Gate-controlled Persistent Spin Helix State in Materials with Strong Spin-Orbit Interaction

TL;DR

This paper demonstrates gate control and detection of a persistent spin helix state in materials with strong spin-orbit interaction, including cubic terms, showing the state persists beyond the equal Rashba and Dresselhaus condition.

Contribution

It provides experimental evidence and numerical analysis of PSH state in strong SOI materials with cubic terms, extending understanding beyond the alpha = beta condition.

Findings

Gate tuning controls the Rashba SOI strength.

Transition from weak antilocalization to localization observed.

PSH state persists even with strong cubic SOI, but not at alpha = beta.

Abstract

In layered semiconductors with spin-orbit interaction (SOI) a persistent spin helix (PSH) state with suppressed spin relaxation is expected if the strengths of the Rashba and Dresselhaus SOI terms, alpha and beta, are equal. Here we demonstrate gate control and detection of the PSH in two-dimensional electron systems with strong SOI including terms cubic in momentum. We consider strain-free InGaAs/InAlAs quantum wells and first determine alpha/beta ~ 1 for non-gated structures by measuring the spin-galvanic and circular photogalvanic effects. Upon gate tuning the Rashba SOI strength in a complementary magneto-transport experiment, we then monitor the complete crossover from weak antilocalization via weak localization to weak antilocalization, where the emergence of weak localization reflects a PSH type state. A corresponding numerical analysis reveals that such a PSH type state indeed prevails even in presence of strong cubic SOI, however no longer at alpha = beta.