Role of orbital states at the interface of a triplet superconductor and a ferromagnet
In order to study the interplay between spin and orbital degrees of freedom in a Triplet Superconductor (TSC) − Ferromagnet (FM) junction we solve a lattice model of a TSC-FM heterostructure using a self-consistent Bogoliubov–de Gennes theory. We show that increasing the angle between the ferromagnetic moment and the triplet vector order parameter enhances or suppresses the p-wave gap close to the interface, according to whether the gap antinodes are parallel or perpendicular to the boundary, respectively. On the contrary, for a px or py TSC, we find that the variation of the gap controls the orientation of the FM’s moment via the change in condensation energy. As a result, the stable configuration is either parallel or perpendicular to the TSC vector order parameter, depending on the alignment of the TSC gap with respect to the interface, thus evidencing a unique form of spin-orbital coupling. The stable configuration for the chiral px+ ipy state reveals competition between the different orbital components, with a first-order transition from the perpendicular to the parallel configuration as the FM exchange field is increased.