Spin Hot Spots in vertically-coupled Few-electron Quantum Dots

TL;DR

This paper investigates how spin-orbit coupling affects optical transitions in single and coupled quantum dots, revealing unique effects like degeneracy lifting and transition suppression depending on electron configuration and dot coupling.

Contribution

It provides new insights into spin-orbit effects in coupled quantum dots, especially the suppression of certain optical transitions as inter-dot distance decreases.

Findings

Degeneracy of dipole-allowed transitions is lifted at B=0 in single-electron dots due to SO coupling.

In coupled dots with one electron each, spectra remain unaffected by coupling.

In two-electron coupled dots, some dipole transitions vanish as dots are brought closer.

Abstract

The effects of spin-orbit (SO) coupling arising from the confinement potential in single and two vertically-coupled quantum dots have been investigated. Our work indicates that a dot containing a single electron shows the lifting of the degeneracy of dipole-allowed transitions at B=0 due to the SO coupling which disappears for a dot containing two electrons. For coupled dots with one electron in each dot, the optical spectra is not affected by the coupling and is the same as the dot containing one electron. However, for the case of two coupled dots where one partner dot has two interacting electrons while the other dot has only one electron, a remarkable effect is observed where the oscillator strength of two out of four dipole-allowed transition lines disappears as the distance between the dots is decreased.