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

Abstract: The Response-Reformulated Time-Dependent Density Functional Theory (RR-TDDFT) enables simulations of non-perturbative electron dynamics by propagating the coefficients of many-body eigenstates using ingredients from the response regime [1]. This method provides the same level of confidence in non-perturbative dynamics as TDDFT offers for response properties, significantly increasing the accuracy of the predictions of the commonly used adiabatic functionals for strong-field dynamics compared with the time-dependent Kohn-Sham scheme. However, it is well-known that adiabatic TDDFT fails to describe states with significant double-excitation character properly. A dressed TDDFT approximation has been shown to correctly reproduce the excitation energies and densities of such states by folding in double KS excitations[2]. Here, we demonstrate that incorporating the dressed TDDFT response quantities into the RR-TDDFT framework enables accurate, fully non-perturbative simulations that access double excitations in a computationally efficient and scalable manner, while employing RR-TDDFT for more than two states for the first time. This development improves the reliability of TDDFT-based approaches to strongly driven, non-equilibrium electron dynamics [3].

[1] D. B. Dar, A. Baranova, and N. T. Maitra, Phys. Rev. Lett. 133, 096401 (2024). https://doi.org/10.1103/PhysRevLett.133.096401

[2] D. B. Dar and N. T. Maitra, J. Chem. Phys. 159, 211104 (2023). https://doi.org/10.1063/5.0176705

[3] D. Ray, A. Baranova, D. B. Dar, and N. T. Maitra, arXiv:2510.17605 [physics.chem-ph] (2025). https://doi.org/10.48550/arXiv.2510.17605