Project C10: Phys. Rev. B 2018
Weak localization of magnons in chiral magnets
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 ωk=ω2KI−k ≠ ω−k, where KI is related to the Dzyaloshinskii-Moriya vectors. The nonequivalence of k and −k also means that time-reversal symmetry is broken. As a result of numerical investigations we find that the backscattering peak of a wave packet with initial wave vector k0 shifts from −k0 to 2KI−k0, 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. Surprisingly, although time-reversal symmetry is broken, our system shows coherent backscattering as a manifestation of weak localization, which is due to the fact that reciprocity is still preserved.
Martin Evers, Cord A. Müller, and Ulrich Nowak
Phys. Rev. B 97, 184423 (2018)
DOI: 10.1103/PhysRevB.97.184423