Dynamical properties of magnetic topological insulator $T$Bi$_{2}$Te$_{4}$ ($T=$Mn, Fe): phonons dispersion, Raman active modes, and chiral phonons study

TL;DR

This study investigates the lattice dynamics and phonon properties of magnetic topological insulators $T$Bi$_{2}$Te$_{4}$ ($T=$Mn, Fe), confirming their stability, analyzing Raman active modes, and exploring chiral phonons.

Contribution

It provides a theoretical analysis of phonon dispersion, Raman modes, and chiral phonons in $T$Bi$_{2}$Te$_{4}$ compounds, confirming their dynamical stability and matching experimental Raman data.

Findings

Phonon dispersion shows no soft modes, indicating stability.

Theoretical Raman frequencies agree with experimental observations.

Chiral phonons could potentially be realized in these materials.

Abstract

Recently discovered magnetic topological insulators $T$Bi$_{2}$Te$_{4}$ ($T=$Mn, Fe) crystallize into the $R\bar{3}m$ 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 $R\bar{3}m$ phase. We perform theoretical analyses of the mode activity at $\Gamma$ 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 realization of chiral phonons.