Berlin 2008 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 51: Poster IV

HL 51.26: Poster

Donnerstag, 28. Februar 2008, 16:30–19:00, Poster D

Long-lived hole spin dynamics in a 2D system at sub-Kelvin temperatures — •Anton Wagner, Tobias Korn, Robert Schulz, Andreas Maurer, Michael Hirmer, Dieter Schuh, Werner Wegscheider, and Christian Schüller — Institut für Experimentelle und Angewandte Physik, Universität Regensburg, Germany

The spin dynamics of holes in semiconductors have, so far, been less intensely studied than the electron spin dynamics. We performed time-resolved Faraday rotation (TRFR) measurements on a 2D hole system within a 15nm wide, modulation-doped GaAs/AlGaAs quantum well grown on a [001] substrate. In the TRFR measurements, the sample is excited by a circularly-polarized laser pulse tuned to the exciton energy. An in-plane magnetic field up to 10 T is applied, causing a precession of the photocreated carriers. At 4.5 K temperature only the fast electron spin precession is observed, whereas a second, long period precession, superimposed on the electron spin precession, appears and gets more intense as the temperature is lowered from 1.2 K to 0.4 K. We identify this signal as the hole spin precession, which has a low frequency due to the small g-factor of holes along the [001] direction. The hole g-factor is highly anisotropic, which we measured by varying the angle of incidence of the pump beam relative to the sample plane. The appearance of the long-lived hole spin precession only at very low temperatures indicates that the hole spin lifetime is increased by localization. Surprisingly, while the hole spin lifetime increases drastically at lower temperatures, the electron spin lifetime is reduced. We acknowledge financial support by the DFG via SFB 689 and SPP 1285.