Harnessing dressed time-dependent density functional theory for the nonperturbative regime: Electron dynamics with double excitations

Recent progress has been made in capturing spectral features of electronic states of double-excitation character in time-dependent density functional theory (TDDFT) through a frequency-dependent kernel. While it might appear that this development is limited to the perturbative regime, we show that when used within response-reformulated TDDFT (RR-TDDFT), it accurately captures strong-field dynamics involving states of double-excitation character. More generally, this demonstrates how RR-TDDFT enables exchange-correlation functional developments in the response regime, which have so far been more successful than those in the nonlinear regime, to be exploited for nonperturbative dynamics, thus significantly broadening their range of applications.