Attosecond transient metallization in silica and diamond probed with inner-shell spectroscopy

Inner-shell attosecond transient absorption (ATA) is a promising technique for measuring ultrafast processes in solids, but experiments often hinge on simulation for relating spectra to underlying dynamics. In this talk, we present a first principles approach to simulating ATA in solids using bulk-mimicking clusters and real-time time-dependent density functional theory along with tuned range-separated hybrid functionals and Gaussian basis sets. This method provides good agreement with experimental data for the breakdown threshold of silica and diamond. This calculated breakdown voltage corresponds to a Keldysh parameter of approximately one in both cases, and thus corresponds to a transition to a tunneling regime. The calculated extreme ultraviolet ATA spectra also compare well with experiment, and in both materials the transient population in the conduction band causes a decrease in the optical density at the corresponding spectral peaks. First-principles approaches such as this are valuable for interpreting the complicated modulations in a spectrum, and for guiding future attosecond experiments on solids. Time permitting, generalizations to molecular X-ray pump/X-ray probe will also be discussed.