Interorbital pair scattering in clean and impure superconductors

TL;DR

This paper investigates how inter-orbital pair scattering affects the properties of two-band superconductors, especially in the presence of impurities and Van Hove singularities, revealing significant differences from single-band systems.

Contribution

It provides a detailed analysis of inter-orbital scattering effects and impurity impacts on two-band superconductors, including local property mappings and the role of Van Hove singularities.

Findings

Inter-orbital scattering significantly alters superconductor properties.

Impurities suppress the order parameter differently depending on scattering type.

Van Hove singularity increases transition temperature in weak coupling.

Abstract

The calculations of the local and global properties of two band superconductors have been presented with particular attention to the role of the inter-orbital scattering of pairs. The properties of such superconductors are very different from a single band or typical two band systems with dominant intra-band pairing interactions. The role of Van Hove singularity in one of the bands on the properties of intra-band clean superconductor has been discussed. It leads to marked increase of superconducting transition temperature in the weak coupling limit. We study the inhomogeneous systems in which the characteristics change from place to place by solving the Bogolubov-de Gennes equations for small clusters. The suppression of the superconducting order parameter by the single impurity scattering the fermions between bands is contrasted with that due to intra-band impurity scattering. The results obtained for impure systems have been shown as a maps of local density of states, the order parameter and gap function. They can be directly compared with STM spectra of the real material.