Experimental evidence for the importance of Hund's exchange interaction for the incoherence of the charge carriers in iron-based superconductors

TL;DR

This study uses ARPES to show that Hund's exchange interaction significantly influences charge carrier incoherence in iron-based superconductors, with larger scattering rates in hole-doped systems indicating strong correlation effects.

Contribution

It provides experimental evidence highlighting the role of Hund's exchange in charge carrier incoherence, supported by theoretical calculations.

Findings

Higher scattering rates in hole-doped compounds compared to electron-doped ones.

Inner hole pocket exhibits spectral weight heavily incoherent.

Experimental results align qualitatively with density functional dynamical mean-field theory.

Abstract

Angle-resolved photoemission spectroscopy (ARPES) is used to study the scattering rates of charge carriers from the hole pockets near Gamma in the iron-based high-Tc hole doped superconductors KxBa1-xFe2As2 x=0.4 and KxEu1-xFe2As2 x=0.55$ and the electron doped compound Ba(Fe1-xCox)2As2 x=0.075. The scattering rate for any given band is found to depend linearly on energy, indicating a non-Fermi liquid regime. The scattering rates in the hole-doped compound are considerably larger than those in the electron-doped compounds. In the hole-doped systems the scattering rate of the charge carriers of the inner hole pocket is about three times bigger than the binding energy indicating that the spectral weight is heavily incoherent. The strength of the scattering rates and the difference between electron and hole doped compounds signals the importance of Hund's exchange coupling for correlation effects in these iron-based high-Tc superconductors. The experimental results are in qualitative agreement with theoretical calculations in the framework of combined density functional dynamical mean-field theory.