Spin-resolved Andreev reflection in ferromagnet-superconductor junctions with Zeeman splitting

Andreev reflection in ferromagnet-superconductor junctions is derived in a regime in which Zeeman splitting dominates the response of the superconduct or to an applied magnetic field. Spin-up and spin-down Andreev reflections are shown to be resolved as the voltage is increased. In the metallic limit , the transition from Andreev to quasiparticle transport in the spin-up cha nnels has a non-trivial behavior when spin polarization increases. The cond uctance is asymmetric in a voltage reversal, which can be used as a new pro be of spin polarization.