Magnetic impurity resonance states and symmetry of the superconducting order parameter in iron-based superconductors

TL;DR

This study explores how magnetic impurities affect quasiparticle states in iron-based superconductors, revealing that impurity-induced bound states can identify the superconducting gap symmetry and nodal structure.

Contribution

It introduces a two-orbital model to analyze impurity effects, demonstrating how bound states vary with different gap symmetries, aiding in identifying the superconducting order parameter.

Findings

Bound states differ qualitatively for each gap symmetry

Impurity states can distinguish nodal structures in superconductors

The model helps identify the extended s-wave ($S^{\pm}$) symmetry

Abstract

We investigate the effect of magnetic impurities on the local quasiparticle density of states (LDOS) in iron-based superconductors. Employing the two-orbital model where 3$d$ electron and hole conduction bands are hybridizing with the localized $f$-orbital of the impurity spin, we investigate how various symmetries of the superconducting gap and its nodal structure influence the quasiparticle excitations and impurity bound states. We show that the bound states behave qualitatively different for each symmetry. Most importantly we find that the impurity-induced bound states can be used to identify the nodal structure of the extended s-wave symmetry ($S^{\pm}$) that is actively discussed in ferropnictides.