoqiang Liu(刘国强), Liang Guo(郭亮), Wenwei Zhang(张文伟),Chaosen Lu(卢朝森), and Hui Xia(夏慧)

Chin. Phys. B, 2023, 32 (5): 054302. DOI: 10.1088/1674-1056/ac872a

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Magneto-acoustic tomography with current injection (MAT-CI) is a type of hybrid imaging; under the excitation of the static magnetic field, the thermoacoustic effect and the Lorentz force effect will exist at the same time. Therefore, the detected signal is a mixed signal generated by the simultaneous action of the two effects, but the influence of excitation parameters on the two effects is different. In this paper, for objects with different conductivity, the proportion of thermoacoustic signal (TA) and magneto-acoustic signal (MA) in the mixed signal is quantitatively analyzed in terms of three aspects: the magnetic induction intensity, pulse excitation and injection current polarity. Experimental and simulation analyses show that the intensity ratio of MA to TA is not affected when the conductivity varies from 0.1 S/m to 1.5 S/m and other conditions remain unchanged. When the amplitude of the pulse excitation and the strength of the magnetic induction are different, the growth rates of MA and TA are different, which has a significant impact on the proportion of the two signals in the mixed signal. At the same time, due to the Lorentz force effect, MA is affected by the polarity of the injected current and the direction of the static magnetic field. The combination of the static magnetic field and the injected current can not only distinguish the two signals in the mixed signal, but also effectively enhance the intensity of the mixed signal and improve the quality of the reconstructed image.

Method for measuring the low-frequency sound power from a complex sound source based on sound-field correction in a non-anechoic tank

Hongzhe Xu(徐宏哲), Qi Li(李琪), Rui Tang(唐锐), and Dajing Shang(尚大晶)

Chin. Phys. B, 2023, 32 (5): 054303. DOI: 10.1088/1674-1056/acb75c

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Similar to air reverberation chambers, non-anechoic water tanks are important acoustic measurement devices that can be used to measure the sound power radiated from complex underwater sound sources using diffusion field theory. However, the problem of the poor applicability of low-frequency measurements in these tanks has not yet been solved. Therefore, we propose a low-frequency acoustic measurement method based on sound-field correction (SFC) in an enclosed space that effectively solves the problem of measuring the sound power from complex sound sources below the Schroeder cutoff frequency in a non-anechoic tank. Using normal mode theory, the transfer relationship between the mean-square sound pressure in an underwater enclosed space and the free-field sound power of the sound source is established, and this is regarded as a correction term for the sound field between this enclosed space and the free field. This correction term can be obtained based on previous measurements of a known sound source. This term can then be used to correct the mean-square sound pressure excited by any sound source to be tested in this enclosed space and equivalently obtain its free-field sound power. Experiments were carried out in a non-anechoic water tank (9.0 m m×3.1 m m×1.7 m) to confirm the validity of the SFC method. Through measurements with a spherical sound source (whose free-field radiation characteristics are known), the correction term of the sound field between this water tank and the free field was obtained. On this basis, the sound power radiated from a cylindrical shell model under the action of mechanical excitation was measured. The measurement results were found to have a maximum deviation of 2.9 dB from the free-field results. These results show that the SFC method has good applicability in the frequency band above the first-order resonant frequency in a non-anechoic tank. This greatly expands the potential low-frequency applications of non-anechoic tanks.

Thermal rectification induced by Wenzel-Cassie wetting state transition on nano-structured solid-liquid interfaces

Haiyang Li(李海洋), Jun Wang(王军), and Guodong Xia(夏国栋)

Chin. Phys. B, 2023, 32 (5): 054401. DOI: 10.1088/1674-1056/aca9c1

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Thermal rectification refers to the phenomenon by which the magnitude of the heat flux in one direction is much larger than that in the opposite direction. In this study, we propose to implement the thermal rectification phenomenon in an asymmetric solid-liquid-solid sandwiched system with a nano-structured interface. By using the non-equilibrium molecular dynamics simulations, the thermal transport through the solid-liquid-solid system is examined, and the thermal rectification phenomenon can be observed. It is revealed that the thermal rectification effect can be attributed to the significant difference in the interfacial thermal resistance between Cassie and Wenzel states when reversing the temperature bias. In addition, effects of the liquid density, solid-liquid bonding strength and nanostructure size on the thermal rectification are examined. The findings may provide a new way for designs of certain thermal devices.

Efficient control of connected and automated vehicles on a two-lane highway with a moving bottleneck

Huaqing Liu(刘华清) and Rui Jiang(姜锐)

Chin. Phys. B, 2023, 32 (5): 054501. DOI: 10.1088/1674-1056/acb918

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This paper investigates the traffic flow of connected and automated vehicles (CAVs) inducing by a moving bottleneck on a two-lane highway. A heuristic rules-based algorithm (HRA) has been used to control the traffic flow upstream of the moving bottleneck. In the HRA, some CAVs in the control zone are mapped onto the neighboring lane as virtual ones. To improve the driving comfort, the command acceleration caused by virtual vehicle is restricted. Comparing with the benchmark in which the CAVs change lane as soon as the lane changing condition is met, the HRA significantly improves the traffic flow: the overtaking throughput as well as the outflow rate increases, the travel delay and the fuel consumption decrease, the comfort level could also be improved.

Improved contact angle measurement in multiphase lattice Boltzmann

Xing-Guo Zhong(钟兴国), Yang-Sha Liu(刘阳莎), Yi-Chen Yao(姚怡辰), Bing He(何冰), and Bing-Hai Wen(闻炳海)

Chin. Phys. B, 2023, 32 (5): 054701. DOI: 10.1088/1674-1056/ac9cbd

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Contact angle is an essential parameter to characterize substrate wettability. The measurement of contact angle in experiment and simulation is a complex and time-consuming task. In this paper, an improved method of measuring contact angle in multiphase lattice Boltzmann simulations is proposed, which can accurately obtain the real-time contact angle at a low temperature and larger density ratio. The three-phase contact point is determined by an extrapolation, and its position is not affected by the local deformation of flow field in the three-phase contact region. A series of simulations confirms that the present method has high accuracy and gird-independence. The contact angle keeps an excellent linear relationship with the chemical potential of the surface, so that it is very convenient to specify the wettability of a surface. The real-time contact angle measurement enables us to obtain the dynamic contact angle hysteresis on chemically heterogeneous surface, while the mechanical analyses can be effectively implemented at the moving contact line.

Discrete Alfvén eigenmodes in the CFETR steady-state scenario

Yuan-Dan Lan(兰源丹), Shuang-Hui Hu(胡双辉), Si-Jie Ouyang(欧阳思杰),Wan-Po Zhu(朱万坡), and Xuan-Ge Huang(黄旋格)

Chin. Phys. B, 2023, 32 (5): 055201. DOI: 10.1088/1674-1056/aca397

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The stability features of discrete Alfvén eigenmodes (α TAEs) trapped by α-induced potential wells are explored in the China Fusion Engineering Test Reactor (CFETR) advanced steady-state operation environment, where α denotes a measure of the pressure gradient. For the reversed magnetic shear (RS) H-mode scenario with an enhanced internal transport barrier (ITB), the α TAEs are trapped in the electron cyclotron (EC) power deposition region and the effects of different pedestals on α TAEs are analyzed. For the negative off-axis magnetic shear scenario, the α TAEs are discussed, and the effect of different magnetic shears on the α TAEs is presented. Finally, the effects of beam energies and pitch-angle distributions on α TAE stability are also presented.

Zr-doping stabilizes spinel LiMn₂O₄ as a low cost long cycle life cathode for lithium ion batteries Suggested by editors

Xiang-Gong Zhang(张祥功), Wei Wu(吴伟), Si-Si Zhou(周思思), Fei Huang(黄飞), Shi-Hao Xu(许诗浩), Liang Yin(尹良), Wei Yang(杨伟), and Hong Li(李泓)

Chin. Phys. B, 2023, 32 (5): 056101. DOI: 10.1088/1674-1056/acb919

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The present commercial spinel LiMn$_{2}$O$_{4}$ delivers only 90 mAh/g-115 mAh/g, far lower than the theoretical specific capacity. It degrades fast caused by the Jahn-Teller effect, Mn dissolution and related side reactions that consume Li inventory. In this work, Zr doping is employed to improve the structural stability and electrochemical performance of spinel LiMn$_{2}$O$_{4}$. Li$_{1.06}$Mn$_{1.94-x}$Zr$_{x}$O$_{4}$ ($x = 0$, 0.01, 0.02, 0.04) have been successfully synthesized by a simple solid-state reaction method and evaluated as cathode for lithium ion batteries (LIB). Li$_{1.06}$Mn$_{1.92}$Zr$_{0.02}$O$_{4}$ is superior cathode material with a high capacity of 122 mAh/g at 1-C rate; long cycle stability, 98.39% retention after 100 cycles at 1-C rate, excellent high rate performance 107.1 mAh/g at 10-C rate, and high temperature performance 97.39% retention after 60 cycles. These are thought to be related to Zr doping effectively stabilizing the spinel LiMn$_{2}$O$_{4}$, by forming stronger Zr-O bonds in the octahedron, suppressing the Jahn-Teller effect, thus improving electrochemical performance.

High-pressure new phases of V-N compounds Suggested by editors

Xu-Han Shi(时旭含), Zhi-Hui Li(李志慧), Yuanyuan Liu(刘媛媛), Yuanyuan Wang(王元元), Ran Liu(刘冉), Kuo Hu(胡阔), and Zhen Yao(姚震)

Chin. Phys. B, 2023, 32 (5): 056103. DOI: 10.1088/1674-1056/acbc6d

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The high-pressure diagram of V-N compounds is enriched by proposed seven new stable high-pressure phases. The $P$-1-VN$_{4}$ with the armchair N-rich structure may be quenched to ambient conditions. The formed N-N covalent bond plays an important role for the structural stability of N-chain. The charge transfer results in a V-N ionic bond interaction, which further improves the stability of N-chain structure. The $P$-1-VN$_{4}$, $P4mnc$-VN$_{8}$, and $Immm$-VN$_{10}$ with the outstanding detonation properties have potential application in explosive field.

Spatial distribution order parameter prediction of collective system using graph network

Huimin Zhao(赵慧敏), Rui Wang(王瑞), Cai Zhao(赵偲), and Wen Zheng(郑文)

Chin. Phys. B, 2023, 32 (5): 056402. DOI: 10.1088/1674-1056/acb9fa

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In the past few decades, the study of collective motion phase transition process has made great progress. It is also important for the description of the spatial distribution of particles. In this work, we propose a new order parameter φ to quantify the degree of order in the spatial distribution of particles. The results show that the spatial distribution order parameter can effectively describe the transition from a disorderly moving phase to a phase with a coherent motion of the particle distribution and the same conclusion could be obtained for systems with different sizes. Furthermore, we develop a powerful molecular dynamic graph network (MDGNet) model to realize the long-term prediction of the self-propelled collective system solely from the initial particle positions and movement angles. Employing this model, we successfully predict the order parameters of the specified time step. And the model can also be applied to analyze other types of complex systems with local interactions.

Thermal expansion behavior of sintered Nd-Fe-B magnets with different Co contents and orientations

Rui-Yang Meng(孟睿阳), Ji-Yuan Xu(徐吉元), Jia-Teng Zhang(张家滕), Jing Liu(刘静), Yi-Kun Fang(方以坤), Sheng-Zhi Dong(董生智), and Wei Li(李卫)

Chin. Phys. B, 2023, 32 (5): 056501. DOI: 10.1088/1674-1056/acc933

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The thermal expansion behavior of sintered Nd-Fe-B magnets is a crucial parameter for production and application. However, this aspect has not been thoroughly investigated. In this study, three different sintered Nd-Fe-B magnets with varying Co content (m Co=0, 6, 12 wt%) were prepared using the conventional powder metallurgy method, and four magnets oriented under different magnetic fields were prepared to compare. The thermal expansion behavior for the magnets was investigated using a linear thermal dilatometry in the temperature range of 20 ℃-500 ℃. It was found that, the coefficient of thermal expansion (CTE) increases with the increase of Co contents, while the anisotropy of thermal expansion decreases. The introduction of Co leads to continuous changes from negative to positive thermal expansion in the vertically oriented direction, which is important for the development of zero thermal expansion magnets. The thermal expansion of non-oriented magnets was found to be isotropic. Additionally, the anisotropy of thermal expansion increases with the increase of orientation degree. These results have important implications for the development of sintered Nd-Fe-B with controllable CTE.

Continuous modulation of charge-spin conversion by electric field in Pt/Co₂FeSi/Pb(Mg_1/3Nb_2/3)O₃-Pb_0.7Ti_0.3O₃ heterostructures

Yibing Zhao(赵逸冰), Xiaoxiao Fang(方晓筱), Zhirui Wang(王志睿), Miao Cheng(程淼), Yongjia Tan(谭永嘉), Dongxiong Wei(韦东雄), Changjun Jiang(蒋长军), and Jinli Yao(幺金丽)

Chin. Phys. B, 2023, 32 (5): 056701. DOI: 10.1088/1674-1056/acb2c0

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The half-metallic Heusler alloy Co$_{2}$FeSi is an ideal material in spintronic devices due to its higher spin polarization, higher Curie temperature and lower damping parameters. In this work, the dynamic magnetism of Co$_{2}$FeSi is modulated by electric field and it is demonstrated that the charge-spin conversion efficiency $\xi $ is continuous and controllable by the electric field. We further find an extremely high $\xi $ in ferromagnetic/ferroelectric (FM/FE) heterostructures, which could be ascribed to interfacial effect in FM/FE interface. Moreover, we investigate that the charge-spin conversion efficiency varies with the electric field in a butterfly-like behavior, which accords with the $S$-$E$ curve of Pb(Mg$_{1/3}$Nb$_{2/3})$O$_{3}$-Pb$_{0.7}$Ti$_{0.3}$O$_{3}$(PMN-PT) and could be attributed to strain effect. The modulation of charge-spin conversion efficiency in FM/FE heterostructures via electric field presents a profound potential for next-generation spintronic devices and applications of current-induced magnetization switching.

Quasi-one-dimensional characters in topological semimetal TaNiTe₅

Ni Ma(马妮), De-Yang Wang(王德阳), Ben-Rui Huang(黄本锐), Kai-Yi Li(李凯仪), Jing-Peng Song(宋靖鹏), Jian-Zhong Liu(刘建忠), Hong-Ping Mei(梅红萍), Mao Ye(叶茂), and Ang Li(李昂)

Chin. Phys. B, 2023, 32 (5): 056801. DOI: 10.1088/1674-1056/aca203

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One-dimensional (1D) topological insulators are superior for low-dissipation applications owing to the 1D character of surface states where scatterings other than prohibited backscattering are further restricted. Among the proposed candidates for 1D topological materials, TaNiTe₅ has attracted intensive attention for its quasi-one-dimensional (quasi-1D) crystalline structure. In this study, we identify the chain-like construction and anisotropic electronic states on TaNiTe₅ surface with scanning tunneling microscopy. The electron scatterings are largely suppressed even with chromium impurities deposited on the surface and magnetic field applied normal to the surface, which endows TaNiTe₅ great potential for low-dissipation spintronic applications.

Thermal spin molecular logic gates modulated by an electric field

Xingyi Tan(谭兴毅), Qiang Li(李强), and Dahua Ren(任达华)

Chin. Phys. B, 2023, 32 (5): 057101. DOI: 10.1088/1674-1056/ac89e5

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Logic gates are fundamental structural components in all modern digital electronic devices. Here, nonequilibrium Green's functions are incorporated with the density functional theory to verify the thermal spin transport features of the single-molecule spintronic devices constructed by a single molecule in series or parallel connected with graphene nanoribbons electrodes. Our calculations demonstrate that the electric field can manipulate the spin-polarized current. Then, a complete set of thermal spin molecular logic gates are proposed, including AND, OR, and NOT gates. The mentioned logic gates enable different designs of complex thermal spin molecular logic functions and facilitate the electric field control of thermal spin molecular devices.

Long-range adsorbate interactions mediated by two-dimensional Dirac fermions

Xiaohui Wang(王晓慧), Zhen-Guo Fu(付振国), Zhigang Wang(王志刚), Feng Chi(迟锋), and Ping Zhang(张平)

Chin. Phys. B, 2023, 32 (5): 057201. DOI: 10.1088/1674-1056/acae77

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We provide here an analytical formalism to describe the indirect interaction between adsorbed atom or molecule pairs mediated by two-dimensional (2D) Dirac fermions. We show that in contrast to the case of traditional 2D electron gas, in the 2D Dirac system, the long-range interaction behaves as 1/r³ decaying Friedel oscillation. This analytical formalism is fully consistent with a tight-binding numerical calculation of honeycomb lattices. Our formalism is suitable for the realistic 2D Dirac materials, such as graphene and surface states of three-dimensional topological insulators.

Room temperature quantum anomalous Hall insulator in honeycomb lattice, RuCS₃, with large magnetic anisotropy energy

Yong-Chun Zhao(赵永春), Ming-Xin Zhu(朱铭鑫), Sheng-Shi Li(李胜世), and Ping Li(李萍)

Chin. Phys. B, 2023, 32 (5): 057301. DOI: 10.1088/1674-1056/aca396

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The quantum anomalous Hall (QAH) effect has attracted enormous attention since it can induce topologically protected conducting edge states in an intrinsic insulating material. For practical quantum applications, the main obstacle is the non-existent room temperature QAH systems, especially with both large topological band gap and robust ferromagnetic order. Here, according to first-principles calculations, we predict the realization of the room temperature QAH effect in a two-dimensional (2D) honeycomb lattice, RuCS₃ with a non-zero Chern number of C = 1. Especially, the nontrivial topology band gap reaches up to 336 meV for RuCS₃. Moreover, we find that RuCS₃ has a large magnetic anisotropy energy (2.065 meV) and high Curie temperature (696 K). We further find that the non-trivial topological properties are robust against the biaxial strain. The robust topological and magnetic properties make RuCS₃ have great applications in room temperature spintronics and nanoelectronics.

Delayed response to the photovoltaic performance in a double quantum dots photocell with spatially correlated fluctuation

Sheng-Nan Zhu(祝胜男), Shun-Cai Zhao(赵顺才), Lu-Xin Xu(许路昕), and Lin-Jie Chen(陈林杰)

Chin. Phys. B, 2023, 32 (5): 057302. DOI: 10.1088/1674-1056/ac8e97

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A viable strategy for enhancing photovoltaic performance is to comprehend the underlying quantum physical regime of charge transfer in a double quantum dots (DQD) photocell. This work explored the photovoltaic performance dependent spatially correlated fluctuation in a DQD photocell. The effects of spatially correlated fluctuation on charge transfer and output photovoltaic efficiency were explored in a proposed DQD photocell model. The results revealed that the charge transport process and the time to peak photovoltaic efficiency were both significantly delayed by the spatially correlated fluctuation, while the anti-spatially correlated fluctuation reduced the output peak photovoltaic efficiency. Further results revealed that the delayed response could be suppressed by gap difference and tunneling coefficient within two dots. Subsequent investigation demonstrated that the delayed response was caused by the spatial correlation fluctuation slowing the generative process of noise-induced coherence, which had previously been proven to improve the quantum photovoltaic performance in quantum photocells. And the reduced photovoltaic properties were verified by the damaged noise-induced coherence owing to the anti-spatial correlation fluctuation and a hotter thermal ambient environment. The discovery of delayed response generated by the spatially correlated fluctuations will deepen the understanding of quantum features of electron transfer, as well as promises to take our understanding even further concerning quantum techniques for high efficiency DQD solar cells.

Hydrogenic donor impurity states and intersubband optical absorption spectra of monolayer transition metal dichalcogenides in dielectric environments

Shu-Dong Wu(吴曙东)

Chin. Phys. B, 2023, 32 (5): 057303. DOI: 10.1088/1674-1056/ac9b30

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The hydrogenic donor impurity states and intersubband optical absorption spectra in monolayer transition metal dichalcogenides (ML TMDs) under dielectric environments are theoretically investigated based on a two-dimensional (2D) nonorthogonal associated Laguerre basis set. The 2D quantum confinement effect together with the strongly reduced dielectric screening results in the strong attractive Coulomb potential between electron and donor ion, with exceptionally large impurity binding energy and huge intersubband oscillator strength. These lead to the strong interaction of the electron with light in a 2D regime. The intersubband optical absorption spectra exhibit strong absorption lines of the non-hydrogenic Rydberg series in the mid-infrared range of light. The strength of the Coulomb potential can be controlled by changing the dielectric environment. The electron affinity difference leads to charge transfer between ML TMD and the dielectric environment, generating the polarization-electric field in ML TMD accompanied by weakening the Coulomb interaction strength. The larger the dielectric constant of the dielectric environment, the more the charge transfer is, accompanied by the larger polarization-electric field and the stronger dielectric screening. The dielectric environment is shown to provide an efficient tool to tune the wavelength and output of the mid-infrared intersubband devices based on ML TMDs.

Density-wave tendency from a topological nodal-line perspective

Tianlun Zhao(赵天伦) and Yi Zhang(张亿)

Chin. Phys. B, 2023, 32 (5): 057304. DOI: 10.1088/1674-1056/acbc6b

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The understanding of density waves is a vital component of our insight into electronic quantum matters. Here, we propose an additional mosaic to the existing mechanisms such as Fermi-surface nesting, electron-phonon coupling, and exciton condensation. In particular, we find that certain two-dimensional (2D) spin density-wave systems are equivalent to three-dimensional (3D) Dirac nodal-line systems in the presence of a magnetic field, whose electronic structure takes the form of Dirac-fermion Landau levels and allows a straightforward analysis of its optimal filling. The subsequent minimum-energy wave vector varies over a continuous range and shows no direct connection to the original Fermi surfaces in 2D. Also, we carry out numerical calculations where the results on model examples support our theory. Our study points out that we have yet to attain a complete understanding of the emergent density wave formalism.

Impact of low-dose radiation on nitrided lateral 4H-SiC MOSFETs and the related mechanisms

Wen-Hao Zhang(张文浩), Ma-Guang Zhu(朱马光), Kang-Hua Yu(余康华), Cheng-Zhan Li(李诚瞻),Jun Wang(王俊), Li Xiang(向立), and Yu-Wei Wang(王雨薇)

Chin. Phys. B, 2023, 32 (5): 057305. DOI: 10.1088/1674-1056/acbd2e

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Lateral type n-channel 4H-SiC metal-oxide-semiconductor field effect transistors (MOSFETs), fabricated using a current industrial process, are irradiated with gamma rays at different irradiation doses in this paper to carry out a profound study on the generation mechanism of radiation-induced interface traps and oxide trapped charges. Electrical parameters (e.g., threshold voltage, subthreshold swing and channel mobility) of the device before and after irradiation are investigated, and the influence of the channel orientation ($[1\overline{1}00]$ and $[11\overline {2} 0]$) on the radiation effect is discussed for the first time. A positive threshold voltage shift is observed at very low irradiation doses ($< 100$ krad (Si)); the threshold voltage then shifts negatively as the dose increases. It is found that the dependence of interface trap generation on the radiation dose is not the same for doses below and above 100 krad. For irradiation $\rm doses < 100 $ krad, the radiation-induced interface traps with relatively high generation speeds dominate the competition with radiation-induced oxide trapped charges, contributing to the positive threshold voltage shift correspondingly. All these results provide additional insight into the radiation-induced charge trapping mechanism in the SiO$_{2}$/SiC interface.

Discrete vortex bound states with a van Hove singularity in the vicinity of the Fermi level

Delong Fang(方德龙) and Yunkang Cui(崔云康)

Chin. Phys. B, 2023, 32 (5): 057401. DOI: 10.1088/1674-1056/aca6d6

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A theoretical study on discrete vortex bound states is carried out near a vortex core in the presence of a van Hove singularity (VHS) near the Fermi level by solving Bogoliubov-de Gennes (BdG) equations. When the VHS lies exactly at the Fermi level and also at the middle of the band, a zero-energy state and other higher-energy states whose energy ratios follow integer numbers emerge. These discrete vortex bound state peaks undergo a splitting behavior when the VHS or Fermi level moves away from the middle of the band. Such splitting behavior will eventually lead to a new arrangement of quantized vortex core states whose energy ratios follow half-odd-integer numbers.

Topological magnetotransport and electrical switching of sputtered antiferromagnetic Ir₂₀Mn₈₀ Suggested by editors

Danrong Xiong(熊丹荣), Yuhao Jiang(蒋宇昊), Daoqian Zhu(朱道乾), Ao Du(杜奥), Zongxia Guo(郭宗夏), Shiyang Lu(卢世阳), Chunxu Wang(王春旭), Qingtao Xia(夏清涛), Dapeng Zhu(朱大鹏), and Weisheng Zhao(赵巍胜)

Chin. Phys. B, 2023, 32 (5): 057501. DOI: 10.1088/1674-1056/acb9ec

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Topological magnetotransport in non-collinear antiferromagnets has attracted extensive attention due to the exotic phenomena such as large anomalous Hall effect (AHE), magnetic spin Hall effect, and chiral anomaly. The materials exhibiting topological antiferromagnetic physics are typically limited in special Mn$_{3}X$ family such as Mn$_{3}$Sn and Mn$_{3}$Ge. Exploring the topological magnetotransport in common antiferromagnetic materials widely used in spintronics will not only enrich the platforms for investigating the non-collinear antiferromagnetic physics, but also have great importance for driving the nontrivial topological properties towards practical applications. Here, we report remarkable AHE, anisotropic and negative parallel magnetoresistance in the magnetron-sputtered Ir$_{20}$Mn$_{80}$ antiferromagnet, which is one of the most widely used antiferromagnetic materials in industrial spintronics. The ab initio calculations suggest that the Ir$_{4}$Mn$_{16}$ (IrMn$_{4}$) or Mn$_{3}$Ir nanocrystals hold nontrivial electronic band structures, which may contribute to the observed intriguing magnetotransport properties in the Ir$_{20}$Mn$_{80}$. Further, we demonstrate the spin-orbit torque switching of the antiferromagnetic Ir$_{20}$Mn$_{80}$ by the spin Hall current of Pt. The presented results highlight a great potential of the magnetron-sputtered Ir$_{20}$Mn$_{80}$ film for exploring the topological antiferromagnet-based physics and spintronics applications.

Bending sensor based on flexible spin valve

L I Naumova, R S Zavornitsyn, M A Milyaev, N G Bebenin, A Y Pavlova, M V Makarova, I K Maksimova, V V Proglyado, A A Zakharov, and V V Ustinov

Chin. Phys. B, 2023, 32 (5): 057502. DOI: 10.1088/1674-1056/ac8923

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Flexible spin valves were prepared by magnetron sputtering on polyimide substrates. The buffer layer that reduces significantly the effect of the polymer substrate on the spin valve microstructure and magnetoresistive properties was revealed. Bending deformation was applied to the microobjects based on the flexible spin valves in parallel to anisotropy axes. It was revealed that during the bend the magnetoresistance changes due to the joint impact of both the change of the magnetic field projection on the film plane and the change of the magnetic properties of the ferromagnetic layers. The obtained dependences have been used in construction of bending sensor, in which the flexible spin valve microstripes were united into the Wheatstone bridge.

Stability analysis of magnetization in a perpendicular magnetic layer driven by spin Hall effect Suggested by editors

Zai-Dong Li(李再东), Xin-Xin Zhao(赵欣欣), and Tian-Fu Xu(徐天赋)

Chin. Phys. B, 2023, 32 (5): 057503. DOI: 10.1088/1674-1056/acb204

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We investigate the stability of magnetization in free layer where the spin torque is induced by the spin Hall effect. In terms of the Landau-Liftshitz-Gilbert equation, we find the low-energy and high-energy equilibrium states, as well as the saddle points. The stability region is defined in the phase diagram spanned by the current density and the spin Hall angle. The spin Hall effect makes the previous saddle point into a stable state above a critical current. However, in the presence of magnetic field, the spin Hall effect leads to the opposite changes in the stable regions of the two low-energy states.

Improved microwave dielectric properties of MgAl₂O₄ spinel ceramics through (Li_1/3Ti_2/3)³⁺ doping

Xiao Li(李潇), Xizhi Yang(杨习志), Yuanming Lai(赖元明), Qin Zhang(张芹), Baoyang Li(李宝阳),Cong Qi(戚聪), Jun Yin(殷俊), Fanshuo Wang(王凡硕), Chongsheng Wu(巫崇胜), and Hua Su(苏桦)

Chin. Phys. B, 2023, 32 (5): 057701. DOI: 10.1088/1674-1056/ac81a8

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A series of nominal compositions MgAl$_{2-x}$(Li$_{1/3}$Ti$_{2/3}$)$_{x}$O$_{4}$ ($x = 0$, 0.04, 0.08, 0.12, 0.16, and 0.20) ceramics were successfully prepared via the conventional solid-state reaction route. The phase compositions, microstructures, and microwave dielectric properties were investigated. The results of x-ray diffraction (XRD) and scanning electron microscopy (SEM) showed that a single phase of MgAl$_{2-x}$(Li$_{1/3}$Ti$_{2/3}$)$_{x}$O$_{4}$ ceramics with a spinel structure was obtained at $x \le 0.12$, whereas the second phase of MgTi$_{2}$O$_{5}$ appeared when $x > 0.12$. The cell parameters were obtained by XRD refinement. As the $x$ values increased, the unit cell volume kept expanding. This phenomenon could be attributed to the partial substitution of (Li$_{1/3}$Ti$_{2/3}$)$^{3+}$ for Al$^{3+}$. Results showed that (Li$_{1/3}$Ti$_{2/3}$)$^{3+}$ doping into MgAl$_{2}$O$_{4}$ spinel ceramics effectively reduced the sintering temperature and improved the quality factor ($Q_{\rm f}$) values. Good microwave dielectric properties were achieved for a sample at $x = 0.20$ sintering at 1500 ${^\circ}$C in air for 4 h: dielectric constant $\varepsilon_{\rm r} =8.78$, temperature coefficient of resonant frequency $\tau_{\rm f} = -85 $ ppm/${^\circ}$C, and ${Q_{\rm f}} = 62 300 $ GHz. The $Q_{\rm f}$ value of the $x = 0.20$ sample was about 2 times higher than that of pure MgAl$_{2}$O$_{4}$ ceramics (31600 GHz). Thus, MgAl$_{2-x}$(Li$_{1/3}$Ti$_{2/3}$)$_{x}$O$_{4}$ ceramics with excellent microwave dielectric properties can be applied to 5G communications.

Theoretical investigation on the fluorescent sensing mechanism for recognizing formaldehyde: TDDFT calculation and excited-state nonadiabatic dynamics

Yunfan Yang(杨云帆), Lujia Yang(杨璐佳), Fengcai Ma(马凤才), Yongqing Li(李永庆), and Yue Qiu(邱岳)

Chin. Phys. B, 2023, 32 (5): 057801. DOI: 10.1088/1674-1056/ac80af

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Inspired by the activity-based sensing method, the hydrazine-modified naphthalene derivative (Naph1) was synthesized and used as a fluorescent probe to detect formaldehyde (FA) in living cells. Through the condensation reaction between the probe Naph1 and analyte FA, researchers observed a ～ 14 folds enhancement of fluorescent signal around 510 nm in an experiment, realizing the high selectivity and sensitivity detection of FA. However, a theoretical understanding of the sensing mechanism was not provided in the experimental work. Given this, the light-up fluorescent detecting mechanism was in-depth unveiled by performing the time-dependent density functional theory (TDDFT) and the complete active space self-consistent field (CASSCF) theoretical calculations on excited-state intramolecular proton transfer (ESIPT) and non-adiabatic excited-state dynamics simulation. The deactivation channel of S₁/T₂ intersystem crossing (ISC) was turned off to successfully recognize FA. Insight into the ESIPT-based fluorescent detecting mechanism indicated that ESIPT was essential to light-up fluorescent probes. This work would provide a new viewpoint to develop ESIPT-based fluorescent probes for detecting reactive carbon species in vivo or vitio.

Low switching loss and increased short-circuit capability split-gate SiC trench MOSFET with p-type pillar

Pei Shen(沈培), Ying Wang(王颖), Xing-Ji Li(李兴冀), Jian-Qun Yang(杨剑群), and Fei Cao(曹菲)

Chin. Phys. B, 2023, 32 (5): 058501. DOI: 10.1088/1674-1056/ac98a1

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A split-gate SiC trench gate MOSFET with stepped thick oxide, source-connected split-gate (SG), and p-type pillar (p-pillar) surrounded thick oxide shielding region (GSDP-TMOS) is investigated by Silvaco TCAD simulations. The source-connected SG region and p-pillar shielding region are introduced to form an effective two-level shielding, which reduces the specific gate-drain charge ($Q_{\rm gd,sp}$) and the saturation current, thus reducing the switching loss and increasing the short-circuit capability. The thick oxide that surrounds a p-pillar shielding region efficiently protects gate oxide from being damaged by peaked electric field, thereby increasing the breakdown voltage ($BV$). Additionally, because of the high concentration in the n-type drift region, the electrons diffuse rapidly and the specific on-resistance ($R_{\rm on,sp}$) becomes smaller. In the end, comparing with the bottom p$^{+}$ shielded trench MOSFET (GP-TMOS), the Baliga figure of merit (BFOM, $BV^{2}/R_{\rm on,sp}$) is increased by 169.6%, and the high-frequency figure of merit (HF-FOM, $R_{\rm on,sp}\times Q_{\rm gd,sp}$) is improved by 310%, respectively.

Realization of high-efficiency AlGaN deep ultraviolet light-emitting diodes with polarization-induced doping of the p-AlGaN hole injection layer

Yi-Wei Cao(曹一伟), Quan-Jiang Lv(吕全江), Tian-Peng Yang(杨天鹏), Ting-Ting Mi(米亭亭),Xiao-Wen Wang(王小文), Wei Liu(刘伟), and Jun-Lin Liu(刘军林)

Chin. Phys. B, 2023, 32 (5): 058503. DOI: 10.1088/1674-1056/ac9de7

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We investigate the polarization-induced doping in the gradient variation of Al composition in the p-Al$_{0.75}$Ga$_{0.25}$N/Al$_{x}$Ga$_{1-x}$N hole injection layer (HIL) for deep ultraviolet light-emitting diodes (DUV-LEDs) with an ultra-thin p-GaN (4 nm) ohmic contact layer capable of emitting 277 nm. The experimental results show that the external quantum efficiency (EQE) and wall plug efficiency (WPE) of the structure graded from 0.75 to 0.55 in the HIL reach 5.49% and 5.04%, which are improved significantly by 182% and 209%, respectively, compared with the structure graded from 0.75 to 0.45, exhibiting a tremendous improvement. Both theoretical speculations and simulation results support that the larger the difference between 0.75 and $x$ in the HIL, the higher the hole concentration that should be induced; thus, the DUV-LED has a higher internal quantum efficiency (IQE). Meanwhile, as the value of $x$ decreases, the absorption of the DUV light emitted from the active region by the HIL is enhanced, reducing the light extraction efficiency (LEE). The IQE and LEE together affect the EQE performance of DUV-LEDs. To trade off the contradiction between the enhanced IQE and decreased LEE caused by the decrease in Al composition, the Al composition in the HIL was optimized through theoretical calculations and experiments.

A SiC asymmetric cell trench MOSFET with a split gate and integrated p⁺-poly Si/SiC heterojunction freewheeling diode

Kaizhe Jiang(蒋铠哲), Xiaodong Zhang(张孝冬), Chuan Tian(田川), Shengrong Zhang(张升荣),Liqiang Zheng(郑理强), Rongzhao He(赫荣钊), and Chong Shen(沈重)

Chin. Phys. B, 2023, 32 (5): 058504. DOI: 10.1088/1674-1056/acbd2d

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A new SiC asymmetric cell trench metal--oxide--semiconductor field effect transistor (MOSFET) with a split gate (SG) and integrated p$^{+}$-poly Si/SiC heterojunction freewheeling diode (SGHJD-TMOS) is investigated in this article. The SG structure of the SGHJD-TMOS structure can effectively reduce the gate-drain capacitance and reduce the high gate-oxide electric field. The integrated p$^{+}$-poly Si/SiC heterojunction freewheeling diode substantially improves body diode characteristics and reduces switching losses without degrading the static characteristics of the device. Numerical analysis results show that, compared with the conventional asymmetric cell trench MOSFET (CA-TMOS), the high-frequency figure of merit (HF-FOM, $R_{\rm on,sp}\times Q_{\rm gd,sp}$) is reduced by 92.5%, and the gate-oxide electric field is reduced by 75%. In addition, the forward conduction voltage drop ($V_{\rm F}$) and gate-drain charge ($Q_{\rm gd}$) are reduced from 2.90 V and 63.5 μC/cm$^{2}$ in the CA-TMOS to 1.80 V and 26.1 μC/cm$^{2}$ in the SGHJD-TMOS, respectively. Compared with the CA-TMOS, the turn-on loss ($E_{\rm on}$) and turn-off loss ($E_{\rm off}$) of the SGHJD-TMOS are reduced by 21.1% and 12.2%, respectively.

Synchronization coexistence in a Rulkov neural network based on locally active discrete memristor

Ming-Lin Ma(马铭磷), Xiao-Hua Xie(谢小华), Yang Yang(杨阳), Zhi-Jun Li(李志军), and Yi-Chuang Sun(孙义闯)

Chin. Phys. B, 2023, 32 (5): 058701. DOI: 10.1088/1674-1056/acb9f7

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At present, many neuron models have been proposed, which can be divided into discrete neuron models and continuous neuron models. Discrete neuron models have the advantage of faster simulation speed and the ease of understanding complex dynamic phenomena. Due to the properties of memorability, nonvolatility, and local activity, locally active discrete memristors (LADMs) are also suitable for simulating synapses. In this paper, we use an LADM to mimic synapses and establish a Rulkov neural network model. It is found that the change of coupling strength and the initial state of the LADM leads to multiple firing patterns of the neural network. In addition, considering the influence of neural network parameters and the initial state of the LADM, numerical analysis methods such as phase diagram and timing diagram are used to study the phase synchronization. As the system parameters and the initial states of the LADM change, the LADM coupled Rulkov neural network exhibits synchronization transition and synchronization coexistence.

Stability and optimal control for delayed rumor-spreading model with nonlinear incidence over heterogeneous networks

Xupeng Luo(罗续鹏), Haijun Jiang(蒋海军), Shanshan Chen(陈珊珊), and Jiarong Li(李佳容)

Chin. Phys. B, 2023, 32 (5): 058702. DOI: 10.1088/1674-1056/acb490

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On the multilingual online social networks of global information sharing, the wanton spread of rumors has an enormous negative impact on people's lives. Thus, it is essential to explore the rumor-spreading rules in multilingual environment and formulate corresponding control strategies to reduce the harm caused by rumor propagation. In this paper, considering the multilingual environment and intervention mechanism in the rumor-spreading process, an improved ignorants-spreaders-1-spreaders-2-removers (I2SR) rumor-spreading model with time delay and the nonlinear incidence is established in heterogeneous networks. Firstly, based on the mean-field equations corresponding to the model, the basic reproduction number is derived to ensure the existence of rumor-spreading equilibrium. Secondly, by applying Lyapunov stability theory and graph theory, the global stability of rumor-spreading equilibrium is analyzed in detail. In particular, aiming at the lowest control cost, the optimal control scheme is designed to optimize the intervention mechanism, and the optimal control conditions are derived using the Pontryagin's minimum principle. Finally, some illustrative examples are provided to verify the effectiveness of the theoretical results. The results show that optimizing the intervention mechanism can effectively reduce the densities of spreaders-1 and spreaders-2 within the expected time, which provides guiding insights for public opinion managers to control rumors.

AIGCrank: A new adaptive algorithm for identifying a set of influential spreaders in complex networks based on gravity centrality

Ping-Le Yang(杨平乐), Lai-Jun Zhao(赵来军), Chen Dong(董晨),Gui-Qiong Xu(徐桂琼), and Li-Xin Zhou(周立欣)

Chin. Phys. B, 2023, 32 (5): 058901. DOI: 10.1088/1674-1056/ac8e56

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The influence maximization problem in complex networks asks to identify a given size of seed spreaders set to maximize the number of expected influenced nodes at the end of the spreading process. This problem finds many practical applications in numerous areas such as information dissemination, epidemic immunity, and viral marketing. However, most existing influence maximization algorithms are limited by the "rich-club" phenomenon and are thus unable to avoid the influence overlap of seed spreaders. This work proposes a novel adaptive algorithm based on a new gravity centrality and a recursive ranking strategy, named AIGCrank, to identify a set of influential seeds. Specifically, the gravity centrality jointly employs the neighborhood, network location and topological structure information of nodes to evaluate each node's potential of being selected as a seed. We also present a recursive ranking strategy for identifying seed nodes one-by-one. Experimental results show that our algorithm competes very favorably with the state-of-the-art algorithms in terms of influence propagation and coverage redundancy of the seed set.

AG-GATCN: A novel method for predicting essential proteins

Peishi Yang(杨培实), Pengli Lu(卢鹏丽), and Teng Zhang(张腾)

Chin. Phys. B, 2023, 32 (5): 058902. DOI: 10.1088/1674-1056/acb9f9

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Essential proteins play an important role in disease diagnosis and drug development. Many methods have been devoted to the essential protein prediction by using some kinds of biological information. However, they either ignore the noise presented in the biological information itself or the noise generated during feature extraction. To overcome these problems, in this paper, we propose a novel method for predicting essential proteins called attention gate-graph attention network and temporal convolutional network (AG-GATCN). In AG-GATCN method, we use improved temporal convolutional network (TCN) to extract features from gene expression sequence. To address the noise in the gene expression sequence itself and the noise generated after the dilated causal convolution, we introduce attention mechanism and gating mechanism in TCN. In addition, we use graph attention network (GAT) to extract protein-protein interaction (PPI) network features, in which we construct the feature matrix by introducing node2vec technique and 7 centrality metrics, and to solve the GAT oversmoothing problem, we introduce gated tanh unit (GTU) in GAT. Finally, two types of features are integrated by us to predict essential proteins. Compared with the existing methods for predicting essential proteins, the experimental results show that AG-GATCN achieves better performance.

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