Multigap superconductivity and interaction driven resonances in superconducting nanofilms with an inner potential barrier

Abstract

We study the crossover in a zero temperature superconducting nanofilm from a single to a double superconducting slab induced by a tunable insulating potential barrier in the middle. The single phase superconducting ground state of this heterostructure is shown to be intrinsically multigapped and to have a new type of resonance caused by the strength of the barrier, thus distinct from the Thompson-Blatt shape resonance which is caused by tuning the thickness of the film. Single particle electronic states are strongly or weakly affected according to their parity (even or odd) with respect to the insulating barrier. The lift of the parity degeneracy at finite barrier strength reconfigures the pairing interaction and leads to a multigapped superconducting state with interaction driven resonances.