物理最新文献

We investigate the possibility of obtaining traversable wormholes supported by real phantom scalar fields in Lorentz-violating gravity with an antisymmetric rank-2 tensor with a non-zero vacuum expectation value non-minimally coupled to the curvature tensor. This Lorentz violation framework shows to be a suitable scenario to search for wormhole solutions in the presence of Lorentz violation since it introduces mild constraints on the areal radius. The vacuum expectation value of the antisymmetric rank-2 tensor, nonetheless, imposes constraints on the lapse function. As a consequence, under the vacuum configuration adopted, the allowed lapse functions can be either constant, linear, or quadratic, depending on the self-interaction potential that drives the spontaneous breaking of the Lorentz symmetry. Thus, we find the Ellis–Bronnikov counterpart in this Lorentz-violating scenario as well as Lorentz-violating wormholes with a Rindler-type acceleration and an effective cosmological constant. Properties of these wormholes, such as their non-flat asymptotics, are investigated.

In this study, a heterojunction photodiode with an Au/α-MnS/p-Si/Al architecture was fabricated via the spin-coating technique. The structural and morphological analyses of the hydrothermally synthesized α-MnS thin films revealed a polycrystalline cubic rock-salt structure with a direct bandgap of 3.4 eV. The electrical and optoelectronic properties of the fabricated device were investigated using current-voltage (I-V) and transient photocurrent measurements under various illumination intensities (20–100 mW/cm²). The device exhibited distinct rectifying behavior, with the barrier height decreasing from 0.79 eV to 0.53 eV under illumination. Key performance parameters, including photosensitivity (S), photoresponsivity (R), and specific detectivity (D^*), were calculated to evaluate the device’s potential as a photodetector. The results showed a supralinear photocurrent response (m = 1.4), leading to peak performance values of S = 8.56, R = 8.73 × 10^− 5 A/W, and D^*=1.53 × 10⁸ Jones at 100 mW/cm². These findings demonstrate that the α-MnS/p-Si heterojunction is a functional photosensor with light-dependent switching characteristics.

In this work, we consider a generalized extended Kadomtsev–Petviashvili (geKP) equation that contains higher order temporal dispersion and mixed derivative terms. This form of the KP equation provides a wider setting for studying nonlinear waves in areas such as fluids, plasmas, and optics. We first test the integrability of the system by using the Painlevé analysis and by constructing multi-soliton solutions, which both lead to the same constraint on the equation’s parameters. On this basis, we study rogue wave (RW) solutions in two ways. A direct symbolic computation method gives higher order rational solutions and also allows us to introduce center-controlled RWs, in which additional parameters can shift and arrange the wave peaks. In parallel, we apply the KP hierarchy reduction method, which produces determinant form rational solutions and clarifies the algebraic structure behind the system. The obtained rational solutions correspond to line-type RWs, which are localized along an oblique direction in the (x, y) plane while remaining invariant along the transverse direction. The comparison shows that the symbolic solutions appear as special cases of the KP reduction approach. Several examples and plots are given to illustrate the dynamics.

In this study, tin sulfide (SnS) thin films were deposited via spray pyrolysis and subsequently functionalized by atmospheric cold plasma for varying durations to improve their hydrogen sulfide (H₂S) gas sensing performance. This work presents the first study of post-deposition cold plasma surface and defect engineering applied to spray-pyrolyzed SnS thin films for gas-sensing applications. Structural and morphological analyses revealed that the plasma treatment induced significant surface modifications, including a reduction in the crystallite size, a phase transformation from the metastable cubic to the dominant, more stable orthorhombic phase, and the development of a finer nanostructure. The resultant-changes enhanced the surface interaction with the gas molecules. Spectroscopic analysis demonstrated a bandgap narrowing from 2.4 eV to 2.2 eV after 10 min of plasma treatment, attributed to defect formation and altered electronic states. The plasma-treated films exhibited significantly improved sensitivity, response time, and recovery time to H₂S. The highest sensitivity was 67% toward 15 ppm H₂S at the optimum operating temperature of 200 °C for the sample plasma-treated for 10 min, compared to 32% for the untreated sample. The 10 min-treated sample exhibited a significant correlation with the H₂S concentration, with sensitivity increased from 31% at 5 ppm to 130% at 40 ppm. The device also showed fast response and recovery times of 20s and 25s, respectively. These findings demonstrate that atmospheric cold plasma treatment is an effective, low-temperature approach to enhance the active-surface-area and tune carrier dynamics in SnS layers, enhancing their gas-sensing performance. Indeed, this study highlights the potential of plasma-assisted SnS sensors for efficient detection of toxic gases.

Cu₂ZnSnS₄ (CZTS), well-known for its use in photovoltaic and photocatalytic systems, has been studied as a solid-state hydrogen storage material. At 10 bar hydrogen pressure, structural and spectroscopic analysis revealed unambiguous lattice changes in the form of enhanced lattice parameters (a = 5.41 Å, c = 10.754 Å), a reduction in crystallite size from 66.37 nm to 56.70 nm. Raman and FTIR spectra confirmed hydrogen incorporation through vibrational mode changes and S–H stretching band emergence. A-mode near 336 cm⁻¹, including intensity changes and slight shifts, reflecting hydrogen-induced strain and defect interactions within the lattice. Through the emergence of an S–H stretching band around 2369 cm⁻¹, which was absent in the pristine sample. The material was observed with a high specific surface area, enhancing the adsorption kinetics for hydrogen. Storage capacity was 0.9 wt%, and the rate of desorption was 0.0108 m³/h at 200 °C. TGA demonstrated enhanced mass loss behavior in hydrogenated samples, suggesting modified thermal stability after hydrogen treatment. Gas chromatography analysis confirmed clean and selective hydrogen release. These findings make CZTS a low-cost and structurally versatile material with a promising reversible hydrogen storage solution in energy conversion applications.

We probe potential variations of the proton-to-electron mass ratio ((mu )) using high-resolution H(_2) Lyman transitions in the white dwarf GD 133, observed with the Hubble Space Telescope Cosmic Origins Spectrograph (HST/COS). White dwarf atmospheres provide a powerful laboratory for testing fundamental physics in strong gravitational fields. Applying a self-consistent spectral analysis, we obtain a tight constraint of (Delta mu /mu = (0.02 pm 0.09)) in a gravitational potential approximately (10^{4}) times stronger than that of Earth. The measured uncertainty implies that any variation of (mu ) is tightly bounded in this strong-field fields, placing meaningful limits on models predicting couplings between fundamental constants and gravity.

In this study, the ionic structure, electronic properties, and transport properties of the NaF-KF-AlF3 molten-salt electrolyte system with a molecular ratio of 1.4 and a NaF content of 25 mol% − 45 mol% were investigated at the microscopic level to elucidate its physicochemical behavior. The result indicated that the ion diffusion in molten salt followed the order of Na + > K+> F-> Al3+. The calculated ionic conductivity is ranged from 0.8 S/cm to 1.35 S/cm, while the viscosity varied between 1.0 mPa·s − 1.8 mPa·s. Among the compositions studied, electrolytes containing 40 mol% NaF exhibited optimal transport properties, making it the most suitable candidate for use as an aluminum electrolysis electrolyte in inert anode systems.

Graphical Abstract

Molecular dynamics simulations are employed to systematically study the effects of grain size and temperature on the mechanical behavior and microstructural evolution of nanocrystalline Ni subjected to tension-compression cyclic loading. The results indicate that for the fine-grained nanostructures (d ≤ 8.6 nm), the stress amplitude decreases continuously with increasing cycle number, accompanied by a reduction in energy dissipation capacity. In contrast, the coarse-grained nanostructures (d > 8.6 nm) exhibit stable fluctuations in stress amplitude after an initial rapid drop, demonstrating superior fatigue resistance. Microstructural analysis reveals that early cyclic deformation in fine-grained structures is dominated by grain boundary activities, which transition to dislocation-mediated plasticity after a polycrystal-to-single-crystal transformation. Coarse-grained structures retain their nanocrystalline polycrystalline structure throughout cycling, with dislocation slip governing plastic deformation. Furthermore, the polycrystal-to-single-crystal transition occurs in fine-grained samples at all tested temperatures, and the number of cycles required for the transition decreases with increasing temperature. In contrast, no such transition is observed in coarse-grained samples under any temperature condition. This study elucidates the coupling effect of grain size and temperature on the microstructural evolution and macroscopic mechanical response of nanocrystalline Ni under cyclic loading, providing insights into the design and life prediction of high-performance nanocrystalline metals.

Graphical Abstract

Evolutions of microstructure in nanocrystalline Ni with different grain sizes