Berlin 2008 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 51: Poster IV
HL 51.14: Poster
Thursday, February 28, 2008, 16:30–19:00, Poster D
Kinetics of high density excitons in a potential trap — •Rico Schwartz1, Nobuko Naka2, Dietmar Fröhlich3, Jan Brandt3, Christian Sandfort3, and Heinrich Stolz1 — 1Institut für Physik, Universität Rostock, D-18051 Rostock, Germany — 2Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan — 3Institut für Physik, Universität Dortmund, D-44221 Dortmund, Germany
At sufficiently high densities and low temperatures excitons are expected to form a BEC. In the past, there have been several claims of observation of excitonic BEC, which, however, could not stand against critical tests. In order to exclude any coherent stimulation by the excitation laser it is necessary to separate the excitation from the detection spatially and spectrally. This criterion is ideally fulfilled by a trap. We report experiments on excitons in Cu2O confined in a stress-induced trap [1, 2]. The paraexcitons were created by resonant excitation of orthoexcitons followed by ortho-para conversion [3]. The pulsed excitation laser has a linewidth of 1 GHz, a repetition rate of 1 kHz and a pulse length of about 100 ns. The paraexciton density was deduced via the phonon assisted Γ5+ sideband similar to [3]. In the experiments the sample temperature and the excitation power were varied, and the temporal evolution of the exciton population was determined.
[1] D. P. Trauernicht, J. P. Wolfe, and A. Mysyrowicz, Phys. Rev. B 34, 2561 (1986). [2] N. Naka and N. Nagasawa, Phys. Rev. B 65, 075209 (2002). [3] J. I. Jang, K. E. O’Hara, and J. P. Wolfe, Phys. Rev. B 70, 195205 (2004)