Equal-spin Andreev reflection in ferromagnet/superconductor junctions with the interfacial Rashba spin-orbit coupling

We study the conductance spectra of ferromagnet/superconductor (F/S) junctions in the presence of the interfacial Rashba spin-orbit coupling (IRSOC). IRSOC provides the spin-flip mechanism with which the equal-spin Andreev reflection occurs. We first investigate the effect of the F spin polarization P on the conductance G and find that a zero-bias G peak forms for the highly polarized F in F/s-wave and F/dx2−y2-wave S junctions, while in F/dxy-wave S junctions with increasing P, G exhibits a conversion from a zero-bias peak to a zero-bias dip. For half-metal F (HMF)/S junctions with s-wave and dx2−y2-wave pairing by varying the magnetization direction α, G first increases and then decreases, exhibiting a maximal zero-bias peak at α = π/2, and in F/dxy-wave S junctions, G at nonzero bias exhibits a nonmonotonic behavior with α. The effect of the Fermi wave vector mismatch on G is also discussed.