Magnetic states of iron-based two-leg ladder tellurides

TL;DR

This study uses Density Functional Theory to predict magnetic states in RbFe$_2$Te$_3$, suggesting potential superconductivity under pressure and revealing new magnetic configurations in iron-based ladder compounds.

Contribution

First DFT prediction of magnetic states in RbFe$_2$Te$_3$, including novel CY-type magnetic order, expanding understanding of iron-based ladder superconductors.

Findings

RbFe$_2$Te$_3$ is predicted to be magnetic with ferromagnetic rungs and antiferromagnetic legs.

Potential for superconductivity in RbFe$_2$Te$_3$ under pressure similar to BaFe$_2$S$_3$.

Discovery of a new CY-type magnetic state with ferromagnetic legs and antiferromagnetic rungs.

Abstract

The recent discovery of superconductivity at high pressure in the two-leg ladder compounds BaFe$_2X_3$ ($X$=S, Se) started the novel field of quasi-one-dimensional iron-based superconductors. In this publication, we use Density Functional Theory (DFT) to predict that the previously barely explored ladder compound RbFe$_2$Te$_3$ should be magnetic with a CX-type arrangement involving ferromagnetic rungs and antiferromagnetic legs, at the realistic density of $n=5.5$ electrons per iron. The magnetic state similarity with BaFe$_2$S$_3$ suggests that RbFe$_2$Te$_3$ could also become superconducting under pressure. Moreover, at $n=6.0$ our DFT phase diagrams (with and without lattice tetramerization) reveal that the stable magnetic states could be either a 2$\times$2 magnetic Block-type, as for $X$=Se, or a previously never observed before CY-type state, with ferromagnetic legs and antiferromagnetic rungs. In the Te-based studies, electrons are more localized than in S, implying that the degree of electronic correlation is enhanced for the Te case.