We reveal the crucial effect of strong spin-charge coupling on high-harmonic generation (HHG) in Mott insulators. In a system with antiferromagnetic correlations, the HHG signal is drastically enhanced with decreasing temperature, even though the gap increases and the production of charge carriers is suppressed. This anomalous behavior, which has also been observed in recent HHG experiments on ${\mathrm{Ca}}_2{\mathrm{RuO}}_4$, originates from a cooperative effect between the spin-charge coupling and the thermal ensemble, as well as the strongly temperature-dependent coherence between charge carriers. We argue that the peculiar temperature dependence of HHG is a generic feature of Mott insulators, which can be controlled via the Coulomb interaction and dimensionality of the system. Our results demonstrate that correlations between different degrees of freedom, which are a characteristic feature of strongly correlated solids, have significant and nontrivial effects on nonlinear optical responses.

中文翻译：

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莫特绝缘体中高次谐波产生的异常温度依赖性

我们揭示了强自旋电荷耦合对 Mott 绝缘体中高谐波产生 (HHG) 的关键影响。在具有反铁磁相关性的系统中，HHG 信号随着温度的降低而显着增强，即使间隙增加并且电荷载流子的产生被抑制。这种异常行为，在最近的 HHG 实验中也观察到了${钙}_2{\mathrm{氧化钌}}_4$，源于自旋电荷耦合和热系综之间的协同效应，以及电荷载流子之间强烈的温度依赖性相干性。我们认为 HHG 的特殊温度依赖性是 Mott 绝缘体的一般特征，可以通过库仑相互作用和系统的维数来控制。我们的结果表明，不同自由度之间的相关性是强相关固体的特征，对非线性光学响应具有显着且非平凡的影响。