Charge doping versus impurity scattering in chemically substituted iron-pnictides

TL;DR

This study systematically investigates the effects of charge doping and impurity scattering in chemically substituted 122 iron pnictides using first principles calculations, revealing how different substitutions influence electronic structure and pairing interactions.

Contribution

It provides a detailed first principles analysis of how various substitutions affect charge doping, impurity scattering, and pairing in iron pnictides, highlighting deviations from rigid band behavior.

Findings

Transition metal substitutions introduce mobile charge carriers.

Impurity scattering causes spectral broadening depending on band character.

Intraband scattering dominates over interband scattering, supporting an $s^{+-}$ pairing state.

Abstract

To reveal the relative importance of charge doping and defect scattering in substitutionally modified 122 iron pnictides, we perform a systematic first principles study on selected bands at the Fermi level. Disorder effects are induced by various substitutions using an orbital based coherent potential approximation (CPA). Pronounced level shifts of individual bands suggest that transition metal substitutions introduce mobile charge carriers into the system. However, important deviations from such a rigid band scenario as well as spectral broadenings due to impurity scattering correlate with the band character. Finally a $T$-matrix analysis exhibits a larger intraband than interband scattering consistent with an $s^{+-}$ pairing state. Comparing different substitutions reveals an increase of pair-breaking along the transition metal series.