We demonstrate that a dynamical modification of the Hubbard $U$ in the model charge-transfer insulator NiO can be observed with state-of-the-art time-resolved absorption spectroscopy. Using a self-consistent time-dependent density functional theory plus $U$ computational framework, we show that the dynamical modulation of screening and Hubbard $U$ significantly changes the transient optical spectroscopy. Whereas we find the well-known dynamical Franz-Keldysh effect when the $U$ is frozen, we observe a dynamical band-gap renormalization for dynamical $U$. The renormalization of the optical gap is found to be smaller than the renormalization of $U$. This work opens up the possibility of driving a light-induced transition from a charge transfer into a Mott insulator phase.

• Received 26 June 2019
• Revised 5 February 2020
• Accepted 16 August 2020

DOI:https://doi.org/10.1103/PhysRevB.102.115106

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Published by the American Physical Society