Speaker
Description
We present an efficient first-principles approach to nonequilibrium electron dynamics in extended systems, leveraging Koopmans-compliant spectral functionals and Wannier functions. Koopmans functionals provide an accurate description of the quasiparticle band structure, which serves as the static starting point for real-time propagation of the electronic density matrix within the Hartree-plus-screened-exchange (HSEX) approximation. The use of localized Wannier functions significantly reduces the computational cost and memory footprint, enabling simulations of larger systems and longer timescales. The HSEX self-energy is efficiently evaluated using density-functional perturbation theory, avoiding explicit calculation of unoccupied states and dielectric matrices. Benchmark calculations reproduce experimental and GW-BSE optical absorption spectra across systems with weakly and strongly bound excitons. We then apply the framework to high-harmonic generation (HHG) showing that the harmonic emission is selectively enhanced at excitonic resonances, providing direct evidence that HHG probes correlated electron-hole excitations rather than the quasiparticle band structure alone.