Berlin 2012 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 25: Poster Session: GaN - Optical Properties & Preparation and Characterization & Devices

HL 25.3: Poster

Montag, 26. März 2012, 16:00–19:00, Poster D

Spectral signatures of excitonic BEC in Cu₂O — •Rico Schwartz¹, Siegfried Sobkowiak¹, Dirk Semkat¹, Thomas Koch², Holger Fehske², and Heinrich Stolz¹ — ¹Institut für Physik, Universität Rostock, D-18051 Rostock, Germany — ²Institut für Physik, Ernst-Moritz-Arndt-Universität Greifswald, D-17489 Greifswald, Germany

When looking for an excitonic BEC one of the most important points to be clarified is the kind of spectral signatures of such a BEC. We present recent theoretical investigations for a weakly luminescing BEC of trapped excitons in Cu₂O. For exciton numbers below the critical density the spectrally resolved integrated intensity behaves Bose-like with a linear dependence on the exciton number. Above the critical number the spectrum consists of a Bose-like distribution (luminescence from thermalized excitons outside the condensate), two gaussian peaks with energetic position symmetrically around the chemical potential (contribution of the Bogoliubov quasiparticles in the condensate), and a third gaussian peak at the chemical potential (the weakly luminecing condensate). The dependence of the total integrated intensity shows a kink at the critical exciton number and has a different slope below and above this point. This results from the different luminescence efficiencies of excitons in a condensate and in thermal states. We also present recent experiments which confirm the theoretical predictions.