Controlling quantum materials with light is of fundamental and technological importance. By utilizing the strong coupling of light and matter in optical cavities1,2,3, recent studies were able to modify some of their most defining features4,5,6. Here we study the magneto-optical properties of a van der Waals magnet that supports strong coupling of photons and excitons even in the absence of external cavity mirrors. In this material—the layered magnetic semiconductor CrSBr—emergent light–matter hybrids called polaritons are shown to substantially increase the spectral bandwidth of correlations between the magnetic, electronic and optical properties, enabling largely tunable optical responses to applied magnetic fields and magnons. Our results highlight the importance of exciton–photon self-hybridization in van der Waals magnets and motivate novel directions for the manipulation of quantum material properties by strong light–matter coupling.
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Work at the City College of New York was supported by the National Science Foundation (DMR-2130544), the National Science Foundation Centers of Research Excellence in Science and Technology - Center for Interface Design and Engineered Assembly of Low-dimensional Systems (CREST IDEALS) centre (V.M.M.), the Defense Advanced Research Projects Agency (DARPA) Nascent Light–Matter Interaction program (R.B.) and the German Research Foundation (451072703; to F.D.). J.Q. and A.A. were supported by the Office of Naval Research, the Air Force Office of Scientific Research and the Simons Foundation. A.A. and V.M.M. acknowledge funding from the US Air Force Office of Scientific Research Multidisciplinary University Research Initiatives (FA9550-22-1-0317). We acknowledge the use of the City University of New York Advanced Science Research Center Nanofabrication Facility for the device fabrication. Z.S. was supported by the European Research Council Czech (ERC-CZ) programme (LL2101) from the Ministry of Education, Youth and Sports. K.M. was supported by the specific university research A2 FCHT 2023 077. The transient magneto-optical measurement at the University of Washington is mainly supported by the Department of Energy, Basic Energy Sciences, Materials Sciences and Engineering Division (DE-SC0012509). This research was supported by an appointment to the Intelligence Community Postdoctoral Research Fellowship Program at the University of Washington, administered by Oak Ridge Institute for Science and Education through an interagency agreement between the US Department of Energy and the Office of the Director of National Intelligence. M.F. and J.K. acknowledge support from the Alexander von Humboldt Foundation. A.K. and F.J.G.-V. acknowledge support from the Spanish Ministry for Science and Innovation–Agencia Estatal de Investigación (PID2021-125894NB-I00 and CEX2018-000805-M through the María de Maeztu program for Units of Excellence in R&D), the Autonomous Community of Madrid, the Spanish Government and the European Union (Mecanismo de Recuperación y Resiliencia (MRR) Advanced Materials MAD2D-CM).
The authors declare no competing interests.
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Dirnberger, F., Quan, J., Bushati, R. et al. Magneto-optics in a van der Waals magnet tuned by self-hybridized polaritons. Nature 620, 533–537 (2023). https://doi.org/10.1038/s41586-023-06275-2