Dynamical properties of the magnetic topological insulator TBi2Te4 (T=Mn, Fe): Phonons dispersion, Raman active modes, and chiral phonons study

Recently discovered magnetic topological insulators TBi2Te4 (T = Mn, Fe) crystallize into the 10m rhombohedral structure and exhibit the antiferromagnetic order. Here, we discuss the lattice dynamics of these compounds to confirm the stability of these systems. We show that the phonon dispersion does not contain soft modes, so both compounds are dynamically stable in the R (3) over barm phase. We perform theoretical analyses of the mode activity at the Gamma point for the discussed compounds. In the case of the Raman active modes, our results are in agreement with the experimentally observed frequencies. Finally, we also discuss the possibility of the realization of chiral phonons.