Anisotropy of spin-orbit induced electron spin relaxation in [001] and [111] grown GaAs quantum dots

TL;DR

This study investigates how the orientation of an in-plane magnetic field affects spin relaxation rates in GaAs quantum dots, revealing anisotropic behavior and specific angles where relaxation is suppressed, influenced by spin-orbit interactions.

Contribution

It provides a systematic analysis of spin relaxation anisotropy in GaAs quantum dots with different orientations, highlighting the role of cubic Dresselhaus terms and symmetry considerations.

Findings

Relaxation rate oscillates with magnetic field orientation.

'Magic' angles exist where relaxation is suppressed significantly.

Differences in suppression angles between [001] and [111] grown QDs.

Abstract

We report a systematic study of the spin relaxation anisotropy between single electron Zeeman sublevels in cuboidal GaAs quantum dots (QDs). The QDs are subject to an in-plane magnetic field. As the field orientation varies, the relaxation rate oscillates periodically, showing ``magic'' angles where the relaxation rate is suppressed by several orders of magnitude. This behavior is found in QDs with different shapes, heights, crystallographic orientations and external fields. The origin of these angles can be traced back to the symmetries of the spin admixing terms of the Hamiltonian. In [001] grown QDs, the suppression angles are different for Rashba and Dresselhaus spin-orbit terms. By contrast, in [111] grown QDs they are the same, which should facilitate a thorough suppression of spin-orbit induced relaxation. Our results evidence that cubic Dresselhaus terms play a critical role in determining the spin relaxation anisotropy even in quasi-2D QDs.