Dynamic nuclear spin polarization at the fractional quantum Hall effect spin transition

Experiments suggest that nuclear spins play a significant role in the quantum Hall effect (QHE) near integer and fractional QHE spin transitions, but this behavior has yet to be understood. Here we study theoretically the dynamic nuclear polarization (DNP) in the two-dimensional electron liquid near a quantum point contact (QPC) or a domain wall between spin polarized and un-polarized phases of QHE state at a filling factor 2/3 and analyze the dependence of the transition on temperature and the magnitude of the flowing current. We demonstrate that nearly all nuclear spins in the QPC or in the domain wall can be fully polarized. The Overhauser effective magnetic field from the DNP can be strong enough to induce (or modify) a phase transition between polarized and un-polarized phases. This changes magnetic field and/or gate voltages that define the spin transitions, and leads to the reconstruction of the boundary between two phases, inducing the DNP beyond the peripheral region of the original boundary. This polarization of nuclear spins can be important for control of non-abelian excitations in hybrid semiconductor/superconductor structures.