Evidence for excitonic polarons in InAs/GaAs quantum dots

Vanessa Preisler (1) , Thomas Grange (1) , Robson Ferreira (1) , Louis-Anne de Vaulchier (1) , Yves Guldner (1) , Fransisco José Teran (2) , Marek Potemski (2) , Aristide Lemaître (3)

1 LPA - Laboratoire Pierre Aigrain
2 LCMI-GHMFL - Laboratoire des champs magnétiques intenses
3 LPN - Laboratoire de photonique et de nanostructures

We investigate the interband transitions in several ensembles of self-assembled InAs/GaAs quantum dots by using photoluminescence excitation spectroscopy under strong magnetic fields up to 28 telsa. Well defined resonances are observed in the spectra. The magnetic field dependence of the resonance energies allows an unambiguous assignment of the interband transitions which involve both discrete states of the quantum dots and wetting layer states. 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 Fröhlich 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.

Mots clés: quantum dots polarons

Domaines: Autre [cond-mat.other]

Vanessa Preisler, Thomas Grange, Robson Ferreira, Louis-Anne de Vaulchier, Yves Guldner, et al.. Evidence for excitonic polarons in InAs/GaAs quantum dots. Physical Review B: Condensed Matter and Materials Physics (1998-2015), 2006, 73, pp.075320. ⟨hal-00018092⟩