Fine-structure splitting of exciton states in quantum dot molecules: symmetry and tunnel-coupling effects

TL;DR

This paper investigates how symmetry, tunnel-coupling, and Coulomb interactions influence the fine-structure splitting of exciton states in quantum dot molecules, revealing how inter-dot separation affects splitting magnitudes.

Contribution

It provides a detailed analysis of the effects of symmetry and tunnel-coupling on exciton fine-structure splitting in quantum dot molecules, including the role of Coulomb correlation.

Findings

Fine-structure splitting increases as inter-dot separation decreases.

Symmetry and tunnel-coupling significantly influence exchange interactions.

Coulomb correlation effects on splitting are explicitly clarified.

Abstract

Exciton levels and fine-structure splitting in laterally-coupled quantum dot molecules are studied. The electron and hole tunneling energies as well as the direct Coulomb interaction are essential for the exciton levels. It is found that fine-structure splitting of the two-lowest exciton levels is contributed from the intra- and inter-dot exchange interactions, both of which are largely influenced by the symmetry and tunnel-coupling between the two dots. As the inter-dot separation is reduced, fine-structure splitting of the exciton ground state is largely increased while those of the excited states are decreased. Moreover, the dependence of the fine-structure splitting in quantum dot molecules on the Coulomb correlation is clearly clarified.