Real-time TDDFT simulations of time-resolved core-level spectroscopies in solid state systems.

The advent of sub-femtosecond time-resolved core-level spectroscopies based on high harmonic generated XUV pulses has enabled the study of electron dyanamics on characteristic femtosecond time-scales. Unambiguous interpretation of these powerful yet complex spectroscopies however requires the development of theoretical algorithms capable of modeling light-matter interaction across a wide energy range spanning both valence and core orbitals. In this context we present a recent implementation of the velocity-gauge formalism of real-time TDDFT [1] within a linear combination of atomic orbital (LCAO) framework, which facilitates efficient numerical treatment of localized semi-core orbitals. Dynamics and spectra obtained from LCAO based simulations are compared to those from a real-space grid implementation [1]. Potential applications are also illustrated by applying the method towards interpreting recent atto-second time-resolved IR-pump XUV-probe spectroscopies investigating sub-cycle excitation dynamics in bulk silicon [2]. \newline \newline [1] Yabana et al., Phys. Rev. B 85, 045134 (2012) \newline \newline [2] Schultze et al., Science, 346, 1348 (2014)