We report on time-resolved nonlinear terahertz spectroscopy of a strongly correlated ruthenate, CaRuO3, as a function of temperature, frequency and terahertz field strength. Third-harmonic radiation for frequencies up to 2.1 THz is observed evidently at low temperatures below 80 K, where the low-frequency linear dynamical response deviates from the Drude model and a coherent heavy quasiparticle band emerges by strong correlations associated with the Hund's coupling.Phenomenologically, by taking an experimentally observed frequency-dependent scattering rate, the deviation of the field driven kinetics from the Drude behavior is reconciled in a time-dependent Boltzmann description, which allows an attribution of the observed third-harmonic generation to the terahertz field driven nonlinear kinetics of the heavy quasiparticles.
@article{arxiv.2310.05760,
title = {Strong terahertz third-harmonic generation by kinetic heavy quasiparticles in CaRuO$_3$},
author = {C. Reinhoffer and Sven Esser and Sebastian Esser and E. A. Mashkovich and S. Germanskiy and P. Gegenwart and F. Anders and P. H. M. van Loosdrecht and Zhe Wang},
journal= {arXiv preprint arXiv:2310.05760},
year = {2024}
}