Damped topological magnons in honeycomb antiferromagnets
Qi-Hui Chen, Fei-Jie Huang, Y. Fu
Abstract
We study magnon excitations and their interactions in honeycomb antiferromagnets with the Dzyaloshinskii-Moriya interaction. When an applied magnetic field is turned on, the classical ground state of the system is in noncollinear antiferromagnetic order. Therefore, it is crucial to consider the interactions between magnons. We find an exact and well-formed solution of the bosonic Bogoliubov--de Gennes Hamiltonian, which allows us to analytically study the topological properties and damping effects of the magnon bands. In particular, the formulas of the Berry phase and Berry curvature for the magnon bands are worked out analytically. The Mn-based trichalcogenide ${\mathrm{MnPS}}_{3}$ is taken as a candidate material realization to estimate the order of magnitude of the thermal Hall conductivity and its evolution with the temperature and the Dzyaloshinskii-Moriya interaction strength. We develop a nonlinear spin wave theory to study the damping effects of the topological magnons and find the different damping behaviors of the upper and lower topological magnon bands when tuning the applied magnetic field. In some parameter regions, the damping effects are so strong that the free magnon description breaks down. Finally, we discuss how to observe these effects in experiments.