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MA: Fachverband Magnetismus

MA 24: Focus Session: Nonlinear Spectroscopy of Collective Excitations in Quantum Magnets (joint session TT/MA)

MA 24.6: Talk

Wednesday, March 19, 2025, 12:15–12:30, H36

Quantitative Prediction of the Dynamics of In-Gap States in Correlated Materials as Seen in Pump-Probe PES, XAS and RIXS Experiments: A NiO Case Study — •Sina Shokri and Maurits W. Haverkort — Universität Heidelberg, Institut für Theoretische Physik, Philosophenweg 19, Heidelberg 69120 Germany

Attosecond pump-probe experiments allow one to study and steer quantum materials on their fundamental time-scales. For atoms and small molecules one can theoretically predict the electronic and vibrational dynamics induced by ultra-fast light pulses [1,2]. In solids a theoretical understanding is much harder. The coupling to many continuous degrees of freedom can result into rapid loss of coherence. Quantitative predictions how coherently driven excitations decohere is highly non-trivial. Correlated Mott- Hubbard or charge transfer insulators can show a variety of long lived excitonic excitations within the optical gap. With attosecond pump-probe spectroscopy it is possible to investigate the propagation and decay of such excitations, as recently shown by two-photon photo-emission spectroscopy of NiO. These experiments show photo-induced, long-lived in-gap states with coherent oscillations [3]. In this talk we will show, using non-linear response theory, how to quantitatively predict the dynamics of in-gap states in correlated materials after an optical excitation. We will furthermore show how this dynamics can be probed with different pump-probe experiments including photo-emission spectroscopy, x-ray absorption spectroscopy and resonant inelastic x-ray scattering.

[1] PRL 128, 153001 (2022).

[2] PRA 108, 032816 (2023).

[3] Nat. Commun. 11, 4095 (2020).

Keywords: ultrafast; attosecond; spectroscopy; pump-probe; NiO