Magnetic states of quasi-one-dimensional iron chalcogenide Ba$_2$FeS$_3$

TL;DR

This study combines first-principles calculations and the Hubbard model to explore the magnetic and electronic phases of Ba$_2$FeS$_3$, revealing a robust antiferromagnetic order and an orbital selective Mott phase in this quasi-one-dimensional iron chalcogenide.

Contribution

It provides the first theoretical phase diagram of Ba$_2$FeS$_3$, identifying magnetic order and orbital selective Mott phases using DFT and DMRG methods.

Findings

Robust antiferromagnetic order along the chain.

Existence of an orbital selective Mott phase at intermediate U.

Mott insulator characteristics at large U/W.

Abstract

Quasi-one-dimensional iron-based ladders and chains, with the 3$d$ iron electronic density $n = 6$, are attracting considerable attention. Recently, a new iron chain system Ba$_2$FeS$_3$, also with $n = 6$, was prepared under high-pressure and high-temperature conditions. Here, the magnetic and electronic phase diagrams are theoretically studied for this quasi-one-dimensional compound. Based on first-principles calculations, a strongly anisotropic one-dimensional electronic band behavior near the Fermi level was observed. In addition, a three-orbital electronic Hubbard model for this chain was constructed. Introducing the Hubbard and Hund couplings and studying the model via the density matrix renormalization group (DMRG) method, we studied the ground-state phase diagram. A robust staggered $\uparrow$-$\downarrow$-$\uparrow$-$\downarrow$ AFM region was unveiled in the chain direction, consistent with our density functional theory (DFT) calculations. Furthermore, at intermediate Hubbard $U$ coupling strengths, this system was found to display an orbital selective Mott phase (OSMP) with one localized orbital and two itinerant metallic orbitals. At very large $U/W$ ($W$ = bandwidth), the system displays Mott insulator characteristics, with two orbitals half-filled and one doubly occupied. Our results for high pressure Ba$_2$FeS$_3$ provide guidance to experimentalists and theorists working on this one-dimensional iron chalcogenide chain material.