Spin Hall effect and spin-orbit coupling in ballistic nanojunctions

We propose an alternative scheme of spin filtering based on nanometric cross junctions in the presence of spin-orbit interaction, employing ballistic nanojunctions patterned in a two-dimensional electron gas. We demonstrate that the flow of a longitudinal unpolarized current through a ballistic X junction patterned in a two-dimensional electron gas with spin-orbit coupling (SOC) induces a spin accumulation which has opposite signs for the two lateral probes. This spin accumulation, corresponding to a transverse pure spin current flowing in the junction, is the main observable signature of the spin Hall effect in such nanostructures. We benchmark the effects of two different kinds of spin-orbit interactions. The first one (alpha-SOC) is due to the interface electric field that confines electrons to a two-dimensional layer, whereas the second one (beta-SOC) corresponds to the interaction generated by a lateral confining potential.