Revealing fingerprints of valence excitons in x-ray absorption spectra with the Bethe-Salpeter equation

The Bethe-Salpeter equation (BSE) is a powerful theoretical approach that is capable to accurately treat electron-hole interactions in materials in an excited state. We developed an ab initio framework based on the BSE to describe a pump-probe experiment, in which an x-ray pulse probes solid-state valence excitons by means of x-ray absorption spectroscopy. Our theoretical framework is of relevance for an accurate modeling of pump-probe experiments of photo-excited materials that utilize novel capabilities offered by x-ray science.