Title: Topological thermal Hall effect due to Weyl magnons,
Abstract: We present the first theoretical evidence of zero magnetic field topological
(anomalous) thermal Hall effect due to Weyl magnons. Here, we consider Weyl
magnons in stacked noncoplanar frustrated kagomé antiferromagnets recently
proposed by Owerre, [arXiv:1708.04240]. The Weyl magnons in this system result
from macroscopically broken time-reversal symmetry by the scalar spin chirality
of noncoplanar chiral spin textures. Most importantly, they come from the
lowest excitation, therefore they can be easily observed experimentally at low
temperatures due to the population effect. Similar to electronic Weyl nodes
close to the Fermi energy, Weyl magnon nodes in the lowest excitation are the
most important. Indeed, we show that the topological (anomalous) thermal Hall
effect in this system arises from nonvanishing Berry curvature due to Weyl
magnon nodes in the lowest excitation, and it depends on their distribution
(distance) in momentum space. The present result paves the way to directly
probe low excitation Weyl magnons and macroscopically broken time-reversal
symmetry in three-dimensional frustrated magnets with the anomalous thermal
Hall effect.