Dresden 2006 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 9: Poster I
HL 9.19: Poster
Montag, 27. März 2006, 15:15–17:45, P3
Optical orientation of electron spins by in-plane excitation of GaAs quantum wells — •Niels Ubbelohde1, Stefan Pfalz1, Roland Winkler1,2, Daniel Hägele1, and Michael Oestreich1 — 1Universität Hannover, Institut für Festkörperphysik, Appelstr. 2, D-30167 Hannover — 2Department of Physics, Northern Illinois University, De Kalb, IL 60115, USA
We study the optical orientation of electron spins in GaAs quantum wells using a light beam propagating parallel to the plane of the two-dimensional (2D) system. A circularly polarized laser pulse is focussed on the cleaved edge of the quantum wells thus creating spin-polarized electrons in the wells. Application of an in-plane magnetic field perpendicular to the excitation direction leads to spin precession which we observe in the emission along the growth direction of the 2D system. From the polarization- and time-resolved photoluminescence, we obtain the initial degree of electron spin polarization P0 which is studied as a function of the excitation energy. In comparison with the optical orientation for excitation in growth direction [1], we observe a qualitatively different behaviour of the energy dependence of P0. While the former geometry yields a high degree of initial spin polarization for excitation of the lowest heavy-hole exciton, we now measure P0=0. Furthermore, we find that the sign of P0 is independent of the excitation energy.
[1] S. Pfalz, R. Winkler, T. Nowitzki, D. Reuter, A. D. Wieck, D. Hägele and M. Oestreich, Phys. Rev. B 71, 165305 (2005)