Picosecond dynamics of optical and electronic properties in GaAs triggered by x-ray inner-shell excitation
Phys. Rev. B 114, 305201 – Published 10 November, 2026
DOI: https://doi.org/10.1103/pvcy-3rxg
Abstract
Femtosecond time-resolved optical absorption spectroscopy of gallium arsenide was performed using an x-ray free-electron laser (XFEL) to excite the K-shell electrons. The transient absorption spectra show a distinct increase in absorption extending to approximately below the band gap within after XFEL irradiation, suggesting the formation of localized states associated with core-hole generation. The transient feature subsequently relaxes on a few-picosecond timescale through many-body processes, accompanied by Pauli blocking arising from the redistribution of hot carriers within the valence and conduction bands. By comparison with near-infrared laser excitation, we found that x-ray excitation is characterized by the formation of transient absorption states below the band gap and reduced carrier accumulation at the conduction-band minimum. These results provide valuable insights into x-ray-induced electronic structure modifications and carrier dynamics in semiconductors on the picosecond timescale, where deep core holes and many-body effects play crucial roles.
