Electronic Structure of Novel Superconductor Ca4Al2O6Fe2As2

TL;DR

This study investigates the electronic structure of the novel superconductor Ca4Al2O6Fe2As2 using first-principles calculations, revealing unique Fermi surface topology and increased electron correlation compared to LaFeAsO.

Contribution

It provides the first detailed electronic structure analysis of Ca4Al2O6Fe2As2, highlighting differences in Fermi surfaces and electron correlation effects.

Findings

Missing hole-like Fermi surface around Gamma point.

Increased localization of xy orbital with decreasing As-Fe-As angle.

Ca4Al2O6Fe2As2 is more correlated than LaFeAsO.

Abstract

We have performed the first-principles electronic structure calculation for the novel superconductor Ca4Al2O6Fe2As2 which has the smallest a lattice parameter and the largest As height from the Fe plane among the Fe-As superconductors. We find that one of the hole-like Fermi surfaces is missing around the Gamma point compared to the case of LaFeAsO. Analysis using the maximally-localized-Wannier-function technique indicates that the xy orbital becomes more localized as the As-Fe-As angle decreases. This induces rearrangement of bands, which results in the change of the Fermi-surface topology of Ca4Al2O6Fe2As2 from that of LaFeAsO. The strength of electron correlation is also evaluated using the constraint RPA method, and it turns out that Ca4Al2O6Fe2As2 is more correlated than LaFeAsO.