Novel Insulating Magnetism in Vacancy-Ordered K2Fe4Se5

TL;DR

This paper uncovers the unique insulating antiferromagnetic behavior in vacancy-ordered K2Fe4Se5, highlighting the coexistence of itinerant and localized electrons, and emphasizing the role of Hund's rule coupling in iron-based superconductors.

Contribution

It introduces a novel understanding of insulating magnetism in vacancy-ordered K2Fe4Se5, challenging simple Fermi-surface or Mott insulator models, and links it to the magnetic properties of related compounds.

Findings

Incompatibility with simple Fermi-surface nesting or Mott insulator models.

Coexistence of itinerant and localized electronic states.

Role of Hund's rule coupling in electronic and magnetic structures.

Abstract

We unveil the novel physical origin of the insulating block checkerboard antiferromagnetism in vacancy-ordered K2Fe4Se5. Our first-principles electronic structure analysis reveals its incompatibility with a simple Fermi-surface nesting or Mott insulator scenario, and suggests the picture of coexisting itinerant and localized electronic states. Consistently, we demonstrate that it can be unified with the metallic collinear or bicollinear antiferromagnetism of the vacancy-free parent compounds LaOFeAs, BaFe2As2, or FeTe in the spin-fermion model. These results indicate that the blocking effects of Hund's rule coupling and the resulting electron correlation are crucial to the electronic and magnetic structures of iron-based superconductors.