Regensburg 2025 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 53: Topology: Other Topics

TT 53.11: Talk

Friday, March 21, 2025, 12:15–12:30, H32

Optical Hopfion quantizes inverse Faraday effect — •Emma L. Minarelli and Matthias R. Geilhufe — Chalmers University of Technology, Department of Physics, 412 96 Göteborg, Sweden

Control and manipulation of quantum materials is of paramount significance, both for fundamental characterization and for quantum technologies. Among others, light-matter interaction has recently gained traction because both optical counterpart of solid-state phenomena and emergent effects can be investigated.

We extend this paradigm to 3D topological optical quasiparticle i.e. optical Hopfion (oHop) - a knotted structure presenting robust topological protection, resolution on ultrafast time-scales, localization on nanometer-scale - as novel source to probe and regulate properties and phases of matter.

We show a first instance of OHop-matter coupling: an oHop travelling through a non-magnetic material induces a net effective magnetization, that is now promoted to be topologically quantized in virtue of the linking number (Hopf index) classifying the oHop source. By relating the induced magnetization to the Hopf index, we identify the quantum inverse Faraday effect. This quantized optical response is obtained without constraints on the material but only by introducing topological light. We conclude with a demonstration for a specific material and we give predictions about its promising application in optical protocols for communication and storage of information.

Keywords: Optical Hopfion; Light-matter interaction; Inverse Faraday effect; Topological quasiparticle; Topological quantum response