A first principles study on the electronic and magnetic properties of Ba$_{1-x}$K$_x$Fe$_2$As$_2$

TL;DR

This study uses first-principles calculations to analyze the electronic and magnetic properties of Ba$_{1-x}$K$_x$Fe$_2$As$_2$ superconductors, revealing how potassium doping influences magnetic instability and density of states.

Contribution

It provides a systematic first-principles analysis of K-doped BaFe$_2$As$_2$, accurately modeling magnetic moments and doping effects, improving upon previous theoretical overestimations.

Findings

Magnetic moment matches experimental values when using negative U

K doping increases density of states at Fermi level

Magnetic instability varies with doping level

Abstract

We report a systematic first-principles study on the recent discovered superconducting Ba$_{1-x}$K$_x$Fe$_2$As$_2$ systems ($x$ = 0.00, 0.25, 0.50, 0.75, and 1.00). Previous theoretical studies strongly overestimated the magnetic moment on Fe of the parent compound BaFe$_2$As$_2$. Using a negative on-site energy $U$, we obtain a magnetic moment 0.83 $\mu_B$ per Fe, which agrees well with the experimental value (0.87 $\mu_B$). K doping tends to increase the density of states at fermi level. The magnetic instability is enhanced with light doping, and is then weaken by increasing the doping level. The energetics for the different K doping sites are also discussed.