International Journal of Modern Physics B

By using the Ginzburg–Landau theory in the nonlinear case, the shape of the inverse domain nucleus in a thin ferroelectric film in a weak electric field is determined. The dependencies of the critical size of the inverse domain nucleus on the film thickness, the strength of external electric field, the temperature and the parameter ${\alpha }_s$, which determines the polarization pinning at the film planes, are calculated. We have established that when the parameter ${\alpha }_s$ increases above a certain critical value, which depends on film thickness and external field strength, the polarization switches uniformly without domain formation. In the framework of Zeldovich theory of nucleation, the average repolarization velocity has been determined as a function of the film thickness, the external field strength and the parameter ${\alpha }_s$.

In this paper, we report the comparative study of some parameters of II–VI ternary alloy ZnCdTe and II–VI–O dilute oxide ZnCdTeO. The purpose of this comparative study is to establish both the ternary and quaternary alloys as superior materials for optoelectronic and solar cell applications in which the quaternary materials show more superiority than the ternary material. In this purpose, we take the data from the experiments previously done and published in renowned journals and books. The parameters of these alloys are mainly being calculated using Vegard’s law and interpolation method of those collected data. It was certainly demonstrated that the incorporation of O atoms produces a high bandgap ($\mathrm{\Delta }{E}_g$) reduction in host ZnCdTe (Zn${}_{1-x}$Cd_xTe) in comparison to the bandgap reduction in host ZnTe material with Cd incorporation. The bandgap of ZnCdTeO (Zn${}_{1-x}$Cd_xTe${}_{1-y}$O_y) was found to be reduced to 1.1357 at $x=y=0.5$ and the spin–orbit splitting energy (${\mathrm{\Delta }}_{\mathrm{\text{SO}}}$) value of ZnCdTeO was calculated to be 1.175eV for Cd concentration of 0.5mole and O concentration of 0.1mole both of which showed excellent results with the prospect of optoelectronic and solar cell applications. The constant rise in the spin–orbit curve signifies a very less internal carrier recombination which decreases the leakage current and augments the efficiency of solar cell. The lattice constants and strain calculation values give very good results and confirm the stability of the materials. Besides, the calculated band offsets values show that for ZnCdTeO, there is higher bandgap reduction than that of ZnCdTe. Moreover, ZnCdTeO covers a wide range of wavelength in the visible region starting from violet region at 393nm upto red region at 601nm. Both ZnCdTe and ZnCdTeO are found to have excellent applications in optoelectronic and solar cell devices though quaternary ZnCdTeO proves much supremacy over ternary ZnCdTe in all aspects of the properties.

In this paper, magnetohydrodynamics of a Casson fluid flow is inspected with the presence of thermal radiation and chemical reaction. Employing the perturbation procedure, the modeling equations are tenacious; the graphs are acquired to illustrate the results. The Casson fluid velocity increases as the perturbation parameter increases. Grashof values for heat and mass transport enhanced Casson fluid velocity. Increasing Casson, magnetic, heat source, and radiation parameters reduce the flow velocity. Prandtl number, heat source, and radiation parameter all reduced the temperature profiles. Chemical reaction parameters lowered the concentration profiles. The skin friction enhances with Casson parameter impact. However, the skin-friction coefficient, Sherwood and Nusselt numbers reduce with an increment in the perturbation parameter. In certain cases, this study’s answers agreed well with the previous literature. Casson liquid with a magnetic region using mixed convection by an exponential vertical boundary layer is the novelty of the work.

Superconducting bulks applied to high-temperature superconducting (HTS) maglev vehicles are susceptible to magnetic field, resulting in alternating current (AC) losses and heat generation, which affect the stability of the suspension system. Therefore, the thermal effect of superconducting bulk under external magnetic field is worth studying. The paper uses finite element software to establish a 2D electromagnetic-thermal coupling model. The distribution and variation of HTS bulks’ temperature under varying external magnetic field are simulated and analyzed, and the loss and temperature rise of rectangular bulks with different thicknesses are studied. Finally, the effect of increasing the critical current density on the thermal effect of the superconducting bulk is discussed. The results show that the temperature rise of bulk has a positive correlation with the amplitude and frequency of external magnetic field. The maximum temperature is affected by the angle of magnetic field. Under the same external magnetic field, the bulk with smaller thickness produces smaller loss and temperature rise. The research results can provide important references for the operation and furniture design of HTS maglev vehicles.

In this paper, we investigate a system composed of two spatially separated cavities, each with a magnon mode of a yttrium iron garnet (YIG) sphere coupled to a microwave (MW) cavity and phonon modes, respectively, via linear beam splitter and magnetostrictive interactions. In addition, two-mode squeezed vacuum fields drive the two cavities. We investigate and compare the behavior of three nonclassicality indicators in two subsystems (i.e., magnon–magnon and phonon–phonon) under the influences of the temperature, the cavity–magnon damping rate, and the magnomechanical coupling rate. We use the entanglement of formation (EoF) to measure the degree of entanglement, the Gaussian quantum discord (GQD) to characterize the quantum correlations beyond entanglement and Gaussian quantum coherence (GQC) to quantify coherence. Considering that the quantifiers share the same entropic definition, we compare the three quantifiers and test the validity of the hypothesis that quantum states with nonzero discord are inherently entangled. We find, on the one hand, that both GQC and GQD exhibit freezing behavior and that they are more robust to the decoherence effect than the EoF. On the other hand, the EoF and the GQD are always upper bounded by GQC, and there is no simple dominance relationship between EoF and GQD; hence these two quantifiers should not be compared. The effect of other parameters is also discussed in detail.

This study investigates the heat and mass transfer of magnetohydrodynamic nanofluids via the Riga plate subjected to convective boundary conditions, including the thermal radiation parameter. Utilizing variable thermal conductivity and mixed convection effects, the heat transfer process is investigated. The peculiarity of the flow model enables us to investigate the importance of thermophoresis and Brownian motion to the kinetics of Newtonian fluids. The governing partial differential equations are converted into non-dimensional ordinary differential equations using proper similarity transformations and numerically solved using bvp4c in Matlab. The graphs explore the effects of pertinent parameters on the transference of heat, mass and velocity profiles. As the Biot number $({\mathrm{\text{B}}}_i)$ increases, so does the thermal boundary layer. The Nusselt number intensifies with radiation parameter but decreases with intensifying magnetic field parameter $(M)$, Eckert number $({\mathrm{\text{E}}}_c)$ and Brownian motion parameter $(N_B)$. The influence of several physical quantities is illustrated and displayed through graphs and tables. Furthermore, it is observed that the thickness of the temperature profile is increased by combining the Biot number, the thermal radiation parameter, the thermal conductivity parameter and the modified Hartmann number.

In momentum space, we investigate the correlation properties of the ground state of Tonks–Girardeau gases. With Bose–Fermi mapping method, the exact ground state wavefunction in coordinate space can be obtained based on the wavefunction of spin-polarized Fermions. By Fourier transformation we obtain the ground state wavefunction in momentum space, and therefore the pair correlation and the reduced one-body density matrix (ROBDM) in momentum space, whose diagonal part is the momentum distribution. The ROBDM in momentum space is the Fourier transformation of the ROBDM in coordinate space and the pair correlation in momentum space is the Fourier transformation of the reduced two-body density matrix in coordinate space. The correlations in momentum space display larger values only in small momentum region and vanish in most other regions. The lowest natural orbital and occupation distribution in momentum space are also obtained.

The single crystals of TlGaTe₂ were grown by the Bridgman method. The current–voltage characteristics were performed for obtained crystals and it was determined that the Poole–Frenkel effect occurs in the nonlinear region of the current in the directions parallel and perpendicular to the crystallographic axis. The calculated values of the concentration of ionized centers $N_t$, the mean free path $\lambda$, the values of the Frenkel coefficient $\beta$ and the shape of the potential well in TlGaTe₂ crystals are determined.

The model presented in this paper deals with the investigation of the unsteady laminar flow past a stretchable disk. The nanofluids Al₂O₃/H₂O and Cu/H₂O are considered for the analysis where the thermal characteristics and flow behavior of these nanofluids are compared. In addition, the system is subjected to the suction force that has significant impacts on velocity of the nanofluid flow. Further, the nanoparticle solid volume fraction is another important parameter that is discussed which has a prominent role on both profiles of the nanofluid. Furthermore, the investigated mathematical model is framed using PDEs that are transformed to ODEs using suitable transformations. The system of equations obtained in this regard is solved by employing the RKF-45 numerical method where the results are obtained in the form of graphs. Various nanofluids flow parameters arise in the study and the impact of all these parameters has been analyzed and interpreted. Some of the major outcomes are that the higher values of nanoparticle solid volume fraction enhance the temperature while it decreases velocity of the flow. The comparison of flow of the two nanofluids concluded that alumina–water nanofluid has a better velocity while the copper–water nanofluid has a better thermal conductivity.

The work aims to explore the exponential rational function technique and the generalized Kudryashov procedure to investigate one of the most important equations which is the equation of cold bosonic atoms in a zig-zag optical lattice. The considered equation is reduced to a supreme equation by using the continuum approximation which describes the soliton’s dynamics with the implication pulse variables. The adopted techniques are accurate, simple, straightforward, and succinct to compute.