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MA: Fachverband Magnetismus
MA 30: Functional Antiferromagnetism
MA 30.9: Vortrag
Mittwoch, 11. März 2026, 11:45–12:00, POT/0151
Direct Observation of Hidden Excitonic States via Exciton-Magnon Coupling in CrSBr — Sophie Bork1, •Richard Leven1, Vincent Wirsdörfer1, Alessandro Ferretti2, Rafael Rojas Lopez1, Mattia Benini1, David Maximilian Janas1, Umut Parlak3, Alberto Brambilla2, Alexey Scherbakov1, and Mirko Cinchetti1 — 1Department of Physics, TU Dortmund University, 44227 Dortmund, Germany — 2CNR-IFN Dipartimento di Fisica, Politecnico di Milano, 20133 Milan, Italy — 3Fachbereich Physik, Universität Konstanz, 78457 Konstanz, Germany
Two-dimensional van der Waals magnets exhibit strong exciton binding and intrinsic magnetic order, enabling exciton-magnon coupling that links collective spin excitations with excitonic states. However, detecting dark excitons and their coupling remains challenging. Here we employ broadband transient reflectivity on CrSBr, a quasi-two-dimensional antiferromagnetic semiconductor, to probe excitonic structures across 1.25 - 1.65 eV under varying magnetic fields. We identify two excitonic resonances: a bright 1s exciton at 1.36 eV and a dark exciton near 1.46 eV, the latter revealed solely through exciton-magnon interactions. The detected GHz magnon mode exhibits magnetic-field-dependent frequency shifts and coupling signatures with both excitons. High-energy excitation modifies magnon dispersion and enhances exciton-magnon hybridization. These findings provide direct insight into exciton-magnon coupling in CrSBr and demonstrate that ultrafast optical probes can uncover hidden excitonic states, advancing understanding of hybrid quasiparticles in van der Waals magnets.
Keywords: Dark exciton; Hybridization; Broadband Transient Reflectivity; CrSBr