Band Narrowing and Mott Localization in Iron Oxychalcogenides La2O2Fe2O(Se,S)2

TL;DR

This paper investigates iron oxychalcogenides La2O2Fe2O(Se,S)2, showing they are Mott insulators with enhanced electronic correlations and complex magnetic interactions, advancing understanding of correlation effects in iron-based materials.

Contribution

It provides theoretical and experimental evidence that La2O2Fe2O(Se,S)2 are Mott insulators with band narrowing effects and discusses their magnetic properties using a frustrated Heisenberg model.

Findings

La2O2Fe2O(Se,S)2 are Mott insulators with moderate charge gaps.

Band narrowing enhances correlation effects compared to LaOFeAs.

Magnetic interactions are described by a frustrated J1-J2-J2' Heisenberg model.

Abstract

Bad metal properties have motivated a description of the parent iron pnictides as correlated metals on the verge of Mott localization. What has been unclear is whether interactions can push these and related compounds to the Mott insulating side of the phase diagram. Here we consider the iron oxychalcogenides La2O2Fe2O(Se,S)2, which contain an Fe square lattice with an expanded unit cell. We show theoretically that they contain enhanced correlation effects through band narrowing compared to LaOFeAs, and we provide experimental evidence that they are Mott insulators with moderate charge gaps. We also discuss the magnetic properties in terms of a Heisenberg model with frustrating J1-J2-J2' exchange interactions on a "doubled" checkerboard lattice.