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HL: Fachverband Halbleiterphysik
HL 60: Poster II: Optical Properties, incl. Photonic Crystals and Ultrafast Phenomena
HL 60.24: Poster
Donnerstag, 25. März 2010, 18:00–20:00, Poster D1
Spatially resolved spectroscopy of dense excitons in potential traps — •Rico Schwartz1, Nobuko Naka2, Dietmar Fröhlich3, Jan Brandt3, Christian Sandfort3, and Heinrich Stolz1 — 1Institut für Physik, Universität Rostock, D-18051 Rostock, Germany — 2Division of Physics and Astronomy, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan — 3Institut für Physik, Universität Dortmund, D-44221 Dortmund, Germany
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 150 ns. In the spatially resolved luminescence spectra we observe a dramatic change from a high temperature shape, where the exciton density follows the potential energy surfaces of the trap, to a low temperature shape with a sharp flank at a z-independent energy. Concomitant, the power dependence of the intensity changes from the usual square root behaviour to a linear law [1]. We discuss whether these observations point towards a condensation of excitons.
[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)