Two relaxation mechanisms observed in transport between spin-split edge states at high imbalance -: art. no. 115330

Using a quasi-Corbino geometry to directly study electron transport between spin-split edge states under high imbalance conditions, we find a pronounced hysteresis in the I-V curves originating from dynamic nuclear polarization near the sample edge. Already in the simplest case of filling factor nu=2 we observe a complicated relaxation, depending on the sign of the electrochemical potential difference. The characteristic relaxation times are about 25 s and 200 s, which points to the presence of two different relaxation mechanisms. The two time constants are ascribed to the formation of a local nuclear polarization due to flip-flop processes and the diffusion of nuclear spins.