Speaker
Description
The microscopic structure and dynamics of valence electrons determine many of a material's properties, including its optical ones. Conventional x-ray scattering can resolve the angstrom-scale electronic structure, but it is difficult to separate the valence electrons from the more localized core electrons. Here we report nonlinear x-ray scattering measurements from optically-driven valence electrons using the LCLS hard x-ray free-electron laser. We measure the phase-matched x-ray-optical sum frequency generation between two optical photons and a single x-ray photon in bulk centrosymmetric silicon.* We show that a single higher-order wave-mixing measurement gives critical information on the optically inaccessible nonlinear driven valence electron density. In particular, we measure the reduced site symmetry of the bonding electrons including their local inversion-symmetry breaking. The results have implications for understanding optically driven materials in both the strong field regime and with exotic properties.
Footnotes
- Ornelas-Skarin, C., Bezriadina, T., Fuchs, M., Ghimire, S., Hastings, J. B., Nguyen, Q. L., ... & Reis, D. A. (2026). Second-order microscopic nonlinear optical susceptibility in a centrosymmetric material: application to imaging valence electron motion. Physical Review X, 16(1), 011006.
Funding Agency
The U.S. Department of
Energy, Office of Science, Office of Basic Energy Sciences,
Chemical Sciences, Geosciences, and Biosciences Division
through the AMOS program
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