Conductance oscillations of a spin-orbit stripe with polarized contacts

TL;DR

This paper studies conductance oscillations in a 2D electron gas stripe with Rashba spin-orbit interaction and polarized contacts, revealing Ramsauer and Fano oscillations influenced by spin polarization and interface effects.

Contribution

It introduces a simplified model to describe conductance oscillations caused by spin-orbit coupling and contact polarization, highlighting the spin transistor behavior at high polarization levels.

Findings

Identification of Ramsauer and Fano conductance oscillations.

Fano oscillations occur even without bound spin states in contacts.

Additional oscillations arise from position-dependent effective mass.

Abstract

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.