Dephasing effects on coherent exciton-polaritons and the breakdown of the strong coupling regime

Naotomo Takemura (1) , Mitchell D. Anderson (1) , Stephane Trebaol (2) , Souvik Biswas (1) , Daniel Oberli (1) , Marcia T. Portella-Oberli (1) , Benoit Deveaud (1)

1 LOEQ - Laboratory of Quantum Optoelectronics
2 FOTON - Fonctions Optiques pour les Technologies de l'informatiON

Using femtosecond pump-probe spectroscopy, we identify excitation-induced dephasing as a major mechanism responsible for the breakdown of the strong coupling between excitons and photons in a semiconductor microcavity. The effects of dephasing are observed on the transmitted probe-pulse spectrum as a density-dependent broadening of the exciton-polariton resonances and the emergence of a third resonance at high excitation density. A striking asymmetry in the energy shift between the upper and the lower polaritons is also evidenced. Using the excitonic Bloch equations, we quantify the respective contributions to the energy shift of many-body effects associated with Coulomb fermion exchange and photon assisted exchange processes and the contribution to collisional broadening.

Mots clés: femtosecond pump-probe spectroscopy

Mots clés: Polaritons en microcavité semi-conductrice

Domaines: Gaz Quantiques [cond-mat.quant-gas]; Optique [physics.optics]

Naotomo Takemura, Mitchell D. Anderson, Stephane Trebaol, Souvik Biswas, Daniel Oberli, et al.. Dephasing effects on coherent exciton-polaritons and the breakdown of the strong coupling regime. Physical Review B: Condensed Matter and Materials Physics (1998-2015), 2015, 92 (23), pp.235305. ⟨10.1103/PhysRevB.92.235305⟩. ⟨hal-01254979⟩