Gillmeister, Konrad Golež, Denis Chiang, Cheng-Tien Bittner, Nikolaj Pavlyukh, Yaroslav Berakdar, Jamal Werner, Philipp Widdra, Wolf 2020-08-14 Charge excitations across an electronic band gap play an important role in opto- electronics and light harvesting. In contrast to conventional semiconductors, studies of above-band-gap photoexcitations in strongly correlated materials are still in their infancy. Here we reveal the ultrafast dynamics controlled by Hund’s physics in strongly correlated photoexcited NiO. By combining time-resolved two-photon photoemission experiments with state-of-the-art numerical calculations, an ultrafast (≲10 fs) relaxation due to Hund excitations and related photo-induced in-gap states are identified. Remarkably, the weight of these in-gap states displays long-lived coherent THz oscillations up to 2 ps at low temperature. The frequency of these oscillations corresponds to the strength of the antiferromagnetic superexchange interaction in NiO and their lifetime vanishes slightly above the Néel temperature. Numerical simulations of a two-band t-J model reveal that the THz oscillations originate from the interplay between local many-body excitations and antiferromagnetic spin correlations. application/pdf https://folia.unifr.ch/global/documents/308820 https://folia.unifr.ch/documents/308820/files/wer_ucc.pdf https://folia.unifr.ch/documents/308820/files/wer_ucc_sm.pdf eng info:eu-repo/semantics/altIdentifier/doi/10.1038/s41467-020-17925-8 info:eu-repo/semantics/openAccess License undefined Nature Communications. - 2020, vol. 11, no. 1, p. 4095 info:eu-repo/classification/udc/53 Ultrafast coupled charge and spin dynamics in strongly correlated NiO http://purl.org/coar/resource_type/c_6501