Speaker
Description
Resonant inelastic x-ray scattering (RIXS) is a premier tool for the investigation of quantum materials with strong electronic correlation. It is used to study high-energy spin excitations, charge transfer and orbital excitations, charge order and its associated fluctuations, electron-phonon coupling and hybrid modes among the listed ones. At synchrotron x-ray sources, high resolution RIXS has been providing landmark results on cuprates, nickelates and a variety of other transition-metal oxides in the last 20 years. More recently, the advent of high repetition rate x-ray free electron lasers (XFELs) has eventually enabled to add time resolution to RIXS experiments, where the sample is photo-excited by a few femtosecond optical laser pulse and probed by a resonant X-ray pulse. In this context, the realization of the hRIXS instrument at the coherent scattering (SCS) beamline of the European XFEL marks a milestone towards high energy-resolution time-resolved RIXS (trRIXS) [1].
The very first results on NiO and La2CuO4 immediately brought new insight on the photo-doped state of these archetypical charge transfer insulators. In particular, we observed that in NiO the above-gap optical excitation generates a transient charge-transfer excitonic state, whose main signature is an energy gain peak in the transient RIXS. The charge transfer exciton delocalizes within few picoseconds, leaving the system in a metastable state lasting for a much longer time [2].
I will present those pioneering results, and the outcome of successive experiments on NiO and cuprates, excited with different photon energy of the optical pump [3,4]. Although the potential of trRIXS to clarify the nature of photoexcited states in quantum materials is apparent from these early results, the interpretation of the data requires the deployment of an ambitious theoretical effort.
[1] J. Schlappa, G. Ghiringhelli, B.E. Van Kuiken, M. Teichmann, P.S. Miedem., J.T. Delitz, ... & A. Föhlisch, “The Heisenberg-RIXS instrument at the European XFEL. J. Synchrotron Radiation 32, 29 (2025).
[2] Giacomo Merzoni, Leonardo Martinelli, Sergii Parchenko, Sophia FR TenHuisen, Vasily Lebedev, Luigi Adriano, Robert Carley, Natalia Gerasimova, Laurent Mercadier, Martin Teichmann, Benjamin E van Kuiken, Zhong Yin, Amina Alic, Denitsa R Baykusheva, Sorin G Chiuzbaian, Stefano Dal Conte, Oleg Dogadov, Alexander Föhlisch, Maurits W Haverkort, Maximilian Kusch, Tim Laarmann, Wei Sheng Lee, Marco Moretti Sala, Ying Ying Peng, Qing Zheng Qiu, Thorsten Schmitt, Sreeju Sreekantan Nair Lalithambika, Simone Techert, Giulio Cerullo, Michael Först, Matteo Mitrano, Mark PM Dean, Justine Schlappa, Andreas Scherz, Giacomo Ghiringhelli “Photo-generated charge-transfer excitons in NiO revealed by time-resolved resonant inelastic x-ray Scattering”, arXiv:2504.16653.
[3] Daniel Jost, Jiarui Li, Jordyn Hales, Jonathan Sobota, Giacomo Merzoni, Leonardo Martinelli, Shuhan Ding, Kejun Xu, Justine Schlappa, Andreas Scherz, Robert Carley, Benjamin E Van Kuiken, Teguh C Asmara, Le Phuong Hoang, Laurent Mercadier, Sergii Parchenko, Martin Teichmann, Patrick S Kirchmann, Giacomo Ghiringhelli, Brian Moritz, Zhi-Xun Shen, Thomas P Devereaux, Yao Wang, Wei-Sheng Lee, “Robust Paramagnon and Acoustic Plasmon in a Photo-excited Electron-doped Cuprate Superconductor”, arXiv:2511.22054
[4] Giacomo Merzoni, Laurent Mercadier, Teguh Citra Asmara, Le Phuong Hoang, Sergii Parchenko, Eugenio Paris, Benjamin E. Van Kuiken, Floriana Lombardi, Robert Carley Riccardo Arpaia, Andreas Scherz, and Giacomo Ghiringhelli, “In-gap optical quenching of charge order in YBa2Cu3O7−δ”, 2026 unpublished
| Scientific Topics | Solid State Physics |
|---|