Dark-bright mixing of interband transitions in symmetric semiconductor quantum dots

TL;DR

This study investigates the complex interplay of magnetic field effects on excitonic transitions in symmetric GaAs/AlGaAs quantum dots, revealing unexpected dark-bright mixing phenomena caused by heavy-hole state mixing.

Contribution

It demonstrates that magnetic-field-induced heavy-hole mixing explains the observed dark-bright transition mixing and exciton splitting behaviors in symmetric quantum dots.

Findings

Observation of dark transitions in photoluminescence spectra

Sign-changing behavior of neutral exciton splitting with magnetic field

Quantitative theory linking heavy-hole mixing to experimental results

Abstract

In photoluminescence spectra of symmetric [111] grown GaAs/AlGaAs quantum dots in longitudinal magnetic fields applied along the growth axis we observe in addition to the expected bright states also nominally dark transitions for both charged and neutral excitons. We uncover a strongly non-monotonous, sign changing field dependence of the bright neutral exciton splitting resulting from the interplay between exchange and Zeeman effects. Our theory shows quantitatively that these surprising experimental results are due to magnetic-field-induced \pm 3/2 heavy-hole mixing, an inherent property of systems with C_3v point-group symmetry.