Imaging interatomic electron current in crystals with ultrafast resonant x-ray scattering

We demonstrate how the technique of ultrafast resonant x-ray scattering can be applied to imaging dynamics of electronic wave packets in crystals. We study scattering patterns from crystals with electron dynamics in valence bands taking into account that inelastic and elastic scattering events induced by a broadband probe pulse cannot be separated through the spectroscopy of the scattered photon. As a result, scattering patterns are not determined by the structure factor at the time of measurement, but can encode the instantaneous electron current between scattering atoms. We provide examples of how the interatomic electron current in a periodic structure can be extracted from a single scattering pattern by considering valence electron-hole motion in ${(\mathrm{KBr})}_{108}$ and ${\mathrm{Ge}}_{83}$ clusters.