Non-rigid band shift and non-monotonic electronic structure changes upon doping in the normal state of the pnictide high temperature superconductor Ba2(Fe1-xCox)2As2

TL;DR

This study uses ARPES to show that doping in Ba(Fe1-xCox)2As2 causes complex, non-monotonic changes in electronic structure that cannot be explained by a simple rigid band model, highlighting the importance of electronic correlations.

Contribution

It demonstrates that doping effects in pnictide superconductors are more complex than previously thought, emphasizing the role of electronic correlations over impurity scattering.

Findings

Doping causes non-monotonic changes in band filling and bandwidth.

Rigid band model fails to describe doping evolution in Ba122.

Electronic correlations dominate doping effects.

Abstract

We report systematic Angle Resolved Photoemission (ARPES) experiments using different photon polarizations and experimental geometries and find that the doping evolution of the normal state of Ba(Fe1-xCox)2As2 deviates significantly from the predictions of a rigid band model. The data reveal a non-monotonic dependence upon doping of key quantities such as band filling, bandwidth of the electron pocket, and quasiparticle coherence. Our analysis suggests that the observed phenomenology and the inapplicability of the rigid band model in Co-doped Ba122 are due to electronic correlations, and not to either the size of the impurity potential, or self-energy effects due to impurity scattering. Our findings indicate that the effects of doping in pnictides are much more complicated than currently believed. More generally, they indicate that a deep understanding of the evolution of the electronic properties of the normal state, which requires an understanding of the doping process, remains elusive even for the 122 iron-pnictides, which are viewed as the least correlated of the high-TC unconventional superconductors.