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HL: Fachverband Halbleiterphysik

HL 71: Exciton polaritons and their condensates (HL, jointly with TT)

HL 71.7: Vortrag

Donnerstag, 14. März 2013, 11:15–11:30, H2

Exciton-polariton pseudospin polarization in a planar microcavity — •Steffen Richter, Chris Sturm, Helena Franke, Rüdiger Schmidt-Grund, and Marius Grundmann — Universität Leipzig, Institut für Experimentelle Physik II, Linnéstr. 5, 04103 Leipzig, Germany

Exciton-polaritons are composite quasi-particles which arise from strong coupling between excitons and photons. An interesting feature is their pseudospin. It expresses at the same time the average exciton spin orientation and the photonic light polarization of a polariton ensemble.
A planar ZnO-based microcavity of thickness λ/2 was investigated by angle-resolved photoluminescence experiments. A slight wedge shape of the cavity allows probing of different detunings. The Stokes vector of the emission from the lower polariton branch was determined under non-resonant excitation. The energetic splitting between the TE- and TM-polarized eigenmodes is found to increase with in-plane wavevector k_|| until the polariton becomes mostly exciton-like. It reaches about 20meV at most. Contrary to expectations, a circular polarization degree of up to 5% is found in the emission from these supposedly linear modes. The extent of this circular polarization reveals the same k_||-dependence as the TE-TM splitting.
The pseudospin model and the impact of related effective magnetic fields are discussed in order to explain the observed polarization behavior. Influences by different detunings, crystal quality and local anisotropic effects are considered.