Normal state resistivity of Ba$_{1-x}$K$_x$Fe$_2$As$_2$: evidence for multiband strong-coupling behavior

TL;DR

This paper combines theoretical Eliashberg analysis with experimental data to reveal multiband strong-coupling effects in the normal state resistivity of Ba$_{1-x}$K$_x$Fe$_2$As$_2$, showing deviations from classical models.

Contribution

It provides the first detailed theoretical explanation of resistivity saturation in high-purity Ba$_{1-x}$K$_x$Fe$_2$As$_2$ based on a multiband strong-coupling framework.

Findings

Resistivity saturates at high temperatures in experiments.

Strong coupling in one band and weak coupling with impurity scattering in another explains the behavior.

Theoretical results align with experimental resistivity data.

Abstract

We present theoretical analysis of the normal state resistivity in multiband superconductors in the framework of Eliashberg theory. The results are compared with measurements of the temperature dependence of normal state resistivity of high-purity Ba$_{0.68}$K$_{0.32}$Fe$_{2}$As$_{2}$ single crystals with the highest reported transition temperature $T_c$ = 38.5 K. The experimental data demonstrate strong deviations from the Bloch-Gr\"{u}neisen behavior, namely the tendency to saturation of the resistivity at high temperatures. The observed behavior of the resistivity is explained within the two band scenario when the first band is strongly coupled and relatively clean, while the second band is weakly coupled and is characterized by much stronger impurity scattering.