The proximity effect in normal metal - multiband superconductor hybrid structures

TL;DR

This paper develops a theoretical framework for understanding the proximity effect in normal metal - multiband superconductor structures, revealing how multiple superconducting bands affect the density of states and supercurrent characteristics.

Contribution

It introduces a quasiclassical Green's function theory for multiband superconductor hybrid structures, highlighting the impact of interband coupling on the proximity effect and supercurrent behavior.

Findings

Multiple superconducting bands cause additional peaks in the density of states.

Interband coupling influences the superconducting gap magnitudes non-trivially.

Supercurrent calculations show differences between multiband Josephson and tunnel junctions.

Abstract

A theory of the proximity effect in normal metal - multiband superconductor hybrid structures is formulated within the quasiclassical Green's function formalism. It is shown that the existence of multiple superconducting bands manifests itself as the occurence of additional peaks in the density of states in the structure. The interplay between the proximity effect and the interband coupling influences the magnitudes of the gaps in a superconductor in a non-trivial way. The developed theory is applied to the calculation of supercurrent in multiband Superconductor - Normal metal - Superconductor Josephson junctions with low-transparent interfaces, and the results are compared with the predictions for multiband tunnel junctions.