Multiple scattering theory for superconducting heterostructures

TL;DR

This paper extends the SKKR method to solve KSBdG equations for superconducting heterostructures, enabling detailed analysis of quasiparticle spectra and Andreev bound states in layered materials.

Contribution

The authors develop a generalized SKKR approach for superconducting heterostructures, allowing for the calculation of quasiparticle spectra and Andreev states at surfaces and interfaces.

Findings

Quasiparticle spectrum includes Andreev bound states with dispersion linked to electronic structure.

The induced superconducting gap is strongly k-dependent and varies with overlayer thickness.

Certain states do not participate in Andreev scattering, affecting the spectrum.

Abstract

We generalize the screened Korringa-Kohn-Rostoker (SKKR) method for solving the corresponding Kohn-Sham-Bogoliubov-de Gennes (KSBdG) equations for surfaces and interfaces. As an application of the newly developed theory we study the quasiparticle spectrum of Au overlayers on a Nb(100) host. We find that, within the superconducting gap region, the quasiparticle spectrum consists of Andreev bound states (ABS) with a dispersion which is closely connected to the underlying electronic structure of the overlayer. We also find that the spectrum has a strongly k-dependent induced gap. The properties of the gap is discussed in relation to the thickness of the overlayer, and it is shown that certain states do not participate in the Andreev scattering process.