Spin-Triplet Andreev Reflection in Ferromagnet/Ferromangnet/s-Wave Superconductor Junctions

Four-component Bogoliubov--de Gennes equations are applied to study the tunnelling conductance spectra G(E) of half-metallic ferromagnet/ferromagnet/s-wave superconductor tunnel junctions. It is found that only for noncollinear magnetizations, there exists nonzero G(E) structure
within the energy gap, which is a signature of appearance of the novel Andreev reflection and spin-triplet pairing correlations.