title: Band narrowing and Mott localization in iron oxychalcogenides La2O2Fe2O(Se,S)2.
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.
authors.affiliation: Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
authors.forename: Jian-Xin
authors.initials: JX
authors.lastname: Zhu
authors.forename: Rong
authors.initials: R
authors.lastname: Yu
authors.forename: Hangdong
authors.initials: H
authors.lastname: Wang
authors.forename: Liang L
authors.initials: LL
authors.lastname: Zhao
authors.forename: M D
authors.initials: MD
authors.lastname: Jones
authors.forename: Jianhui
authors.initials: J
authors.lastname: Dai
authors.forename: Elihu
authors.initials: E
authors.lastname: Abrahams
authors.forename: E
authors.initials: E
authors.lastname: Morosan
authors.forename: Minghu
authors.initials: M
authors.lastname: Fang
authors.forename: Qimiao
authors.initials: Q
authors.lastname: Si