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Current-induced spin polarization and the spin Hall effect: a quasiclassical approach

2007-11-30T23:00:00Z

Current-induced spin polarization and the spin Hall effect: a quasiclassical approach Raimondi, Roberto; Gorini, Cosimo; Dzierzawa, Michael; Schwab, Peter 2007-12 Solid State Communications 144 524-528 The quasiclassical Green function formalism is used to describe charge and spin dynamics in the presence of spin–orbit coupling. We review the results obtained for the spin Hall effect on restricted geometries. The role of boundaries is discussed in the framework of spin diffusion equations.

Quasiclassical approach and spin–orbit coupling

2008-03-04T23:00:00Z

Quasiclassical approach and spin–orbit coupling Gorini, Cosimo; Schwab, Peter; Dzierzawa, Michael; Raimondi, Roberto 2008-03-05 Physica E: Low-dimensional Systems and Nanostructures 40 1078-1080 We discuss the quasiclassical Green function method for a two-dimensional electron gas in the presence of spin–orbit coupling, with emphasis on the meaning of the ξ-integration procedure. As an application of our approach, we demonstrate how the spin-Hall conductivity, in the presence of spin-flip scattering, can be easily obtained from the spin-density continuity equation.

Quasiclassical approach to the spin-Hall effect in the two-dimensional electron gas

2006-07-26T22:00:00Z

Quasiclassical approach to the spin-Hall effect in the two-dimensional electron gas Raimondi, Roberto; Gorini, Cosimo; Schwab, Peter; Dzierzawa, Michael 2006-07-27 Physical Review B-Condensed Matter and Material Physics 74 035340 We study the spin-charge coupled transport in a two-dimensional electron system using the method of quasiclassical (-integrated) Green's functions. In particular we derive the Eilenberger equation in the presence of a generic spin-orbit field. The method allows us to study spin and charge transport from ballistic to diffusive regimes and continuity equations for spin and charge are automatically incorporated. In the clean limit we establish the connection between the spin Hall conductivity and the Berry phase in momentum space. For finite systems we solve the Eilenberger equation numerically for the special case of the Rashba spin-orbit coupling and a two-terminal geometry. In particular, we calculate explicitly the spin Hall induced spin polarization in the corners, predicted by Mishchenko et al. [Phys. Rev. Lett. 93, 226602 (2004)]. Furthermore we find universal spin currents in the short-time dynamics after switching on the voltage across the sample, and calculate the corresponding spin Hall polarization at the edges. Where available, we find perfect agreement with analytical results.

Spin relaxation in narrow wires of a two-dimensional electron gas

2006-10-18T22:00:00Z

Spin relaxation in narrow wires of a two-dimensional electron gas Schwab, Peter; Dzierzawa, Michael; Gorini, Cosimo; Raimondi, Roberto 2006-10-19 Physical Review B-Condensed Matter and Material Physics 74 155316 How does an initially homogeneous spin polarization in a confined two-dimensional electron gas with Rashba spin-orbit coupling evolve in time? How does the relaxation time depend on system size? We study these questions for systems of a size that is much larger than the Fermi wavelength, but comparable and even shorter than the spin relaxation length. Depending on the confinement spin relaxation may become faster or slower than in the bulk. An initially homogeneously polarized spin system evolves into a spiral pattern.

Spin polarizations and spin Hall currents in a two-dimensional electron gas with magnetic impurities

2008-09-28T22:00:00Z

Spin polarizations and spin Hall currents in a two-dimensional electron gas with magnetic impurities Gorini, Cosimo; Schwab, Peter; Dzierzawa, Michael; Raimondi, Roberto 2008-09-29 Physical Review B-Condensed Matter and Material Physics 78 125327 We consider a two-dimensional electron gas in the presence of Rashba spin-orbit coupling, and study the effects of magnetic s-wave and long-range nonmagnetic impurities on the spin-charge dynamics of the system. We focus on voltage induced spin polarizations and their relation to spin Hall currents. Our results are obtained using the quasiclassical Green function technique, and hold in the full range of the disorder parameter αpF.

Spin Hall effect in a 2DEG in the presence of magnetic couplings

2009-01-31T23:00:00Z

Spin Hall effect in a 2DEG in the presence of magnetic couplings Gorini, Cosimo; Schwab, Peter; Dzierzawa, Michael; Raimondi, Roberto; Milletarì, Mirco 2009-02 1-4 It is now well established that the peculiar linear-in-momentum dependence of the Rashba (and of the Dresselhaus) spin-orbit coupling leads to the vanishing of the spin Hall conductivity in the bulk of a two-dimensional electron gas (2DEG). In this paper we discuss how generic magnetic couplings change this behaviour providing then a potential handle on the spin Hall effect. In particular we examine the influence of magnetic impurities and an in-plane magnetic field. We find that in both cases there is a finite spin Hall effect and we provide explicit expressions for the spin Hall conductivity. The results can be obtained by means of the quasiclassical Green function approach, that we have recently extended to spin-orbit coupled electron systems.

Quasiclassical methods for spin-charge coupled dynamics in low-dimensional systems

2009-06-11T22:00:00Z

Quasiclassical methods for spin-charge coupled dynamics in low-dimensional systems Gorini, Cosimo 2009-06-12 Spintronics is a new ﬁeld of study concerned with the manipulation of the spin degrees of freedom in solid state systems. One of its main goals is the realization of a new generation of devices capable of making full use of, besides the charge, the electronic – and possibly nuclear – spin. At least in principle all-electrical control of the spin, which would be preferable from the point of view of applications, can be achieved through spin-orbit interaction. In recent years a number of spin-orbit related effects in low-dimensional fermionic systems have made this possibility much more concrete. We cite as prominent example the spin Hall effect, ﬁrst proposed in 2003 for a twodimensional hole gas and soon after observed. In more general terms, the description of spin-charge coupled dynamics in mesoscopic, disordered low-dimensional systems is a non-trivial matter. For the task we relied on the quasiclassical formalism, an approximate quantum-ﬁeld theoretical formulation ideally suited for tackling transport problems on the mesoscopic scale, with a solid microscopic foundation and a resemblance to standard Boltzmann transport theory that makes for physical transparency. The goal of this thesis has been two-fold: on one hand the generalization of the quasiclassical equations so as to make them capable of describing spincharge coupled dynamics, on the other the application of such equations to particular physical problems. Among them the spin Hall effect and voltageinduced spin polarization in two-dimensional, disordered electron gases under a variety of conditions – static or time dependent, in inﬁnite systems, in conﬁned geometries with different boundary conditions.