Coherent transport and Andreev reflection in ferromagnetic semiconductor/superconductor/ferromagnetic semiconductor double tunneling junctions

We apply an extended Blonder-Tinkham-Klapwijk approach to studying the coherent spin polarized transport in an ferromagnetic semiconductor (FS)/superconductor (SC)/FS double tunneling junction, in which the Andreev reflection, mismatches in the effective mass and Fermi velocity between the FS and SC, as well as strengths of potential scattering at the interface are included. It is demonstrated that they have different effects on the oscillations of all the reflection and transmission probabilities, and differential conductances with energy, which is quite different from that in an FM/SC/FM double tunneling junction. We also reveal a direct robust measure of the spin polarization of the FS using conductance spectroscopy, being very weakly dependent on the strengths of potential scattering and energy.