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TT: Fachverband Tiefe Temperaturen

TT 23: Topological Insulators and Weyl Semimetals (joint session MA/TT)

TT 23.8: Talk

Tuesday, March 19, 2024, 11:30–11:45, H 2013

Electrical Activity of Topological Chiral Edge Magnons — •Robin R. Neumann¹, Alexander Mook², Jürgen Henk¹, and Ingrid Mertig¹ — ¹Martin Luther University Halle-Wittenberg, Halle (Saale), Germany — ²Johannes Gutenberg University, Mainz, Germany

Magnons, the bosonic quasiparticles of spin waves, have been predicted to feature similar topological phases as electrons. In particular, the topological band structure of the quantum Hall systems has its magnonic analogue in the topological magnon insulator (TMI), which hosts topologically protected chiral edge excitations. Beyond theoretical studies, however, there exist no direct experimental evidence of their existence as the lack of charge renders them invisible to most surface-sensitive probes.

In this talk I demonstrate how magnetoelectric coupling imparts an electric dipole moment to the chiral magnons that manifests in equilibrium and nonequilibrium. Considering a two-dimensional ferromagnetic TMI, an electric edge polarization perpendicular to the sample's edges is driven by thermal fluctuations of the collinear magnetic ground state in equilibrium. On the other hand, the TMI features a unique in-gap resonance in its electrical absorption spectrum that stems from the chiral magnons showcasing their electrical activity. These results suggest THz spectroscopy as promising probe for topological magnons.

Keywords: Magnons; Topology; Magnetelectric Coupling; Electric Polarization; Electric Absorption