Coulomb mediated hybridization of excitons in artificial molecules

TL;DR

This paper demonstrates Coulomb-mediated hybridization of excitonic states in an artificial quantum dot molecule, revealing a new coupling mechanism driven by Coulomb interactions that causes hybridization over multiple orbitals.

Contribution

It uncovers a novel Coulomb interaction-based coupling mechanism causing exciton hybridization in quantum dot molecules, supported by experimental and microscopic theoretical analysis.

Findings

Observation of unexpected avoided level crossings.

Identification of Coulomb resonances involving multiple orbitals.

Good agreement between experiment and 8-band $k \, p$ calculations.

Abstract

We report the Coulomb mediated hybridization of excitonic states in an optically active, artificial quantum dot molecule. By probing the optical response of the artificial molecule as a function of the static electric field applied along the molecular axis, we observe unexpected avoided level crossings that do not arise from the dominant single particle tunnel coupling. We identify a new few-particle coupling mechanism stemming from Coulomb interactions between different neutral exciton states. Such Coulomb resonances hybridize the exciton wave function over four different electron and hole single-particle orbitals. Comparisons of experimental observations with microscopic 8-band $k \cdot p$ calculations taking into account a realistic quantum dot geometry show good agreement and reveal that the Coulomb resonances arise from broken symmetry in the artificial molecule.