Search

Article

x
中国物理学会期刊
Chinese Physics Letters Chinese Physics B 物理学报 物理 中国物理学会期刊网
Advance Search

留言板

尊敬的读者、作者、审稿人, 关于本刊的投稿、审稿、编辑和出版的任何问题, 您可以本页添加留言。我们将尽快给您答复。谢谢您的支持!

姓名
邮箱
手机号码
标题
留言内容
验证码

Accepted Papers

Recent catalogue
Field
Article Type

GENERAL

Full-process simulation of XPCS speckle dynamics based on Monte Carlo method and analysis of key parameter dependencies
ZHOU Zimu, CUI Chenhui, LI Songlin, XU Yihui, TIAN Feng, ZHOU Ping, ZHANG Mingjun, GUO Zhi, TAI Renzhong
2025, 74 (18): 180201. doi: 10.7498/aps.74.20250673
Abstract +
X-ray photon correlation spectroscopy (XPCS) is important for probing mesoscale material dynamics by using synchrotron radiation. However, the complex influences of parameters such as light source properties, beam propagation, and detector response on speckle dynamics are hard to directly observe. In this study, a Monte Carlo-based full optical path numerical model is developed to systematically analyze these effects, thereby aiding experimental optimization.A simulation framework integrating Brownian dynamics, beam coherence, and detector response is constructed to replicate the entire photon emission-to-detection process. A Fraunhofer diffraction-based speckle generation algorithm reproduces speckle fluctuations via atomic position evolution and phase modulation. Feasibility is validated via Siegert relation fitting ($\beta, \gamma$), $\varGamma{\text{-}}q^2$ linearity ($R^2=0.99904$), and consistency with the Einstein-Stokes law.Key parameter sensitivity analysis reveals some points below. 1) Optimal aperture matching ($r/\sigma=1$) balances coherence and photon flux; 2) Mechanical vibrations with $\Delta x/s=1500$ induce periodic oscillations in $g_2(q,\tau)$, masking intrinsic relaxation, which is validated by a 24.658-Hz pump experiment; 3) Poisson noise and intensity fluctuations degrade low-light signal-to-noise ratio, with Poisson noise causing discrete errors and classical noise inducing baseline shifts.This framework clarifies how source properties, optical parameters, and noise affect experimental results, providing guidance for XPCS optimization and a foundation for extending its applications to high-precision coherent scattering scenarios.

GENERAL

Non-Hermitian topological phase induced by next-nearest-neighbor transitions in periodic drive systems
BAO Xixi, GUO Gangfeng, TAN Lei, LIU Wuming
2025, 74 (18): 180301. doi: 10.7498/aps.74.20250599
Abstract +
A non-Hermitian system with long-range hopping under periodic driving is constructed in this work. The Hamiltonian has chiral symmetry, implying that a topological invariant can be determined. Using the non-Bloch band theory and the Floquet method, the relevant operators and topological number can be determined, thereby providing quantitative approaches for studying topological properties. For example, by calculating the non-Bloch time-evolution factor, the Floquet operator, etc., it can be found that the topological invariant is determined by changing the phase of $U^{+}_{\epsilon=0,\pi}(\beta)$ as it moves along the generalized Brillouin zone, corresponding to the emergence of quasi-energy zero mode and π mode.The results show that the topological structure of the static system can be significantly affected by periodic driving. The topological phase boundary of the zero mode can be changed. In the absence of periodic driving, energy spectrum does not exhibit π mode. After introducing periodic driving, a gap appears at the quasi-energy $\epsilon=\pi$, thereby inducing a non-trivial π-mode phase and enriching the topological phase diagram. Furthermore, the next nearest neighbor hopping has a unique effect in this system. It can induce large topological numbers. However, unlike the static system, large topological numbers only appear in specific parameter intervals under periodic driving. As the strength of the next nearest neighbor hopping increases, the large topological number phase disappears, reflecting the non-monotonic regulation characteristics of the Floquet system. In addition, introducing the phase of the next nearest neighbor hopping can change the topological phase boundary, providing new ideas for experimentally regulating topological states.This research is of significance in the field of topological phase transitions in non-Hermitian systems. Theoretically, it reveals the synergistic effect of long-range hopping and periodic driving, and improves the theoretical framework for the cross-research of long-range and dynamic regulation in non-Hermitian systems. From an application perspective, it provides theoretical support for experimentally realizing the controllable modulation of topological states, which is helpful in promoting the development of fields such as low energy consumption electronic devices and topological quantum computing.

GENERAL

Parameter optimization method for space channel continuous-variable quantum key distribution based on Unet network
ZHENG Tian, CHEN Yujie, CHENG Jin, CHEN Lanjian, LIU Ao, DONG Chen
2025, 74 (18): 180302. doi: 10.7498/aps.74.20250740
Abstract +
Continuous-variable quantum key distribution (CV-QKD) has made significant progress in the field of quantum communication, operating under strict conditions such as optical diffraction limit, maximum communication distance, and photoelectric detection limit. The optimization of protocol parameters, particularly the modulation variance ($ {V}_{\mathrm{A}} $), is crucial for the feasibility of CV-QKD. However, in space-to-ground CV-QKD scenarios, the high-speed relative motion between low-earth-orbit satellites and ground stations, coupled with limited on-board computing resources, poses challenges for traditional optimization algorithms to meet the real-time demands of rapidly changing space channels.To cope with these challenges, a novel method of optimizing Gaussian-modulation CV-QKD in space channels using a Unet-based approach is proposed in this work. A comprehensive simulation platform for CV-QKD links, generating a substantial training dataset of 126575 samples by changing parameters such as orbital height and zenith angle, is developed in this work. The Unet network, renowned for its symmetric architecture and powerful feature fusion capabilities, is utilized to achieve near-real-time prediction of modulation variance. Our simulation results demonstrate the effectiveness of the proposed method, with the Unet network achieving a remarkable prediction accuracy of 99.25%–99.41% on 6328 datasets, orbital heights between 510 and 710 km, and excess noise levels between 0.01 and 0.03.Compared with the local search algorithm, which takes 14754 s, the Unet-based approach significantly reduces the inference time to just 1.08 s, representing a speed-up ratio of 1.48 × 106. These findings provide a solid theoretical foundation for optimizing real-time parameters in future space-channel CV-QKD experiments, and have made significant progress in the field of quantum communication. The proposed method not only enhances the efficiency of parameter optimization but also ensures the security and reliability of CV-QKD in dynamic space environments.

GENERAL

Ground state topological properties of ultracold atoms in composite scalar-Raman optical lattices
LIANG Chenggong, YANG Caixia, XIE Siyu, WEI Min, ZHAO Yan
2025, 74 (18): 180303. doi: 10.7498/aps.74.20250692
Abstract +
The ground-state topological properties of ultracold atoms in composite scalar-Raman optical lattices are systematically investigated by solving the two-component Gross-Pitaevskii equation through the imaginary time evolution method. Our study focuses on the interplay between scalar and Raman optical lattice potentials and the role of interatomic interactions in shaping real-space and momentum-space structures. The competition between lattice depth and interaction strength gives rise to a rich phase diagram of ground-state configurations. In the absence of Raman coupling, atoms in scalar optical lattices exhibit topologically trivial periodic density distributions without forming vortices. When only Raman coupling exists, a regular array of vortices of equal size will appear in one spin component, while the other spin component will remain free of vortices. Strikingly, when scalar and Raman lattices coexist, the system develops complex vortex lattices with alternating large and small vortices of opposite circulation, forming a staggered vortex configuration in real space. In momentum space, the condensate wave function displays nontrivial diffraction peaks carrying a well-defined topological phase structure, whose complexity increases with the depth of the optical potentials increasing. In spin space, we observe the emergence of a lattice of half-quantized skyrmions (half-skyrmions), each carrying a topological charge of ±1/2. These topological textures are confirmed by calculating the spin vector field and integrating the topological charge density. Our results demonstrate how the combination of scalar and Raman optical lattices, together with tunable interactions, can induce nontrivial real-space spin textures and momentum-space topological features. These findings offers new insights into the controllable realization of topological quantum states in cold atom systems.

GENERAL

Modification of TOV equation in Poincaré gauge gravity
GUO Zhengrui, LIU Helei, LV Guoliang, MA Yongge
2025, 74 (18): 180401. doi: 10.7498/aps.74.20250644
Abstract +
In recent years, Poincaré gauge gravity theory has attracted widespread attention and has been applied to the fields of gravitation and astrophysics. Therefore, how to distinguish between general relativity and Poincaré gauge gravity theory through experimental observations has become an important subject. The core of Poincaré gauge gravity theory is the introduction of torsion in spacetime. General relativity can be regarded as a special case of Poincaré gauge gravity theory in the absence of torsion. Neutron stars, as celestial bodies with extremely strong gravitational fields, serve as an ideal laboratory for Poincaré gauge gravity theory. At present, research on the properties of neutron stars based on the Poincaré gauge theory of gravitation is very scarce. In view of the significance of Poincaré gauge gravity theory, it is necessary to study the properties of neutron stars within the framework of this theory and check whether observations of neutron stars can be used to distinguish and test Poincaré gauge gravity theory and general relativity.In this work, a specific gravitational field Lagrangian is chosen for Poincaré gauge gravity theory to derive the corresponding gravitational field equations. Based on these equations, the modified Tolman-Oppenheimer-Volkoff (TOV) equation is further derived for spherically symmetric static neutron stars. When the spacetime torsion is zero, the modified static neutron star TOV equation decreases precisely to the TOV equation in general relativity.Then, the influence of torsion on the mass-radius relation of static neutron stars is investigated. Our analysis shows that in spherically symmetric spacetime, when the neutron star is static and only the spin tensor of particles is considered (the order of magnitude is ${10^{ - 34}}$), the mass-radius relation of static neutron stars calculated by this theoretical model is consistent with the result in general relativity. This indicates that under static conditions, the correction effect of torsion on the mass-radius relation of neutron stars can be neglected.This study is limited to static neutron star models under the condition of spherically symmetric spacetime metrics. However, in realistic astrophysical environments, neutron stars possess significant angular momentum. In the final section of this paper, the effect of neutron star rotation is discussed and the selected Poincaré gauge gravity model is found to be unsuitable for investigating the mass–radius relation of rotating neutron stars. This work provides a theoretical foundation and reference methods for further investigating the mass–radius relation of rotating neutron stars within the framework of Poincaré gauge gravity.

NUCLEAR PHYSICS

Improvements of traditional optical model and its applications in heavy-ion collision reaction
LIANG Chuntian, SUN Xiaojun, HUANG Junxi, YANG Haoyu, LI Xiaohua, CAI Chonghai
2025, 74 (18): 182401. doi: 10.7498/aps.74.20250633
Abstract +
To describe the projectile-target interaction in heavy-ion collision, the traditional optical model is improved and a corresponding optical model for heavy-ion collisions is established in this work The program APOMHI is developed accordingly. In heavy-ion collisions, the mass of the projectile is comparable to the mass of target nucleus. Therefore, the projectile and target nucleus must be treated equally. The potential field for their relative motion must arise from an equivalent contribution of both nuclei, not just from the target nucleus. Consequently, the angular momentum coupling scheme must adopt L - S coupling, instead of j - j coupling. The projectile spin i and target spin I first couple to form the projectile-target system spin S (which varies between $ \left| {I - i} \right| $ and $ i + I $). Then, the spin S of this system couples with the orbital angular momentum L of relative motion, forming a total angular momentum J . Thus, the radial wave function UlSJ (r) involves three quantum numbers: l , S , and J , while traditional optical model only involves l and j . Furthermore, since the mass of projectile is similar the mass of target, the form of the optical model potential is symmetrical relative to the projectile and target. The projectile nucleus and the target nucleus are still assumed to be spherical, and their excited states are not considered. The projectile may be lighter or heavier than the target, but they cannot be identical particles. By using this optical model program APOMHI, the elastic scattering angular distributions and compound nucleus absorption cross sections for heavy-ion collisions can be calculated. Taking for example a series of heavy-ion collision reactions with 18O as the projectile nucleus, a corresponding set of universal optical potential parameters is obtained by fitting experimental data. The comparisons show that the theoretical calculations generally accord well with the available experimental data. Here, the results for fusion cross-sections and elastic scattering angular distributions using several representative target nuclei (lighter, comparable in mass, heavier, and heavy compared to the projectile nucleus) are taken for example. Specifically, the fusion cross-section results correspond to targets 9Be, 27Al, 63Cu and 150Sm, while the elastic scattering angular distributions correspond to targets 16O, 24Mg, 58Ni, and 120Sn.

NUCLEAR PHYSICS

Average energy data of β– decay nuclei based on neural networks
WEI Kaiwen, SHANG Tianshuai, TIAN Ronghe, YANG Dong, LI Chunjuan, CHEN Jun, LI Jian, HUANG Xiaolong, ZHU Jiali
2025, 74 (18): 182901. doi: 10.7498/aps.74.20250655
Abstract +
The average β energy data and average γ energy data of the β–-decay nuclei play an important role in many fields of nuclear technology and scientific research, such as the decay heat and antineutrino spectrum calculation for different kinds of reactors. However, the reliable experimental measurements of the average energies for many nuclei are lacking, and the theoretical calculation needs to be improved to meet the requirements for accuracy in the technical applications.In this study, the average β, γ and neutrino energies of the β–-decay nuclei are investigated by the neural network method based on the newly evaluated experimental data of 543 nuclei that are selected from a total of 1136 β–-decay nuclei. In the neural network approach, three different feature sets are used for model training. Each feature set contains a feature characteristic value (one of the $T_{1/2}$, $\left( {1}/{T_{1/2}} \right)^{1/5}$, and$Q/3$), along with five identical feature values (Z, N, parity of Z, parity of N, and $\Delta Z$).The three feature values are selected based on the physical mechanism below. 1) The average energy is obviously related to Q value and approximately taken as $Q/3$ in the reactor industry. Therefore, the $Q/3$ is chosen as one feature value. 2) The half-live is related to the Q value of β–-decay, and $T_{1/2}$ is considered. 3) According to the Sargent’s law, $\left( {1}/{T_{1/2}} \right)^{1/5} \propto Q$, a more accurate $\left( {1}/{T_{1/2}} \right)^{1/5}$ value is selected.As a result, for the feature set of $T_{1/2}$, the training results for all three types of average energies are unsatisfactory. For the other groups, the relative errors of the average β energy data, are 19.32% and 28.11% for $\left( {1}/{T_{1/2}} \right)^{1/5}$ and $Q/3$ feature groups in the training set, and 82% and 56.9% in the validation set; the relative errors of the average γ energy are 28.9% and 76.9% for $\left( {1}/{T_{1/2}} \right)^{1/5}$ and $Q/3$ feature sets, respectively, and they are both >100% in the validation set; for the average neutrino energy, the relative errors in the training set are 27.82% and 35.33% for $\left( {1}/{T_{1/2}} \right)^{1/5}$ and $Q/3$ feature group, and 76.32% and 37.76% in the validation set, respectively.Considering the accuracy comparison of the three groups, the $Q/3$ feature set is chosen to predict the average energy data of nuclei in the fission product region (mass numbers range from 66 to 172), which lacks reliable experimental data. As a result, the average energy data with predicted values for 291 nuclei are supplemented. Besides, a comparison is made between the calculated data and the evaluated experimental data through the nuclide chart. It is found that the neural network accurately predicts the experimental data for the average β and neutrino energies which exhibit relatively strong regularity. However, it shows significant deviations in predictions for average gamma energy (relative error in the training set is 76.9%). Large deviation also emerges in the odd-odd nuclei and nuclei near magic numbers. This study confirms that integrating empirical relationships and physical principles can effectively improve the performance of the neural network, and simultaneously reveals the relationship between data regularity and model generalization capability. These findings provide a basis for using physical mechanisms to optimize machine learning models in the future.

ATOMIC AND MOLECULAR PHYSICS

Electroosmotic slip reduction mechanism of solutions in domain-limited channels
WU Jicheng, LU Yan
2025, 74 (18): 183101. doi: 10.7498/aps.74.20250440
Abstract +
Electroosmosis drives a large slip velocity at the interface by altering the electrokinetic double layer effect at the fluid-solid interface, thereby generating high shear rates within the channel. In this paper, molecular dynamics simulations are used to construct an electroosmotic flow nanochannel model, and the fluid flow characteristics and wall slip reduction properties within graphene charged-wall nanochannels are investigated. The results show that the electroosmotic flow changes the structure of the bilayer to increase the mobility of its diffusion layer, and at the same time, the ions in the diffusion layer under the action of the applied electric field undergo directional migration and drive the overall fluid flow through the viscous effect, which enhances the mobility performance. After the introduction of ions, Na+ is adsorbed at the wall surface, which weakens the adsorption force between the fluid and the wall surface and enhances the driving force of the fluid in the confined domain space, thus increasing the slip length and flow rate. Finally, by modulating the charge size on the upper and lower wall surfaces, asymmetric channel wall charges are formed. The electric field gradient superimposed on the applied electric field further enhances the driving force of ions, changes the distribution of the of Na+ adsorption layer and the migration behavior of Cl–, thereby increasing the transport of the solution in the channel. Therefore, in this paper, a method is proposed to realize the ultrafast transport of solution in the channel by modulating the asymmetric wall charge of graphene, successfully achieving the slip reduction effect of the electroosmotic flow of solution in the graphene channel. A theoretical basis is laid for the fast and energy-saving transportation of microfluidics in the nano-limited space.

ATOMIC AND MOLECULAR PHYSICS

Multi-objective and multi-constraint optimization of ultracold molecular orientation with limited rotational states
YU Zhenyang, HONG Qianqian, YI Yougen, SHU Chuancun
2025, 74 (18): 183102. doi: 10.7498/aps.74.20250684
Abstract +
The design of shaping pulse fields for controlling molecular orientation is of great importance in fields of stereochemical reactions, strong-field ionization, and quantum information processing. Traditional quantum optimal control algorithms typically solve the problem of molecular orientation in an infinite-dimensional rotational space, but they often overlook the constraints imposed by experimental limitations. In this work, a multi-objective and multi-constraint quantum optimal control algorithm is proposed to design a pulse field that conforms to the constraints of pulse area and energy. Specifically, the algorithm enforces a zero pulse area condition to eliminate the static field components and maintains constant pulse energy, ensuring compatibility with realistic experimental setups. Under these constraints, the algorithm optimizes the population and phase distribution of a selected number of low-lying rotational states in ultracold molecules to achieve maximum molecular orientation. The effectiveness of the proposed algorithm is demonstrated through numerical studies involving two- and three-state target subspaces, where the creation of a coherent superposition state with optimized population and phase distribution leads to the desired molecular orientation. Furthermore, its scalability is validated by applying it to a more complex 17-state subspace, where a maximum orientation value of 0.99055 is obtained, approaching the global optimal value of 1. Our findings demonstrate that by effectively managing these constraints, the influence of rotational states in the non-target state subspace can be substantially suppressed. The time-frequency analysis of the optimized pulses, combined with the Fourier transform spectrum of the time-dependent degree of orientation, indicates that the maximum molecular orientation is mainly achieved through ladder-climbing excitation of multi-color pulse fields, with the contributions from highly excited states being minimal. This work provides a valuable reference for designing experimentally feasible pulse fields using multi-constraint optimization algorithms, which helps to precisely control a limited number of rotational states to achieve maximum molecular orientation.

ATOMIC AND MOLECULAR PHYSICS

Preparation of single-quantum-state-selected helium for neutral atom-molecule merged-beams collisions
WEI Long, DU Xiaojiao, WEN Jinlu, DONG Junfeng, SUN Yu, HU Shuiming
2025, 74 (18): 183103. doi: 10.7498/aps.74.20250812
Abstract +
Studying low-temperature atomic and molecular reaction dynamics in quantum state selection is one of the key research methods for exploring the collision reaction mechanisms and revealing quantum effects in scattering processes. The merging beam collision experimental method is a powerful approach to achieving cold collisions of mK collision energy, by deflecting one reactant beam to collide with another reactant beam in a collinear manner.In this work, based on the Zeeman effect, the interaction between atomic magnetic moments and a magnetic field, a permanent-magnet “magnetic guide” system is developed to deflect metastable helium atom beams, with the aim of achieving collinear transport of neutral helium atoms and molecules in cold merged-beams collisions. Metastable helium atoms He(23S1) are produced through RF discharge. Utilizing this “magnetic guide”, the quantum-state-resolved neutral helium atoms (He(23S1), $ {M_J} = + 1 $) are prepared. Helium flux measurements demonstrate about 10°deflection of metastable helium atoms with a flux exceeding 106 atoms/s, accompanied by successful preparation of $ {M_J} = + 1 $ magnetic sublevel helium atoms. Furthermore, by combining the magnetic field measurements and magnetic force calculations for 23S1 metastable helium atom, the simulated trajectories propagating through the magnetic guide are analyzed.This work lays an experimental foundation for quantum-state-resolved cold collisions between excited-state helium and molecules below 1 K, advancing the understanding of cold reaction mechanisms governing the evolution of interstellar media and promoting chemical reaction control. The developed magnetic guidance technology in this study also has important application prospects in fields such as atomic velocity filtering and cold atom transport.In the future, optical pumping experimental methods will be employed to pump 23S1 helium atoms into the $ {M_J} = + 1 $ magnetic sublevel helium atoms, enhancing the population of single quantum state. Moreover, two-dimensional magneto-optical traps and optical molasses will be implemented to optimize beam, which is expected to further improve the beam flux of helium atoms.
  • 1
  • 2
  • 3
  • 4
  • 5
  • ...
  • 16
  • 17

Authors

Referees

About Journal

About

Copyright ©Acta Physica Sinica All Rights Reserved. 京ICP备05002789号-1

Address： PostCode：100190

Phone：010-82649829，82649241,82649863 Email：apsoffice@iphy.ac.cn   百度统计