Engineering magnetic topological insulators in Eu$_5M_2X_6$ Zintls

TL;DR

This paper computationally designs magnetic topological insulators within Eu$_5M_2X_6$ Zintl compounds, demonstrating their potential for quantum phenomena and tunability via strain, advancing material realization for quantum applications.

Contribution

It introduces a new class of magnetic topological insulators based on Eu$_5M_2X_6$ Zintl compounds, utilizing the Zintl concept and non-symmorphic symmetries for material engineering.

Findings

Eu$_5$Ga$_2$Sb$_6$, Eu$_5$Tl$_2$Sb$_6$, Eu$_5$In$_2$Bi$_6$ are stable with non-trivial $ ext{Z}_2$ indices.

Strain can modulate the $ ext{Z}_2$ index and energy gap.

Discussion of experimental synthesis progress for these compounds.

Abstract

Magnetic topological insulator provide a prominent material platform for quantum anomalous Hall physics and axion electrodynamics. However, the lack of material realizations with cleanly gapped surfaces hinders technological utilization of these exotic quantum phenomena. Here, using the Zintl concept and the properties of non-symmorphic space groups, we computationally engineer magnetic topological insulators. Specifically, we explore Eu$_5M_2X_6$ ($M$=metal, $X$=pnictide) Zintl compounds and find that Eu$_5$Ga$_2$Sb$_6$, Eu$_5$Tl$_2$Sb$_6$ and Eu$_5$In$_2$Bi$_6$ form stable structures with non-trivial $\mathbb{Z}_2$ indices. We also show that epitaxial and uniaxial strain can be used to control the $\mathbb{Z}_2$ index and the bulk energy gap. Finally, we discuss experimental progress towards the synthesis of the proposed candidates and provide insights that can be used in the search for robust magnetic topological insulators in Zintl compounds.