Magnetic-order-driven metal-insulator transitions in the quasi-one-dimensional spin-ladder compounds BaFe$_2$S$_3$ and BaFe$_2$Se$_3$

TL;DR

This study investigates how magnetic order influences metal-insulator transitions in quasi-one-dimensional spin ladder compounds BaFe$_2$S$_3$ and BaFe$_2$Se$_3$, revealing a Slater-type insulating state driven by magnetic order.

Contribution

It combines infrared spectroscopy and DFT calculations to demonstrate that magnetic order induces an insulating state via Slater physics rather than Mott correlations in these compounds.

Findings

Optical gap fills above antiferromagnetic transition

Insulating state linked to magnetic order, not correlations

Optical and DFT data support Slater insulator mechanism

Abstract

The quasi-one-dimensional spin ladder compounds, BaFe$_2$S$_3$ and BaFe$_2$Se$_3$, are investigated by infrared spectroscopy and density functional theory (DFT) calculations. We observe strong anisotropic electronic properties and an optical gap in the leg direction that is gradually filled above the antiferromagnetic (afm) ordering temperature, turning the systems into a metallic phase. Combining the optical data with the DFT calculations we associate the optical gap feature with the $p$-$d$ transition that appears only in the afm ordered state. Hence, the insulating ground state along the leg direction is attributed to Slater physics rather than Mott-type correlations.