Regensburg 2022 – scientific programme

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 30: Skyrmions 3 (joint session MA/KFM)

KFM 30.11: Talk

Friday, September 9, 2022, 12:00–12:15, H37

Resonant optical Hall conductivity from skyrmions — •Sopheak Sorn¹, Luyi Yang², and Arun Paramekanti³ — ¹Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, Karlsruhe, Germany — ²Department of Physics, Tsinghua University, Beijing, China — ³Department of Physics, University of Toronto, Toronto, Canada

Metallic magnets hosting topological skyrmions exhibit the topological Hall effect, which arises from a real-space Berry-phase mechanism, and it has been used as an indirect signature of skyrmions in transport experiments. This talk will focus on the less explored impact of skyrmions on optical Hall conductivity which is studied using a two-dimensional model of conduction electrons coupled to a background skyrmion spin texture via an effective Hund's coupling. For a skyrmion crystal, a Kubo-formula calculation reveals a resonant feature in the optical Hall response at a frequency set by the Hund's coupling. A linear relation between the area under the Hall resonant curve and the skyrmion density is discovered numerically and is further elucidated in a gradient expansion analysis. The presence of the resonance is robust, persisting in a system with an isolated skyrmion and even in a three-site system hosting a trimer of noncoplanar spins, which implies the indispensable role of the local noncoplanarity. Our results suggest that the resonance can be used as a basis for a magneto-optical Kerr microscopy for visualizing skyrmions.