Exciton and negative trion dissociation by an external electric field in vertically coupled quantum dots

TL;DR

This paper investigates how external electric fields cause exciton and negative trion dissociation in vertically coupled quantum dots, revealing unique Stark shift behaviors and stability differences between excitons and trions.

Contribution

It provides a detailed analysis of exciton and trion dissociation mechanisms under electric fields in coupled quantum dots, including the effects of symmetry and tunnel coupling.

Findings

Electric field induces exciton dissociation via avoided crossing of energy levels.

Trions are more stable against dissociation than excitons in symmetric dots.

Asymmetry in dots causes positive curvature in the recombination energy with electric field.

Abstract

We study the Stark effect for an exciton confined in a pair of vertically coupled quantum dots. A single-band approximation for the hole and a parabolic lateral confinement potential are adopted which allows for the separation of the lateral center-of-mass motion and consequently for an exact numerical solution of the Schr\"odinger equation. We show that for intermediate tunnel coupling the external electric field leads to the dissociation of the exciton via an avoided crossing of bright and dark exciton energy levels which results in an atypical form of the Stark shift. The electric-field-induced dissociation of the negative trion is studied using the approximation of frozen lateral degrees of freedom. It is shown that in a symmetric system of coupled dots the trion is more stable against dissociation than the exciton. For an asymmetric system of coupled dots the trion dissociation is accompanied by a positive curvature of the recombination energy line as a function of the electric field.