# Comprehensive Eliashberg analysis of microwave conductivity and penetration depth of K-, Co-, and P-substituted BaFe2As2

## TL;DR

This study combines experimental measurements and Eliashberg theoretical modeling to analyze microwave conductivity and penetration depth in various doped BaFe2As2 superconductors, revealing insights into their superconducting properties.

## Contribution

It provides a comprehensive Eliashberg analysis of microwave response in doped BaFe2As2, linking experimental data with a three-band $s_{}$-wave model to understand superconducting behavior.

## Key findings

- Validated the three-band $s_{}$-wave Eliashberg model against experimental data
- Identified the role of Fe-As planes in superconductivity
- Discussed the presence of nodes and coherence effects in the order parameter

## Abstract

We report on the combined experimental and theoretical analysis of the microwave-frequency electromagnetic response of BaFe2As2 single crystals with different substitutions: K in the Ba site (hole doping), Co in the Fe site (electron doping), and P in the As site (isovalent substitution). Measurements using a coplanar resonator technique lead to the experimental determination of the penetration depth and microwave conductivity as a function of temperature. The whole set of data is analyzed within a self-consistent three-band $s_{\pm}$-wave Eliashberg approach, able to account for all the main observed features in the different properties. Besides the validation of the model itself, the comparison between experiment and theory allows discussing the possible role of the Fe-As planes in defining the superconducting properties of these compounds, the relevance of coherence effects, and the presence of nodes in the superconducting order parameter.