Eliashberg Analysis of the Electrodynamic Response of Ba(Fe_1−xRh_x)₂As₂ Across the s_± to s₊₊ Order Parameter Transition

We report on the Eliashberg analysis of the electrodynamic response of Ba(Fe_1−xRh_x)₂As₂ single crystals across the disorder-induced s_± to s₊₊ transition. We previously experimentally identified the transition by its signature in the low temperature value of the penetration depth and observed a peculiar dependency of the critical temperature on disorder; subsequently, we proposed new hallmarks in the quasiparticle conductivity and surface impedance. Here we show that this whole set of data can be self consistently reproduced within an effective two-bands Eliashberg model with disorder treated beyond the Born approximation and with a small set of input parameters.