Heusler, Weyl and Berry

Heusler materials, initially discovered by Fritz Heusler more than a century ago, have grown into a family of more than 1000 compounds, synthesized from combinations of more than 40 elements. These materials show a wide range of properties, but new properties are constantly being found. Most recently, by incorporating heavy elements that can give rise to strong spin-orbit coupling (SOC), non-trivial topological phases of matter, such as topological insulators (TIs), have been discovered in Heusler materials. Moreover, the interplay of symmetry, SOC and magnetic structure allows for the realization of a wide variety of topological phases through Berry curvature design. Weyl points and nodal lines can be manipulated by various external perturbations, which results in exotic properties such as the chiral anomaly, and large anomalous spin and topological Hall effects. The combination of a non-collinear magnetic structure and Berry curvature gives rise a non-zero anomalous Hall effect, which was first observed in the antiferromagnets Mn3Sn and Mn3Ge. Besides this k-space Berry curvature, Heusler compounds with non-collinear magnetic structures also possess real-space topological states in the form of magnetic antiskyrmions, which have not yet been observed in other materials. The possibility of directly manipulating the Berry curvature shows the importance of understanding both the electronic and magnetic structures of Heusler compounds. Together, with the new topological viewpoint and the high tunability, novel physical properties and phenomena await discovery in Heusler compounds.