Berlin 2012 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 54: Optical Properties
HL 54.1: Talk
Wednesday, March 28, 2012, 11:00–11:15, EW 203
Exciton-polariton condensates in a ZnO-based microcavity — Helena Franke1, Chris Sturm1, •Rüdiger Schmidt-Grund1, Tom Michalsky1, Gerald Wagner2, and Marius Grundmann1 — 1Universität Leipzig, Institut für Experimentelle Physik II, Linnéstr. 5, 04103 Leipzig — 2Universität Leipzig, Institut für Mineralogie, Kristallographie und Materialwissenschaft, Josephinenstr. 7, 04317 Leipzig
We report on the observation of macroscopically coherent states of exciton-polaritons in a ZnO-based bulk planar microcavity (MC) up to 250 K. The threshold behaviour of the photoluminescence intensity as a function of the laser excitation power together with the corresponding spectral narrowing of the emission reveals clear signatures of a Bose-Einstein condensate for negative detunings. For positive detunings however, no condensation occurred but the emission from an electron-hole plasma was detected. At low temperatures and very negative detuning, we find ballistic propagation of the condensate polaritons in the pump-induced potential landscape, which makes these ZnO-based MC promising candidates for application based on polariton transport. The determined propagation length amounts to several µm, similar to values which can be estimated from data on GaAs-based wire-MC [1]. Our effect is caused by strong repulsive interactions of excitons in our system, leading to an immense blueshift of the condensate emission up to 30 meV and hence to pronounced dynamic effects. Due to photonic disorder in our samples the condensate reveals signatures of Bose-glass like states at certain detuning/temperature values.
[1] E. Wertz et al., Nature Phys. 6, 860 (2010).