Filming vibronic core excitons in graphite with femtosecond inelastic X-ray scattering

Our latest research, published in Nature Communications, highlights a new result from the MagneDyn beamline at FERMI: femtosecond time-resolved resonant inelastic X-ray scattering can directly track the ultrafast dynamics of vibronically dressed core excitons in graphite.
image nat comm

By combining an ultrafast optical pump with femtosecond X-ray probe pulses at the carbon K edge, the experiment follows in real time how photoexcitation modifies the coupling between core excitons and lattice vibrations.
A central outcome of the work is the observation of a detuning-controlled crossover between distinct nonequilibrium regimes. By tuning the incident photon energy across the C 1s to σ resonance, the inelastic RIXS response becomes a sensitive probe of how electronic screening and vibrational dynamics evolve on the femtosecond timescale.
These results establish tr-RIXS as a powerful element-specific and symmetry-sensitive approach for investigating ultrafast electron-phonon interactions in graphite and related quantum materials. Supported by phenomenological modeling and first-principles calculations, this work expands the capabilities of the MagneDyn beamline for studying transient excitations in condensed matter with exceptional selectivity and time resolution.


Vibronic scattering concept
The figure illustrates the physical picture behind the experiment. A femtosecond X-ray pulse creates a short-lived core exciton that can couple to lattice vibrations before radiative decay. In the pump-probe scheme, the optical pulse drives the system out of equilibrium, while the delayed X-ray pulse measures how the inelastic phonon sideband evolves in time.
Detuning-controlled crossover
The figure shows the detuning dependence of the integrated inelastic RIXS signal across the carbon K-edge resonance. This behavior reveals a crossover between different dynamical regimes and demonstrates how the choice of probe photon energy can selectively emphasize complementary scattering pathways.

Ultrafast delay dynamics
The figure reports the transient evolution of the inelastic RIXS response as a function of pump-probe delay for different incident photon energies. Near resonance, the signal changes on an ultrafast timescale associated with the transient modification of core-exciton–phonon coupling. At larger detuning, the dynamics reflect a different interplay between electronic screening and hot-phonon relaxation.
Reference
M. Malvestuto, B. Volpato, E. Babici, R. Bhardwaj, A. Caretta, S. Laterza, F. Parmigiani, M. Manfredda, A. Simoncig, M. Zangrando, A. Demidovich, P. Susnjar, E. M. Allaria, A. D. Brynes, D. Garzella, L. Giannessi, P. Rebernik, F. Sottocorona, and D. Novko, “Ultrafast dynamics of vibronically dressed core excitons in graphite: a femtosecond RIXS perspective,” Nature Communications 17, 1158 (2026). DOI: 10.1038/s41467-025-67919-7.

 

Ultima modifica il Mercoledì, 25 Marzo 2026 11:34