Anisotropic magnons in the layered honeycomb ferromagnet CrSiTe 3

Recent experimental and theoretical studies have suggested a possible Dirac magnon gap in the two-dimensional ferromagnetic semiconductor CrSiTe 3 . Detailed neutron scattering measurements were performed to shed light on the existence of the magnon gap, and suggest that the gap is very small or nonexistent, with previous measurements being complicated by experimental factors. During these measurements, it was found that the out-of-plane couplings could explain the usual property of the increase in the magnetic transition temperature when CrSiTe 3 is exfoliated to monolayers. Furthermore, the material was shown to have anisotropic magnons along the out-of-plane direction, through the proposed Dirac point. We speculate that this is due to an exchange anisotropy, though Kitaev-like interactions alone cannot explain the spectra.