Electron-hole bilayer quantum dots: Phase diagram and exciton localization

TL;DR

This paper investigates a vertical electron-hole bilayer quantum dot system, revealing various ground state phases influenced by carrier density and interdot distance, including shell effects, degeneracy lifting, and exciton formation.

Contribution

It introduces a detailed phase diagram for electron-hole bilayer quantum dots, highlighting mechanisms like Hund's rule and Jahn-Teller effects in degeneracy removal and exciton localization at low densities.

Findings

Different phases depend on carrier density and interdot distance

Shell structure influences degeneracy removal mechanisms

Bound electron-hole pairs form at low densities and large distances

Abstract

We studied a vertical ``quantum dot molecule'', where one of the dots is occupied with electrons and the other with holes. We find that different phases occur in the ground state, depending on the carrier density and the interdot distance. When the system is dominated by shell structure, orbital degeneracies can be removed either by Hund's rule, or by Jahn-Teller deformation. Both mechanisms can lead to a maximum of the addition energy at mid-shell. At low densities and large interdot distances, bound electron-hole pairs are formed.