Spin-orbit interaction is usefully classified as extrinsic or intrinsic depending on its origin: the potential due to random impurities (extrinsic), or the crystalline potential associated with the band or device structure (intrinsic). In this paper
we will show how by using a SU(2) formulation the two sources of spin-orbit interaction may be described in an elegant and unified way. As a result we obtain a simple description of the interplay of the two types of spin-orbit interaction, and a physically transparent explanation of the vanishing of the d.c. spin Hall conductivity in a Rashba two-dimensional electron gas when spin relaxation is neglected, and its reinstatement when spin relaxation is allowed. Furthermore, we obtain an explicit formula for the transverse spin polarization created by an electric current, which generalizes the standard formula obtained by Edelstein and Aronov and Lyanda-Geller by including extrinsic spin-orbit interaction and spin relaxation.
Two recent experiments successfully observed Landau levels in the tunneling spectra of the topological insulator Bi2Se3. To mimic the influence of a scanning tunneling microscope tip on the Landau levels we solve the two-dimensional Dirac equation in
the presence of a localized electrostatic potential. We find that the STM tip not only shifts the Landau levels, but also suppresses for a realistic choice of parameters the negative branch of Landau levels.
We derive a kinetic equation for the electrons moving on the surface of a three-dimensional topological insulator. Due to the helical nature of the excitations backward scattering is suppressed in the collision integral, and the spin dynamics is enti
rely constrained by that of the charge. We further analyze the tunneling between the helical and a conventional metal or ferromagnet. We find that the tunnel resistance strongly depends on the angle between the magnetization in the ferromagnet and the current in the helical metal. A nonmagnetic layer on top of the helical metal amplifies the current-induced spin polarization.
We study both static and transport properties of model quantum dots, employing density functional theory as well as (numerically) exact methods. For the lattice model under consideration the accuracy of the local-density approximation generally is po
or. For weak interaction, however, accurate results are achieved within the optimized effective potential method, while for intermediate interaction strengths a method combining the exact diagonalization of small clusters with density functional theory is very successful. Results obtained from the latter approach yield very good agreement with density matrix renormalization group studies, where the full Hamiltonian consisting of the dot and the attached leads has to be diagonalized. Furthermore we address the question whether static density functional theory is able to predict the exact linear conductance through the dot correctly - with, in general, negative answer.
We study the excitation dynamics of a single molecular nanomagnet by static and pulsed magnetic fields. Based on a stability analysis of the classical magnetization dynamics we identify analytically the fields parameters for which the energy is stoch
astically pumped into the system in which case the magnetization undergoes diffusively and irreversibly a large angle deflection. An approximate analytical expression for the diffusion constant in terms of the fields parameters is given and assessed by full numerical calculations.
We study the coupled dynamics of spin and charge currents in a two-dimensional electron gas in the transport diffusive regime. For systems with inversion symmetry there are established relations between the spin Hall effect, the anomalous Hall effect
and the inverse spin Hall effect. However, in two-dimensional electron gases of semiconductors like GaAs, inversion symmetry is broken so that the standard arguments do not apply. We demonstrate that in the presence of a Rashba type of spin-orbit coupling (broken structural inversion symmetry) the anomalous Hall effect, the spin Hall and inverse spin Hall effect are substantially different effects. Furthermore we discuss the inverse spin Hall effect for a two-dimensional electron gas with Rashba and Dresselhaus spin-orbit coupling; our results agree with a recent experiment.
We study the magnetization dynamics of a molecular magnet driven by static and variable magnetic fields within a semiclassical treatment. The underling analyzes is valid in a regime, when the energy is definitely lower than the anisotropy barrier, bu
t still a substantial number of states are excited. We find the phase space to contain a separatrix line. Solutions far from it are oscillatory whereas the separatrix solution is of a soliton type. States near the separatrix are extremely sensitive to small perturbations, a fact which we utilize for dynamically induced magnetization switching.
We provide a theoretical framework for the electric field control of the electron spin in systems with diffusive electron motion. The approach is valid in the experimentally important case where both intrinsic and extrinsic spin-orbit interaction in
a two-dimensional electron gas are present simultaneously. Surprisingly, even when the extrinsic mechanism is the dominant driving force for spin Hall currents, the amplitude of the spin Hall conductivity may be considerably tuned by varying the intrinsic spin-orbit coupling via a gate voltage. Furthermore we provide an explanation of the experimentally observed out-of-plane spin polarization in a (110) GaAs quantum well.
