Topological Magnons in the Bi-layer Honeycomb Ferromagnet

Over the last couple of years, magnetic systems have also been shown to host topological excitations. We explore the particular case of ferromagnet bi-layer honeycomb lattice which, when considering nearest- and next nearest-neighbor exchange interactions, Dzyaloshinskii-Moriya interaction, and easy-axis anisotropy, allows for topological magnons to arise [1]. We extend the Hamiltonian of Ref. [1] via the inclusion of extra interlayer interactions, in addition to various layers stack, i.e. A-B stacking or A-A stacking. We show this Hamiltonian hosts topological magnons that are controllable via the interlayer interactions. Most importantly, these new interactions provide a novel way to tailor and engineer different topological magnon frequency dispersion. Finally, we also calculate the magnon thermal Hall conductivity as a function of temperature and magnetic field.

[1] H. Kim and S. K. Kim, Phys. Rev. B 106, 104430 (2022)