Photo-generated charge-transfer excitons in NiO revealed by ultrafast time-resolved resonant inelastic x-ray scattering

Giacomo Merzoni; Leonardo Martinelli; Sergii Parchenko; Sophia F. R. 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 P. M. Dean; Justine Schlappa; Andreas Scherz; Giacomo Ghiringhelli

arXiv · 2504.16653

Photo-generated charge-transfer excitons in NiO revealed by ultrafast time-resolved resonant inelastic x-ray scattering

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Abstract

Strong electronic correlation can lead to insulating behavior and to the opening of large optical gaps, even in materials with partly filled valence shells. Although the non-equilibrium optical response encodes both local (quasi atomic) and collective (long range) responses, optical spectroscopy is usually more sensitive to the latter. Resonant x-ray techniques are better suited to investigate the quasi-atomic properties of correlated solids. Using time-resolved resonant inelastic x-ray scattering (RIXS), here we study the ultrafast non-equilibrium processes in NiO following photo-excitation by ultraviolet photons with energy exceeding the optical gap. We observe the creation of charge-transfer excitons that decay with a time constant of about 2\,ps, while itinerant photo-doping persists for tens of picoseconds. Following our discovery, which establishes time-resolved high-resolution RIXS as a powerful tool for the study of transient phenomena in condensed matter, the possible presence of charge-transfer excitons will need to be considered when interpreting optical pump-probe experiments on correlated quantum materials.

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Giacomo Merzoni, Leonardo Martinelli, Sergii Parchenko, Sophia F. R. 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 P. M. Dean, Justine Schlappa, Andreas Scherz, Giacomo Ghiringhelli. 2025-04-23. Photo-generated charge-transfer excitons in NiO revealed by ultrafast time-resolved resonant inelastic x-ray scattering. https://arxiv.org/abs/2504.16653

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