Characterization of spin-orbit interactions of GaAs heavy holes using a quantum point contact

TL;DR

This study investigates the complex spin-orbit interactions in GaAs heavy holes within quantum point contacts, revealing novel phenomena like level crossing and anti-crossing, and providing a detailed effective Hamiltonian relevant for quantum computing.

Contribution

It introduces a comprehensive heavy hole spin-orbit Hamiltonian that accounts for cubic and quadratic momentum terms, explaining observed transport phenomena and g-factor behaviors.

Findings

Observation of level crossing and anti-crossing depending on subband and magnetic field.

Characterization of spin-orbit components in terms of magnitude and spin structure.

Confirmation of out-of-plane g-factor saturation near 7.2, matching bulk predictions.

Abstract

We present transport experiments performed in high quality quantum point contacts embedded in a GaAs two-dimensional hole gas. The strong spin-orbit interaction results in peculiar transport phenomena, including the previously observed anisotropic Zeeman splitting and level-dependent effective g-factors. Here we find additional effects, namely the crossing and the anti-crossing of spin-split levels depending on subband index and magnetic field direction. Our experimental observations are reconciled in an heavy hole effective spin-orbit Hamiltonian where cubic- and quadratic-in-momentum terms appear. The spin-orbit components, being of great importance for quantum computing applications, are characterized in terms of magnitude and spin structure. In the light of our results, we explain the level dependent effective g-factor in an in-plane field. Through a tilted magnetic field analysis, we show that the QPC out-of-plane g-factor saturates around the predicted 7.2 bulk value.