Theory of Spin Relaxation in Two-Electron Lateral Coupled Quantum Dots

TL;DR

This paper provides a comprehensive numerical analysis of phonon-induced two-electron spin relaxation in GaAs double quantum dots, revealing how magnetic anisotropy and nuclear spins influence relaxation processes relevant for quantum computing.

Contribution

It introduces a detailed numerical framework to analyze spin relaxation, highlighting the control of magnetic anisotropy via detuning and the significant role of nuclear spins in relaxation mechanisms.

Findings

Magnetic anisotropy of singlet-triplet relaxation can be controlled by detuning.

Nuclear spins can dominate relaxation even at high magnetic fields.

Detuning switches the principal axes of anisotropy.

Abstract

A global quantitative picture of the phonon-induced two-electron spin relaxation in GaAs double quantum dots is presented using highly accurate numerical calculations. Wide regimes of interdot coupling, magnetic field magnitude and orientation, and detuning are explored in the presence of a nuclear bath. Most important, the unusually strong magnetic anisotropy of the singlet-triplet relaxation can be controlled by detuning switching the principal anisotropy axes: a protected state becomes unprotected upon detuning, and vice versa. It is also established that nuclear spins can dominate spin relaxation for unpolarized triplets even at high magnetic fields, contrary to common belief. These findings are central to designing quantum dots geometries for spin-based quantum information processing with minimal environmental impact.