Understanding the Unique Structural and Electronic Properties of SrFeO2

TL;DR

This study uses first-principles calculations to explore the unique structural and electronic properties of SrFeO2, highlighting the role of 3d orbital hybridization and high-spin Fe2+ in its behavior.

Contribution

It reveals the electronic origin of SrFeO2's properties, emphasizing the double occupation of 3d_{z^2} orbitals due to orbital hybridization, a novel insight.

Findings

Fe atoms in SrFeO2 are in a high-spin state with double occupation of 3d_{z^2} orbitals.

Hybridization of Fe 3d_{z^2} and 4s orbitals reduces intra-atomic exchange splitting.

The electronic structure explains the material's unique structural and electronic features.

Abstract

We report a first-principles study of SrFeO$_2$, an infinite-layer oxide with Fe atoms in a perfect square-planar coordination down to essentially 0 K. Our results reveal this striking behavior relies on the double occupation of the 3$d_{z^2}$ orbitals of high-spin Fe$^{2+}$. Such an electronic state results from the hybridization of iron's 3$d_{z^2}$ and 4$s$ orbitals, which enables a large reduction of the intra-atomic exchange splitting of the $z^2$ electrons. The generality of the phenomenon is discussed.