Accepted
, , Received Date: 2025-10-09
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Hydrogen energy, as one of the most promising clean and renewable energy sources, has received much attention due to its green production technology. Electrolytic water splitting is regarded as a critical pathway for large-scale green hydrogen production due to its environmentally friendly reaction process, high product purity, and operational simplicity, However, electrocatalysts for water electrolysis commonly face challenges such as high costs and complex synthesis processes, thereby severely hindering the industrial application. Low-temperature plasma (LTP) technology, with its advantages of mild processing conditions, high reactivity, and unique electromagnetic field effects, has demonstrated remarkable potential in the surface modification of materials. This review systematically summarizes the applications of LTP in the preparation and modification of electrocatalytic materials for water splitting, focusing on the mechanism of plasma-induced enhancement in electrocatalytic efficiency. First, the physical characteristics and fundamental principle of typical non-equilibrium low-temperature plasma are elucidated. Subsequently, recent advances in plasma-assisted modification strategies for catalytic materials are categorized and critically discussed, including surface microstructure modulation, surface property regulation and interface optimization. Finally, based on the current limitations in mechanistic understanding and practical applications, future research directions for LTP technology in catalyst design are proposed.
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Photoionization time delay in atoms and molecules is a fundamental phenomenon in attosecond physics, encoding essential information about electronic structure and dynamics. Compared with atoms, molecules exhibit anisotropic potentials and additional nuclear degrees of freedom, which make the interpretation of molecular photoionization time delays more intricate but also more informative. In this work, we investigate the dependence of the photoionization time delay on the internuclear distance in the $ 5\sigma \to k\sigma$ ionization channel of carbon monoxide (CO) molecules. The molecular ground state is obtained using the Hartree-Fock method, and the photoionization process is treated within quantum scattering theory based on the iterative Schwinger variational principle of the Lippmann–Schwinger equation. Numerical calculations are performed with the ePolyScat program to obtain molecular-frame differential photoionization cross sections and time delays at various internuclear distances. Our results show that the extrema of the photoionization time delay occur near the peaks and dips of the differential cross section and shift toward lower energies as the internuclear distance R increases. At low energies, the time delay along the oxygen end increases with R, while that along the carbon end decreases, which is attributed to the asymmetric charge distribution and the resulting short-range potential difference between the two atomic sites. Around the shape-resonance energy region, both cross section and time delay display pronounced peaks associated with an $ l=3$ quasi-bound state. As R increases, the effective potential barrier broadens, the quasi-bound state energy moves to lower values, and its lifetime becomes longer, leading to enhanced resonance amplitude and increased time delay. In the high-energy region, opposite-sign peaks of time delay are found along the O and C directions, corresponding to minima in the cross section. These features are well explained by a two-center interference model, where increasing R shifts the interference minima and the associated time-delay peaks toward lower energies. This study provides deeper insights into the photoionization dynamics of CO molecules, accounting for the role of nuclear motion, and offers valuable references for studying the photoelectron dynamics of more complex molecular systems.
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Magnetic proximity effects (MPE) are crucial for topological quantum devices because they enable control of boundary states between a ferromagnetic insulator and a topological insulator. The InAs/GaInSb double quantum well system—especially when combined with a superconductor and influenced by MPE—shows promise for producing topological qubits. Nonetheless, researchers still debate the exact strength of the MPE between europium sulfide (EuS) and InAs.
To directly probe the MPE, this work focuses on a EuS/InAs/GaInSb heterostructure. The heterostructure was fabricated by depositing EuS onto the passivated surface of a Hall bar formed from an InAs/GaInSb double quantum well, utilizing an electron beam evaporation system. Structural analysis using Reflection High-Energy Electron Diffraction and magnetic measurements revealed that, although the resulting EuS thin films were polycrystalline, they nonetheless displayed desired magnetic properties, making them suitable for further study of MPE phenomena.
Low-temperature magnetoresistance measurements on the fabricated Hall bar revealed several key phenomena that collectively provide evidence for the MPE. Application of a positive gate voltage caused the electron wavefunction within the InAs layer to shift toward the EuS interface, thereby enhancing the MPE. Under a perpendicular magnetic field, the magnetoresistance exhibited an increasing slope for the odd-parity component. Additionally, a transition from positive to negative magnetoresistance near zero field was observed. When an in-plane magnetic field was applied, a gate-enhanced negative magnetoresistance emerged. Hysteretic magnetoresistance, corresponding to the reversal of EuS magnetization, was also detected during these measurements.
The resistance-temperature curve for the heterostructure displayed a pronounced upturn at low temperatures. This behavior was well described by the Kondo model, indicating the presence of exchange coupling between InAs electrons and the localized magnetic moments of EuS near the interface. Such coupling is a strong indicator of the magnetic proximity effect at work in the system.
These findings collectively demonstrate the existence of a gate-tunable MPE in the EuS/InAs/GaInSb heterostructure. The ability to control the MPE through gate voltage establishes this heterostructure as a compelling platform for the exploration of proximity-induced magnetism. Furthermore, these results underscore the potential applications of such systems in the development of spin-based electronic devices and highlight their significance for future research in topological quantum computing.
To directly probe the MPE, this work focuses on a EuS/InAs/GaInSb heterostructure. The heterostructure was fabricated by depositing EuS onto the passivated surface of a Hall bar formed from an InAs/GaInSb double quantum well, utilizing an electron beam evaporation system. Structural analysis using Reflection High-Energy Electron Diffraction and magnetic measurements revealed that, although the resulting EuS thin films were polycrystalline, they nonetheless displayed desired magnetic properties, making them suitable for further study of MPE phenomena.
Low-temperature magnetoresistance measurements on the fabricated Hall bar revealed several key phenomena that collectively provide evidence for the MPE. Application of a positive gate voltage caused the electron wavefunction within the InAs layer to shift toward the EuS interface, thereby enhancing the MPE. Under a perpendicular magnetic field, the magnetoresistance exhibited an increasing slope for the odd-parity component. Additionally, a transition from positive to negative magnetoresistance near zero field was observed. When an in-plane magnetic field was applied, a gate-enhanced negative magnetoresistance emerged. Hysteretic magnetoresistance, corresponding to the reversal of EuS magnetization, was also detected during these measurements.
The resistance-temperature curve for the heterostructure displayed a pronounced upturn at low temperatures. This behavior was well described by the Kondo model, indicating the presence of exchange coupling between InAs electrons and the localized magnetic moments of EuS near the interface. Such coupling is a strong indicator of the magnetic proximity effect at work in the system.
These findings collectively demonstrate the existence of a gate-tunable MPE in the EuS/InAs/GaInSb heterostructure. The ability to control the MPE through gate voltage establishes this heterostructure as a compelling platform for the exploration of proximity-induced magnetism. Furthermore, these results underscore the potential applications of such systems in the development of spin-based electronic devices and highlight their significance for future research in topological quantum computing.
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The spin-reorientation transition (SRT) in rare-earth orthoferrites offers an important platform for exploring the coupling and manipulation of spin dynamics, which is crucial for developing high-frequency spintronic and terahertz (THz) magneto-optical devices. In this work, we systematically investigate the temperature- and magnetic-field-induced SRT behavior and the associated electron paramagnetic resonance (EPR) transitions of Yb3+ ions in a-cut YbFeO3 single crystals using time-domain terahertz spectroscopy (THz-TDS). The temperature-dependent measurements from 1.6 to 300 K reveal a distinct SRT near 7 K, marked by a sudden shift of the magnetic resonance mode frequency. This indicates a transition of the Fe3+ spin configuration from the low-temperature Γ2 phase to the high-temperature Γ4 phase, driven primarily by the temperature evolution of the anisotropic Fe3+-Yb3+ exchange interaction.
Under an external magnetic field applied along the a-axis at 20 K, the system exhibits an incomplete field-induced SRT from the Γ4 phase toward the Γ2 phase. In the intermediate Γ24 phase, both the quasi-AntiFerroMagnetic (q-AFM) and quasi-FerroMagnetic (q-FM) modes are simultaneously excited, as observed in the THz absorption spectra. Notably, even at the maximum field of 7 T, the transition remains incomplete, indicating the stabilization of the intermediate phase over a wide field range. In the low-frequency region (<0.8 THz), two absorption peaks exhibiting clear blue shifts with increasing magnetic field are identified as EPR transitions between Zeeman sublevels of the crystal-field-split Kramers doublets of Yb3+ ions.
All experimental observations, including the temperature- and magnetic-field-dependent frequency responses of the q-AFM and q-FM modes as well as the evolution of the electron paramagnetic resonance signals with magnetic field, have been quantitatively described by coupling a spin dynamics model with crystal field theory. The model successfully reproduces the continuous rotation of the macroscopic Fe3+ magnetization vector within the ac plane under an applied magnetic field, revealing the microscopic mechanism of the field-induced SRT. The analysis demonstrates that the SRT process results from the competition and synergy between the external magnetic field and the anisotropic Fe3+-Yb3+ exchange interaction, which collectively modulate the internal effective field and determine the stability of the intermediate Γ24 phase.
This study confirms the effective control of spin configurations in YbFeO3 via both temperature and magnetic field, provides a deeper understanding of the Fe3+-Yb3+ exchange interaction mechanism, and offers important experimental insights for the design of terahertz functional devices based on rare-earth orthoferrites.
Under an external magnetic field applied along the a-axis at 20 K, the system exhibits an incomplete field-induced SRT from the Γ4 phase toward the Γ2 phase. In the intermediate Γ24 phase, both the quasi-AntiFerroMagnetic (q-AFM) and quasi-FerroMagnetic (q-FM) modes are simultaneously excited, as observed in the THz absorption spectra. Notably, even at the maximum field of 7 T, the transition remains incomplete, indicating the stabilization of the intermediate phase over a wide field range. In the low-frequency region (<0.8 THz), two absorption peaks exhibiting clear blue shifts with increasing magnetic field are identified as EPR transitions between Zeeman sublevels of the crystal-field-split Kramers doublets of Yb3+ ions.
All experimental observations, including the temperature- and magnetic-field-dependent frequency responses of the q-AFM and q-FM modes as well as the evolution of the electron paramagnetic resonance signals with magnetic field, have been quantitatively described by coupling a spin dynamics model with crystal field theory. The model successfully reproduces the continuous rotation of the macroscopic Fe3+ magnetization vector within the ac plane under an applied magnetic field, revealing the microscopic mechanism of the field-induced SRT. The analysis demonstrates that the SRT process results from the competition and synergy between the external magnetic field and the anisotropic Fe3+-Yb3+ exchange interaction, which collectively modulate the internal effective field and determine the stability of the intermediate Γ24 phase.
This study confirms the effective control of spin configurations in YbFeO3 via both temperature and magnetic field, provides a deeper understanding of the Fe3+-Yb3+ exchange interaction mechanism, and offers important experimental insights for the design of terahertz functional devices based on rare-earth orthoferrites.
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Among the graphene family, bilayer graphene (BLG) exhibits more diverse electronic structures and higher tunability than monolayer graphene due to its unique interlayer coupling effect, emerging as a crucial branch in functionalization research. By utilizing its interlayer as an embedding channel, BLG avoids impairing graphene's intrinsic conductivity-a common issue with surface modification. Furthermore, the interlayer coupling allows for synergistic engineering of its electronic structure, yielding performance superior to that of monolayer graphene. Therefore, the interface of BLG represents a potential functionalization site. Based on the aforementioned research status and issues, all calculations in this study are performed using density functional theory (DFT) via the Vienna Ab-initio Simulation Package (VASP). To accurately describe the van der Waals (vdW) interactions (π-π stacking) between the layers of AB-stacked BLG, the DFT-D3 method is employed for vdW correction to investigate the influence of functional groups on BLG electrical properties. This study focuses on four functional groups (-OH, -CO, -CHO, and -COOH), whose contained O and H atoms can readily form chemical bonds with the carbon atoms in BLG. Through interlayer modification, the interactions between these functional groups and the carbon atoms are analyzed to realize the regulation of interlayer coupling and electronic structure characteristics of BLG. The insertion of -OH and -CHO into the interlayer of BLG results in higher stability and lower interfacial binding energy, whereas the insertion of -CO and -COOH leads to reduced stability. The Fermi level of BLG shifts to varying degrees upon the insertion of functional groups. Specifically, the insertion of -OH or -COOH causes the Fermi level to shift toward lower energy levels, reducing the highest occupied energy level. In contrast, the insertion of -CO or -CHO shifts the Fermi level toward higher energy levels, exciting more electrons to higher energy states and resulting in electron filling at elevated energy levels. The band structure of BLG undergoes significant modifications due to the insertion of functional groups. The original parabolic band dispersion is disrupted, and the band distribution becomes more complex, with altered line trajectories and crossing characteristics. Partial density of states (PDOS) and charge density difference calculations reveal orbital hybridization and charge transfer between the functional groups and BLG. All four functional groups form covalent bonds with the carbon atoms of BLG, exhibiting characteristics of chemical adsorption. Moreover, the extent of charge transfer and the perturbation of charge density vary significantly among the different functional groups. This study aims to elucidate the regulatory mechanisms and underlying principles of functional groups, providing a theoretical basis for designing BLG-based electronic materials with specific functionalities, while also enriching the research framework of interlayer functionalization in two-dimensional layered materials.
, , Received Date: 2025-09-28
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, , Received Date: 2025-05-15
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An unresolved issue in the study of baryon non-leptonic decays is that the theoretical values describing the s- and p-wave amplitudes of such decays cannot simultaneously accord well with experimental values. Compared with previous literature, this paper adopts the covariant chiral effective theory framework and calculates the one-loop corrections to the s- and p-wave amplitudes by using the extended minimal subtraction (EMS) scheme, and also takes into account the contributions from intermediate pion states that are neglected in previous studies (the contributions from intermediate decuplet states are not considered here). Unlike infrared regularization and the extended on-shell subtraction scheme, EMS is easier to implement and also avoids over-subtraction. Apart from the typical chiral logarithmic term mslnms obtained in heavy-baryon formalism, the covariant calculation retains many non-local contributions that are not negligible. These non-local contributions vary with loop diagrams and intermediate states, making the complete covariant results significantly different from those from the simple chiral logarithmic structures in heavy-baryon formalism, which may alleviate the tension between the s- and p-wave components of the decay amplitudes. Subsequent numerical analysis confirms this conjecture. Two approaches are adopted to obtain covariant theoretical predictions: s-wave fitting and p-wave fitting. According to the fitted predictions and chi-squares of fitness, the s-wave fitting yields s-wave predictions slightly inferior to those under heavy-baryon formalism, but the resulting p-wave predictions are considerably improved compared with the heavy-baryon formalism predictions. The p-wave fitting produces p-wave predictions closer to experimental values, while the heavy-baryon predictions differ significantly from the experimental values. The resulting s-wave predictions from p-wave fitting show noticeable discrepancies with experimental data, but the heavy-baryon predictions are even worse. Therefore, working in the covariant framework, the tension between s- and p-wave amplitudes for baryon non-leptonic decays is significantly alleviated in comparison with that in heavy-baryon formalism. In addition, it is found that the contributions from intermediate pion states may be neglected in many cases, but are important and must be kept for decays with smaller experimental values.
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Magnetic exchange interactions and the magnetic structures they induce are among the key factors determining magnetization switching. Dzyaloshinskii-Moriya interaction (DMI) is an asymmetric exchange interaction arises from spin-orbit coupling and structural inversion symmetry breaking, which is one of the key mechanisms to induce non-collinear magnetic order and chiral magnetic structures, including magnetic Skyrmion, vortex, chiral domain wall, etc. These magnetic structures enable novel information proceeding devices with ultralow power consumption. More importantly, compared to conventional collinear magnetic structures, non-collinear magnetic order exhibits richer and more novel physical behaviors. With ongoing exploration and research in magnetic materials, Rare-Earth Transition Metal ferrimagnetic materials (CoGd, CoTb, GdFeCo, etc.), which combine spin-orbit coupling of rare-earth elements with the magnetic exchange of transition metals, have been discovered to exhibit ultrafast magnetization dynamics, tunable magnetic structures and rich spin transport phenomena. These properties provide an ideal material platform for studying and manipulating DMI, demonstrating significant potential in designing future high-density magnetic storage and spintronic devices. This review systematically elucidates the microscopic physical origin of DMI, outlines the fundamental characteristics of Rare-Earth Transition Metal ferrimagnetic materials and explores the coupling mechanisms between DMI and ferrimagnetic order. we introduce the fundamental properties of RE-TM systems and their applications in spin logic devices and magnetic memory devices. We focus on discussing the physical phenomena related to DMI in RE-TM systems, including the scaling relationship of DMI in RE-TM, DMI-related spin-orbit torque effects, and the principles and applications of skyrmion-based devices, which would provide both theoretical foundations and technical guidance for future development of advanced spintronic technologies.
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Atom interferometer enables high-precision measurement of recoil frequency, which is crucial for determining the fine structure constant. Large momentum transfer (LMT) based on Bloch oscillations in atom interferometers can significantly enhance the measurement precision of the recoil frequency. Typically, applying Bloch oscillations to an atomic ensemble requires the atoms to be cooled within the first Brillouin zone. However, deep cooling of lithium atoms is challenging, making it diffcult to directly apply Bloch oscillations. Therefore, this paper develops an LMT technique based on Bloch oscillations in a relatively high-temperature ensemble of 6Li atoms. By constructing a deep potential optical lattice, the high-temperature atoms can be effciently loaded into the lattice. Subsequently, the optical lattice is adiabatically chirped to suppress interband transitions of the atoms and enable atoms to accelerate with the lattice. Although the effciency of a single Bloch oscillation decreases under the tight-binding approximation, this method simultaneously relaxes the temperature requirements of the LMT technique. Consequently, we achieve a large momentum transfer of 40 recoil momenta at 80 μK (far above the recoil temperature), with the number of transferred atoms reaching up to 5 × 106. Subsequent analysis of the atomic momentum spectrum before and after the Bloch oscillations revealed that, due to Doppler broadening, the atomic momentum shows a continuous distribution between the initial momentum and the target momentum, which limits the momentum transfer effciency. It was found that for a fixed optical lattice depth and pulse duration, the momentum distribution of atoms participating in the Bloch oscillations is independent of the number of oscillations. Furthermore, atoms with initial velocities aligned with the acceleration direction of the optical lattice are more easily accelerated. This LMT technique is expected to substantially enhance the measurement precision of the 6Li atomic recoil frequency, providing an important reference for the subsequent high-precision calibration of the fine structure constant using 6Li atom interferometers.
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High-pressure polarized Raman spectroscopy (HPRS) refers to a spectroscopic technique in which a diamond anvil cell (DAC) is employed as the pressure-generating device, and the polarization orientations of both incident and scattered light are systematically controlled to measure the angular dependence of Raman spectral intensities under varying pressures. This enables the quantitative extraction of the pressure evolution of Raman tensor elements. In this study, we developed an in-situ high-pressure polarized Raman setup based on a backscattering configuration incorporating a half-wave plate, allowing continuous variation of the polarization angle without rotating the sample. Quantitative determination of Raman tensor elements was achieved through polar coordinate fitting of the measured intensity profiles. Singlecrystal Si(100), commonly used for Raman calibration, and two-dimensional Te(110) flakes exhibiting in-plane anisotropy were selected as model systems for investigation. Our results show that over the pressure range of 0~12 GPa, the angular distribution pattern and periodicity of Si(100) remain unchanged, while the main Raman peak exhibits an approximately linear blue shift with increasing pressure. The Raman tensorelement associated with the active mode decreases according to an inverse power-law function, reflecting the response of the polarizability derivative to volume compression in the absence of phase transitions. For two-dimensional Te(110), the in-plane anisotropy increases with pressure, accompanied by deviations of certain modes from ideal symmetry-predicted behavior. Notably, the ratio of Raman tensor elements displays an inflection point near 1.5 GPa, transitioning from a decreasing to an increasing trend, with clearly observable changes in polarized Raman responses within the 1.2~1.6 GPa range. It is in close proximity to the electronic structure phase transition point determined from transport experiments (~2 GPa). Collectively, studies on single-crystal Si(100) and two-dimensional Te(110) demonstrate that HPRS is a robust in-situ method for probing symmetry evolution, anisotropic behavior, and incipient electronic rearrangements in materials under compression.
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Quantum weak measurement technology has significantly advanced the detection limits of quantum precision measurement due to its minimal disturbance to the measured system and the weak value amplification (WVA) effect. This technique has been successfully applied in phase difference and time difference measurements, leading to a series of important achievements. Previous standard weak measurement typically utilize only a single momentum parameter as the measurement pointer and rely on a single weak interaction (SWI) to detect minute phase shifts. Although some studies have attempted to introduce quantum resources to further enhance the amplification factor and measurement precision, the practical application is hindered by thechallenges associated with quantum state preparation. Therefore, practical quantum weak measurement systems still require in-depth research and exploration to overcome these technical bottlenecks.
In this study, we propose and experimentally validate a dual -parameter quantum weak measurement scheme based on tunable spectral control and iterative weak interactions. Theoretical analysis demonstrates that adjusting the spectral width and the number of weak interactions, can effectively enhance the weak value amplification effect. Experimentally, a phase weak measurement system based on iterative weak interactions (IWI) was constructed using a tunable light source as the optical input. The setup incorporates three sets of half-wave plates (HWP) to realize triple weak interactions. By fixing the postselection angle and rotating the HWP to introduce a weak phase delay, high-precision detection of the phase shift is achieved by monitoring both the spectral shift and light intensity variations. Experimental results indicate that at a spectral width of 700 GHz, the momentum parameter M achieves the 4.06 × 10-8 rad optimal phase difference measurement accuracy, which is 2.78 times higher than that of single weak interactions (SWI). As the spectral width decreases, the signal-to-noise ratio gradually degrades, and the shift signal of parameter M is submerged in the electronic noise of the spectrometer, necessitating a switch to the intensity parameter I for detection. When a narrow-linewidth source with a linewidth of 500 kHz isemployed, the intensity parameter I enables phase difference measurements at the level of 5.99×10-7 rad while maintaining a high signal-to-noise ratio (SNR) of 17.4 dB. Its measurement precision is 2.97 times higher than that of SWI. In optical experiments, the optical phase can serve as a proxy for other physical quantities such as displacement, temperature, and magnetic field strength. Therefore, this scheme provides crucial technical support for practical enhanced quantum precision sensing.
In this study, we propose and experimentally validate a dual -parameter quantum weak measurement scheme based on tunable spectral control and iterative weak interactions. Theoretical analysis demonstrates that adjusting the spectral width and the number of weak interactions, can effectively enhance the weak value amplification effect. Experimentally, a phase weak measurement system based on iterative weak interactions (IWI) was constructed using a tunable light source as the optical input. The setup incorporates three sets of half-wave plates (HWP) to realize triple weak interactions. By fixing the postselection angle and rotating the HWP to introduce a weak phase delay, high-precision detection of the phase shift is achieved by monitoring both the spectral shift and light intensity variations. Experimental results indicate that at a spectral width of 700 GHz, the momentum parameter M achieves the 4.06 × 10-8 rad optimal phase difference measurement accuracy, which is 2.78 times higher than that of single weak interactions (SWI). As the spectral width decreases, the signal-to-noise ratio gradually degrades, and the shift signal of parameter M is submerged in the electronic noise of the spectrometer, necessitating a switch to the intensity parameter I for detection. When a narrow-linewidth source with a linewidth of 500 kHz isemployed, the intensity parameter I enables phase difference measurements at the level of 5.99×10-7 rad while maintaining a high signal-to-noise ratio (SNR) of 17.4 dB. Its measurement precision is 2.97 times higher than that of SWI. In optical experiments, the optical phase can serve as a proxy for other physical quantities such as displacement, temperature, and magnetic field strength. Therefore, this scheme provides crucial technical support for practical enhanced quantum precision sensing.
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Amorphous tungsten trioxide (a-WO3) has emerged as an ideal candidate material for non-volatile memristors, attributed to its high concentration of oxygen vacancies, moderate band gap, and compatibility with CMOS technology. This renders it broad application prospects in neuromorphic computing systems. However, its poor analog switching performance severely hinders its practical application in high-efficiency artificial intelligence data processing. To enhance the analog switching performance of WO3 memristors, this study adopts radio frequency (RF) magnetron sputtering technology to deposit a five-layer amorphous tungsten trioxide (a-WO3) thin film with a gradient distribution of oxygen vacancy concentration on a platinum/silicon (Pt/Si) substrate. X-ray Photoelectron Spectroscopy (XPS) analysis confirms that the oxygen vacancy (Vo) concentration decreases gradually from the bottom to the top layer,verifying the successful fabrication of the five-layer a-WO3 thin film with a gradient distribution of oxygen vacancies. Compared with a-WO3 memristors with a uniform Vo concentration, the device with the Vo gradient distribution exhibits highly reliable analog switching characteristics (low cycle-to-cycle variability, high linearity in potentiation/depression processes), ultra-long data retention (>104 s), and self-current-limiting behavior. An artificial neural network (ANN) based on this structured memristor achieves a handwritten digit recognition accuracy of 97.64%. The RS essence of a-WO3 memristors with Vo concentration gradient distribution lies in the formation/rupture of VOdominated conductive filaments (CFs). The Vo gradient distribution enables controllable evolution of CFs by modifying the electric field and ion migration rules. During CF formation, oxygen ions migrate toward the top electrode, and Vo accumulates gradually first in the bottom electrode region; meanwhile, the electric field induced by Vo gradient suppresses the local abrupt growth of CFs, leading to the formation of uniform nonconical structures and avoiding resistance mutation. During CF rupture, ions migrate toward the bottom electrode, and non-conical CFs can rupture synchronously and progressively, ultimately achieving precise regulation of multi-level conductance. The conduction mechanism shows that the low-voltage region of the high-resistance state (HRS) exhibits an I-V linear relationship, corresponding to the ohmic conduction mechanism. In thehigh-voltage region of HRS, I has a linear relationship with both V2 and V2.5, which conforms to the space-charge-limited current (SCLC) theory. The gradient distribution of oxygen vacancies (VO) regulates the formation and rupture of conductive filaments (CFs), thereby solving the core issue of poor analog switching performance in traditional WO3 memristors. This provides a critical “Vo gradient regulation” design strategy for highdensity neuromorphic computing. It is expected to play a significant role in fields such as image recognition, speech recognition, and intelligent robots.
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The nonlinear acoustic propagation in shallow-sea waveguides is a fundamental issue for the propagation of sound waves in complex marine environments. It holds significant importance for applications such as underwater nonlinear sound field regulation and target detection. In this study, a theoretical model and a numerical method are established to investigate nonlinear sound propagation in waveguides. The physical characteristics of the reflection of difference-frequency beams at the waveguide boundaries during nonlinear interaction processes are examined. Based on the quasi-linear theory of the nonlinear wave equation, a theoretical model capable of accurately computing wide-angle sound field information at large grazing angles is developed by introducing a high-precision non-paraxial approximation approach and employing the image source method to analyze the nonlinear sound field in the waveguide. The effects of frequency (200–500 Hz), source depth (20 m and 80 m), and grazing angle (±60°) on nonlinear sound propagation are studied, and the underlying mechanisms are analyzed. Results indicate that an increase in frequency enhances the orientation performance of the nonlinear beam, thereby enhancing its resistance to interference in the waveguide. When the sound source is near a waveguide boundary, the nonlinear beam develops side lobes in the area close to this boundary. The beam energy that was originally concentrated near the sound axis and varies uniformly shows obvious discontinuity, and the sound pressure distribution along the sound axis shows fluctuations. The grazing angle of the source directly affects the sequence of boundary reflections, which in turn alters the sound energy distribution and leads to enhanced or weakened interference effects. Waveguide boundaries influence the spatial amplitude and phase distribution of the nonlinear virtual source, modifying the spatial accumulation process and significantly affecting the final sound field distribution. The model developed in this work accounts for the diffraction characteristics of beams emitted by real sources and ensures accuracy in wide-angle sound field modeling. It helps reveal the propagation laws of difference-frequency beams under waveguide boundary reflection during the nonlinear interaction process at large grazing angles, and provides theoretical support for fine regulation technologies of directional beams such as active noise control and low-frequency active detection in underwater waveguide environments.
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Generally, when individuals obtain information about epidemic risks, they will arouse their awareness of self-protection and thus take various effective self-protection measures independently. However, there is often significant different response for different individual. To explore more comprehensively the impact of differences in individuals' ability to identify or accept external information on awareness diffusion, as well as on epidemic spreading, this paper constructs an awareness-epidemic double-layer network with higher-order interactions, innovatively introduces an individual heterogeneity factor, and proposes the UAU-SIS （ Unaware- Aware- Unaware- Susceptible- Infected- Susceptible ） awareness-epidemic spreading model. The heterogeneity in this model is mainly reflected by individuals' first-order degree, second-order degree, coordination factor, and response factor. Based on the Microscopic Markov Chain Approach (Microscopic Markov Chain Approach， MMCA) and the proposed UAU-SIS model, this paper conducts a theoretical analysis of the coevolution of awareness and epidemic, and theoretically deduces the mathematical expression of the epidemic threshold. Monte Carlo（ Monte Carlo， MC） numerical simulations verify the feasibility and effectiveness of the MMCA theoretical analysis. Meanwhile, numerous numerical simulations have explored the impact of individual heterogeneity on awareness diffusion, epidemic spreading, and epidemic threshold. The results show that reasonable regulation of the first-order average degree and second-order average degree of the awareness layer can effectively promote awareness diffusion and improve the overall effect of epidemic prevention and control. In addition, reducing the coordination factor or increasing the response factor can effectively promote awareness diffusion, raise the epidemic threshold, and thus block epidemic spreading.
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