Rationalizing doping and electronic correlations in LaFe$_2$As$_2$

TL;DR

This study uses advanced theoretical methods to analyze the electronic correlations in LaFe$_2$As$_2$, revealing that its strong correlations are due to reduced bandwidth rather than doping level, aligning it with the broader 122 superconductor family.

Contribution

It demonstrates the importance of correlation strength over doping in understanding the phase diagram of iron-based superconductors, using slave-spin mean-field+density-functional theory.

Findings

Reproduces experimental specific heat coefficient with correlations

Identifies reduced bandwidth as key to correlations in LaFe$_2$As$_2$

Provides a unified picture of the 122 superconductor family

Abstract

We compute the electronic properties of the normal state of uncollapsed LaFe$_2$As$_2$, taking into account local dynamical correlations by means of slave-spin mean-field+density-functional theory. Assuming the same local interaction strength used to model the whole electron- and hole-doped BaFe$_2$As$_2$ family, our calculations reproduce the experimental Sommerfeld specific heat coefficient, which is twice the value predicted by uncorrelated band theory. We find that LaFe$_2$As$_2$ has a reduced bare bandwidth and this solves the apparent paradox of its sizeable correlations despite its nominal valence d$^{6.5}$, which would imply extreme overdoping and uncorrelated behaviour in BaFe$_2$As$_2$. Our results yield a consistent picture of the whole 122 family and point at the importance of the correlation strength, rather than sheer doping, in the interpretation of the phase diagram of iron-based superconductors