Microwave response of superconducting pnictides: extended $s_{\pm}$ scenario

TL;DR

This paper models the microwave response and NMR relaxation in ferropnictides using a two-band superconductor with a $$ phase difference, analyzing impurity effects on low-temperature behaviors.

Contribution

It introduces a detailed model for ferropnictides considering impurity scattering effects beyond standard limits, predicting diverse low-temperature power law behaviors.

Findings

Impurity scattering significantly affects low-temperature properties.

Various power law dependencies emerge based on scattering rates.

The model explains experimental observations in ferropnictides.

Abstract

We consider a two-band superconductor with relative phase $\pi $ between the two order parameters as a model for the superconducting state in ferropnictides. Within this model we calculate the microwave response and the NMR relaxation rate. The influence of intra- and interband impurity scattering beyond the Born and unitary limits is taken into account. We show that, depending on the scattering rate, various types of power law temperature dependencies of the magnetic field penetration depth and the NMR relaxation rate at low temperatures may take place.