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In this work, transmittance spectrum for a quasiperiodic one-dimensional photonic crystal, composed of high-temperature superconductor and semiconductor layers arranged within the crystal based on a Dodecanacci sequence, has been calculated using the transfer matrix method and the two-fluid model. The critical temperature of the superconductor depends on the hydrostatic pressure, while the semiconductor’s plasma frequency and dielectric constant were considered to be dependent on both the pressure and temperature applied. We have found that the transmittance spectrum shows the band gaps unfolded and increased in number when the Dodecanacci sequence increased. In addition, this work shows that transmission responses can be tuned to higher frequencies as pressure increases. However, a small red shift of the transmittance spectrum can be observed as temperature increases. Finally, the research observed the maximization of the band gaps by increasing the thickness of the superconductor layers. We hope this work may be considered for application in tunable narrowband filters.

In this work, we present a study of the structural, optical, elastic, thermoelectric and thermodynamic properties of iridium manganese (IrMn) using the code “WIEN2k” with the full potential linearized augmented plane wave (FP-LAPW) method. The lattice constants of the IrMn compound are calculated by the generalized gradient approximation with Perdew–Burke–Ernzerhof (GGA-PBE). Indeed, we have studied the magnetism exhibited by the compound IrMn. We found that the antiferromagnetic phase of this material is the most stable phase. The magnetic moment, plasma frequency, bandgap, elastic constants, and electronic and magnetic properties of this material are deduced and discussed. We have shown that the antiferromagnetic phase is the most stable with a minimum energy value of around −1034947.477eV. We optimized the $c∕a$ ratio and found that its value is approximately $c∕a\approx$ 0.923133. On the other hand, the absorption and reflectivity coefficients, the optical conductivity and the dielectric tensor are studied. In addition, the thermo-electric and thermodynamic properties have been illustrated. The IrMn compound could be useful for different applications of spintronics.

In the weak field approximation, we study the gravitational lensing by spherical symmetric compact object immersed in magnetic field in the presence of magnetized plasma. The external magnetic field causes the split of the deflection angle of the photon, Einstein ring and Einstein cross as the counterpart of the Zeeman effect. In particular, the magnetic field affects the magnification of images, creating additional components. We also study the time delay of an electromagnetic signal due to the geometry and the gravitational field around the lensing source. We show that the time delay of the electromagnetic signal strongly depends on the plasma parameters, and it slightly decreases in the plasma in comparison with that in vacuum.

Five compositions of the system As₂₅Se_75-xTl_x (x = 12, 16, 20, 24 and 28%) have been prepared using melt quench technique. Thin films of the same thickness (200 nm) were deposited by electron beam evaporation technique. Optical and other parameters of the films have been studied. The optical band gap E_op found to decrease by increasing the coordination number r and average number of bonds per atom N_av and by decreasing the heat of atomization H_s. Other parameters as an oscillator energy E_o, dispersion energy E_d and plasma frequency ω_p found to be affected by changing thallium content.

By applying the Keeton and Petters technique, we find the deflection angle as a series expansion with a specific factor of mass. We investigate the shadow structure of a regular black hole with cosmic string with a non-magnetized, pressure-free plasma around it. In order to separate the Hamilton equation and locate the photon areas, certain plasma distributions are taken into consideration. Moreover, by utilizing a new ray-tracing technique, we analyze the photon’s path around a regular black hole with cosmic string in the presence of plasma whose density depends on the radius coordinate. We also analyze the plasma effects on the shadow of black hole. We obtain an analytical formula that describes the boundary curve of the shadow for such a black hole in an expanding universe for an observer at any finite location outside the horizon. In the presence and absence of plasma, we detect deviations that are further investigated by analyzing the geometry of shadow angle at a particular value of plasma frequency.

We study in the weak field limit the gravitational lensing by spherically symmetric compact object immersed in an asymptotically uniform magnetic field in the presence of plasma and our approach is based on the medium modified Hamiltonian one. We show that the magnetized plasma in the environment of compact object may lead to split of the Einstein cross, creating additional lensed components. Finally we calculate magnification and time delay related to the individual images.