Dr. Florian Dirnberger

Department of Physics, TU Munich

A number of materials from the family of van der Waals magnetic insulators was re-
cently found to support magnetic excitons – a rare type of optical excitation formed by
spin-polarized electronic states. With properties that have no analog amongst excitons
in conventional band insulators, these optical quasiparticles and their coupling to mag-
netic order are adding new flavors to the list of magneto-optic effects. In this talk, I
will discuss how interactions of magnetic excitons with magnons and photons brings to-
gether concepts from semiconductor physics, magnetism, and photonics. The elemental
role of strong light-matter coupling and the emergent hybrid light-matter states known as
exciton-polaritons will be analyzed in the context of the optical properties of the layered
magnetic semiconductor CrSBr [1, 2]. In the second part, I will also present our latest
experimental and theoretical advances on unraveling the impact of magnons on the prop-
agation of excitons. Highly non-linear exciton transport features, such as propagation
enhanced at the antiferromagnet-to-paramagnet phase transition, will be discussed along-
side the anomalous observations of exciton cloud contraction and superdiffusive behavior.

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[1] Dirnberger, F. et al. Spin-correlated exciton–polaritons in a van der Waals magnet. Nature
Nanotechnology 17, 1060–1064 (2022).
[2] Dirnberger, F. et al. Magneto-optics in a van der Waals magnet tuned by self-hybridized
polaritons. Nature 620, 533–537 (2023).