Conductance properties of topological insulator based ferromagnetic insulator/d-wave superconductor and normal metal/ferromagnetic insulator/d-wave superconductor junctions

We study theoretically the conductance properties of a ferromagnetic insulator/d-wave superconductor (FI/d-wave SC) junction and a normal metal/ferromagnetic insulator/d-wave superconductor (NM/FI/d-wave SC) junction formed on the surface of a three dimensional topological insulator, where the direction of the magnetization m in ferromagnetic region is perpendicular to the surface. We find that with increasing the magnetization of the ferromagnetic region, a conductance peak to conductance dip conversion occurs, at a bias voltage depending on the d-wave superconducting orientation angular. We find also that the gate voltage applied across the ferromagnetic region strongly affects the influence of the magnetization on the zero bias conductance of the NM/FI/d-wave SC junction.