Dresden 2006 – scientific programme

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HL: Halbleiterphysik

HL 41: Heterostructures

HL 41.7: Talk

Thursday, March 30, 2006, 12:30–12:45, BEY 154

Statistics of microcavity polaritons under non-resonant excitation — •Paolo Schwendimann and Antonio Quattropani — Institute of Theoretical Physics, Ecole Polytechnique Fédérale, CH 1015 Lausanne-EPFL

In this contribution we present a model describing polariton amplification and coherence observed in non-resonantly excited polariton systems. We consider a quantum well embedded in a microcavity, excited by a continuous laser field at energy near the conduction band edge. The laser intensity is such that the exciton density in the microcavity remains much smaller than the exciton saturation density. The emission characteristics of this system are described in terms of interacting microcavity exciton-polaritons, which are admixtures of excitons and photons. As it is well known, the pump polariton state decays along the exciton-polariton dispersion curve, until the dispersion flattens. In this energy region a bottleneck effect is observed. We exploit this result by assuming that the polariton modes in the bottleneck may be considered as a thermal reservoir. Since emission is observed into the lowest energy state of the system at k = 0, we derive a master equation describing the evolution of this mode under the influence of the bottleneck reservoir. We show that this mode exhibits a threshold depending on the material parameters and on the injected exciton density. In particular we show that above threshold the statistics of the polaritons approaches that of a laser. As an example, we present the statistics for polaritons obtained in GaAs and CdTe microcavities.