Evidence for excitonic polarons in InAs/GaAs quantum dots

TL;DR

This study provides experimental evidence for excitonic polarons in InAs/GaAs quantum dots by observing anticrossings in photoluminescence excitation spectra and matching them with theoretical calculations.

Contribution

It demonstrates the existence of excitonic polarons in quantum dots through combined experimental and theoretical analysis, which was not previously confirmed.

Findings

Observation of strong anticrossings in spectra

Agreement between theory and experiment on polaron energies

Confirmation of excitonic polarons in quantum dots

Abstract

We investigate the interband transitions in several ensembles of self-assembled InAs/GaAs quantum dots by using photoluminescence excitation spectroscopy under strong magnetic field. Well defined resonances are observed in the spectra. A strong anticrossing between two transitions is observed in all samples, which cannot be accounted for by a purely excitonic model. The coupling between the mixed exciton-LO phonon states is calculated using the Fr\"{o}hlich Hamiltonian. The excitonic polaron energies as well as the oscillator strengths of the interband transitions are determined. An anticrossing is predicted when two exciton-LO phonon states have close enough energies with phonon occupations which differ by one. A good agreement is found between the calculations and the experimental data evidencing the existence of excitonic polarons.