8 February 2015 Exciton-polariton Bose-Einstein condensation with a polymer at room temperature
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We create exciton-polariton quasi-particles by exciting optically a microcavity filled with a ladder-type conjugated polymer in the strong coupling regime. At room temperature thermalization of these quasi-particles occurs while it is suppressed at low temperature due to a relaxation bottleneck. Above a certain excitation threshold with incoherent offresonant picosecond laser pulses, we observe the emergence of non-equilibrium Bose-Einstein condensation in the lower polariton branch. This is evidenced by several distinct features such as a blue-shifted emission peak at zero in-plane momentum, accompanied by a nonlinear increase in the emission intensity and a sudden drop of the line width. In contrast to conventional lasing, we find a strong increase in threshold when decreasing the temperature, which can be explained by the peculiar thermalization properties. Single-shot measurements of the emission spectrum allow studying single realizations of the condensate, giving access to non-averaged properties from each individual condensation process. Our approach demonstrates a radically simplified route to investigate Bose-Einstein condensation physics at ambient conditions with easy-to-process non-crystalline materials.
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Thilo Stöferle, Johannes D. Plumhof, Lijian Mai, Ullrich Scherf, Rainer F. Mahrt, "Exciton-polariton Bose-Einstein condensation with a polymer at room temperature", Proc. SPIE 9370, Quantum Sensing and Nanophotonic Devices XII, 93702T (8 February 2015); doi: 10.1117/12.2083831; https://doi.org/10.1117/12.2083831

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