Resummed Topological Magnons in Honeycomb Ferromagnets

Topological magnon materials hold great promise for spintronics applications, particularly through their potential for back-scattering-free edge currents. In this work, we explore many-body interaction effects at finite temperatures in van der Waals honeycomb ferromagnets using an interacting spin-wave theory approach, which incorporates resummed Feynman diagrams [1]. Our study reveals that interactions between magnons and bimagnon-bound states can play a crucial role in the energy shifts and broadening of magnon bands in CrBr3 [2], offering new insights beyond previous analyses that emphasized the van-Hove singularity. Additionally, we clarify the nature of the thermally induced topological transition in CrI3, related to the Chern-insulating gap, by showing that earlier predictions [3] were based on approximations that can now be improved. These findings contribute to a deeper understanding of many-body interactions in topological magnon systems and open pathways for more precise quantitative analyses in this exciting field.

[1] R. Eto, M. Mochizuki, and A. Mook, in preparation.

[2] S. E. Nikitin et al., Phys. Rev. Lett. 129, 127201 (2022).

[3] Y.-S. Lu et al., Phys. Rev. Lett. 127, 217202 (2021); Comment (2024); Reply (2024).

* Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) - Project No. 504261060 (Emmy Noether Programme), JST CREST (Grant No. JPMJCR20T1), JSPS KAKENHI (Grants No. 20H00337, No. 23H04522, No. 24H02231), Waseda University Grant for Special Research Projects (Grants No. 2023C-140, No. 2024C-153), a Grant-in-Aid for JSPS Fellows (Grant No. 23KJ2047), JSPS Overseas Challenge Program for Young Researchers