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HL: Fachverband Halbleiterphysik

HL 69: Poster Session: II-VI semiconductors; Organic semiconductors; Heterostructures

HL 69.21: Poster

Mittwoch, 13. März 2013, 16:00–20:00, Poster A

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

Strong light-matter coupling between excitons and photons leads to the formation of exciton-polaritons. These quasi-particles inherit exciton spin orientation as well as light polarization. Both are expressed by the pseudospin of a polariton ensemble. The effect of magnetic fields on the pseudospin was studied experimentally and theoretically. External magnetic fields of 3T were applied in three spatial orientations while the polarization was measured in photoluminescence experiments. The experimental findings cannot be explained by a simple model consisting of pseudospin precession, spin-independent scattering and decay. For the total magnetic field, an effective field arising from linear polarization splitting was considered additionally to the external one.
The planar microcavity under study consists of a λ/2 layer of ZnO with a slight wedge shape. The complete Stokes vector of the lower polariton branch was determined under non-resonant excitation. For the probed detuning, an energetic splitting of about 20meV between the TE- and TM-polarized eigenmodes is found for an emission angle of 37^∘. Unexpectedly, the emission from these modes shows even without external magnetic field a fraction of ca. 5% circular polarization with different sign for the TE and TM mode, respectively.