Triplet-Singlet Spin Relaxation in Quantum Dots with Spin-Orbit Coupling

TL;DR

This paper models triplet-singlet spin relaxation in quantum dots considering spin-orbit coupling and phonon interactions, explaining experimental observations and highlighting how confinement and magnetic fields influence relaxation times.

Contribution

It provides a unified theoretical framework for understanding triplet-singlet relaxation trends in quantum dots with different electron counts, emphasizing the roles of spin-orbit coupling and phonon emission.

Findings

Relaxation rates depend on confinement strength and magnetic field.

Long-lived triplet states are achievable under certain conditions.

Selective population of Zeeman sublevels is possible.

Abstract

We estimate the triplet-singlet relaxation rate due to spin-orbit coupling assisted by phonon emission in weakly-confined quantum dots. Our results for two and four electrons show that the different triplet-singlet relaxation trends observed in recent experiments under magnetic fields can be understood within a unified theoretical description, as the result of the competition between spin-orbit coupling and phonon emission efficiency. Moreover, we show that both effects are greatly affected by the strength of the confinement and the external magnetic field, which may give access to very long-lived triplet states as well as to selective population of the triplet Zeeman sublevels.