Indian Journal of Physics最新文献

In this work, the influence of light on the temperature dependence of transverse magnetoresistance oscillations is studied. A generalized mathematical expression that calculates the temperature and light dependence of the quasi-Fermi levels of small-scale p-type semiconductor structures in a quantizing magnetic field is derived. New analytical expressions have been found to represent the temperature dependence of transverse differential magnetoresistance ossillations in dark and light situations, taking into account the effect of light on the ossillations of the Fermi energy of small-scale semiconductor structures. A mathematical model determining the light dependence of the second-order derivative of oscillations of transverse magnetoresistance of p-type semiconductors with quantum wells on magnetic field induction is developed. A new theory explaining the reasons for the significant shift of oscillations of differential magnetoresistance along the vertical axis measured in the experiment for dark and light conditions is proposed.

This study provides a comprehensive analysis of the Friedmann–Robertson–Walker model within Chern–Simons modified gravity, incorporating the holographic dark energy model. The scale factor, deceleration parameter, Hubble parameter, and cosmological constants ((Lambda ) and G) are examined. The findings help to distinguish between models of acceleration and deceleration, supporting recent data that indicate an accelerating universe. The decreasing trend observed in the cosmological constant (Lambda (t)) aligns with type Ia supernovae observations. Additionally, the observed correlation between the gravitational constant G(t) and cosmic time supports specific critical density assumptions. State finder parameters (r, s) offer insights into various cosmological scenarios. Overall, this study advances our understanding of the universe’s evolving nature under the FRW model with Chern–Simons modified gravity.

In this paper, we generate the anisotropic strange star models using a new form of metric potential. We determine the another metric coefficient by assuming a suitable form of anisotropy function, in such a way that both are free from any kind of singularities. We analyze the thermodynamic physical variables and geometric features extensively for the compact stars SMC X-4, LMC X-4. The trends of all the variables are well defined and physically acceptable. The masses and radii of the stellar objects SMCX-4, LMCX-4 are in close agreement with the available known parameters. The interior spacetime metric is to be matched with the Schwarzschild Vacuum Solution to ascertain the constant parameters. The adiabatic index exhibits physically reasonable trend and exceeds 4/3 throughout inside the compact fluid spheres. The stability of stellar models is analyzed via Herrera’s cracking concept and Harrison–Zel’dovich–Novikov criterion. The causality condition is well obeyed by the proposed stellar models. The TOV equation for the equilibrium of the fluid spheres is properly maintained inside the stellar models.

Solvable model of moire superlattice in a homogeneous magnetic field is constructed. The system consists of two parallel plane layers with 2D lattices. The lattice at one plane is turned in respect to another one. The dependence of the spectrum of the model Hamiltonian on the magnetic field (i.e. energy-flux diagram) has Hofstadter butterfly type. We compared the energy-flux diagrams for different angles between the orientations of the lattices.

To investigate the influence of the vacuum environment on the near-infrared nanosecond pulse laser irradiation of silicon materials, irradiation effects such as the distribution and evolution of the microstructure, as well as the erosion morphology of silicon under various vacuum levels, are investigated. The experimental results show that when the laser energy density is low, silicon’s temperature rises and volume expands due to the laser energy absorption, resulting in thermal stress within the irradiation area and the appearance of cracks on the surface. As the laser energy density increases, a molten pit appears at the ablation center, and the size of the molten pit increases with the energy density, resulting in a significant increase in the damaged area. The damage diameter decreases with the vacuum level. However, the effect of vacuum level on the damage diameter is not significant when the excitation energy density is low. The damage area of monocrystalline silicon increases approximately linearly with the laser repetition rate. Laser absorption is primarily Finier absorption in high vacuum conditions, whereas reverse toughening absorption is predominant in low vacuum conditions. This study can be used as a reference for surface treatment, drilling, and development of new monocrystalline silicon materials.

The electron paramagnetic resonance (EPR) and crystallographic data have been previously documented in literature for Mn2 + doped zinc pentafluorooxodiobate (V) hexahydrate ZnNbOF5.6H20 (CPH) and cobalt pentafluorooxonibotae (V) hexahydrate CoNbO₅.6H₂O single crystal. In this study, a theoretical investigation of these crystals has been conducted using the superposition model (SPM). The superposition model (SPM) distinguish the geometrical and physical properties that are essential in crystal field parameters. By employing a simple linear least square fit of parameters to intrinsic parameters, the zero field splitting parameters (ZFS) of Mn²⁺ in ZPH and CPH can be determined from crystal structure din the lattice. This observation suggests that Mn2 + effectively replace Zn²⁺ and Co²⁺. The SPM analysis, relying on the assumption of n no. of identical structure around host and guest ions, consider only the immediately coordinated ions. Close agreement between theoretical values of ({b}_{0}^{2}) is achieved by adopting a reference distance of R₀ = 0.22 nm. The exponent power law t₂ = 7 ± 1 and t₄ = 10 ± 1 are determined for Mn²⁺ surrounded by oxygen. The fine structure constants are indicative of the specific arrangement of ligands nearby all the impurity ions, with zero-field splitting parameters ({b}_{2}^{0}), ({b}_{2}^{2}), ({b}_{4}^{ 0}), ({b}_{4}^{2}) and ({b}_{4}^{4}) showing sensitivity in the case where Mn²⁺ ions are coordinated by oxygen in single crystals. The results obtained from the superposition model align well with the experimental findings, especially when accounting for local distortion around the Mn²⁺ ion at substitutional site in the host crystal. This paper aims to investigate the local distortion caused by substituting Mn²⁺ in the host crystal, exploring its potential impact on its magnetic properties.

The critical unwinding field was studied theoretically using Landau-Ginzburg free energy model of pure antiferroelectric liquid crystals (AFLC), influenced by flexoelectric effect in presence of spin–spin interaction. In this study, we constructed an appropriate Landau free energy using the flexoelectric effect and spin–spin interaction in AFLC. Using the Landau-Ginzburg equation of azimuthal angles, we observed that the flexoelectric effect in AFLC did not make any difference in the critical unwinding for both the cases when elastic constant was keeping as constant or inter-layer interaction strength was keeping as constant. But for AFLC in presence of spin–spin interaction, the reverse electric field and the modified elastic constant were created a significant change in the critical unwinding field in compare to others.

The paper attempts to investigate string cosmological model within the framework of f(R, T) theory of gravity in homogeneous but anisotropic Bianchi Type-V space-time. We have considered cosmic string as a source of energy-momentum tensor. We derived the solutions of the corresponding field equations by assuming power-law form of scale factor and also evaluated and discussed the various physical and kinematic properties including the jerk parameter, energy condition of the model. The variation of the cosmological parameters has been graphically presented for some specific values of the constants.

The structural, elastic, mechanical, optoelectronic, and Debye temperatures of ({text{MAs}}_{2}) (M = W, Cr, Mo) were explored at ambient pressure using first-principles calculations. Lattice constants and cell volume are calculated to be in good consistent with other findings. We investigated the mechanical properties of ({text{MAs}}_{2}) materials using elastic moduli, the machinability index, and Vickers hardness. Poisson’s and Pugh’s ratios indicate that ({text{WAs}}_{2}) material is ductile, whereas ({text{CrAs}}_{2}) and ({text{MoAs}}_{2}) are brittle at ambient pressure. Analyzing electronic properties offers crucial support for assessing optical performance. In the higher energy range, the refractive index value falls and flattens. Due to their high reflectivity, these phases are excellent candidates for solar heating reduction in the infrared and ultraviolet wavelength regions. The minimum thermal conductivity values for ({WAs}_{2}), ({CrAs}_{2}), and (Mo{As}_{2}) are 0.571, 0.732, and 0.666, respectively, making them attractive thermal insulators above their Debye temperatures (({theta }_{D})). Melting temperatures show that (Cr{As}_{2}) melts at 1389.12 °C, ({MoAs}_{2}) at 1587.60 °C, and ({WAs}_{2}) at 1648.86 °C. It indicates that ({WAs}_{2}) is the most thermally stable of the three compounds, whereas (Cr{As}_{2}) is the least. Lastly, we anticipate that the present findings will have profound implications for future studies of various aspects of related materials.