New Research in Physics

Abstract Based on the density functional theory and the GGA approximation, by applying the improved potential of TB-mbJ the structural, electronic, optical, and thermodynamic properties of the XVSi semiconductor compounds (X = Co, Rh) and its [001] films Were studied. These two heusler compounds with the non-magnetic semiconductor behavior are stable in the MgAgAs-type cubic structure with F4-3m space group. Due to the good responses of the real and imaginary parts of the dielectric function for CoVSi and RhVSi in the visible spectrum range and the low electronic loss function, these two heuslers will be suitable for optical applications in this energy range. An examination of the stability phase diagram of [001] films showed that all 6 of its possible terminations would be thermodynamically stable. The electronic structure of these films indicates the emergence of half-metallic magnetic behavior only for two terms of V-Si: CoVSi [001] and V-Si: RhVSi[001]. The responses of the dielectric function, as well as the absorption spectra of the two terms, are similar to those of the Bulk state, but with less intensity, while the electron loss in these two films is greater than that of the Bulk.

Abstract Starting from 11-dimensional supergravity over AdS_4×CP^3⋉S^1/Z_k and adding a new 4-form field-strength, we get a consistent Kaluza-Klein reduction. In fact, the resulting SU(4)×U(1)-singlet (pseudo)scalars in the 4-dimensional Euclidean anti-de Sitter space arise from probe (anti)M-branes wrapped around directions of the internal space, in the (Wick-rotated) skew-whiffed background; and the resulting anti-M2-branes theory breaks all supersymmetries and parity of the original theory. In addition, the bulk (scalar) equations and solutions break the scale-invariance. Taking the backreaction on the external and internal spaces, the resulting equations correspond to exactly marginal (Δ_+=3) and marginally irrelevant boundary operators. Presenting exact solutions for the equation when taking the backreaction and solving the main bulk equation in probe approximation for the massless (m^2=0) and a massive (m^2=40) mode with math methods and especially the Adomian decomposition method, we get perturbative solutions appropriate for near the boundary analyzes. Such solutions have at least the SO(4) symmetry and present instantons responsible for tunnelling among almost degenerate vacua of the Higgs-like scalar potential or true-vacuum bubbles growing from the false vacuum in the form of bounce solutions. To realize the bulk symmetries and in particular supersymmetry breaking, we swap the three fundamental representations of SO(8) for gravitino and as a result, we realize the desired singlet (pseudo)scalars in the spectrum. As the same way, by focusing on the U(1)×U(1) part of the original quiver gauge group of the 3-dimensional boundary Chern-Simons-matter (ABJM) theory, taking just a single boundary scalar and a single fermion, introducing various marginal and irrelevant (Δ_+=8) boundary operators and deforming the boundary action with them, we finally arrive at exact solutions with finite actions which are in fact small instantons on a three-sphere at infinity. In addition, using the AdS_4/CFT_3 duality rules, we confirm the state-operator correspondence in the leading order and match elements of the bulk and boundary solutions.

Abstract Muon particles are produced by the interaction of cosmic rays with molecules in the atmosphere and are decayed to an electron and two neutrinos with a lifetime of 2.2 µs. These electrons move in the water environment faster than the speed of light in the same environment. Therefore, the electrons emit radiation in the blue and violet light range which is known as Cherenkov radiation. In this research, using the Geant4 simulation code, a simple water Cherenkov detector was simulated to study the Cherenkov radiation of electrons caused by muon decay. Using the energy spectrum of optical photons, the detection efficiency of the water Cherenkov detector was calculated 0.067. Also, the mean lifetime and maximum energy of the electrons produced by the muon decay were measured 2.197±0.014 µs and Emax=52.6 MeV, respectively.

Abstract Properties of charge carriers transport in organic semiconductors depend on the presence and distribution of trap sites. As we know, traps are the result of disorder in polymer molecules and chains caused by physical or chemical impurities in the structure of organic semiconductors. From the point of view of crystal defects that cause changes in energy levels and create an energy gap in the band theory, The transport properties of the charge carriers in these types of systems will also undergo changes, and the most important parameter will be localized or getting trapped in the conduction process. In this paper, we have investigated the effects of basic parameters on the performance of heterojunction organic solar cells as well as charge transfer using different carrier recombination models. In order to simulate these processes, we have studied the basic parameters of bulk organic solar cells with P3HT:PCBM structure by using the self-consistent solution of drift- diffusion equations and Poisson's equation, as well as using different recombination models through the finite element method. We have also investigated the effects of n-type and p-type impurity in the polymers used in a bulk organic solar cell with P3HT:PCBM structure by using the drift-diffusion model and the use of different models presented for the recombination of charge carriers. In most of the presented theoretical models and studies, the active area in organic solar cells is assumed to be intrinsic, while this assumption has some problems for their study and optimization, and the contribution of doping polymers. The studied structure is shown in figure (3). This structure includes the active area with a P3HT:PCBM bulk structure with a thickness of 100 nm.

Abstract In this paper, for the first time, improved lasing performance of a red AlGaInP laser diode is demonstrated by introducing a new extreme triple asymmetric waveguide structure. In the new proposed waveguide structure, at the first step, n-waveguide and n- cladding layer thicknesses are increased, and then a triple asymmetry is introduced on the design of the n-type and p-type cladding and waveguide layers inside the red laser diode structure. The conventional symmetric and the new extreme triple asymmetric laser structures performances are theoretically investigated using simulation software PICS3D. 3D simulations of carrier transport, optical waveguiding and self-heating are combined self-consistently in the software. Numerical results show that the new proposed structure performance is significantly improved in comparison to the conventional symmetric structure. The reasons of improvements are discussed in this investigation. The simulation results show that the use of the new structure reduces the overlap of the optical mode with of high doping regions. On the other hand, by reducing the electron leakage current, an increase in the stimulated recombination rate occurs, which leads to a decrease in the threshold current and an increase in the output power. By reducing the series resistance and increasing the thermal stability of the new proposed structure, the optimality of this structure is confirmed.

Abstract In the present work, we have studied and simulated the electronic, dynamical and elastic properties of the TaCRu₃ compound using QuantunEspreeso code within the framework of density functional theory and density functional perturbation theory in the generalized gradient approximation (GGA). We have concluded some properties of this compound such as metallic and magnetic behavior by obtaining the density of states and band structure.In order to study the dynamicaland elastic properties, at first we have calculated the phonon dispersion and phonondensity of the states and then obtained the elastic constants. Then the bulk,shear and young modulus, lames coefficients, poisons ratio, elastic heterogeneity parameter, Debye temperatureand also ductility parameter are calculated. We have compared the results with available experimental and theoretical data for this compound and also for the NbCRu₃ and VCRu₃ compounds. The lattice parameter is estimated about 2.62 % less than experimental data. For other calculated parameters, there are 0.12 and 22.9 as minimum and maximum percent difference between this work and others theoretical works. These values are predicable in the computational condensed matter physics