Spontaneous spin current near the interface between unconventional superconductors and ferromagnets

Abstract

We study theoretically the proximity effect between ferromagnets (F) and superconductors (S) with broken time-reversal symmetry (T). A chiral (p x±ipy)-wave and a dx2-y2-wave superconductor, the latter of which can form T-breaking surface state - i.e., (dx2-y2±is) state - are considered for the S side. The spatial variations of the superconducting order parameters and the magnetization are determined by solving the Bogoliubov - de Gennes equation. In the case of a chiral (px±ipy)-wave superconductor, a spontaneous spin current flows along the interface, but not in the case of a d x2-y2-wave superconductor. For a F/S(px±ip y)/F trilayer system, total spin current can be finite while total charge current vanishes, if the magnetizations of two F layers are antiparallel.