Importance of Itinerancy and Quantum Fluctuations for the Magnetism in Iron Pnictides

TL;DR

This paper investigates the magnetic properties of iron pnictides, revealing that their magnetism is driven by itinerant electrons and quantum fluctuations, which influence the magnetic moment and ordering.

Contribution

It demonstrates the itinerant nature of magnetism in iron pnictides and shows how quantum fluctuations and band coupling lead to observed magnetic behaviors.

Findings

Magnetism in iron pnictides is itinerant in nature.

Quantum fluctuations reduce magnetic moments.

Coupling between frustrated and unfrustrated bands explains magnetic properties.

Abstract

By applying density functional theory, we find strong evidence for an itinerant nature of magnetism in two families of iron pnictides. Furthermore, by employing dynamical mean field theory with continuous time quantum Monte Carlo as an impurity solver, we observe that the antiferromagnetic metal with small magnetic moment naturally arises out of coupling between unfrustrated and frustrated bands. Our results point to a possible scenario for magnetism in iron pnictides where magnetism originates from a strong instability at the momentum vector ($\pi$, $\pi$, $\pi$) while it is reduced by quantum fluctuations due to the coupling between weakly and strongly frustrated bands.