Photo-doped states in strongly correlated charge transfer insulators are characterized by d-d and d-p interactions and the resulting intertwined dynamics of charge excitations and local multiplets. Here we use femtosecond x-ray absorption spectroscopy in combination with dynamical mean-field theory to disentangle these contributions in NiO. Upon resonant optical excitation across the charge transfer gap, the Ni L3 and O K absorption edges red-shift for >10 ps, associated with photo-induced changes in the screening environment. An additional signature below the Ni L3 edge is identified for <1 ps, reflecting a transient nonthermal population of local many-body multiplets. We employ a nonthermal generalization of the multiplet ligand field theory to show that the feature originates from d-d transitions. Overall, the photo-doped state differs significantly from a chemically doped state. Our results demonstrate the ability to reveal excitation pathways in correlated materials by x-ray spectroscopies, which is relevant for ultrafast materials design.
@article{arxiv.2305.10145,
title = {Photo-induced charge-transfer renormalization in NiO},
author = {Tobias Lojewski and Denis Golez and Katharina Ollefs and Loïc Le Guyader and Lea Kämmerer and Nico Rothenbach and Robin Y. Engel and Piter S. Miedema and Martin Beye and Gheorghe S. Chiuzbăian and Robert Carley and Rafael Gort and Benjamin E. Van Kuiken and Giuseppe Mercurio and Justina Schlappa and Alexander Yaroslavtsev and Andreas Scherz and Florian Döring and Christian David and Heiko Wende and Uwe Bovensiepen and Martin Eckstein and Philipp Werner and Andrea Eschenlohr},
journal= {arXiv preprint arXiv:2305.10145},
year = {2024}
}