SKM 2023 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 10: Topological Insulators (joint session MA/TT)
MA 10.8: Vortrag
Montag, 27. März 2023, 17:00–17:15, HSZ 403
Limitations of the Bulk-Boundary Correspondence in Topological Magnon Insulators due to Magnon-Magnon Interactions — •Jonas Habel1, Johannes Knolle1, Alexander Mook2, and Josef Willsher1 — 1Technical University of Munich, Germany (Theory of Quantum Matter and Nanophysics) — 2Johannes Gutenberg University Mainz, Germany
Magnon excitations in ordered quantum magnets can exhibit topological band structures characterized by non-zero Chern numbers. Such magnonic Chern insulators are widely believed to host protected chiral edge modes due to the bulk-boundary correspondence, in analogy to electronic Chern insulators. However, in contrast to electrons, magnons are bosons and can thus be subject to exotic number-non-conserving many-body interactions, enabling potentially strong spontaneous decays at zero temperature.
To assess their effect on the chiral edge magnons, we study a topological honeycomb-lattice ferromagnet with Dzyaloshinskii-Moriya interactions using many-body perturbation theory. We discover that non-harmonic terms of the spin-wave expansion may lead to severe lifetime reduction of edge modes and their delocalisation into the bulk. For sufficiently strong interactions, the spectral weight of the chiral edge magnons vanishes entirely. These findings indicate that topological magnon bands within the harmonic framework do not necessarily give rise to protected edge modes in the full spin theory, suggesting limitations of the bulk-boundary correspondence in this case.