Multichannel effects in Rashba quantum wires

We investigate intersubband mixing effects in multichannel quantum wires in the presence of Rashba spin-orbit coupling and attached to two terminals. When the contacts are ferromagnetic and their magnetization direction is perpendicular to the Rashba field, the spin-transistor current is expected to depend in a oscillatory way on the Rashba coupling strength due to spin coherent oscillations of the travelling electrons. Nevertheless, we find that the presence of many propagating modes strongly influences the spin precession effect, leading to (i) a quenching of the oscillations and (ii) strongly irregular curves for high values of the Rashba coupling. We also observe that in the case of leads' magnetization parallel to the Rashba field, the conductance departs from a uniform value as the Rashba strength increases. We also discuss the Rashba interaction induced current polarization effects when the contacts are not magnetic and investigate how this mechanism is affected by the presence of several propagating channels.Comment: 8 pages, 7 figure

g-Factor anisotropy of hole quantum wires induced by the Rashba interaction

We present calculations of the g factors for the lower conductance steps of 3D hole quantum wires. Our results prove that the anisotropy with magnetic field orientation, relative to the wire, originates in the Rashba spin-orbit coupling. We also analyze the relevance of the deformation, as the wire evolves from 3D towards a flat 2D geometry. For high enough wire deformations, the perpendicular g factors are greatly quenched by the Rashba interaction. On the contrary, parallel g factors are rather insensistive to the Rashba interaction, resulting in a high g factor anisotropy. For low deformations we find a more irregular behavior which hints at a sample dependent scenario.Comment: 7 pages, 6 figures (expanded from previous version

Linear conductance oscillations of quantum wires and stripes with Rashba interaction

An analysis of the linear conductance of 2D quantum wires and stripes with Rashba spin-orbit interaction and attached to spin polarized leads is presented. Differences and similarities between both systems are highlighted. We discuss the dependence of the conductance with both energy and Rashba intensity.We acknowledge R. L´opez and D. S´anchez for valuable discussions. This work was supported by the Grant No. FIS2008-00781.Peer reviewe

Arqueología de la cuenca del río Samalá: Tierras Bajas.

Sin resume

Conductance oscillations of a spin-orbit stripe with polarized contacts

We investigate the linear conductance of a stripe of spin-orbit interaction in a 2D electron gas; that is, a 2D region of length $\ell$ along the transport direction and infinite in the transverse one in which a spin-orbit interaction of Rashba type is present. Polarization in the contacts is described by means of Zeeman fields. Our model predicts two types of conductance oscillations: Ramsauer oscillations in the minority spin transmission, when both spins can propagate, and Fano oscillations when only one spin propagates. The latter are due to the spin-orbit coupling with quasibound states of the non propagating spin. In the case of polarized contacts in antiparallel configuration Fano-like oscillations of the conductance are still made possible by the spin orbit coupling, even though no spin component is bound by the contacts. To describe these behaviors we propose a simplified model based on an ansatz wave function. In general, we find that the contribution for vanishing transverse momentum dominates and defines the conductance oscillations. Regarding the oscillations with Rashba coupling intensity, our model confirms the spin transistor behavior, but only for high degrees of polarization. Including a position dependent effective mass yields additional oscillations due to the mass jumps at the interfaces.Comment: 8.5 pages, 9 figure