Virtual Andreev Reflection in Topological Insulator-Based Ferromagnet/Insulator/Superconductor

The property of quasiparticle tunneling on the surface of topological insulator (TI) ferromagnet-insulator-superconductor (FM-I-SC) junction is investigated. The virtual Andreev reflection (VAR) takes place when the wave vectors of electron and hole-like quasiparticles in FM are different due to gauge filed. We find that the VAR exhibits anisotropy in contrast to those in conventional and graphene-based junctions, because of gauge field on the surface of TI. The current in the junction can be carried by pure VAR, by tuning in-plane magnetic field. We also find that, the perfect linear slope of the conductance under varying in-plane magnetic fields is predicted, applicable for TI-based spintronic devices.