Accepted Papers
Recent catalogue
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Vol.74 No.22
2025-11-20
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Vol.74 No.21
2025-11-05
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Vol.74 No.20
2025-10-20
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Vol.74 No.19
2025-10-05
- All Archive
SPECIAL TOPIC—2D materials and future information devices
2025, 74 (22): 220101.
doi: 10.7498/aps.74.220101
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SPECIAL TOPIC—Research progress on nickelate superconductors
2025, 74 (22): 220102.
doi: 10.7498/aps.74.220102
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GENERAL
2025, 74 (22): 220201.
doi: 10.7498/aps.74.20251026
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Magnetic skyrmions, characterized by their topological properties, serve as core components for developing next-generation non-volatile memory devices that demand high density, high speed, and low power consumption. Two-dimensional Janus magnetic materials inherently break spatial inversion symmetry, and easily generate strong DMI, providing an ideal platform for skyrmion generation and novel racetrack memory applications. Identifying high Curie temperature (Tc) materials is essential for ensuring magnetic stability and high-temperature application viability. This study integrates literature and open-source databases to construct a dataset of 16880 ABC-type two-dimensional materials. By utilizing stoichiometric ratios, intrinsic elemental properties, and electronic structure features as descriptors, four machine learning models, i.e. random forest (RF), gradient boosting decision tree (GBDT), extreme gradient boosting (XGBoost), and extra trees (ET) are employed for Tc prediction. Model performance is evaluated via ten-fold cross-validation, revealing that the XGBoost model exhibits superior prediction accuracy and generalization capability. Leveraging this model, Tc is predicted for 4024 unexplored two-dimensional Janus materials. This screening identifies 54 promising candidates possessing thermal stability, high magnetic moment, and a Tc exceeding 300 K. To verify reliability, four candidate systems (EuFeO, GdKTi, DyFeTb, ErFeGd) are randomly chosen for theoretical validation by using first-principles calculations combined with the Heisenberg model. For systems exhibiting strong correlation effects (containing d-orbital electrons), the Hubbard U parameter is included to describe on-site Coulomb repulsion. Exchange coupling constants are derived using the VASP software package. Subsequently, Tc values are calculated via classical Monte Carlo simulations performed using the MCSOLVER program. The research results show that the mean absolute error (MAE) of the predicted Tc is in good agreement with the model calculations for EuFeO and GdKTi, while larger deviations are observed for DyFeTb and ErFeGd. Nevertheless, the calculated Tc values for all four candidates exceed room temperature. This work establishes a new computational framework for the efficient screening of high-performance two-dimensional Janus magnetic materials, contributing to the advancement of magnetic storage technologies.
GENERAL
2025, 74 (22): 220701.
doi: 10.7498/aps.74.20250944
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Rydberg atoms possess a large electric dipole moment and exhibit high sensitivity to electromagnetic signals. Receivers based on Rydberg atoms represent a novel reception mechanism, demonstrating broad application prospects in the field of communication. Current research has not addressed the influence of the operating parameters of Rydberg atomic receiver on channel capacity. This study establishes a channel capacity model for Rydberg atomic receiver based on Shannon's formula and the response mechanism of the electromagnetically induced transparency (EIT) effect. Using this model, the influences of atomic number density, laser beam waist, and coupling laser Rabi frequency on the channel capacity of Rydberg atomic receiver are analyzed. A strategy for optimizing channel capacity by adjusting the coupling laser Rabi frequency is proposed, and an analytical solution for the Rabi frequency that maximizes channel capacity is derived. The accuracy of this analytical solution is then verified through numerical simulations. The channel capacity corresponding to the analytical solution in this study is similar to the optimal channel capacity obtained using the one-dimensional optimization method (Newton’s method) and is superior to the results obtained by the quadratic interpolation method, demonstrating the effectiveness of the proposed analytical solution in optimizing the channel capacity of Rydberg atomic receiver. This research provides theoretical guidance for designing high-performance Rydberg atomic receiver and optimizing channel capacity.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
2025, 74 (22): 220702.
doi: 10.7498/aps.74.20250892
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Silicon photomultipliers (SiPMs) have been widely used in the field of weak light detection. However, SiPMs utilizing small-sized Geiger-mode avalanche photodiode (G-APD) cells face the limitations due to a restricted effective geometric fill sactor (GFF), which leads to relatively low photon detection efficiency (PDE), and additionally, constrained by the intrinsic properties of silicon materials, their PDE in the near-infrared band is also relatively insufficient. To address the above issues, this work proposes a regional optical field modulation approach based on topological photonic crystals (TPCs), aiming to improve the PDE of SiPMs without modifying their internal structure. Through COMSOL electromagnetic wave frequency-domain simulation, the multi-band synergistic mechanism of dead-zone topological edge state guidance, photosensitive region slow-light effect, and Bragg scattering is revealed. In the 460–700 nm band, the honeycomb lattice in the dead zone induces topological edge states via Floquet periodic analysis, while the periodic dielectric distribution of the lattice excites Bragg scattering to reduce photon reflection loss at the metal surface and precisely couples photons to the photosensitive region, leading to an increase in effective GFF from 46.4% to 63.1% at 621 nm. In the 700–1100 nm band, in addition to reducing reflection loss via Bragg scattering, the designed periodic silicon pillar structure can effectively extend the transverse propagation path of photons through the slow-light effect, thereby increasing the coupling probability with the photosensitive region, resulting in a significant increase in absorption efficiency from 41.19% to 55.94% at 900 nm. Simulation results show that this design scheme increases the average PDE of SiPMs by 50% in the 460–1100 nm band (with a peak value of 81%) and can be implemented via mainstream etching processes (electron beam lithography + reactive ion etching). Compared with traditional microlens and plasmonic structures, TPCs exhibit significant advantages in broad-spectrum response and process simplification. This work provides a new topological photonics approach for photon recycling and PDE enhancement of SiPMs.
SPECIAL TOPIC—Thematic Data in Nuclear Physics: Experimental, Theoretical and Applied Research
2025, 74 (22): 222801.
doi: 10.7498/aps.74.20250928
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Metal hydrides are promising moderator materials in advanced reactors, where their thermal neutron scattering cross sections significantly affect the accuracy of reactor design. This study uses special quasi random structure (SQS) and first-principles lattice dynamics methods to calculate parameters such as the phonon densities of states of sub-stoichiometric zirconium hydride (ZrHx) and yttrium hydride (YHx). Based on these parameters, thermal scattering law (TSL) data for sub-stoichiometric hydrides are generated using the nuclear data processing code NECP-Atlas. The influences of hydrogen content on the thermal scattering cross sections of hydrides and the effective multiplication factor (keff) values of critical assemblies are analyzed. The result shows that variations in hydrogen content within hydrides lead to differences in thermal scattering cross sections, consequently affecting the neutron transport calculations of nuclear reactor. For the ICT003 and ICT013 benchmarks loaded with ZrHx (with H/Zr ≈ 1.6), using the TSL data derived from ZrHx with other hydrogen content results in a maximum deviation of 104 pcm in keff. For the HCM003 benchmarks loaded with ZrH2, the use of TSL from ZrHx with other hydrogen content leads to a maximum deviation of 147 pcm in keff.
ATOMIC AND MOLECULAR PHYSICS
2025, 74 (22): 223101.
doi: 10.7498/aps.74.20251196
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Using first-principles calculations based on density functional theory with a plane-wave ultrasoft pseudopotential approach, we conduct computations using the CASTEP (Cambridge Sequential Total Energy Package) module within the Materials Studio software. The electronic band structures, densities of states, and optical properties of intrinsic monolayer WTe2, monolayer WTe2 with a single tellurium vacancy (VTe), and rare-earth-doped VTe-containing monolayer WTe2 (VTe-X, where X = Ce, Yb, Eu) are systematically investigated to explore the synergistic effects of rare-earth doping and tellurium vacancy defects on the optical properties of monolayer WTe2. The results indicate that compared with the VTe model, the VTe-X models lead to a more pronounced enhancement of the optical performance in the infrared region (0–1.2 eV). All of VTe-X structures exhibit metallic characteristics, with a notable increase in the density of states near the Fermi level. In particular, the VTe-Yb model demonstrates significant improvement in the infrared range: the absorption coefficient, reflectivity, static dielectric constant, and peak value of the imaginary part of the dielectric function are enhanced by factors of 3.76, 1.83, 2.63, and 24.20, respectively, compared with those of pristine monolayer WTe2. This study provides a theoretical foundation for designing infrared photodetectors based on monolayer WTe2 substrates.
ATOMIC AND MOLECULAR PHYSICS
2025, 74 (22): 223201.
doi: 10.7498/aps.74.20251237
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ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS
2025, 74 (22): 224201.
doi: 10.7498/aps.74.20250828
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To address the frequency sweeping nonlinearity of frequency-modulated continuous-wave signals generated by a current-modulated distributed feedback laser diode, we propose and experimentally demonstrate a pre-distortion method based on a feedforward neural network. For this method, the beat frequency signals of the distributed feedback laser diode under a sawtooth-waveform current modulation are first experimentally obtained, and then the time-frequency curves of the distributed feedback laser diode output are obtained by performing a Hilbert transform on the beat signals. Subsequently, three-layer feedforward neural networks with 10, 5, and 3 hidden-layer neurons are constructed, respectively. By taking the driving current and the time-frequency curves as the input and output of the feedforward neural network, respectively, the nonlinear mapping relationship between them is established. Finally, a backpropagation algorithm is utilized to obtain the pre-distortion modulation current. Taking this current under the modulation frequency from 1 kHz to 10 kHz to drive the distributed feedback semiconductor laser (DFB-LD), the performance of the generated frequency-modulated continuous-wave (FMCW) signals is analyzed. We use nonlinear regression coefficients and residual root mean square values to characterize the performance. For the modulation frequency set at 4 kHz, the frequency sweeping nonlinearity and the residual root mean square value are reduced from 5.29×10–3 and 281 MHz to 1.77×10–5 and 15.15 MHz, respectively. With the modulation frequency fixed at 6 kHz, the frequency sweeping nonlinearity decreases from 5.58×10–3 to 1.52×10–5 and the residual root mean square declines from 251.98 MHz to 12.17 MHz in the proposed scheme. Across the entire tested frequency range from 1 kHz to 10 kHz, the nonlinearity remains stable at ~10–5 after adopting the pre-distortion scheme, with RMS values consistently below 20 MHz. The proposed method is expected to provide a new scheme for the linearization technology of the sweep signal in high-precision frequency-modulated continuous-wave light detection and ranging systems.
ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS
2025, 74 (22): 224202.
doi: 10.7498/aps.74.20251109
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The high-order Hermite-Gaussian (HG) mode squeezed light, as one of the important quantum sources, has significant application in quantum precision measurement and quantum imaging. The enhancement of spatial measurement precision largely depends on the squeezing level of high-order HG-mode quantum states. However, the squeezing level of high-order HG modes is primarily limited by the external pump power in the optical parametric oscillator (OPO) cavity. As is well known, the OPO with dual resonance for both squeezed light and pump light can lower external pump power. The generation of HG10 mode squeezed light differs from that of HG00 mode squeezed light, with an additional Gouy phase shift introduced between the HG20 pump mode and HG10 down-conversion mode within the OPO cavity. In this work, we conduct theoretical analysis and experimental generation of HG10 mode squeezed light at lower external pump power by using a doubly-resonant OPO based on a wedged periodically poled KTiOPO4 (PPKTP) crystal. By precisely controlling both the propagation length of the optical field and temperature in the wedged PPKTP crystal, we simultaneously compensate for the Gouy phase shift between the HG20 and HG10 modes and the astigmatism induced by the frequency-dependent refractive index. This configuration allows for dual resonance of the HG20 pump mode and the HG10 squeezed mode, while operating under the condition close to optimal phase matching. Increasing the reflectivity of the input coupler of OPO cavity enhances the intra-cavity circulating power of the pump light, thereby reducing the required external pump power. Here, the bow-tie-shaped OPO cavity consists of two plane mirrors and two concave mirrors with a curvature radius of 50 mm. The wedged PPKTP is placed in the smallest beam waist of the cavity. The mode converter is employed to generate high-purity HG20 pump mode with a measured purity of 98.0%. The mode-matching effciency of 93.0% is achieved between the high-purity HG20 pump mode and the OPO cavity. The homodyne visibility of the HG10 mode is 98.1%. We experimentally demonstrate the generation of 9.10 dB HG10 mode squeezed light by using a doubly-resonant OPO with only 51 mW of HG20 pump mode, and simultaneously achieve 9.20 dB of squeezing in the HG00 mode with 27 mW of HG00 pump mode. The inferred squeezing levels of both HG10 mode and HG00 mode squeezed light both reach up to 12.15 dB. The quantum technology has solved the pump power limitations in optical parametric oscillators, generating high-order HG mode states with high squeezing level and providing an effective method for enhancing spatial measurement precision.
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