Proximity of antiferromagnetism and superconductivity in LaO$_{1-x}$F$_x$FeAs: effective Hamiltonian from ab initio studies

TL;DR

This study uses density functional theory to analyze LaOFeAs, revealing its antiferromagnetic ground state and deriving an effective Hamiltonian, highlighting the close relationship between antiferromagnetism and superconductivity in this material.

Contribution

The paper provides an ab initio derived effective Hamiltonian for LaOFeAs, linking its electronic structure to magnetic and superconducting properties.

Findings

Ground state is antiferromagnetic with 2.3μ_B moment.

Fermi surface modeled accurately with Wannier functions.

Proximity of superconductivity to antiferromagnetism suggests a cuprate-like behavior.

Abstract

We report density functional theory calculations for the parent compound LaOFeAs of the newly discovered 26K Fe-based superconductor LaO$_{1-x}$F$_x$FeAs. We find that the ground state is an ordered antiferromagnet, with staggered moment about 2.3$\mu_B$, on the border with the Mott insulating state. We fit the bands crossing the Fermi surface, derived from Fe and As, to a tight-binding Hamiltonian using maximally localized Wannier functions on Fe 3d and As 4p orbitals. The model Hamiltonian accurately describes the Fermi surface obtained via first-principles calculations. Due to the evident proximity of superconductivity to antiferromagnetism and the Mott transition, we suggest that the system may be an analog of the electron doped cuprates, where antiferromagnetism and superconductivity coexist.