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We have studied the tunneling time of the spin-polarized electron passing through the non-homogenous Rashba barrier in a graphene sheet. Results have shown that Hartmann effect is strongly depend on Rashba strength and other parameter of the system.

Using the transfer matrix method, we study the electron transport through a single-layer graphene superlattice with alternating layers of ferromagnetic and normal regions with Rashba spin–orbit coupling. We show that the transport properties of the system depend strongly on the superlattice parameters. As another result, Rashba spin–orbit coupling manifests to be of crucial importance in controlling the transmission probabilities and Giant Magneto Resistance (GMR).

Low field response function calculations have been performed on a two-dimensional electron gas with well-defined electron-surface roughness scattering. The Lindhard model was employed to compute the response function. In particular, detailed investigations were made on the system searching for an interplay between surface roughness with well-defined correlation function, (characterizes by asperity height and correlation length) spatial confinement and the dielectric function. We analyze to what extent the normal behavior and functionality of dielectric function of two-dimensional devices are modified by random scattering events caused by the contribution from the surface roughness. Results of the current work indicate that contribution of the surface roughness on scattering and absorption process could not be considered as an underestimating effect. We find, however, that functionality of the dielectric function seems to be quite independent of the particular roughness features.

We have studied spin-depend electron tunnelling through the Rashba barrier in a monolayer graphene lattice. The transfer matrix method, have been employed to obtain the spin dependent transport properties of the chiral particles. It is shown that graphene sheets in presence of Rashba spin-orbit barrier will act as an electron spin- inverter., 7 pages

The Rayleigh–Benard Convection (RBC) were studied theoretically in the homeotropic nematic liquid crystal (NLC) cell due to the absorption of a normally incident Gaussian light beam from upper side of the cell. It was shown that a convection of hydrodynamic motion in the NLC can be induced and eventually the molecular director coupling with hydrodynamics reorients the director. An external magnetic field parallel to the director decreases the director reorientation and the radial flow velocity, while the velocity in the z direction is unaffected. The results were found to be in a range that can easily be checked experimentally.

We have performed a non-equilibrium quantum transport calculations for a two-terminal mesoscopic system including a magnetic quantum dot. Using the non-equilibrium Green’s function technique, we have obtained electric current and charge distribution in the temperature range from 1 to 10 K as a function of magnetic field. Results indicate that the density of carriers essentially can be controlled by temperature and bias voltage.

The absorption of a Gaussian laser beam creates a temperature gradient. In this study, a surface tension gradient was created with a temperature gradient, and this surface tension gradient caused a mass transfer (Marangoni effect). The velocity and the director reorientation, which are the results of the Marangoni effect, were investigated. Both the change of velocity and the reorientation of the director in the r direction followed the gradient of the Gaussian profile of temperature. In addition, applying a magnetic field to the case was studied. The results were found to be in a range that can easily be checked experimentally.

The conductivity of a graphene ring with two semi-infinite, armchair and zigzag leads has been investigated. We have performed numerical calculations based on the nearest neighbor tight-binding Hamiltonian and Dirac point approximation. A Non-Equilibrium Green's Function (NEGF) approach has been employed to calculate the electric current under an applied bias voltage, in this two terminal mesoscopic system. We have studied the effect of the external magnetic field on transport characteristics of this graphene-based quantum ring. Coherent transport features of the system have been studied. It was shown that there is significant distinction between the I---V characteristics (and also the Aharonov-Bohm effect) of the graphene rings depending on the edge structure of the leads.

In the current work, a detailed calculation has been presented for spin-current and spin torque in a domain wall (DW). Specifically, we analyze both spin and momentum relaxation that are relevant to the spin-transport process. It was shown that the vibrational induced relaxations play important roles in the amount of the spin-current generated by the Rashba interaction.

We have investigated the influence of the electron–phonon interaction on magnetoelectric properties and spin-related transport effects of a two dimensional electron gas in the presence of the spin–orbit couplings. We have employed a semiclassical method that has been extended to include the anisotropic effects of band structure in the presence of the spin–orbit couplings. We found that resistivity and anisotropic resistance (AR) can be controlled by Rashba spin–orbit coupling.

Pyrazinamidase (PZase), a metalloenzyme, is responsible for acidic modification of pyrazinamide (PZA), a drug used in tuberculosis treatment. The metal coordination site of the enzyme is able to coordinate various divalent metal cofactors. Previous experimental studies have demonstrated that metal ions, such as Co2+, Mn2+, and Zn2+, are able to reactivate metal-depleted PZase, while others including Cu2+, Fe2+, and Mg2+, cannot restore activity. In this study, we investigated binding of various metal ions to the metal coordination site (MCS) of the enzyme using quantum mechanical calculations. We calculated the metal-ligand (residue) binding energy and the atomic partial charges in the presence of various ions. The results indicated that the tendency of alkaline earth metals to bind to PZase MCS is very low and not suitable for enzyme structural and catalytic function. In contrast, Co2+ and Ni2+ ions have very high binding affinity and are favorable to the structural and functional properties of the enzyme. Furthermore, we observed that the rate at which Ni2+, Co2+ and Fe2+ ions in PZase MCS polarize the OH bond of coordinated water molecules is much higher than the polarization rate created by other ions. This finding suggests that the coordination of Ni2+, Co2+, or Fe2+ to PZase facilitates the deprotonation of coordinated water molecules to generate a nucleophile that catalyzes the enzymatic reaction.

Spin–orbit induced spin torque and spin current in a smooth domain wall (DW) are theoretically investigated. We have analyzed the effect of the Rashba and Dresselhaus interactions on DW spin torque and spin current in the presence of magnetic impurities within the Boltzmann semi-classical model. It has been previously shown that in the non-equilibrium regime, the Rashba and Dresselhaus couplings can not be responsible for spin-current and both transverse and longitudinal spin-currents identically vanish. In the present work it has been found out that in the case of non-collinear magnetic structures such as DW, Rashba, and Dresselhaus couplings can generate and control both components of the spin current. Results of this investigation verify that the spin current of the DW strongly depends on density of impurities and non-adiabaticity of transport process. In addition results of the current work reveals that manipulation of the DW displacement can be realized by the Rashba and Dresselhaus couplings.

Spin current and spin accumulation of a finite width quantum ring (QR) in the presence of a homogeneous perpendicular magnetic field and Rashba spin-orbit coupling have been investigated. A non-equilibrium Green's function (NEGF) approach has been followed in coherent regime. Numerical results show that spatial magnetization of the transport electrons oscillates throughout the QR and the spin current and spin accumulation can be controlled by the Rashba coupling, bias voltage, and magnetic field.

A Non-equilibrium Green’s function (NEGF) approach has been employed to calculate the spin current and spin polarization of the carriers in a two terminal mesoscopic system including a magnetic quantum dot. Numerical results show that spatial magnetization of the conduction electrons can be controlled by bias voltage in coherent regime. In this regime and for low magnetic flelds the bias voltage appears to be more efiective than magnetic fleld for spin injection inside a magnetic quantum dot.

In the present paper, the effect of non-polar longitudinal optical phonons on domain wall resistance has been studied using the semiclassical approach. The analysis has been based on the Boltzmann transport equation, within the relaxation time approximation. We have determined the magnetoresistance of domain wall in nanowires based on diluted magnetic semiconductors. The modulation of the exchange and the impurity interactions by lattice vibrations, and the hole–phonon interaction are considered. The results indicate that the scattering role of phonons becomes significant by increasing temperature, which leads to the resistivity enhancement. It is also found that the magnetic impurities play an impressive role in enhancing the contribution of the domain wall in the resistance. In providing room temperature spintronics devices, understanding the effects of phonons and magnetic impurities on the domain wall resistance is crucial.

In the present paper, the influence of longitudinal optical phonons on domain wall resistance in nanowires based on diluted magnetic semiconductors has been studied within the semiclassical approach. The analysis has been based on the Boltzmann transport equation within the relaxation time approximation. The modulation of the exchange and the impurity interactions by lattice vibrations have been taken into account and the hole-phonon interaction has also been considered. The results indicate that phonons have a considerable effect on increasing the domain wall resistance. The resistance enhancement is observed by increasing the temperature. The magnetic impurities are also effective on enhancing the domain wall resistance. In designing spintronics devices based on diluted magnetic semiconductors, considering the effects of phonons and magnetic impurities on the domain wall resistance is crucial.

The effect of bulging of domain wall (DW) on the magnetoresistance (MR) is investigated. With taking into account the auto-correlation between the points of the interface, one can formulate the mobility within the relaxation time approximation scheme. The results show that the bulging of DW, evaluated with the commonly accepted magnetic parameters for typical ferromagnetic materials of Co, Fe and Ni, has a countable role into the MR.

Domain walls in ferromagnetic metals are known to be a source of resistance. In the present work resistance of a domain wall in a ferromagnetic nanojunction is investigated using the semiclassical approach. The analysis is based on the Boltzmann transport equation, within the relaxation time approximation. The one-dimensional Neel-type magnetic domain wall is considered and the effect of the electron-photon interaction on the resistance is studied. The results indicate that polarization and wavelength of the photon play a significant role in the magnetoresistance. The resistance of the nanojunction decreases as the wavelength of the photon increases. It is also shown that the domain wall resistance decreases by increasing the Fermi energy.

According to the group theory approach, linear magnetoelectric effect (ME) can not be obtained for the spatial group of YMn2O5, which was known to be mmm. Regard to the magnetic structure of these type of materials, we propose a magnetic group structure for the YMn2O5 by considering spin orientation of the Mn3+ and Mn4+ ions. According to the landau theory of phase transition it can be shown, how symmetrical rules result in relationship between quantities such as magnetic order, polarization, and etc. This relation shows a weak ferromagnetic state, associated with spontaneous polarization, arisen by Dzyaloshinskii-Moriya type interaction and a field induced change in magnetoelectrical susceptibility.

Non-equilibrium spin accumulation in two-dimensional domain wall (DW) in the presence of external electric field and Rashba type spin-orbit coupling within the Boltzmann semi-classical model is investigated. Transport and relaxation of spin polarized current in the DW is governed by spin-flip rates which are determined by the Rashba interaction and magnetic impurities. Numerical results show that at low impurity densities and nonadiabatic transport regimes, the Rashba interaction significantly enhances spin polarization of conduction electrons inside the DW.

Domain walls in ferromagnetic metals are known to be a source of resistance. We have studied the resistance resulting from a one-dimensional Neel-type magnetic domain wall in presence of Rashba spin-orbit coupling and external magnetic field. The analysis has been based on Boltzmann transport equation, within the relaxation time approximation. Through this formalism, we have shown that the spin-flip scattering and the resulting resistance originating from the Rashba spin-orbit coupling can be suppressed by the applied external magnetic field.

Recently it has been recognized that the electromotive force (emf) can be induced just by the spin precession where the generation of the electromotive force has been considered as a real-space topological pumping effect. It has been shown that the amount of the electromotive force is independent of the functionality of the localized moments. It was also demonstrated that the rigid domain wall (DW) motion cannot generate electromotive force in the system. Based on real-space topological pumping approach in the current study we show that the electromotive force can be induced by rigid motion of a deformed DW. We also demonstrate that the generated electromotive force strongly depends on the DW bulging. Meanwhile results show that the DW bulging leads to generation of the electromotive force both along the axis of the DW motion and normal to the direction of motion.

For an ideal one-dimensional ferromagnetic wire with a magnetic domain wall (DW), contribution of the DW to the resistivity of the system has been investigated. We have studied the resistance due to the magnetic impurities in the domain wall which was suspended in a weak magnetic field for two types of chiralities. The analysis has been based on Boltzmann transport equation, within the relaxation time approximation. Through this formalism, both increasing and decreasing of the resistance due to the DW have been predicted in presence of Zeeman interaction as an extrinsic mechanism.

A Berry curvature investigation has been made on the magnetic modulated structures such as domain walls (DWs) and helimagnetic spin configurations. Results of the present study show that the geometry of the spin configuration and the direction of the magnetic field creating the spin precession are of crucial importance in the magnitude of obtained electromotive force. It has recently been recognized that the Rashba coupling increases significantly the electromotive force when this coupling is high enough to give predominant contribution in the magnetization dynamics. However, in the opposite case when the Rashba interaction has negligible contribution in the magnetization dynamics it was shown that the magnitude of the electromotive force decreases slightly by increasing the Rashba coupling strength. Therefore the effect of the Rashba interaction in the electromotive force of the moving DWs rests largely on the strength and also effectiveness of this interaction in the magnetization dynamics.

In the current work we have investigated the influence of the Rashba spin-orbit coupling on spin-current of a single layer gapped graphene. It was shown that the Rashba coupling has a considerable role in generation of the spin-current of vertical spins in mono-layer graphene. The behavior of the spin-current is determined by density of impurities. It was also shown that the spin-current of the system could increase by increasing the Rashba coupling strength and band-gap of the graphene and the sign of the spin-current could be controlled by the direction of the current-driving electric field.

In this study, the optical conductivity of substitutionary doped graphene is investigated in the presence of the Rashba spin orbit coupling (RSOC). Calculations have been performed within the coherent potential approximation (CPA) beyond the Dirac cone approximation. Results of the current study demonstrate that the optical conductivity is increased by increasing the RSOC strength. Meanwhile it was observed that the anisotropy of the band energy results in a considerable anisotropic optical conductivity (AOC) in monolayer graphene. The sign and magnitude of this anisotropic conductivity was shown to be controlled by the external field frequency. It was also shown that the Rashba interaction results in electron–hole asymmetry in monolayer graphene.

The dielectric function of graphene based quantum dot under uniaxial pressure has been studied using the density functional theory (DFT) with local-density approximated (LDA) exchange-correlation functionals. The frequency dependent dielectric function has been obtained and the linear optical properties have been studied. It has been shown that stress results in red shift in which the absorption rate depends on the direction of the polarization and the value of the stress. It has also been shown that the uniaxial stress can remove or decrease the band gap obtained due to the geometrical isolation of the quantum dot.

The influence of the electrons interaction with longitudinal acoustic phonons on magnetoeletric and spin-related transport effects are investigated. The physical system under consideration has been assumed to be a two dimensional electron gas system with both Rashba and Dreesselhaus spin-orbit couplings. In the works which have been previously performed in this field it has been shown that in the non-equilibrium regime, the Rashba and Dreesselhaus couplings can not be responsible for spin-current where in the absence of other interactions such as lattice vibrations identically vanishes. In the current work we have employed a semi-classical method by using the Boltzmann approach. It was shown that the spin-current of the system, in general, does not go all the way to zero at any value of the spin-orbit couplings. It was also shown that the spin accumulation of the system can be influenced by the electron-phonon coupling.

The influence of phonons on domain wall magnetoresistance in magnetic nanowires has gained crucial importance. In the present work, the resistance of a magnetic domain wall in a magnetic nanowire has been investigated in the presence of a longitudinal acoustic phonon using the semiclassical approach. The analysis has been based on the Boltzmann transport equation, within the relaxation time approximation. The resistance resulting from the one-dimensional N\'eel-type domain wall has been studied when the modulation of the exchange interaction by lattice vibrations and the electron-phonon interaction are considered. The results indicate that phonons play a significant role in resistance, and increasing the number of phonons leads to enhancement of the domain wall resistance. Increasing and decreasing the domain wall resistance is observed via enhancing the temperature and mass of the domain wall, respectively. The effect of phonons on the resistance of the domain wall is considerable in providing new spintronics devices based on the nanowires at high temperatures.

The effect of the Rashba-type spin-orbit interaction on the domain-wall (DW) magnetoresistance (MR) is investigated for a smooth linear DW within the semiclassical approach. Results of this study are indicative of a negative MR for current-in-wall geometry for some ranges of the impurity densities and the chirality dependence of the DW MR. The increase of the Rashba coupling strength can effectively increase the MR of the DW in the samples with low impurity concentrations.

This paper aims at presenting petal-shaped optical vortices using a one-dimensional photonic crystal nanostructure with a graded-index defect layer under the irradiation of a Gaussian beam. A manufacturable graded-index medium with a spatial refractive index distribution function is introduced into the defect layer. Petal-shaped vortices, which are known as dark traps, with engineerable petal numbers are obtained on the output intensity plane. The transfer matrix method under the incident Gaussian beam is applied to simulate the results. As a potential application, we suggest an optical microparticle-sorting device using the introduced modulated optical vortices. The proposed device can benefit microfluidic and optofluidic lab-on-a-chip devices.

A theory is suggested in this study which predicts both positive and negative magnetoresistances (MRs) due to the domain wall (DW) in weak magnetic fields. The analysis showed two distinct regimes which are specified by the impurity density, the Fermi wave vector of the system and the external magnetic field. These two regimes correspond to positive and negative MRs. When the Zeeman interaction strength is comparable to the impurity scattering amplitude at Fermi level, the contribution of the DW to MR should be negative, also it can be shown analytically that, in contrast to the pure system for an impure DW, MR is not symmetric for magnetic fields which are parallel or anti-parallel to the DW rotation axis, and for a pure DW, the contribution to the MR is always positive.