Abstract
Time-resolved resonant inelastic X-ray scattering (tr-RIXS) is a powerful technique for probing quasiparticle interactions in quantum materials under nonequilibrium conditions. Here, we implement tr-RIXS at the carbon K-edge to investigate the ultrafast dynamics of core excitons coupled to vibrational modes in graphite. Using femtosecond X-ray pulses from a free-electron laser, we monitor the temporal evolution of vibronically dressed excitons and their interaction with symmetry-selective optical phonons. By tuning the incident photon energy across the 1s → σ* resonance and analyzing the integrated inelastic sideband intensity, we reveal a detuning-controlled crossover between two complementary dynamical regimes. Phenomenological modeling and first-principles calculations reproduce both the magnitude and detuning dependence of the spectral-weight changes. In this work, enabled by the unique capabilities of X-ray free-electron lasers, we demonstrate how tr-RIXS can access coupled electronic and lattice dynamics with elemental and symmetry specificity, opening new routes to control vibronic interactions in light-element and low-dimensional quantum materials.
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Data availability
The data that support the findings of this study, including raw and processed RIXS spectra, XAS profiles, and analysis outputs, are publicly available in the Elettra Sincrotrone Trieste S.C.p.A. repository under the title Dataset of Ultrafast dynamics of vibronically dressed core excitons in graphite at https://doi.org/10.34965/i53456. Source data for Figs. 1-4 and Supplementary Figs. are provided with the paper.
Code availability
All analysis scripts and fitting routines used in this study are available in the same repository at https://doi.org/10.34965/i53456under a CC-BY-SA-4.0 license.
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Acknowledgements
We acknowledge the assistance of the staff at FERMI during the beamtimes 20209081 and 20214052. M.M. thanks Dr. Carlo Alberto Brondin (ISM-CNR) for the preparation of graphite crystals.
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M.M., A.C., R.B., and S.L. carried out the experiment, collected the data, and contributed to the preliminary analysis. B.V. and E.B. participated in the data analysis. The theoretical investigation was conducted by D.N., M.M., and A.C. were responsible for the MagneDyn endstation. P.R., E.M.A., A.D.B., L.G., D.G., and F.S. optimized the accelerator and provided the FEL beam. M.Ma., A.S., and M.Z. optimized the optical transport of the MagneDyn beamline and characterized the FEL pulses. A.C., A.D., and P.S. optimized the optical laser system. S.L., D.N., and F.P. contributed to the revision of the manuscript. M.M. wrote the manuscript, which all authors discussed. M.M. proposed and led the project.
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Malvestuto, M., Volpato, B., Babici, E. et al. Ultrafast dynamics of vibronically dressed core excitons in graphite: a femtosecond RIXS perspective. Nat Commun (2025). https://doi.org/10.1038/s41467-025-67919-7
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DOI: https://doi.org/10.1038/s41467-025-67919-7
