We report on time-resolved nonlinear terahertz spectroscopy of a strongly correlated ruthenate, ${\mathrm{CaRuO}}_3$, 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.

中文翻译：

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CaRuO3 中动重准粒子产生强太赫兹三次谐波

我们报告了强相关钌酸盐的时间分辨非线性太赫兹光谱，${\mathrm{氧化钙}}_3$，作为温度、频率和太赫兹场强的函数。在低于 80 K 的低温下可以明显观察到频率高达 2.1 THz 的三次谐波辐射，其中低频线性动态响应偏离德鲁德模型，并且通过与洪德耦合相关的强相关性出现了相干的重准粒子带。在现象学上，通过采用实验观察到的与频率相关的散射率，场驱动动力学与德鲁德行为的偏差在与时间相关的玻尔兹曼描述中得到调和，这允许将观察到的三次谐波产生归因于太赫兹场驱动重准粒子的非线性动力学。