مجله فیزیک کاربردی
سال چهاردهم شماره 1 (پیاپی 36، بهار 1403)

In this paper, the thermo-electric, phonon, electronic, and optical properties of the C3N monolayer have been investigated using the Wien2K computational code based on first principles calculations in the framework of the density functional theory. The study of electronic properties shows the behavior of non-magnetic semiconductors with an indirect gap with a value of 0.5 electron volts for this two-dimensional structure. Also, optical properties such as dielectric function, reflection, energy loss function, absorption coefficient, and optical conductivity are calculated. C3N monolayer is optically anisotropic in z and x direction, which according to the refractive index diagram leads to birefringence, which is a key parameter for this compound's linear optical performance. The results provide a fundamental understanding of the design of composite structures used in nanodevices based on two-dimensional advanced materials. The linear response approach along the symmetric points calculates the phonon dispersion diagram. The results indicate the absence of negative modes in the phonon spectrum, indicating that the structure is dynamically stable. Investigating the thermoelectric properties of the C3N monolayer using the semi-classical Boltzmann theory shows that this monolayer has a value coefficient (ZT) close to one at room temperature and temperatures lower than room temperature. As a result, it can be proposed as a candidate for thermoelectric applications.

Entanglement plays a fundamental role in the field of quantum computing and quantum communication. In real conditions, a physical system is never isolated and inevitably interacts with its surroundings. Temperature is one of these effects that mainly reduces entanglement. In real conditions, the system is at a non-zero temperature, which will lead to a mixed state. Therefore, in the present work, the combined thermal entanglement of electron spin-oscillation in an anisotropic two-dimensional quantum dot is investigated using the negativity criterion. The results show that the combined entanglements are strongly dependent on the changes of the controllable parameters, such as the Rashba parameter and the magnetic field. The thermal entanglement between the spin and the assembly of oscillators is zero at absolute zero temperature and reaches a maximum with increasing temperature and then tends to zero asymptotically. This temperature, at which the amount of entanglement reaches its maximum value, can be controlled by changing the magnetic field and the coupling of the Rashba parameter. These two factors also control the rate of reaching the asymptotic state. These results provide a way to control the degree of entanglement between electron degrees of freedom, which is a fundamental requirement of quantum information processing.

Gene expression is known as a phenomenon that shapes human life. This very complex phenomenon is formed from two stages: transcription and translation. In this study, we used the Nose-Hoover thermostat to model the effect of ambient temperature on gene expression since temperature regulates the biological clock of living systems. We have used the Lyapunov exponent approach to investigate the effect of control parameters on gene expression, including the degradation rates of messenger RNA and proteins, and to find critical points (phenomenon boundary limits), mRNA, and protein level boundary values. The rate of degradation in the process of protein synthesis has been investigated with the help of the Lyapunov exponent approach. According to this study, the optimal temperature for the production of mRNA molecules by Escherichia coli bacteria is 306 Kelvin. The study also used the chaos approach to show that the faster the mRNA molecules are degraded, the more they are transcribed, and the more chaotic the system becomes.

In the last two decades, photonic crystals and structures that are based on them (photonic structures) have been examined and have been widely utilized in various optical applications. In this article, a theoretical and numerical model for the propagation of electromagnetic waves in multilayer dielectric structures is developed. The propagation of ultra-short light pulses in multilayer media and microresonators is investigated, and the energy reflection and transmission coefficients depending on the parameters of the environment and duration of the optical pulse are calculated. A method for calculating the transmission and reflection spectra of one-dimensional photonic crystal based on FDTD modeling with the emission of ultra-short optical pulses is proposed. To calculate the transmission and reflection spectrum of a one-dimensional photonic crystal and to simulate the propagation of ultra-short light pulses, in multilayer dielectric structures and microresonators, based on the numerical solution of Maxwell's equations with the finite difference approximation in the space-time domain, is performed.

In this work, considering the moment theory propagation of the laser beam with relativistic intensity in thermal quantum plasma is studied. Using the Maxwell equation and dielectric function obtained by the quantum hydrodynamic model, the mathematical equation for the laser beam width parameter is achieved and solved numerically by the fourth-order Runge-Kutta method. The results show that the stronger self-focusing effect is found in the moment theory compared to paraxial approximation. Also, similar to paraxial approximation, with growing Fermi temperature, plasma density and laser intensity, the oscillation frequency of the beam width parameter increases and focusing length decreases which means improving the self-focusing effect. Furthermore, it is seen that behaviors of the critical radius are not similar in the two theories, as in the moment theory, with increasing laser intensity, critical radius decreases until it becomes independent of the beam intensity, but in the paraxial approximation, the critical radius after a minimum value is enhanced with increasing laser intensity.

Many non-classicality indicators are used to measure the quantum effects of different systems. Kenfack's and Sadeghi's non-classicality indicators are introduced regarding the amount of Wigner distribution function's negativities and interferences in phase space quantum mechanics, respectively. Kenfack’s non-classicality indicator is used for cases just in the Wigner representation, whereas Sadeghi’s non-classicality indicator is effectively, applied for some real distribution functions. In this paper, we investigate these non-classicality indicators for the entangled photon number states in the Wigner, Husimi, and Rivier representations. It is shown that for a two-level entangled state, Sadeghi's indicator has more benefits to measure entanglement with respect to Kenfack's indicator. For the two-level entangled state, we also show a correspondence between Sadeghi's non-classicality indicator and the Von Neumann entropy. It is also shown that for the superposition of the squeezed number state and ground number state, the squeezing parameter affects the entanglement feature and Sadeghi's non-classicality indicator increases with the increase of the squeezing parameter.

Using the experimental results and data, the thermodynamic characteristics and thermal analysis of the electrical arc of torch electrodes and energy deposition in the waste-incinerator primary designed chamber were investigated. The temperature of arc in the intermediate electrode which is called the float nozzle was measured at 7000-8000 Kelvin based on the input power of 2 kW. The plasma plume temperature implied to be lower than the arc temperature according to the cold gas flow in the nozzle. The efficiency of energy transferring to the plasma plume is dependent on the geometrical electrode and nozzle design, and gas flow rate. After ten seconds, the chamber temperature was measured at 1193 Kelvin by thermocouple with the performance of electrical elements and plasma torch. The chamber temperature increasing in an adiabatic process was calculated at 1230 Kelvin after this time. According to the isothermal approach, the heat flow rate, and conduction loss calculation, the chamber temperature was obtained at about 900-1000 Kelvin. Using two approaches with inevitable approximations, the calculated temperature ranges for arc and plasma plume energy estimation have reasonable compatibility and this led to the road map of optimization and development for future torch planning and waste-incinerator chamber design.

In this study, The surface plasmon excitations in a dimer structure of closely spaced metallic nanospheres with different radii are investigated using the hydrodynamic model. Initially, an expression was derived to calculate this structure's multipolar surface plasmon excitations. Subsequently, the surface plasmon excitations in the dipole approximation were examined.The surface plasmon excitations in a dimer structure of closely spaced metallic nanospheres with different radii are examined using the hydrodynamic model in this study. It has been observed that the energy of in-phase modes is lower than that of out-of-phase modes in longitudinal or transverse excitations. Furthermore, at each separation distance between the nanospheres, the energy difference between in-phase and out-of-phase longitudinal modes is greater than that of transverse modes. The results show that with an increase in the separation distance between the nanospheres, the energies of in-phase modes increase, and the energies of out-of-phase modes decrease. At large separation distances, two plasmon modes are obtained, with the higher energy mode corresponding to the smaller nanosphere and the lower energy mode corresponding to the larger nanosphere. Finally, the local limit results are presented for comparison.

In this study, the optical and electronic properties of bulk and nano-layer of zinc selenide (ZnSe) and zinc sulfide (ZnS) are investigated. The calculations for solving the many-body Schrodinger equations are performed in the framework of density functional theory using the WIEN2K computational package. The Engel-Vosko and gradient generalized approximation (GGA) treat the exchange-correlation potential. To investigate the electronic and optical properties of zinc selenide and zinc sulfide nano layers, the electronic band structure and the real and imaginary parts of complex dielectric function for the bulk and nano-layer with different thicknesses are calculated and compared. The results of electronic band structures show that the energy band gap of zinc selenide and zinc sulfide nano-layers with various thicknesses decreases to zero and are metal. In contrast, the bulk of zinc selenide and zinc sulfide compounds are semiconductors. The results also show that for each compounds the static dielectric function for the perpendicular and parallel direction to the nano-layer surface is different from the bulk static dielectric function. Comparison between the real parts of complex dielectric function for the bulk and nano-layer shows that absorption of electromagnetic radiation for the ZnSe and ZnS nano-layer in comparison to corresponding bulk results occur in lower energies.