Correlation Effects on Antiferromagnetism in Fe Pnictides

TL;DR

This study uses a variational Monte Carlo approach on a two-orbital model to show that correlation effects are crucial for accurately describing antiferromagnetism in Fe pnictides, aligning with experimental data.

Contribution

It demonstrates that correlation effects significantly influence antiferromagnetic order, providing a more accurate description than previous mean-field approaches.

Findings

Small ordered moment consistent with experiments

Correlation effects are quantitatively important

Hartree-Fock overestimates ordered moments

Abstract

To investigate correlation effects on antiferromagnetic order in Fe pnictides, we apply a variational Monte Carlo method to a two-orbital model. We obtain a small ordered moment consistent with experimental observations even for a Coulomb interaction comparable to the band width. Studies of estimation of the Coulomb interaction for Fe pnictides suggest values comparable to or slightly smaller than the band width, and much larger ordered moments have been obtained by the Hartree-Fock approximation for such a large Coulomb interaction. Thus, the correlation effect is important for Fe pnictides at least quantitatively.