Fine-structure splitting of exciton states in semiconductor quantum dot molecules

Abstract

Exciton levels and fine-structure splitting in laterally coupled quantum dot molecules arestudied. The electron and hole tunnelling energies as well as the direct Coulomb interactionare essential for the exciton levels. It is found that fine-structure splittings of the two lowestexciton levels are contributed by the intra- and interdot exchange interactions which aregreatly influenced by the symmetry and tunnel-coupling between the two dots. As theinterdot separation is reduced, fine-structure splitting of the exciton ground state is largelyincreased while those of the second and fourth states are decreased. Moreover, thedependence of the fine-structure splitting in quantum dot molecules on the Coulombcorrelation is clearly clarified.