From Quantum Hall Ferromagnetism to Huge Longitudinal Resistance at the 2/3 Fractional Quantum Hall State

Abstract

We observe the transition from a spin-unpolarized to a polarized ν=2/3 fractional quantum Hall state at low currents (<5  nA), recently described in terms of quantum Hall ferromagnetism, versus density and parallel magnetic field. At larger currents the time and current dependent huge longitudinal resistance (HLR) is always initiated at the transition. Transport in the HLR regime is linear and the amount of current-induced nuclear polarization in the HLR is comparable to the thermal nuclear polarization at ≈20  mK and 10 T. A current-induced disorder in the nuclear polarization is speculated to cause the enhanced resistance in the HLR regime.