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HL: Halbleiterphysik

HL 36: Optical properties

HL 36.3: Vortrag

Mittwoch, 29. März 2006, 16:45–17:00, POT 151

Theory of bosonic signatures in semiconductor luminescence — •Stefan Pfalz, Daniel Hägele, and Michael Oestreich — Universität Hannover, Institut für Festkörperphysik, Abteilung Nanostrukturen, Appelstr. 2, D-30167 Hannover

Much experimental and theoretical effort has been devoted to the goal of observing Bose-Einstein Condensation (BEC) of excitons in semiconductors. While this ultimate goal is still to be reached, recent experiments showed that stimulated bosonic scattering of excitons leaves a characteristic signature in the photoluminescence of direct quantum wells [1]. Luminescence at the biexciton energy is usually unpolarized due to the opposite spin orientation within the bound exciton pair. In the presence of spin polarized excitons, however, the photoluminescence exhibits a finite degree of polarization due to stimulated scattering. This signature appears already at temperatures far above the critical value for BEC. The level of theory required to explain this effect exceeds available microscopic photoluminescence theories as inclusion of exciton correlations beyond the biexcitonic level is required. Using a one-dimensional model and exact diagonalization, we calculate photoluminescence spectra for the case of high exciton densities and find good qualitative agreement with experiments. Bosonic signatures are also found in cases where the Bose-commutation relations are not perfectly fulfilled.

[1] D. Hägele, S. Pfalz, and M. Oestreich, Solid State Commun. 134(3), 171 (2005).