Weak localization of magnons in chiral magnets

Abstract

We report on the impact of the Dzyaloshinskii-Moriya interaction on the coherent backscattering of spin waves in a disordered magnetic material. This interaction breaks the inversion symmetry of the spin-wave dispersion relation, such that $\omega_\mathbf{k} = \omega_{2\mathbf{K}^\mathrm{I}-\mathbf{k}} \neq \omega_{-\mathbf{k}}$, where $\mathbf{K}^\mathrm{I}$ is related to the Dzyaloshinskii-Moriya vectors. As a result of numerical investigations we find that the backscattering peak of a wave packet with initial wave vector $\mathbf{k}_0$ shifts from $-\mathbf{k}_0$ to $2\mathbf{K}^\mathrm{I}-\mathbf{k}_0$, such that the backscattering wave vector and the initial wave vector are in general no longer antiparallel. The shifted coherence condition is explained by a diagrammatic approach and opens up an avenue to measure sign and magnitude of the Dzyaloshinskii-Moriya interaction in weakly disordered chiral magnets.