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The design of epitaxial interfaces is a pivotal way to engineer artificial structures where new electronic phases can emerge. Here, we report a systematic emergence of an interfacial superconducting state in epitaxial heterostructures of LaTiO3 and KTaO3. The superconductivity transition temperature increases with decreasing thickness of LaTiO3. Such a behavior is observed for both (110) and (111) crystal oriented structures. For thick samples, the finite resistance developing below the superconducting transition temperature increases with increasing LaTiO3 thickness. Consistent with previous reports, the (001) oriented heterointerface features a high electron mobility of 250 cm2 V−1 s−1 and shows no superconducting transition down to 40 mK. Our results imply a non-trivial impact of LaTiO3 on the superconducting state and indicate how superconducting KTaO3 interfaces can be integrated with other oxide materials. [ABSTRACT FROM AUTHOR]

The dynamics of self-induced magnetization of a single-domain ferromagnet are studied by employing the Landau-Lifshitz-Gilbert equation along with other methods. The results demonstrate the relation between the energy flow due to spin current and the magnetization switching velocity, as it can be seen that the switching time between different states is directly related to the half-width of the time derivative of the system energy.

We present theoretical and experimental results on tunneling current in single Fe/MgO/GaAs and double Fe/MgO/GaAs/MgO/Fe tunnel junctions. The charge and spin currents are calculated as a function of external voltage for different sets of parameters characterizing the semiconducting GaAs layer. Transport characteristics of a single Fe/MgO/GaAs junction reveal typical diode as well as spin diode features. The results of numerical calculations are compared with current-voltage characteristics measured experimentally for double tunnel junction structures, and a satisfactory agreement of the theoretical and experimental results has been achieved. [ABSTRACT FROM AUTHOR]

We study the role of thermal fluctuations on the spin dynamics of a thin permalloy film with a focus on the behavior of spin torque and find that the thermally assisted spin torque results in new aspects of the magnetization dynamics. In particular, we uncover the formation of a finite, spin torque-induced, in-plane magnetization component. The orientation of the in-plane magnetization vector depends on the temperature and the spin-torque coupling. We investigate and illustrate that the variation of the temperature leads to a thermally induced rotation of the in-plane magnetization. [ABSTRACT FROM AUTHOR]

We consider the problem of electron states related to the strongly localized potential of a single impurity in graphene. Our model simulates the effect of a neutral impurity atom (substituting for the carbon atom) on the energy spectrum of electrons near the Dirac points. The model also can describe the effect of an adatom on the surface of graphene. We take into account the internal spin-orbit interaction, which essentially modifies the structure of electron bands near the Dirac points, leading effectively to an energy gap. This might result in the occurrence of additional impurity states in the vicinity of the energy gap. As a result, the spin-orbit gap in graphene can be experimentally unobservable due to a large number of adsorbed light atoms at the graphene surface, which create the impurity states in the gap. [ABSTRACT FROM AUTHOR]

We develop a classical description of the current-induced torque due to spin transfer in a layered system consisting of two ferromagnetic films separated by a nonmagnetic layer. The description is based on the classical equations for time-space evolution of the macroscopic magnetization. It is assumed that the perpendicular component of the nonequilibrium magnetization relaxes very fast in ferromagnetic films. Such a fast relaxation is due to a strong exchange field. Accordingly, the perpendicular component is totally absorbed at the interfaces giving rise to the torque. The longitudinal component, on the other hand, decays on a much longer distance defined by the spin diffusion length. [ABSTRACT FROM AUTHOR]

We analyze the possibility of optical generation of charge and spin currents in graphene by light carrying an orbital angular momentum (OAM). The graphene is assumed to be deposited on a substrate that induces Rashba spin-orbit coupling. In addition, a weak external magnetic field is assumed to be applied in the plane of graphene. We show that the photon absorption and the magnitude of the generated charge and spin currents depend remarkably on the parameters characterizing the light with OAM. [ABSTRACT FROM AUTHOR]

We consider the effect of the Rashba spin-orbital coupling in two-dimensional GaAs semiconductor heavily doped with Mn, on the spin polarization of holes. Due to the strong internal spin-orbit interaction in GaAs, the spin of a hole is not a good quantum number but the hole in some energy state has a certain mean value of spin, which can be strongly affected by the Rashba spin-orbital interaction related to the substrate for 2D material. [ABSTRACT FROM AUTHOR]

An array of semiconductor quantum dots introduced into photoelectric materials is currently an effective tool to increase the efficiency of photoelectric devices and photovoltaic cells. This is related to additional energy levels which expand the range of absorption frequencies towards the infrared. We consider the model with a semiconductor quantum dot in form of nanodisc surrounded by another semiconductor material. The results of calculation of the generation of non-equilibrium carriers in the conduction and valence bands are presented. The calculations account for discrete levels of the quantum dots embedded into perovskite material. Using the calculated generation and relaxation rates, the photocurrent is also determined. [ABSTRACT FROM AUTHOR]

We present our calculations of on-site magnetic anisotropy (MA) in graphene with magnetic atoms. We assume that the graphene layer is placed on a substrate, which generates the homogeneous Rashba spin-orbit field. The resonant state in the presence of Rashba spin-orbit interaction is calculated for two possible orientations of the magnetic moment namely perpendicular, Sz = 1, and parallel, Sz = 0, to the graphene plane. The magnetic anisotropy is calculated as a difference between the energies of these states and presented as a function of impurity potential g0 and magnitude of the Rashba spin-orbit coupling α. [ABSTRACT FROM AUTHOR]

Magnetic textures in ferromagnets are not confined only to the appearance of domain walls, but can also include more complicated structures such as one-dimensional skyrmions. Such different magnetization textures can give rise not only to different magnetoresistance effects, but also to different dynamics of the various magnetic textures caused by applied currents and fields. In this article we investigate the dynamics of different magnetic textures caused by applied currents in the wires. [ABSTRACT FROM AUTHOR]

We propose a simple analytical model to explain the possible appearance of the metallic conductivity in the two-dimensional (2D) LaAlO3/SrTiO3 interface. Our model considers the interface within a macroscopic approach, which is usual for semiconductor heterojunctions and is based on drift-diffusion equations. The solution of these equations allows us to obtain the positions of band edges as a function of distances from the interface. We show that for the 2D metallic conductivity to appear at the interface, the constituting substances should have the same type (either electronic or hole) of conductivity; in the opposite case the possible transition to metallic phase has a three-dimensional character. The results of our model calculations are in agreement with available experimental data. [ABSTRACT FROM AUTHOR]

We consider theoretically a wide graphene ribbon that is attached on both ends to electronic reservoirs, which generally have different temperatures. The graphene ribbon is assumed to be deposited on a substrate that leads to a spin-orbit coupling of the Rashba type. We calculate the thermally induced charge current in the ballistic transport regime as well as the thermoelectric voltage (Seebeck effect). Apart from this, we also consider thermally induced spin current and spin polarization of the graphene ribbon. The spin currents are shown to have generally two components; one parallel to the temperature gradient and the other perpendicular to this gradient. The latter corresponds to the spin current due to the spin Nernst effect. Additionally, we also consider the heat current between the reservoirs due to transfer of electrons. [ABSTRACT FROM AUTHOR]

We analyze theoretically the optical generation of a spin-polarized charge current (photogalvanic effect) and spin polarization in graphene with Rashba spin-orbit coupling. An external magnetic field is applied in the graphene plane, which plays a crucial role in the mechanism of current generation. We predict a highly efficient resonant photogalvanic effect in a narrow frequency range that is determined by the magnetic field. A relatively less efficient photogalvanic effect appears in a broader frequency range, determined by the electron concentration and spin-orbit coupling strength. [ABSTRACT FROM AUTHOR]

Theoretical analysis of the electron excitations in graphene on substrate by twisted, linear and circular polarization light is presented. We use a model of graphene with constant Rashba spin-orbit interaction. In this case, the band structure of electrons includes four energy bands. The main objective of this work is to compare light absorptions in graphene for different kinds of light, namely, twisted (with nonzero orbital angular momentum) and linear polarized light. The orbital angular momentum light is characterized by some parameters q and l, which can modify the response, while for the linear polarization, the absorption is modified only in the region determined by the Rashba spin-orbit coupling α. [ABSTRACT FROM AUTHOR]

We discuss the role of spin-flip scattering of electrons from the magnetized edges in graphene nanoribbons. The spin-flip scattering is associated with strong fluctuations of the magnetic moments at the edge. Using the Boltzmann equation approach, which is valid for not too narrow nanoribbons, we calculate the spin-relaxation time in the case of Berry-Mondragon and zigzag graphene edges. We also consider the case of ballistic nanoribbons characterized by very long momentum relaxation time in the bulk, when the main source of momentum and spin relaxation is the spin-dependent scattering at the edges. We found that in the case of zigzag edges, an anomalous spin diffusion is possible, which is related to very weak spin-flip scattering of electrons gliding along the nanoribbon edge. [ABSTRACT FROM AUTHOR]

We calculate the efficiency of infrared optical spin injection in single-layer graphene with Rashba spin-orbit coupling and for the in-plane magnetic field. The injection rate in the photon frequency range corresponding to the Rashba splitting is shown to be proportional to the ratio of the Zeeman and Rashba splittings. As a result, a large spin polarization can be controllably achieved for experimentally available values of the spin-orbit coupling and in magnetic fields below 10 T, without using ferromagnetic contacts. [ABSTRACT FROM AUTHOR]

We consider the dynamics of the polarization of a single domain wall in a magnetic nanowire, which is strongly pinned by impurities. In this case the equation of motion for the polarization parameter does not include any other dynamical variables and is nonlinear due to magnetic anisotropy. We calculated numerically the magnetization dynamics for different choices of parameters under short current pulses inducing polarization switching. Our results show that the switching is most effective for very rapid current pulses. Damping also enhances the switching probability. [ABSTRACT FROM AUTHOR]

We discuss the contribution of edge scattering to the conductance of graphene nanoribbons and nanoflakes. Using different possible types of the boundary conditions for the electron wave function at the edge, we found dependences of the momentum relaxation time and conductance on the geometric sizes and on the carrier density. We also consider the case of ballistic nanoribbon and nanodisk, for which the edge scattering is the main mechanism of momentum relaxation [ABSTRACT FROM AUTHOR]

We calculate shot noise and the corresponding Fano factors in magnetic double-barrier tunnel junctions. Two situations are analyzed: (i) the central metallic layer is nonmagnetic while the external ones are ferromagnetic, and (ii) all of the metallic layers are ferromagnetic. In the latter case, the number of various magnetic configurations of the junctions is larger, which improves the functionality of such devices. The corresponding shot noise and Fano factor are shown to depend on the magnetic configuration of the junctions. The effect of spin relaxation in the central layer is also taken into account. The theoretical results are compared with experimental data on the shot noise in Fe/MgO/Fe/MgO/Fe structures. [ABSTRACT FROM AUTHOR]

We predict two spin-dependent transport phenomena in two-dimensional electron systems, which are induced by a spatially fluctuating Rashba spin-orbit interaction. When the electron gas is magnetized, the random Rashba interaction leads to the anomalous Hall effect. An example of such a system is a narrow-gap magnetic semiconductor-based symmetric quantum well. We show that the anomalous Hall conductivity reveals a strongly nonlinear dependence on the magnetization, decreasing exponentially at large spin density. We also show that electron scattering from a fluctuating Rashba field in a two-dimensional nonmagnetic electron system leads to a negative magnetoresistance arising solely due to spin-dependent effects. [ABSTRACT FROM AUTHOR]

We study the energy spectrum and electronic properties of graphene in a periodic magnetic field of zero average with a symmetry of triangular lattice. The periodic field leads to the formation of a set of minibands separated by gaps, which can be manipulated by an external field. The Berry phase, related to the motion of electrons in k space, and the corresponding Chern numbers characterizing the topology of the energy bands are calculated analytically and numerically. In this connection, we discuss the anomalous Hall effect in the insulating state, when the Fermi level is located in the minigap. The results of calculations show that in the model of a gapless Dirac spectrum of graphene, the anomalous Hall effect can be treated as a sum of fractional quantum numbers, related to the nonequivalent Dirac points. [ABSTRACT FROM AUTHOR]

We consider a stationary spin current in a (110)-oriented GaAs-based symmetric quantum well due to a nonlinear response to an external periodic electric field. The model assumed includes the Dresselhaus spin-orbit interaction and the random Rashba spin-orbit coupling. The Dresselhaus term is uniform in the quantum well plane and gives rise to spin splitting of the electron band. The external electric field of frequency ω—in the presence of random Rashba coupling—leads to virtual spin-flip transitions between spin subbands, generating a stationary pure spin current proportional to the square of the field amplitude. [ABSTRACT FROM AUTHOR]

We investigated how the dynamics of a domain wall are affected by the presence of spin-density waves in a ferromagnetic wire. Domain walls and other scattering centers can cause coherent spin-density waves to propagate through a wire when a current is applied. In some cases, the spin torque due to these scattered electrons can be enhanced such that it is on a par with the exchange and anisotropy energies controlling the shape and dynamics of the domain wall. In such a case, we find that the spin-density waves enhance the current-induced domain-wall motion, allowing for domain-wall motion with smaller current pulses. Here, we consider a system involving two domain walls and focus on how the motion of the second domain wall is modified by the spin-density waves caused by the presence of the first domain wall. [ABSTRACT FROM AUTHOR]

We consider spin effects related to the random spin-orbit interaction in graphene. Such a random interaction can result from the presence of ripples and/or other inhomogeneities at the graphene surface. We show that the random spin-orbit interaction generally reduces the spin dephasing (relaxation) time, even if the interaction vanishes on average. Moreover, the random spin-orbit coupling also allows for spin manipulation with an external electric field. Because of the spin-flip interband as well as intraband optical transitions, the spin density can be effectively generated by a periodic electric field in a relatively broad range of frequencies. [ABSTRACT FROM AUTHOR]

Transport and magnetic properties of the IV-VI ferromagnetic multinary, mixed compounds Get-xMnx,Te, Get-x-yMnxEuyTe and Ge1-x-yMn,xYbyTe (0.045 ≤ x <≤ 0.47, y < 0.04) were investigated in magnetic fields up to 13 T and in the temperature range 1.6-300 K. The Curie temperatures of studied samples exceed 100 K. Based on the dependences of the Hall resistivity and magnetization on magnetic field, the anomalous Hall coefficients Rs were calculated, and Rs dependences on crystal composition and temperature were found. [ABSTRACT FROM AUTHOR]