Multiband theory of quantum-dot quantum wells: Dark excitons, bright excitons, and charge separation in heteronanostructures

TL;DR

This paper develops a multiband theoretical model for quantum-dot quantum wells that accurately describes dark and bright excitons and charge separation, surpassing previous single-band approaches.

Contribution

It introduces a comprehensive multiband theory incorporating valence-band mixing and conduction band nonparabolicity for quantum-dot quantum wells.

Findings

Accurately describes dark-exciton ground state

Identifies charge separation in pair states

Matches recent experimental observations

Abstract

Electron, hole, and exciton states of multishell CdS/HgS/CdS quantum-dot quantum well nanocrystals are determined by use of a multiband theory that includes valence-band mixing, modeled with a 6-band Luttinger-Kohn Hamiltonian, and nonparabolicity of the conduction band. The multiband theory correctly describes the recently observed dark-exciton ground state and the lowest, optically active, bright-exciton states. Charge separation in pair states is identified. Previous single-band theories could not describe these states or account for charge separation.