Spin relaxation and anticrossing in quantum dots: Rashba versus Dresselhaus spin-orbit coupling

TL;DR

This paper investigates how Rashba and Dresselhaus spin-orbit couplings differently affect spin relaxation, anticrossing, and decoherence in quantum dots under magnetic fields, highlighting the unique cusp-like relaxation behavior caused by Rashba coupling.

Contribution

It provides a comparative analysis of Rashba and Dresselhaus effects on spin dynamics and level anticrossing in quantum dots, including calculations of relaxation and decoherence times.

Findings

Rashba coupling causes level anticrossing and spin mixing at degeneracy points.

Spin relaxation rate exhibits a cusp-like structure with Rashba but not Dresselhaus.

Dresselhaus coupling does not induce level anticrossing or spin mixing.

Abstract

The spin-orbit splitting of the electron levels in a two-dimensional quantum dot in a perpendicular magnetic field is studied. It is shown that at the point of an accidental degeneracy of the two lowest levels above the ground state the Rashba spin-orbit coupling leads to a level anticrossing and to mixing of spin-up and spin-down states, whereas there is no mixing of these levels due to the Dresselhaus term. We calculate the relaxation and decoherence times of the three lowest levels due to phonons. We find that the spin relaxation rate as a function of a magnetic field exhibits a cusp-like structure for Rashba but not for Dresselhaus spin-orbit interaction.