SKM 2021 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 29: Topological Superconductors

TT 29.6: Talk

Friday, October 1, 2021, 14:45–15:00, H7

Interaction-Stabilized Topological Magnon Insulator in Ferromagnets — •Alexander Mook, Kirill Plekhanov, Jelena Klinovaja, and Daniel Loss — University of Basel, Basel, Switzerland

Condensed matter systems admit topological collective excitations above a trivial ground state, an example being Chern insulators formed by Dirac bosons with a gap at finite energies. However, in contrast to electrons, there is no particle-number conservation law for collective excitations, which gives rise to particle-number-nonconserving many-body interactions whose influence on single-particle topology is an open issue of fundamental interest in the field of topological quantum materials.

Taking magnons in ferromagnets as an example, we uncover topological magnon insulators that are stabilized by interactions through opening Chern-insulating gaps in the magnon spectrum. This finding can be traced back to the fact that the particle-number nonconserving interactions break the effective time-reversal symmetry of the harmonic theory. Hence, magnon-magnon interactions are a source of topology that can introduce chiral edge states. Importantly, interactions do not necessarily cause detrimental damping but can give rise to topological magnons with exceptionally long lifetimes. Our results demonstrate that particle-number-nonconserving many-body interactions play an important role in generating nontrivial single-particle topology.
[1] A. Mook, K. Plekhanov, J. Klinovaja, D. Loss, Phys. Rev. X 11, 021061 (2021)