Tunable THz surface plasmon polariton based on a topological insulator/layered superconductor hybrid structure

Abstract

We theoretically investigate the surface plasmon polariton (SPP) at the interface between a three-dimensional strong topological insulator (TI) and a layered superconductor/magnetic insulator structure, within the random phase approximation. The tunability of the SPP through electronic doping can be enhanced when the magnetic permeability of the layered structure becomes higher. When the interface is gapped by superconductivity or perpendicular magnetism, the SPP dispersion is further distorted, accompanied by a shift of group velocity and penetration depth. Such a shift of the SPP reaches a maximum when the magnitude of the Fermi level approaches the gap value, and may lead to observable effects. The tunable SPP at the interface between layered-superconductor and magnetic materials in proximity to the TI surface may provide new insight in the detection of Majorana fermions.