Theory of Single Electron Spin Relaxation in Si/SiGe Lateral Coupled Quantum Dots

TL;DR

This paper models spin relaxation in Si/SiGe quantum dots caused by acoustic phonons and spin-orbit interactions, revealing a strong magnetic field dependence and anisotropic effects, with rates significantly lower than in GaAs.

Contribution

It provides a detailed numerical analysis of spin relaxation rates in single and double quantum dots considering acoustic phonons and spin-orbit coupling effects.

Findings

Relaxation rate scales with the seventh power of magnetic field in single dots.

Double dots show relaxation dominated by spin hot spots and are sensitive to dot spectrum.

Relaxation rates in Si are about 100 times smaller than in GaAs due to material properties.

Abstract

We investigate the spin relaxation induced by acoustic phonons in the presence of spin-orbit interactions in single electron Si/SiGe lateral coupled quantum dots. The relaxation rates are computed numerically in single and double quantum dots, in in-plane and perpendicular magnetic fields. The deformation potential of acoustic phonons is taken into account for both transverse and longitudinal polarizations and their contributions to the total relaxation rate are discussed with respect to the dilatation and shear potential constants. We find that in single dots the spin relaxation rate scales approximately with the seventh power of the magnetic field, in line with a recent experiment. In double dots the relaxation rate is much more sensitive to the dot spectrum structure, as it is often dominated by a spin hot spot. The anisotropy of the spin-orbit interactions gives rise to easy passages, special directions of the magnetic field for which the relaxation is strongly suppressed. Quantitatively, the spin relaxation rates in Si are typically 2 orders of magnitude smaller than in GaAs due to the absence of the piezoelectric phonon potential and generally weaker spin-orbit interactions.