Abstract
Excitons in recently discovered two-dimensional magnetic semiconductors have emerged as a promising vehicle for optoelectronic and spin-photonic applications. To exploit novel possibilities magnetic degrees of freedom offer, insight into the interplay of magnetism, lattice and optical excitations becomes essential. We consider Chromium Sulphur Bromide, which has two kinds of excitons, XB at 1.8 eV and XA at 1.38 eV. Here we show, through a combination of many body perturbation theory and experiment, that XB is an order of magnitude more sensitive to magnetic and lattice perturbations than XA. We trace the difference to the latter being localised (Frenkel-like), while the former is delocalised (Wannier-Mott-like) – a coexistence rarely seen in two-dimensional materials. This finding is supported by the strong temperature and magnetic field (up to 85 Tesla) dependent shifts in optical response for XB (much smaller for XA), and we show it is related to XB’s tendency for delocalisation (in-plane and out-of-plane) and enhanced coupling with Ag phonon modes.
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The magneto—optical data generated and/or analysed during the study are available without restrictions in the Zenodo database under the following online repository accesion code: https://doi.org/10.5281/zenodo.17941646.
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Acknowledgements
This work was authored in part by the National Renewable Energy Laboratory for the U.S. Department of Energy (DOE) under Contract No. DE-AC36-08GO28308. For S.A., D.P., and MvS, funding was provided by the Computational Chemical Sciences programme within the Office of Basic Energy Sciences, U.S. Department of Energy. S.A., D.P., and M.v.S. acknowledge the use of the National Energy Research Scientific Computing Centre, under Contract No. DE-AC02-05CH11231 using NERSC award BES-ERCAP0021783 and we also acknowledge that a portion of the research was performed using computational resources sponsored by the Department of Energy’s Office of Energy Efficiency and Renewable Energy and located at the National Renewable Energy Laboratory and computational resources provided by the Oakridge leadership Computing Facility. The views expressed in the article do not necessarily represent the views of the DOE or the U.S. Government. The U.S. Government retains and the publisher, by accepting the article for publication, acknowledges that the U.S. Government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this work, or allow others to do so, for U.S. Government purposes. Z.S and K.M. were supported by project LUAUS25268 from Ministry of Education Youth and Sports (MEYS) and by the project Advanced Functional Nanorobots (reg. No. CZ.02.1.01/0.0/0.0/15_003/0000444 financed by the EFRR). The publication was created as part of a project co-financed by the Polish Ministry of Science and Higher Education under contract no. 2025/WK/01.
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M.Ś. carried out all optical experiments, drafted the text and figures representing experimental results of the main manuscript and the supplementary information. M.R. participated in low magnetic field measurements and data processing, K.P. and P.Pe supported high magnetic field measurements. M.D. participated in data analysis and interpretation. D.P. contributed to the theoretical calculations. K.M. synthesised the CrSBr crystal with the support and supervision of Z.S. M.v.S. contributed to the theoretical calculation and manuscript writing. F.D. was involved in data interpretation and manuscript writing. M.B., together with P.P. supervised magnetic field measurements, participated in data analysis interpretation, and manuscript writing. S.A. performed theoretical calculations, helped in interpreting the observations, conceived the main theme of the work and contributed to manuscript writing.
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Śmiertka, M., Rygała, M., Posmyk, K. et al. Distinct magneto-optical response of Frenkel and Wannier excitons in CrSBr. Nat Commun (2026). https://doi.org/10.1038/s41467-026-68482-5
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DOI: https://doi.org/10.1038/s41467-026-68482-5
