Floquet DMFT Analysis of High Harmonic Generation in Mott Insulators

TL;DR

This paper investigates high harmonic generation in Mott insulators using Floquet DMFT, revealing how the HHG spectrum varies with field strength and the underlying doublon-holon dynamics, providing insights into strongly correlated electron systems.

Contribution

The study applies Floquet DMFT to analyze HHG in Mott insulators, highlighting the different spectral features and scaling laws in weak and strong fields, which advances understanding of nonlinear optical responses in correlated materials.

Findings

HHG in Mott insulators is mainly due to doublon-holon recombination.

Weak-field HHG shows a single plateau with a linear cutoff scaling.

Strong-field HHG exhibits multiple plateaus with cutoff scaling as U + mE_0.

Abstract

We study the high harmonic generation (HHG) in Mott insulators using Floquet dynamical mean-field theory (DMFT). We show that the main origin of the HHG in Mott insulators is the doublon-holon recombination, and that the character of the HHG spectrum differs depending on the field strength. In the weaker-field regime, the HHG spectrum shows a single plateau as in the HHG from gases, and its cut-off energy $\epsilon_{\rm cut}$ scales linearly with the field strength $E_0$ as $\epsilon_{\rm cut}=\Delta_{\rm gap} + \alpha E_0$, where $\Delta_{\rm gap}$ is the Mott gap. On the other hand, in the stronger-field regime, multiple plateaus emerge and the $m$-th cut-off scales as $\epsilon_{\rm cut,m}=U + m E_0$. We show that this difference originates from the different dynamics of the doublons and holons in the weak- and strong-field regimes. We also comment on the similarities and differences between HHG from Mott insulators and from semiconductors. This proceedings paper complements our recent work, Phys. Rev. Lett. 121, 057405 (2018), with additional results and analyses.