Ballistic spin transport in the presence of interfaces with strong spin-orbit coupling

The inversion symmetry breaking at the interface between different materials generates a strong interfacial spin-orbit coupling (ISOC) that may influence the spin and charge transport in hybrid structures. Here we use a simple analytically solvable model to study in the ballistic approximation various spin transport phenomena induced by ISOC in a bilayer metallic system. In this model a nonequilibrium steady state carrying a spin current is created by applying a spin-dependent bias across the metallic junction. Physical observables are then calculated using the scattering matrix approach. In particular we calculate the absorption of the spin current at the interface (the interface spin loss) and study the interface spin-to-charge conversion. The latter consists of an in-plane interface charge current generated by the spin-dependent bias applied to the junction, which can be viewed as a spin-galvanic effect mediated by ISOC. Finally, we demonstrate that ISOC leads to an interfacial spin-current swapping; that is, the ``primary'' spin current flowing through the spin-orbit active interface is necessarily accompanied by a ``secondary'' swapped spin current flowing along the interface and polarized in the direction perpendicular to that of the primary current. Using the exact spin continuity equation, we relate the swapping effect to the interfacial spin loss and argue that this effect is generic and independent of the ballistic approximation used for specific calculations.