مجله فیزیک کاربردی
سال چهاردهم شماره 2 (پیاپی 37، تابستان 1403)

Using the first-principles calculations, we have investigated the structural, electronic, and magnetic properties of the two-dimensional Janus MnSX (X= Cl, Br, I) monolayers. The dynamical stability for the 2D Janus monolayers has been confirmed by phonon spectrum calculation. Also, all manganese sulfide halide monolayers show half-metal with 100% spin polarization and a wide half-metallic gap. The noncollinear DFT calculations indicate that the two-dimensional Janus monolayers are ferromagnetically ordered systems and the preferred direction of magnetization lies in-plane of Janus manganese sulfide halide monolayers. The magnetic anisotropy energy increases from MnSCl to MnSI, related to the strong spin-orbit coupling at the I atom and the increased asymmetry between the sulfide and halide planes. The dispersion relation of magnetic excited states is obtained by applying the linear order Holstein–Primakoff transformation to the anisotropic Heisenberg Hamiltonian. We estimated Curie temperature for the monolayers by a self-consistent calculation of magnetization as a function of temperature. Our study presents a new class of 2D magnetic materials for future spintronics and valleytronics.

In this work, we study the interaction of femtosecond laser with formaldehyde molecule and investigate the effect of intensity and angle of laser polarization on the high harmonic generation. The calculation is done with time-dependent density functional theory in three-dimensional real space. The effect of the ellipticity parameter and the role of different orbitals of this molecule on the high harmonic spectrum is investigated, so that the contribution of different orbitals of the formaldehyde molecule in this process can be controlled. The maximum intensity and the maximum width of the high harmonic spectrum are obtained for the ellipticity parameter of 0.15. Also, if the large diameter of the ellipse of laser polarization is along the y-axis, the intensity of the harmonic spectrum is increased, and the reason for this process is discussed by analyzing the time evolution of the population of ionized electrons. In the following, the effect of incident laser polarization on the output attosecond pulse polarization and its width is investigated, which is resulted in the generation of an elliptically polarized attosecond pulse.

The fields resulting from the brain's neural activities provide essential information in diagnosing and treating brain diseases such as epilepsy, convulsions, and brain tumors. Recording brain magnetic field signals is one of the non-invasive brain functional imaging methods, which usually requires magnetic shielding besides expensive and bulky instruments. Although atomic magnetometers are inherently less sensitive than superconducting quantum interference devices, they are considered the best candidate for measuring bio-magnetic fields due to their low manufacturing cost, small size, and no need for cryogenic equipment. Atomic magnetometers measure the low-strength brain magnetic fields based on detecting Zeeman energy splitting and recording changes in the laser light intensity passing through an alkali vapor cell. To improve the sensitivity of these magnetometers, it is common to remove homogeneous noises in two magnetometer channels. For this purpose, we have presented a gradiometer to suppress unwanted magnetic noises. This gradiometer consists of two atomic magnetometers capable of detecting the field produced by the human brain in an unshielded environment in the presence of the Earth's magnetic field. The gradiometer has a sensitivity of 900 fT⁄√Hz. The designed and built gradiometer is suitable for detecting brain magnetic fields, which can be expanded as a multichannel to record the map of the brain's magnetic field.

The shock wave or plasma pulse method was presented for the first time in oil wells to solve the problem of worldwide pressure drop and well production. In this study, the technology of underwater electric wire explosion (UWEWE) has been investigated to generate shock waves by using a sudden discharge of very hot plasma energy at a point and then creating a shock wave. The constructed plasma emitting device consists of two electrodes, a set of high voltage capacitors with a voltage of 5 kV and a capacity of 80 microfarads, an electronic block, a Rogovsky coil installed in the electric discharge circuit, and a relay block. For aluminum wire with a diameter of 400 and 500 mm and a length of 30 mm, with a pulsed current at a discharged voltage of 3.8 kV, the total energy deposition is 400 and 500 J, with the energy conversion efficiency of 68 and 66.3%, respectively, and a maximum power of 168 MW.

In this study, we present the design and fabrication of a V-shaped resonator that served as an absorption chamber in a laser spectroscopy system for water stable isotope measurement (2H, 17O, 18O) based on optical feedback cavity-enhanced absorption spectroscopy. In the design of a resonator, its length and the radius of curvature of the mirrors guarantee the optical stability of the system. The resonator mirrors are designed considering the condition of stability and based on the desired mode structure of the resonator output. The V-shaped resonator is designed with two arms of 40 cm and inner diameters of 5 mm making an angle of 1.7°. This resonator has an internal volume of 20 cm3 which provides fast response of laser spectrometer. The high reflectivity of mirrors leads to an effective absorption optical path length of 13 km and a high finesse optical resonator of   Ƒ~52،000. These values allow low concentration water vapor isotope analyses and resolution of the absorption spectrum of isotopes for accurate isotope measurements, respectively. Resonator mirrors are designed using Mcleod software to have maximum reflectance at a wavelength of 1.4 micrometers. By making a V-shaped optical resonator for measuring stable isotopes of water and subsequent development for measuring stable isotopes of other elements, the possibility of developing the application of stable isotopes in different areas of research will be provided.

In this article, we suggested a three-photon quantum scissor that truncates all multiphoton number states with four or more photons and amplifies the remaining photon number states in a probabilistic way. To this end, by assuming the ideality of all beam splitters and detectors of the proposed scheme, the output state of this quantum scissor and its success probability have been derived analytically. In contrast to the one-photon or two-photon quantum scissor, this setup works perfectly for superpositions of up to three photons. For the input coherent state, our results show that the fidelity between ideal amplification and the amplification obtained by this suggested three-photon quantum scissor is as good as that obtained with a network of six one-photon or two two-photon amplifiers. Moreover, the success probability of this generalized quantum scissor is larger than the success probability of six one-photon amplifiers and is comparable to the success probability of two two-photon amplifiers. Therefore, based on the fact that the resources required by the three-photon amplifier are smaller than those required for a network of one-photon or two-photon amplifiers, this proposed device is much more efficient than several one-photon or two two-photon amplifiers.

In this research, graphene oxide was prepared by Hamers' improved method, then, with the electric arc method, silver nanoparticles enter the graphene oxide environment diluted with deionized water, and a colloid of core-shell,silver-silver oxide is prepared. After the samples were prepared, graphene oxide plates containing silver nanoparticles were fixed on them, and samples with the same concentration and volume were placed under ultraviolet radiation for 0, 30, 60, 120, and 240 minutes, respectively. Then, various spectra are prepared from the samples and their linear and non-linear behavior is studied in two experiments, Z-scan and phase spatial modulation. The results of ultraviolet-visible spectroscopy, infrared Fourier transform, and X-ray diffraction show that the resulting solution contains graphene oxide nanoplates and silver oxide nanoparticles. Investigating the nonlinear optical properties of the samples also shows that the nonlinear refractive index of the samples is of the order of , which by ultraviolet radiation to the samples, their nonlinear refractive index changes slightly, and on the other hand, the diffraction pattern with two peaks is observed in the formed structure.

Here, we explore the sensitivity of the Casimir force between two topological insulator plates on thermal fluctuation using weak and strong magnetizations on the surface of plates via Lifshitz theory. Thermal fluctuations between two plates made of topological insulators in vacuum lead to attractive interactions. By considering a weak magnetization, the influence of thermal fluctuations becomes stronger compared to the magnetoelectric effect in the regime of large separations which leads to generating the strong attractive Casimir force. Moreover, by considering strong magnetizations it is observed that thermal effects cannot make a change in the attractive and repulsive Casimir forces, and magnetoelectric effect determines both the magnitude and direction of Casimir forces. In the range of small magnetization, thermal effects have a significant effect on the repulsive Casimir force. It has been shown that at high temperatures, repulsive interaction due to antiparallel magnetization becomes weak, so that they disappear by increasing the separation.

The aim is to study nonlinear wave dynamics in solar spicules and jets. The life of jets in the context of Alfven wave dynamics is focused. Here, further insight into the solar atmospheric effects together with initial conditions on the dynamics of Alfven waves along with the characteristic parameters of the spicule or jet itself are provided. Results are based on the theory of magnetohydrodynamics. the location of shock formation by the interplay of the internal and external plasma-beta conditions together with the initial steady flow speeds which are rooted in the initiation location of the solar jet are illustrated. It was known that the plasma-beta of a solar jet affects the shock formation time of torsional Alfven waves. However, its efficiency is shown to be dependent on the external plasma beta conditions. The shock formation time for plasma-beta conditions over unity is directly proportional to the plasma-beta, similar to plasma-beta conditions equal to or below unity. In the case where the plasma-beta inside the magnetic structure is small, the shock formation time is accelerated by increasing the external plasma-beta. In photospheric conditions, as for coronal conditions, the time of shock formation is inversely proportional to the external plasma-beta. When the internal plasma-beta is fixed, for various steady flow speeds, the external plasma-beta accelerates the formation of shocks. These results help us to better understand the role of Alfven waves in solar jets in the transfer of energy to the solar system.