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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 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 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]

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]

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 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 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 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]

We discuss transport properties of graphene related to the resonant scattering from impurities and defects. Two different models describing defects in the bulk of graphene or at the graphene surface are used for the calculation of self energy of electrons scattered from short-range impurities or defects. The results of numerical calculations demonstrate a resonant character of resistance. In the case of neutral impurities or defects the scattering also leads to a resonant decrease of the spin relaxation time. [ABSTRACT FROM AUTHOR]

Thermoelectric effects in graphene are considered theoretically with particular attention paid to the role of resonant scattering on impurities. Using the T-matrix method we calculate the impurity resonant states and the momentum relaxation time due to scattering on impurities. The Boltzmann kinetic equation is used to determine the thermoelectric coefficients. It is shown that the resonant impurity states near the Fermi level give rise to a resonant enhancement of the Seebeck coefficient and figure of merit ZT. The Wiedemann-Franz ratio deviates from that known for ordinary metals, where this ratio is constant and equal to the Lorentz number. This deviation appears for small chemical potentials and in the vicinity of the resonant states. In the limit of a constant relaxation time, this ratio has been calculated analytically for μ = 0. [ABSTRACT FROM AUTHOR]