# Electrodynamic response of Ba(Fe1-xRhx)2As2 across the s+- to s++ order parameter transition

## TL;DR

This study investigates the electrodynamic response of Ba(Fe1-xRhx)2As2 superconductors to identify signatures of the transition from s+- to s++ order parameter symmetry induced by disorder, revealing peculiar surface resistance and conductivity behaviors.

## Contribution

It provides the first analysis of electrodynamic properties across the s+- to s++ transition in iron-based superconductors, highlighting observable signatures of the order parameter change.

## Key findings

- Surface resistance shows anomalies at the transition.
- Normal conductivity exhibits distinctive behavior near the transition.
- Electrodynamic response traces the order parameter transition.

## Abstract

Most iron-based superconductors are characterized by the s+- symmetry of their order parameter, and are expected to go through a transition to the s++ state if enough disorder is introduced. We previously reported the observation of this transition in Ba(Fe1-xRhx)2As2 through a study of the disorder dependence of the critical temperature and low-temperature London penetration depth. In this paper we report on the analysis of the electrodynamic response of the same sample across the transition and we identify peculiarities in the behaviour of the surface resistance and normal conductivity, that can be considered as traces of the transition itself.