Weyl Fermions in antiferromagnetic Mn(3)Sn and Mn(3)Ge

TL;DR

This paper investigates the electronic structure of antiferromagnetic Mn(3)Sn and Mn(3)Ge, revealing Weyl points that explain their large anomalous Hall effects and associated transport properties.

Contribution

It provides the first ab initio identification of Weyl points in Mn(3)Sn and Mn(3)Ge, linking them to observed large anomalous Hall conductivities.

Findings

Weyl points are located below the Fermi energy in Mn(3)Sn and Mn(3)Ge.

Large Berry flux 'hot spots' at the Fermi surface are caused by Weyl nodes.

The electronic structure explains the large anomalous Hall effect in these materials.

Abstract

The anomalous Hall effect in the noncollinear antiferromagnetic metals Mn(3)Ge and Mn(3)Sn has been observed after a theoretical prediction made by us (EPL, 108, 67001 (2014)). The experimental values of the anomalous Hall conductivities (AHC) are large as are the theoretical values. Recently measured thermoelectric properties mirror the large AHC and clearly show that the transport is by quasiparticles at the Fermi energy. We here make an attempt to unravel the origin of the large AHC and propose that both Mn(3)Sn and Mn(3)Ge host Weyl points, which were recently discovered in semimetals. For this purpose we determine the electronic structure ab initio in the local spin-density functional approximation. The Weyl points are found to occur below the Fermi energy and we argue that spots of large Berry flux ('hot spot') that are seen at the Fermi surface are produced by the Weyl nodes.