Accepted
, , Received Date: 2025-08-06
Abstract +
The key security of quantum key distribution (QKD) is guaranteed by the basic principle of quantum mechanics, which makes it possible to combine information theory security communication with one-time encryption. The key is usually encoded on the polarization dimension or phase dimension of a single-photon. It is considered that the birefringence effect of single-mode fiber leads to a random variation of polarization state, which would induce the bit error rate. So it is of great significance to keep the single-photon linear polarization state stable for both polarization encoding QKD system and phase encoding QKD system. By using the single-photon polarization modulation technology, the single-photon linear polarization state periodically varies with the external modulation signal. The flicker noise is suppressed effectively, and the signal-to-noise ratio (SNR) of single-photon counting is increased as indicated by the phase-sensitive detection with a lock-in amplifier (LIA). The error signal is generated by demodulating the modulated single photons and it is used to lock an arbitrary 1550 nm single-photon linear polarization state to the optical axis of in-line polarizer (ILP). The modulation frequency reaches up to 5 kHz, which can eliminate the influence of low frequency flicker noise. The LIA demodulates the single-photon pulses by using 78.1 Hz filter bandwidth, with a time constant of 1 ms and a filter slope of 24 dB. The error signal with a signal-to-noise ratio(SNR) of 20 is shown in Fig. 3 of the main text. The zero-crossing point of error signal represents the single photon’s linear polarization state aligned to the optical axis of ILP. The linear slope around the zero-crossing point for the polarization state angle versus the error signal amplitude is 1.267 rad/V. When the negative feedback loop does not work, the polarization drift of single-photon pulses is 0.082 rad due to the random environmental noise. However, by using the single-photon polarization modulation technology and the precise and dynamic control of the polarization rotator, the polarization drift of stable single-photon pulse is limited to 0.0011 rad within 2000 s, 6.7×10–5 in an integration time of 128 ms. The advantages for the single-photon polarization modulation technology are as follows: i) the linear polarization state drift is compensated for real-time at the single-photon level; ii) single frequency polarization modulation can be extended to multiple frequency polarization modulation in order to achieve locking of multiple linear polarization states of single photons simultaneously; iii) these 1550 nm single-photon pulses with the 0.0011 rad linear polarization state stability can be directly used as the single-photon source in either polarization encoding or phase encoding QKD system.
, , Received Date: 2025-09-19
Abstract +
Fluid simulations of capacitively coupled plasmas (CCP) are crucial for understanding their discharge physics, yet the high computational cost poses a major bottleneck. To overcome this limitation, we have developed a deep learning-based surrogate model designed to replicate the output of a one-dimensional CCP fluid model with near-instantaneous inference speed. Through a systematic evaluation of three architectures—Feedforward Neural Network (FNN), Attention-enhanced Long Short-Term Memory network (ALSTM), and Convolutional-Transformer hybrid network (CTransformer)—we found that the sequence-structured ALSTM model achieves the optimal balance between speed and accuracy, with an overall prediction error of only 1.73% for electron density, electric field, and electron temperature in argon discharge. This study not only achieves simulation acceleration but also reveals that the model can accurately extrapolate from low-pressure conditions dominated by complex non-local effects to high-pressure conditions governed by simple local effects, whereas the reverse extrapolation fails. This phenomenon suggests that training under low-pressure conditions enables the model to capture more comprehensive data features. From the perspective of model weights, both low-pressure and high-pressure models assign key weights to the sheath region, but the low-pressure model exhibits higher weight peaks in the sheath, indicating a stronger ability to capture the key physical process of sheath dynamics. In contrast, the high-pressure model, due to its lower weights in the sheath region, may fail to adequately resolve the complex dynamics of the sheath when predicting new operating conditions, thereby limiting its ability for high-fidelity extrapolation. To ensure the reliability of this data-driven model in practical applications, we established a trust boundary of 5% normalized mean absolute spatial error for model performance through systematic extrapolation experiments. When the model's extrapolation error falls below this threshold, the spatial distribution curves of predicted parameters such as electron density and electron temperature closely match the true physical distributions. However, once the error exceeds this critical point, systematic deviations such as morphological distortion and amplitude discrepancies begin to appear in the predicted spatial distributions, significantly diverging from the true physical laws. In the future, we will develop neural network models capable of processing high-dimensional spatial data and incorporating multi-dimensional input features such as various discharge gases, ultimately realizing a dedicated AI model for the field of capacitively coupled plasmas.
, , Received Date: 2025-08-28
Abstract +
,
Abstract +
The pantograph-catenary system (PCS) serves as the exclusive means of power supply for high-speed trains. With increasing train speeds, higher traction power, and operation in complex and variable environments, the occurrence of pantograph arc has become more frequent, accompanied by alterations in physical properties and increased hazards, which seriously threaten the safety of high-speed railways. This paper presents a systematic review of recent research on pantograph arc, outlining physical characteristics, experimental techniques, and simulation methodologies. The study focused on analyzing the effects and mechanisms of operating parameters and environmental conditions on pantograph arc, with summarized prevention strategies and explored applications such as arc energy utilization. Existing research has sufficiently examined how operational parameters affect arc hazards, yet studies on arc physical properties and evolution mechanisms remain limited, particularly regarding special conditions like icing. Current protection methods also require adaptation to complex environments to meet growing arc management demands. Two future research priorities are proposed: first, clarifying arc physical properties under special environments and establishing the "environmental condition - physical property - arc behavior" correlation to enable accurate prediction; second, developing an efficient arc prevention system through "source suppression - interface protection - process intervention". This review aims to provide theoretical and practical guidance for reliable current collection and effective arc control in high-speed railway PCS in China.
,
Abstract +
Stable and remarkable valley polarization effect is the key to utilizing valley degree of freedom in valleytronic devices. Recently, a novel collinear magnetic material known as altermagnet, distinct from ferromagnets and antiferromagnets, has attracted widespread attention. Theoretical studies have revealed that the monolayer altermagnet V2Se2O exhibits spin-valley locking induced by crystal symmetry rather than conventional time-reversal symmetry. Uniaxial strain can break the corresponding crystal symmetry, leading to a remarkable non-relativistic valley polarization effect. Therefore, beyond uniaxial strain, are there alternative strategies to break the crystal symmetry in altermagnets and achieve remarkable valley polarization? Based on firstprinciples calculations and symmetry analysis, we reveal that valley polarization effect in monolayer V2Se2O altermagnet is correlated with the net magnetic moment between magnetic atoms V under uniaxial strain, proposing two strategies for achieving giant valley polarization effect. Firstly, substituting one V atom in V2Se2O with Cr to construct a ferrimagnetic monolayer VCrSe2O enhances the net magnetic moment between magnetic atoms, thereby realizing giant valley polarization effect. Applying uniaxial strain along either the a-axis or b-axis significantly increases the value of valley polarization which exhibits a nearly linear relationship with the net magnetic moments between the magnetic atoms. Secondly, constructing a van der Waals heterostructure composed of V2Se2O and α-SnO monolayers breaks mirror symmetry, as a result, inducing a net magnetic moment, which in turn induces remarkable valley polarization effect. Compressing the interlayer distance of the heterostructure enables an increment of the net magnetic moment between V atoms, enhancing the value of valley polarization to nearly 400 meV. This work reveals that valley polarization in monolayer altermagnets is correlated with the net magnetic moment between magnetic atoms. Then, we propose two strategies to achieve giant valley polarization based on monolayer altermagnets, providing theoretical guidance for the potential applications of ferrimagnetic monolayers and heterostructures constructed from altermagnets in valleytronics.
, , Received Date: 2025-07-09
Abstract +
The recent discovery of high-temperature superconductivity in the bilayer nickelate La3Ni2O7 under high pressure has attracted significant attention, further catalyzing intensive research on nickel-based superconductors. Systematic comparative studies of nontraditional superconductors are essential for advancing the mechanistic understanding of high-Tc superconductivity. In contrast to cuprate superconductors, nickel-based bulk materials show significant differences in crystal structure, electronic properties, and physical behaviors, while their experimental investigation faces additional challenges including the influences of hydrostatic conditions on zero-resistance state and diamagnetic response measurements, oxygen vacancy defects in single crystals, and pressure-induced structural phase transitions. This review comprehensively examines high-temperature superconductivity and the related research challenges in trilayer nickelate bulk materials, and provides important theoretical insights for future studies on nickel-based superconducting systems.
, , Received Date: 2025-08-30
Abstract +
Two-dimensional (2D) magnetic materials refer to nanomaterials with an extremely thin thickness that can maintain long-range magnetic order. These materials exhibit significant magnetic anisotropy, and due to the quantum confinement effect and high specific surface area, their electronic band structures and surface states undergo remarkable changes. As a result, they possess rich and tunable magnetic properties, showing great application potential in the field of spintronics. The 2D magnetic materials include layered materials, where layers are stacked by weak van der Waals forces, and non-layered materials, which are bonded via chemical bonds in all three-dimensional directions. Currently, most of researches focus on 2D layered materials, but their Curie temperatures are generally much lower than room temperature, and they are always unstable when exposed to air. In contrast, the non-layered structure enhances the structural stability of the materials, and the abundant surface dangling bonds increase the possibility of modifying their physical properties. Such materials are attracting increasing attention, and significant progress has been made in their synthesis and applications. This review first systematically summarizes various preparation methods for 2D non-layered magnetic materials, including but not limited to ultrasound-assisted exfoliation, molecular beam epitaxy, and chemical vapor deposition. Meanwhile, it systematically reviews the 2D non-layered intrinsic magnetic materials obtained in various types of materials in the past five years, as well as a series of novel physical phenomena emerging under the ultrathin limit, such as thickness-dependent magnetic reconstruction dominated by quantum confinement effects and planar topological spin textures induced by 2D structures. Furthermore, it also discusses the critical role played by theoretical calculations in predicting new materials through high-throughput screening, revealing microscopic mechanisms by analyzing magnetic interactions, as well as some important methods of modifying magnetism. Finally, from the perspectives of material preparation, physical mechanisms, device fabrication, and theoretical calculations, the current challenges in the field are summarized, and the application potential and development directions of 2D non-layered magnetic materials in spintronic devices are prospected. This review aims to provide comprehensive references and scientific perspective for researchers engaged in this field, thereby promoting further exploration of the novel magnetic properties of 2D non-layered magnetic materials and their applications in spintronic devices.
, , Received Date: 2025-08-28
Abstract +
Polarization detection is a fundamental way to obtain the vectorial nature of light, supporting advanced technologies in the fields of optical communication, intelligent sensing, and biosensing. Two-dimensional van der Waals materials have become a promising platform for high-performance polarization-sensitive photodetectors due to their inherent anisotropy and tunable electronic properties. Nevertheless, their intrinsically weak light absorption and limited photoresponse efficiency remain major bottlenecks. Plasmonic nanostructures, which can achieve strong localized field confinement and manipulation on a nanoscale, provide an effective strategy to overcome these limitations and substantially improve device performance. In this review, we systematically summarize the coupling mechanisms between plasmonic architectures and vdW materials, highlighting near-field enhancement, plasmon-induced hot-carrier generation, and mode-selective polarization coupling as key physical processes for enhancing photocarrier generation and polarization extinction. Representative devices including metallic gratings, hybrid nanoantennas, and chiral metasurfaces are compared in terms of responsivity, detection speed, operating bandwidth, and polarization extinction ratio, revealing consistent improvements of one to two orders of magnitude over bare vdW devices. We further survey emerging applications in the fields of high-speed polarization-encoded optical communication, on-chip optical computing and information processing, and bioinspired vision and image recognition systems, where plasmonic-vdW hybrid detectors demonstrate unique advantages in miniaturization and energy efficiency. Finally, we discuss current challenges such as large-scale fabrication of uniform plasmonic arrays, spectral bandwidth broadening, and seamless integration with complementary photonic circuits, and outline future opportunities for next-generation polarization-resolved optoelectronic platforms.
,
Abstract +
Electron-ion collision is one of the fundamental processes in atomic and molecular physics, and the study of this process can provide insight into the mechanism of electron-atom/ion interaction. It has important applications in plasma physics and astrophysics. Accurate electron-impact cross-sections are important in plasma modeling. In generally, total EISI cross-sections consists of the direct ionization (DI) and the indirect ionization processes, with the latter further divided into excitation autoionization (EA), resonant excitation double auto-ionization (REDA) and resonant excitation auto- double ionization (READI) processes. In this work, the electron-impact single ionization (EISI) crosssections for the ground state [Kr]4d105s24f13 of W13+ ions are calculated in detail by using the level-to-level distorted-wave (LLDW) method, which mainly includes the contributions of direct ionization (DI) and excited auto-ionization (EA) cross-sections to the EISI cross-sections. Our computational results demonstrate that when configuration interaction are incorporated, the calculated values show excellent agreement with experimental data for electron impact energies exceeding 500 eV. However, significant discrepancies persist near the ionization threshold. we have confirmed that these discrepancies primarily originate from the presence of long-lived metastable ions. To achieve better agreement with experimental observations, we further calculated EISI cross-sections for 71 energy levels of the metastable state 4 d10 5 s2 4 f12 5p with lifetimes greater than 1.5×10-5s. The total EISI cross-sections of these 71 energy levels were obtained by theoretical fitting and compared with the experimental results by Schury et al. (Figure), and it was found that our results were in good agreement with the experimental results of Schury et al. after considering the contribution of long-lived metastable.
,
Abstract +
The lower friction coefficient and better mechanical properties of palladium (Pd) alloys make them potentially advantageous for use in high-precision instruments and devices that require long-term stable performance. However, due to the high cost of raw materials and experimental expenses, there is a lack of fundamental data, hindering the design of high-performance Pd alloys. Therefore, in this study, first-principles calculations were used to determine the lattice constant and elastic modulus of Pd. A dilute solid solution model was established for Pd alloys with 33 elements, including Al, Si, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, and others. The mixing enthalpy, elastic constants, and elastic modulus were calculated. The results show that, except for Mn, Fe, Co, Ni, Ru, Rh, Os, and Ir, all other alloying elements can form solid solutions with Pd. Alloying elements from both sides of the periodic table enhance the ductility of Pd solid solutions, with La, Ag, and Zn having the most significant effects, while Cu and Hf reduce the ductility of Pd. Differential charge density analysis indicates that the electron cloud formed after doping with Ag is spherically distributed, which improves ductility. After doping with Hf, the degree of delocalization around the atoms is maximized, suggesting a strong ionic bond between Hf and Pd, leading to a higher hardness of Pd31Hf.
The datasets presented in this paper are openly available at https://www.doi.org/10.57760/sciencedb.j00213.00186(https://www.scidb.cn/s/uqMzye)
The datasets presented in this paper are openly available at https://www.doi.org/10.57760/sciencedb.j00213.00186(https://www.scidb.cn/s/uqMzye)
,
Abstract +
Terahertz (THz) polarization converters are essential components for advancing THz applications in imaging, sensing, and high-speed communications. However, achieving both broad bandwidth and high conversion efficiency remains a significant challenge. In this work, we propose, fabricate, and experimentally validate a transmissive linear polarization converter (TTPC) operating in the terahertz band, utilizing a bilayer metallic metamaterial structure. The device consists of a top-layer metasurface with a square patch and split-ring resonators and a bottom-layer metallic grating, separated by a polyimide substrate. Through full-wave electromagnetic simulations and surface current analysis, we reveal that the high-performance broadband polarization conversion arises from the synergistic interaction among three distinct resonance modes. Stokes parameter analysis further confirms that the polarization rotation angle remains stable at approximately 90° with near-linear output across the operational band. Experimental characterization using a terahertz time-domain spectroscopy (THz-TDS) system demonstrates that the device achieves a polarization conversion ratio (PCR) exceeding 92% over a broad frequency range of 0.53–1.77 THz, corresponding to a relative bandwidth of 108%. The measured insertion loss varies between 5.5 dB and 12 dB within the operating band, which is attributed to ohmic loss, dielectric absorption, and resonant energy dissipation. Despite these losses, the converter maintains high polarization purity and practical utility. With a compact and fabrication-friendly architecture, the proposed TTPC offers a viable route toward high-performance, broadband polarization control in terahertz systems, paving the way for its integration into next-generation THz communication and imaging devices.
,
Abstract +
In order to distinguish the interaction responses between unsteady thermal waves and thermal diffusion in graphene, the relaxation time of the heat flux vector τq and the relaxation time of the temperature gradient τT are introduced based on the Fourier's law, and a two-phase relaxation theoretical model is established. Parameter B describing ratio of the two phase relaxation times is employed to reveal the influencing rules of the interaction between thermal waves and thermal diffusion, and to investigate the regulatory mechanism of heat transport modes. When B approaches zero, the thermal wave effect dominates the heat transfer. When B approaches 0.5, the thermal diffusion characteristics are significant. When B is between zero and 0.5, both of them jointly dominate heat transfer, and the interaction between the two is of great significance. The results uncover the rules of thermal diffusion induced wave attenuation and thermal wave promoted thermal diffusion. They exhibit strong coupling characteristics. The unique contribution of third-order partial derivatives to local thermal wave disturbances is also revealed. A molecular dynamics model of short-pulse thermal shock for zigzag graphene is developed to unveil the coupling behaviors of thermal waves and thermal diffusion. The calculation parameters of two-phase relaxation theoretical model are calibrated. The main findings are presented in the figure below. The black, red, and yellow lines correspond to the in-plane longitudinal vibration, in-plane transverse vibration, and out-of-plane transverse vibration of carbon atoms, respectively. The solid lines denote elastic waves, while the dashed lines represent the second sound. The temperature field following the second sound is the outcome of the combined action of thermal waves and thermal diffusion. It merits attention that except for speed of the out-of-plane thermal wave is higher than that of the out-of-plane transverse elastic wave, speeds of the other two thermal waves are both lower than their elastic wave velocities.
,
Abstract +
Inorganic cesium halide perovskites (CsPbX3, X=I,Br) are promising candidates as the light-harvesting materials of new-generation photovoltaic devices owing to their intrinsic advantages, such as the high thermal stability, excellent optoelectronic properties, and facile solution fabrication process. In particular, CsPbI2Br perovskite which balances the light-harvesting ability and phase stability has attracted ever-increasing attention in the field of the single junction, the tandem, and the semitransparent photovoltaic devices. In the past several years, inorganic CsPbI2Br perovskite solar cells (PSCs) have achieved great progress in both the power conversion efficiency and the stability through versatile device engineering. Nevertheless, the inferior buried interface derived from the uncontrollable up-to-bottom perovskite crystallization process leads to the serious charge recombination and energy loss within CsPbI2Br PSCs, which considerably hinders the further development and practical deployment of CsPbI2Br PSCs. This highlights the necessity of developing facile but effective strategy to modify buried interface towards achieving superior cell performance. In this work, we report a facile additive strategy to in situ modify the buried interface of CsPbI2Br PSCs through forming a dipolar interlayer. The polar 4-mercaptophenylboronic acid (4-MPBA) additive is directly added into CsPbI2Br precursor solution. 4-MPBA molecules can't incorporate into the crystal lattice of CsPbI2Br perovskite due to its large size. Therefore, 4-MPBA molecules are excluded from CsPbI2Br perovskite crystal and pushed downwards the buried interface of TiO2 electron-transport-layer and CsPbI2Br perovskite film during the perovskite crystallization process. Because of the strong interaction between the -B(OH)2 group of 4-MPBA molecule and TiO2, 4-MPBA molecules tend to accumulate at the buried interface between CsPbI2Br perovskite and TiO2 layer and form a dipolar interlayer. Scanning electron microscopy, X-ray photoelectron spectroscopy, and ultraviolet photoelectron spectroscopy measurements clearly demonstrate that the formation of 4-MPBA interlayer greatly enhance the interface contact, improve the interfacial energy level structure, and passivate the interface defects, which effectively suppresses the charge recombination and promotes the charge collection within the cell. As a result, the assembled carbon-based CsPbI2Br PSC without hole-transport layer delivers a power conversion efficiency of 14.83%, which is increased by 26% compared to the efficiency of the cell without 4-MPBA interlayer. Moreover, the cell without any encapsulation retains ~90% of the original efficiency after 960 h of aging in ambient air, suggesting a superior long-term stability. Therefore, this work highlights a facile strategy to in situ modify the buried interface for effectively enhancing the photovoltaic performance of inorganic perovskite solar cells.
, , Received Date: 2025-07-29
Abstract +
To meet the urgent demand for high-performance photodetectors in emerging solar-blind ultraviolet communication applications, this study systematically designs and implements a fully transparent β-Ga2O3 solar-blind photodetector based on a back-illumination architecture. The device is fabricated using RF magnetron sputtering to epitaxially grow high-quality β-Ga2O3 films (~300 nm in thickness, ~4.98±0.05 eV in bandgap) on double-polished sapphire substrates, with indium tin oxide (ITO) interdigitated electrodes forming efficient quasi-Ohmic contacts with n-type Ga2O3. The core advantage of this design lies in exploiting the high deep-UV transmittance of double-polished sapphire substrates, enabling incident photons to completely bypass the UV-absorbing ITO electrodes and eliminate photon loss caused by electrode shadowing effects in traditional front-illumination configurations. Consequently, the device demonstrates exceptional optoelectronic performance: a maximum responsivity of 0.46 A/W corresponding to an external quantum efficiency of 222.4%, an outstanding UV/visible rejection ratio of 1.2×104, a minimum noise equivalent power of 1.52 pW/Hz1/2, and a peak specific detectivity of 1.39×1011 Jones, with fast response times of 24 μs (rise) and 1.24 ms (decay). Building on this high-performance detector platform, we further explore its multifunctional application potential by constructing a polarization detection system that utilizes the intrinsic lattice anisotropy of monoclinic β-Ga2O3, and successfully demonstrating a non-line-of-sight (NLOS) UV communication system that validates high-fidelity information transmission in complex scattering channels. This work provides effective physical insights and experimental basis for developing next-generation Ga2O3-based optoelectronic devices with integrated high sensitivity, polarization resolution, and NLOS communication capabilities, showing promising applications in secure communications and polarization imaging.
, , Received Date: 2025-08-25
Abstract +
- 1
- 2
- 3
- 4
- 5
- ...
- 14
- 15
