Observation of oscillating $g$-factor anisotropy arising from strong crystal lattice anisotropy in GaAs spin-3/2 hole quantum point contacts

TL;DR

This study reveals strong oscillations in the in-plane hole g-factor anisotropy in GaAs quantum point contacts caused by crystal lattice anisotropy, highlighting the complex interplay of spin-orbit interactions and quantum confinement.

Contribution

We experimentally observe and theoretically model the oscillating in-plane hole g-factor anisotropy driven by crystal lattice asymmetry in GaAs quantum point contacts, separating Rashba and cubic crystal effects.

Findings

g-factor varies by a factor of 5 with 45° rotation

Crystal anisotropy dominates over symmetric models

Theoretical models match experimental data well

Abstract

Many modern spin-based devices rely on the spin-orbit interaction, which is highly sensitive to the host semiconductor heterostructure and varies substantially depending on crystal direction, crystal asymmetry (Dresselhaus), and quantum confinement asymmetry (Rashba). One-dimensional quantum point contacts are a powerful tool to probe both energy and directional dependence of spin-orbit interaction through the effect on the hole $g$-factor. In this work we investigate the role of cubic crystal asymmetry in driving an oscillation in the in-plane hole $g$-factor anisotropy when the quantum point contact is rotated with respect to the crystal axes, and we are able to separate contributions to the Zeeman Hamiltonian arising from Rashba and cubic crystal asymmetry spin-orbit interactions. The in-plane $g$-factor is found to be extremely sensitive to the orientation of the quantum point contact, changing by a factor of $5$ when rotated by $45^{\circ}$. This exceptionally strong crystal lattice anisotropy of the in-plane Zeeman splitting cannot be explained within axially symmetric theoretical models. Theoretical modelling based on the combined Luttinger, Rashba and Dresselhaus Hamiltonians that we use here reveals new spin-orbit contributions to the in-plane hole $g$-factor and provides an excellent agreement with our experimental data.