Over the last two decades, intense ultrashort electromagnetic fields have enabled observing and controlling a number of emergent states in quantum materials. Some of most spectacular light-induced phenomena, such as superconducting-like phases, transient charge density wave ordering, and excitonic condensation, are found to occur in materials dominated by strong electronic correlations with a large susceptibility to external stimuli. A major need towards developing a microscopic understanding of these states of matter is the capability to directly measure their transient electronic dynamics and effective interactions.

In this talk, I will show how novel ultrafast x-ray spectroscopic methods, such as time-resolved x-ray absorption (trXAS) and time-resolved resonant inelastic x-ray scattering (trRIXS), enable tackling these questions with unprecedented detail [1]. I will particularly focus on light-driven Mott insulators, which are key to the emergence of light-induced superconductivity and are theoretically argued to host other exotic ordering phenomena upon photoexcitation, such as - pairing condensation. I will discuss how trXAS allows to accurately determine transient effective electronic interactions in 1D and 2D copper oxides, and how we can fully reconstruct the driven many-body state from the transient absorption spectrum [2,3]. Further, I will discuss how advances in trRIXS [1,4,5] enable mapping the excitation spectrum of the driven state, and the implications of these experiments for the realization of new light-induced states in photoexcited Mott insulators.

[1] M Mitrano & Y. Wang, Commun. Phys. 3, 184 (2020).
[2] D. R. Baykusheva, et al., Phys. Rev. X 12, 011013 (2022).
[3] D. R. Baykusheva, et al., forthcoming (2023).
[4] M. Mitrano, et al., Sci. Adv. 5, eaax3346 (2019).
[5] Y. Wang, et al., Commun. Phys. 4, 212 (2021).