Study of spin dynamics in quantum hall regime by time resolved Kerr rotation spectroscopy

Time-resolved Kerr rotation (TRKR) spectroscopy has been applied to a two-dimensional (2D) electron gas in GaAs/AlGaAs hetero-junction to probe the electron and nuclear spin dynamics in quantum Hall regime. A large and long-lasting Kerr rotation signal was ascribed to the high-mobility 2D-electron gas, since the Kerr signal from etched high purity GaAs substrate was much smaller and shorter. In a configuration where an out-of-plane magnetic field quantizes 2D-electrons into Landau levels, the spin coherence time, T-2* exhibits a drastic increase. Furthermore, both T2* and effective g factor exhibit an oscillation behavior as a function of the magnetic field. Under a circularly polarized pump, we observed an Overhauser shift up to 40 mu eV, which corresponds to 30 % dynamic nuclear polarization (DNP).