Deviating band symmetries and many-body interactions in a model hole doped iron pnictide superconductor

TL;DR

This study uses polarization-resolved ARPES to investigate the low energy band structure of an optimally doped iron pnictide superconductor, revealing deviations from theoretical predictions due to many-body interactions.

Contribution

It identifies and characterizes deviations in band symmetries from LDA calculations caused by many-body effects in a hole-doped iron pnictide superconductor.

Findings

Discovered inconsistency with LDA-predicted symmetries along high symmetry axes.

Revealed strong rotational anisotropy in electron kinetics.

Discussed the impact of many-body interactions on superconducting pairing.

Abstract

We present a polarization resolved study of the low energy band structure in the optimally doped iron pnictide superconductor Ba$_{0.6}$K$_{0.4}$Fe$_2$As$_2$ (T$_c$=37K) using angle resolved photoemission spectroscopy. Polarization-contrasted measurements are used to identify and trace all three low energy hole-like bands predicted by local density approximation (LDA) calculations. The photoemitted electrons reveal an inconsistency with LDA-predicted symmetries along the $\Gamma$-X high symmetry momentum axis, due to unexpectedly strong rotational anisotropy in electron kinetics. We evaluate many-body effects such as Mott-Hubbard interactions that are likely to underlie the anomaly, and discuss how the observed deviations from LDA band structure affect the energetics of iron pnictide Cooper pairing in the hole doped regime.