Engineering magnetic topological insulators in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mrow><mml:mi>Eu</mml:mi></mml:mrow><mml:mn>5</mml:mn></mml:msub><mml:msub><mml:mi>M</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi>X</mml:mi><mml:mn>6</mml:mn></mml:msub></mml:mrow></mml:math> Zintl compounds
Nicodemos Varnava, Tanya Berry, Tyrel M. McQueen, David Vanderbilt
Abstract
Magnetic topological insulators 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 nonsymmorphic space groups, we computationally engineer magnetic topological insulators. Specifically, we explore ${\mathrm{Eu}}_{5}{M}_{2}{X}_{6}$ (M=metal, X=pnictide) Zintl compounds and find that ${\mathrm{Eu}}_{5}{\mathrm{Ga}}_{2}{\mathrm{Sb}}_{6}$, ${\mathrm{Eu}}_{5}{\mathrm{Tl}}_{2}{\mathrm{Sb}}_{6}$, and ${\mathrm{Eu}}_{5}{\mathrm{In}}_{2}{\mathrm{Bi}}_{6}$ form stable structures with nontrivial ${\mathbb{Z}}_{2}$ 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.