Direct determination of spin orbit interaction coefficients and realization of the persistent spin helix symmetry

TL;DR

This paper introduces a straightforward, parameter-free experimental method to directly measure the ratio and absolute values of Rashba and Dresselhaus spin orbit interaction coefficients in semiconductor heterostructures, and demonstrates persistent spin helix symmetry tuning.

Contribution

It presents a novel, simple technique for directly determining spin orbit coefficients without fitting ambiguities and shows gate-controlled realization of persistent spin helix symmetry.

Findings

Successful direct measurement of alpha/beta ratio and absolute values.

Observation of persistent spin helix symmetry via gate tuning.

Enhanced spin lifetimes due to symmetry realization.

Abstract

The spin orbit interaction plays a crucial role in diverse fields of condensed matter, including the investigation of Majorana fermions, topological insulators, quantum information and spintronics. In III V zinc blende semiconductor heterostructures, two types of spin orbit interaction, Rashba and Dresselhaus act on the electron spin as effective magnetic fields with different directions. They are characterized by coefficients alpha and beta, respectively. When alpha is equal to beta, the so called persistent spin helix symmetry is realized. In this condition, invariance with respect to spin rotations is achieved even in the presence of the spin orbit interaction, implying strongly enhanced spin lifetimes for spatially periodic spin modes. Existing methods to evaluate alpha/beta require fitting analyses that often include ambiguity in the parameters used. Here, we experimentally demonstrate a simple and fitting parameter free technique to determine alpha/beta and to deduce the absolute values of alpha and beta. The method is based on the detection of the effective magnetic field direction and the strength induced by the two spin orbit interactions. Moreover, we observe the persistent spin helix symmetry by gate tuning.