Electron transport in waveguides with spatially modulated strengths of the Rashba and Dresselhaus terms of the spin-orbit interaction

TL;DR

This paper investigates how spatial variations in Rashba and Dresselhaus spin-orbit interactions influence electron transport in waveguides, revealing resonance behaviors and the impact of subband mixing on spin-dependent transmission.

Contribution

It provides a detailed analysis of electron transport in waveguides with spatially modulated spin-orbit coupling, highlighting the effects of equal SOI strengths and subband mixing on transmission properties.

Findings

Transmission exhibits square-like shape for narrow waveguides.

Resonances occur as a function of SOI-free region length, especially when α=β.

Subband mixing shifts resonances and reduces spin-flip transmission.

Abstract

We study electron transport through waveguides (WGs) in which the strengths of the Rashba ($\alpha$) and Dresselhaus ($\beta$) terms of the spin-orbit interaction (SOI) vary in space. Subband mixing, due to lateral confinement, is taken into account only between the two first subbands. For sufficiently narrow WGs the transmission $T$ exhibits a square-like shape as a function of $\alpha$ or $\beta$. Particular attention is paid to the case of equal SOI strengths, $\alpha=\beta$, for which spin-flip processes are expected to decrease. The transmission exhibits resonances as a function of the length of a SOI-free region separating two regions with SOI present, that are most pronounced for $\alpha=\beta$. The sign of $\alpha$ strongly affects the spin-up and spin-down transmissions. The results show that the main effect of subband mixing is to shift the transmission resonances and to decrease the transmission from one spin state to another. The effect of possible band offsets between regions that have different SOI strengths and effective masses is also discussed.