International Journal of Modern Physics B

We propose a simple optical model, which consists of two Kerr nonlinear parallel planar waveguides sandwiching a one-dimensional photonic crystal for demonstrating the phenomenon of spontaneous symmetry breaking in optics. We study the shape and stability of soliton pairs propagating in two planar waveguides and the spontaneous symmetry breaking of the power distribution of solitons in the two waveguides. The results of numerical simulation show that there is supercritical type of spontaneous symmetry breaking in this system. More optical power P and smaller refractive index of photonic crystals $C_0$ make soliton solutions more prone to spontaneous symmetry breaking bifurcation. Asymmetric soliton solutions and symmetric soliton solutions correspond to different dispersion relations. Under the given total power P, for the symmetric soliton solutions, the propagation constant k increases linearly with $C_0$, and for asymmetric soliton solutions, the propagation constant k decreases nonlinearly with $C_0$. The minimum point of $k(C_0)$ is just the demarkation between the symmetric soliton solutions and the asymmetric soliton solutions. If $C_0$ is fixed, the minimum point of the Hamiltonian of the system, $E(P)$, is also the critical point of the two different kinds of soliton solutions. We also study stable and unstable distributions of two kinds of soliton solutions.

This paper presents an investigation into solutions of two types of nonlinear Schrödinger equations of logarithmic form. This model is of particular interest to researchers due to its vast application in the field of the implication of nanofibers. Through a comprehensive analysis, it was found that the solutions take the form of Gaussian-type solitary solutions. These solutions possess a variety of new structures due to the presence of many arbitrary constants and time-dependent functions in their general expressions. By fixing these constants and functions appropriately, Gaussian solitary waves for nonlinear perturbed Schrödinger equations can be represented, which could be beneficial in understanding the dynamics of these equations in nanooptical fibers. The results obtained from this study may provide a useful tool for further research into nonlinear Schrödinger equations and can be extended to fit more applications.

In this paper, we report the optoelectronic, thermoelectric properties and dynamic stability under the pressure of LiGaC half-Heusler within the Density Functional Theory (DFT) and semi-classical Boltzmann Transport Theory (BTT). The obtained results of the ground state show that the compound is structural, chemical, mechanical and dynamically stable in type I structure and maintains its stability under pressure. The obtained electronic properties reveal that the compound has a semiconducting nature with an indirect bandgap and the bandgap values slightly increase with pressure increase. The optical properties such as real and imaginary parts of dielectric function, refractive index and extinction coefficient, reflectivity and absorption coefficient and optical conductivity are calculated and discussed. The highest peaks of reflectivity and absorption coefficient are found in the ultra-violet (UV) region, suggesting that the compound LiGaC has a high potential for use in UV optoelectronic applications. The thermoelectric properties are also calculated in the temperature range from 300K to 900K and pressure range from 0GPa to 40GPa. At 300K and for all pressures selected, the maximum value of figure of merit is close to unity. Finally, we could make our conclusion that LiGaC is well suitable for multiple optical and thermoelectric applications.

This paper investigates the Magnetohydrodynamics (MHD) convective flow over a cone with the influence of viscous dissipation, variable viscosity, chemical reaction and variable thermal conductivity effects. Related equations are tackled by the Homotopy analysis method (HAM). The impacts of physical variables on concentration, velocity and temperature are presented through numerical tables and graphs. It is noticed that the heat transfer rate (Nusselt number) increases against Prandtl number. Similarly, the mass transfer rate (Sherwood number) increases against Schmidt number. Also, it is seen that skin friction in tangential and azimuthal direction increases against the buoyancy forces ratio parameter. Current results are validated with previous literature work.

In this work, we study the quantum Fisher information on the Heisenberg model in presence of the Dzyaloshinskii–Moriya interaction, basing on the multi-parametric estimation strategy in quantum metrology. First, we employ the density matrix vectorization method with a tool of the quantum Fisher information matrix through quantum Cramer–Rao bound. Second, we show that the multi-parameter quantum Cramer–Rao bound for simultaneous and individual estimation of the temperature and Dzyaloshinskii–Moriya interaction strongly relies on the concepts of the quantum Fisher information matrix. We confirm also the simultaneous strategy that provides a high precision than the individual.

In this paper, we investigate the Bloch bands and develop a linear response theory for nonlinear systems, where the interplay between topological parameters and nonlinearity leads to new band structures. The nonlinear system under consideration is described by the Qi–Wu–Zhang model with Kerr-type nonlinearity, which can be treated as a nonlinear version of Chern insulator. We explore the eigenenergies of the Hamiltonian and discuss its Bloch band structures as well as the condition of gap closing. A cone structure in the ground Bloch band and tubed structure in the excited Bloch band is found. We also numerically calculate the linear response of the nonlinear Chern insulator to external fields, finding that these new band structures break the condition of adiabatic evolution and make the linear response not quantized. This feature of response can be understood by examining the dynamics of the nonlinear system.

In order to study the forming mechanism of metal jet under electromagnetic loading, numerical simulation for electromagnetic coupled jet forming was realized by using AUTODYN software with secondary development. Through secondary development, the magnetic pressure on the liner during the collapse process is calculated iteratively, which enables numerical simulation for electromagnetically coupled jets. The influence and threshold condition of electromagnetic parameters for jet forming are obtained through this. The results show that the head velocity and length of the jet are improved for liner without a tip. The electromagnetic parameters and structural parameters need to match with each other. The head velocity and effective length of the jet increase with the increase in wall thickness and cone angle. The liner diameter has little effect on the head velocity and effective length of the jet. The head velocity and effective length of the jet first increase and then decrease with the increase in cone radius.

First-principles calculations are performed, revealing a significant enhancement of the piezoelectric properties of wurtzite Zn${}_{36}$O${}_{36}$ upon the incorporation of a single Cu atom. Research has demonstrated that the piezoelectric constant $d_{33}$ reaches its maximum value at a doping concentration of 1.4% for Cu atoms. The lattice parameters a and c of Zn${}_{36}$O${}_{36}$ are decreased and the piezoelectric strain coefficient $d_{33}$ is increased by replacing one Cu atom in Zn${}_{36}$O${}_{36}$. It is found that elastic softening is the primary factor responsible for the increase of $d_{33}$ in Zn${}_{35}$Cu₁O${}_{36}$. By differential charge density analysis, it is found that the covalency between Cu–O bonds is lower than that of Zn–O bonds, and the covalent bonding characteristics are weakened. Bader charge analysis shows that the charge of Cu is higher than that of Zn, indicating a more significant ionic bonding feature than that of Zn. Thus, a weaker covalent and stronger ionic bond are considered to play an essential role in promoting elastic softening for ZnO, which eventually promotes a significant enhancement in piezoelectric properties.

We propose a theoretical model for the single photon quantum router that consists of two plasmonic waveguides, one of which is infinite and the other is semi-infinite, coupled to two two-level quantum dots (QDs) with dipole–dipole interaction (DDI). The infinite waveguide, the main branch, couples with both QDs, and the semi-infinite, the side branch, couples with the main branch at the position of one of the QDs. In such a system the incident single photon can also be transferred to the side branch, not only be transmitted or reflected. The results show that the transfer rate mainly depends on the coupling strength between the QDs and the two waveguides, but there exists a certain limit in the increase of the transfer rate. The DDI between the QDs gives a remarkable change to the routing spectra and the routing properties are different according to the position of the side branch. The proposed system is indeed multi-channel single photon quantum router, which has more practical significance than the one-dimensional router and can be employed in multi-user quantum networking.

Due to the numerous practices of non-Newtonian fluids in technological and industrial fields, the attention towards such fluids increases incredibly. The highly nonlinear equations emerge in the modeling of the non-Newtonian fluids. The differential transform method is one of the analytical methods which is used to acquire the solution to these complicated nonlinear equations in the series form. The current analysis comprises the squeeze flow of non-Newtonian fluid in two dimensions. Two infinite parallel plates are considered in which the time-dependent fluid is squeezed. The heat transfer mechanism is deliberated with the significance of heat absorption/generation. The nonlinear setup of ordinary differential equations is acquired by practicing the appropriate similarity variables on the governing equations of the concerned flow mechanism. The nonlinear setup is analytically resolved with the help of an analytical differential transform method. For the authenticity of the differential transform method, the analytical outcomes are compared with the numerical results. Graphical illustrations of fluid temperature and velocity profiles relative to the pertinent parameters are briefly explicated numerically and analytically. The fluid velocity demonstrates the descending behavior and the temperature field exhibits the expanding nature relative to the squeezing parameter.

Complex oxides La${}_{0.97}$Ba${}_{0.03}$MnO₃, La${}_{0.73}$Ba${}_{0.27}$MnO₃ and La${}_{0.5}$Ba${}_{0.5}$MnO₃ were synthesized and their structural properties were studied. The structural investigation of the samples is done by incorporating X-ray diffraction (XRD) and scanning electron microscope (SEM) technique at room temperature. The Rietveld method was successfully used for the analysis of the obtained diffraction spectra. It was determined that these compounds have a perovskite structure. Partial substitutions La→Ba do not disturb the ideal perovskite structure and the cubic crystal structure with the space group Pm-3m is preserved. Crystallographic parameters, lattice parameters and interatomic distances were determined for each compound. As a result of SEM studies, it was determined that the size of crystallites in La_xBa${}_{1-x}$MnO₃ solid solutions ranged from 2 to 10$\mu$m.

Ni-doped molybdenum disulfide (MoS${}_2)$ powders at 1%, 2%, 3%, 4%, 5% and 7% of Ni are prepared by the hydrothermal method. Sophisticated analytical studies such as X-ray diffraction, Raman, TEM and photoluminescence (PL) were analyzed to predict their structural, morphological and optical properties. Effects of Ni-doping with MoS₂ on crystalline structure, morphology as well their optical phenomenon were examined in detail. Ni doping on MoS₂ revealed tetragonal crystal structure of the parent compound. A significant decrease in their optical energy gap (from 1.86 to 1.76eV) was perceived with Ni doping concentration increment. PL intensity exhibited a considerable improvement with Ni-doped MoS₂ samples at room temperature. From a theoretical viewpoint, the compact density matrix method is applied for Ni–MoS₂ to calculate their linear and nonlinear absorption coefficients as well as refractive index modulations for undoped and Ni-doped samples at the focal points of their corresponding intra-band and inter-band transitions. Observed findings are well correlated with the practical results which prove that Ni–MoS₂ layers are promoters for potential applications in optoelectronic technology.

In this paper, new exact traveling wave solutions are obtained by Hirota–Ramani equation. The many exact complex solutions of several types of nonlinear partial differential equations (NPDEs) are presented using the modified extended direct algebraic approach and new extended direct algebraic method, which is among the most effective mathematical techniques for finding a precise solution to NPDEs and put into a framework of algebraic computation. By selecting different bright and solitary soliton forms and by creating various analytical optical soliton solutions for the investigated equation, we hope to demonstrate how the analyzed model’s parameter impacts soliton behavior. It is possible to obtain new, complex solutions for nonlinear equations like the $(1+1)$-dimensional Hirota–Ramani equation.

Nanostructured ZnS films of various molar concentrations have been deposited using chemical bath deposition (CBD) method on glass substrates in the matrix of polyvinyl alcohol (PVA). Structural analysis of the samples with the help of X-ray diffraction (XRD) shows that the films are of cubic phase structure and diffraction peaks shift toward higher diffraction angle with the increase of molar concentration. Crystallite size is obtained using Scherrer’s formula, Williamson–Hall (WH) plot as well as size–strain plot (SSP), and reveals decrease in size with increasing molar concentration. Surface morphology and surface texture of the samples are observed with the help of atomic force microscopy (AFM) and high-resolution transmission electron microcopy (HRTEM) which exhibit the roughly spherical shape of the particles as well as formation of cluster by a large number of ZnS nanoparticles. Observation from selected area electron diffraction (SAED) pattern also confirms the cubic phase of nanostructured ZnS samples. Surface topographic study using scanning electron microscopy (SEM) also shows particle agglomeration forming nanoclusters and energy-dispersive X-ray spectroscopy observation reveals that the films are composed of zinc and sulfur. With the increase of molar concentration, the optical bandgap energy increases whereas the refractive index as well as dielectric constant decrease, and in comparison to ZnS bulk counterpart, the samples are found to be blue-shifted. Samples exhibit blue emission photoluminescence (PL) band and second-order Raman scattering. Fourier-transform infrared (FTIR) technique is utilized to detect the presence of stabilizing agent.

In this work, efficient catalyst is prepared using ZnO and $\alpha$-Fe₂O₃ along with a surface modification using 2-methylimidazole. Surface modified feature of the catalyst is confirmed by the shifting of vibrational frequency to higher wavenumber. Photocatalytic properties of the as-synthesized and surface modified composites are investigated by measuring the degradation of Methylene Blue (cationic) dye under sunlight irradiation. Both the samples exhibited a similar photocatalytic efficiency of 78% under 300 min. The effect of surface modification shows no significant enhancement on the cationic dye removal. Further, the samples are tested for the degradation of Methyl Blue (anionic) dye in dark condition to validate the effect of functionalization. Surface functionalized sample exhibits 96% efficiency compared to 86% for the pristine sample. Thus, surface modification has extended to be one of the promising techniques for enhancing the catalytic properties of composites.