Colossal magnetoresistance in a nonsymmorphic antiferromagnetic insulator

TL;DR

This study explores the magnetic and topological properties of Eu$_{5}$In$_{2}$Sb$_{6}$, revealing its insulating behavior, large negative magnetoresistance, and potential axion insulator state, contributing to the understanding of magnetic topological materials.

Contribution

It provides the first detailed investigation of Eu$_{5}$In$_{2}$Sb$_{6}$'s magnetic, electronic, and topological properties, highlighting its potential as a magnetic topological insulator.

Findings

Eu$_{5}$In$_{2}$Sb$_{6}$ is highly insulating with large negative magnetoresistance.

GGA calculations show a topologically nontrivial semimetal in the paramagnetic state.

GGA+U suggests the antiferromagnetic phase may host an axion insulator state.

Abstract

Here we investigate antiferromagnetic Eu$_{5}$In$_{2}$Sb$_{6}$, a nonsymmorphic Zintl phase. Our electrical transport data show that Eu$_{5}$In$_{2}$Sb$_{6}$ is remarkably insulating and exhibits an exceptionally large negative magnetoresistance, which is consistent with the presence of magnetic polarons. From {\it ab initio} calculations, the paramagnetic state of Eu$_{5}$In$_{2}$Sb$_{6}$ is a topologically nontrivial semimetal within the generalized gradient approximation (GGA), whereas an insulating state with trivial topological indices is obtained using a modified Becke-Johnson potential. Notably, GGA+U calculations suggest that the antiferromagnetic phase of Eu$_{5}$In$_{2}$Sb$_{6}$ may host an axion insulating state. Our results provide important feedback for theories of topological classification and highlight the potential of realizing clean magnetic narrow-gap semiconductors in Zintl materials.