Dresden 2006 – scientific programme
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HL: Halbleiterphysik
HL 24: Ultra fast phenomena
HL 24.7: Talk
Tuesday, March 28, 2006, 16:45–17:00, POT 151
Ultrafast Dynamics at the Quantum Hall Ferromagnet — •Bertram Su1, Detlef Heitmann1, Werner Wegscheider2, and Christian Schüller2 — 1Institut für Angewandte Physik und Zentrum für Mikrostrukturforschung, Universität Hamburg — 2Institut für Experimentelle und Angewandte Physik, Universität Regensburg
We report ultrafast spectroscopy experiments at the v = 1 quantum Hall state of a high-mobility two-dimensional electron system (2DES) in a GaAs single quantum well. Via a semitransparent metallic gate, the density of the 2DES can be tuned in a broad range. By spectrally-resolved four-wave-mixing (SR-FWM) experiments we have investigated the coherent dynamics of photo-excited electron-hole pairs. We observe a strong maximum of the SR-FWM signal around v = 1 in the right-circularly polarized spectra, i.e., if we selectively excite into the empty upper spin level. In this situation, the dephasing time T2 is as long as 14 ps. At v < 1 and v > 1, the dephasing time decreases dramatically, where the decreasing is faster for v < 1. We assume that around v = 1 the formation dynamics of spin textures is dominating the ultrafast dynamics.