Dark-bright magneto-exciton mixing induced by Coulomb interaction in strained quantum wells

TL;DR

This paper reports the observation of coupled magneto-exciton states in strained quantum wells, showing Coulomb interaction-induced mixing between bright and dark states, with detailed experimental and theoretical analysis of the phenomena.

Contribution

It demonstrates Coulomb interaction as the key mechanism for dark-bright exciton mixing in strained quantum wells, supported by both experiments and theory.

Findings

Large energy splittings (~10 meV) in mixed states

Anticrossing behavior independent of polarization

Coulomb interaction, not valence band complexity, causes splittings

Abstract

Coupled magneto-exciton states between allowed (`bright') and forbidden (`dark') transitions are found in absorption spectra of strained In$_{0.2}$Ga$_{0.8}$As/GaAs quantum wells with increasing magnetic field up to 30 T. We found large (~ 10 meV) energy splittings in the mixed states. The observed anticrossing behavior is independent of polarization, and sensitive only to the parity of the quantum confined states. Detailed experimental and theoretical investigations indicate that the excitonic Coulomb interaction rather than valence band complexity is responsible for the splittings. In addition, we determine the spin composition of the mixed states.