Impurity bands in magnetic superconductors with spin density wave

TL;DR

This paper investigates how impurity bands form in magnetic superconductors with spin density waves, showing that superconductivity can remain fully gapped despite impurity effects, with implications for understanding coexistence of magnetism and superconductivity.

Contribution

It provides an exact T-matrix solution for a multiband disordered magnetic superconductor with coexistence of superconductivity and spin-density-wave, revealing impurity effects on the density of states.

Findings

Superconductivity remains fully gapped in a broad coexistence region.

Interband scattering induces Yu-Shiba-Rusinov bound states.

Impurity bands do not necessarily close the superconducting gap.

Abstract

Magnetic superconductors define a broad class of strongly correlated materials in which superconductivity may coexist with either localized or itinerant long-range magnetic order. In this work we consider a multiband model of a disordered magnetic superconductor which realizes coexistence of unconventional superconductivity and a spin-density-wave. We derive an exact $T$-matrix and compute a single particle density of states in this system. In a purely superconducting state the interband scattering potential leads to an appearance of the localized Yu-Shiba-Rusinov bound states. Our main finding is that in the fairly broad swath of the coexistence region superconductivity remains fully gapped despite the presence of the impurity bands. We also discuss the effects of spatial inhomogeneities on the density of states in strongly contaminated superconductors.