Determination of the spin Hamiltonian in predicted topological magnon insulator MnTe₂

The topological classification of non-interacting magnons has been used to predict large classes of materials that host different kinds of bulk topological magnons and their corresponding surface states [1]. One predicted topological magnon material is MnTe₂, a cubic antiferromagnet where the S=5/2 Mn spins form an FCC lattice. It is expected that Heisenberg interactions up to third neighbors lead to a collinear spin ground state [2]. MnTe₂, however, is a non-collinear antiferromagnet where the 4 spins in the FCC tetrahedral unit cell point along a local [111] direction. To obtain this ground state, we need to include the anisotropic interactions: Kitaev, antisymmetric Dzyaloshinskii-Moriya, and anisotropic symmetric exchange. Using this expanded model Hamiltonian we are able to reproduce the magnetic field dependence of the magnon energies measured using polarization-dependent magneto-Raman spectroscopy on single crystals of MnTe₂.

[1] M. Karaki, et al. Sci. Adv. 9, eade7731 (2023).

[2] P. Balla, et al. Phys Rev. Res. 2, 043278, (2020).