Shot noise in topological insulator-based ferromagnet/p-wave superconductor junctions

Abstract

The differential shot noise and Fano factor in topological insulator-based ferromagnet/p-wave superconductor (TI-based FM/p-wave SC) junctions is theoretically investigated based on the Dirac-Bogoliubov-de Gennes equation. Three kinds of pairings px, py, and px+ipy-waves for SC are chosen. It is found that the shot noise spectrum strongly depends on the finite-quasi-particle lifetime, the magnetic gap m induced by an applied magnetization, the Fermi-energy mismatch between FM and SC as well as the type of the pair potential symmetry. Shortening the quasi-particles lifetime leads to the dips in the shot noise smoothed out. Increasing the magnetic gap can suppress the shot noise and Fano factor when the conventional Andreev retro-reflection is the dominant process but the shot noise can be enhanced when the dominant process is the specular Andreev reflection. Which type of reflection dominates the tunneling process with a turning point at the Fermi energy EF =m, where the values of shot noise in all energy ranges become zero. This result can be used not only to distinguish the specular Andreev reflection from the Andreev retro-reflection in thin film TI-based FM/p-wave SC structures but also to determine the energy-mass gap induced by the applied magnetization.