Spin-polarized Andreev reflection tunneling through a precessing magnetic spin

We study theoretically the spin-polarized Andreev reflection tunneling through a local precessing magnetic spin weakly coupled to a ferromagnet and to a superconductor. The linear Andreev reflection conductance is obtained at zero temperature by using a nonequilibrium Green function approach. It shows that the spin-exchange interaction on the local spin-site can result in two spin-coherent states, from which the Andreev reflection conductance resonance with either a double peak or a single peak is developed. We find that the spin-orbit interaction in the barrier between the local spin-site and the ferromagnet-electrode leads only to a conductance oscillation with base frequency twice the Larmor frequency, 2 omega(L), and a variable amplitude with equilibrium chemical potential and spin-flip tunneling coupling.