Possible Flat Magnon Band and Dirac Magnon in FeSn

Two-dimensional (2D) layered Kagome compounds are of great interest because they serve as platforms for studying not only frustrated magnetism hosting possible novel quantum phases, say, valence bond state and quantum spin liquids, but also topological phases that realize flat bands, or Dirac bands, or even both. The Kagome magnetic compounds show great potential to host Dirac magnons or flat bands which can be detected by neutron scattering. Because Kagome lattice lack inversion symmetry, we expect the presence of nearest neighbor DM interactions, which may open a spin gap near the Dirac point similar to CrI3. However, the spin-orbit coupling of the system is not large in FeSn, it is therefore interesting to completely map out spin waves of the system and determine the possible presence of an anisotropic gap, Dirac magnon, and flat band features.