Triplet-singlet relaxation in semiconductor single and double quantum dots

TL;DR

This paper investigates triplet-singlet relaxation in semiconductor quantum dots, highlighting the effects of electron interactions, spin-orbit coupling, and structural parameters on relaxation processes in single and double quantum dots.

Contribution

It provides a detailed analysis of triplet-singlet relaxation mechanisms, correcting common selection rule assumptions and exploring parameter influences in double quantum dots.

Findings

Spin mixing is caused by spin-orbit coupling.

Selection rules are invalid near crossing points.

Relaxation rates are affected by barrier height, inter-dot distance, magnetic field, and dot size.

Abstract

We study the triplet-singlet relaxation in two-electron semiconductor quantum dots. Both single dots and vertically coupled double dots are discussed. In our work, the electron-electron Coulomb interaction, which plays an important role in the electronic structure, is included. The spin mixing is caused by spin-orbit coupling which is the key to the triplet-singlet relaxation. We show that the selection rule widely used in the literature is incorrect unless near the crossing/anticrossing point in single quantum dots. The triplet/singlet relaxation in double quantum dots can be markedly changed by varying barrier height, inter-dot distance, external magnetic field and dot size.