The search for topological surface magnon in MnTe₂

The concept of topology has proliferated in the field of condensed matter physics in recent years. Originally used to describe electronic (fermionic) bands, new mathematical machinery was developed to describe the topology of bosonic bands in solids, such as phonons and magnons. This led to a search for candidate materials that might host the exotic topological bosonic edge state, analogous to the edge conduction electrons in the topological insulator materials. Some inelastic scattering experiments have been able to identify materials that contain bulk magnon and phonon bands with non-trivial topology. However, experimental detection of the topological phonon or magnon edge states has been difficult to achieve. In this talk, I will present some progress we have made in the search for topological magnon edge states in antiferromagnetic materials, using polarized magneto-Raman spectroscopy. We highlight some lessons learned from inelastic light scattering experiments on the ferromagnetic magnon edge state, first conducted in the 1970s. Extending the same approach to the antiferromagnetic system MnTe₂, we report the first potential evidence of the topological magnon edge state in this non-collinear antiferromagnetic system.