Edge spin current and spin polarization in quantum Hall regime

We study the edge spin current and spin polarization, and their repsonses to an external electric field in a two-dimensional electron gas with a Rashba spin-orbit coupling in the quantum Hall regime. The edge state carries a large spin current, which drops sharply away from the boundary. The spin Hall current of the edge states has a resonance at a critical magnetic field, accompanied by a spin rotation in the bulk. The spin Hall current is shown to be proportional to the spin polarization, which provides an explicit way to extract the spin current in experiment.