Tracking doublon-holon dynamics in high-harmonic generation from Mott insulators

TL;DR

This study investigates high-harmonic generation in Mott insulators using exact methods, revealing how doublon-holon dynamics and filling-dependent responses influence the nonlinear optical behavior.

Contribution

It introduces a doublon-based diagnostic approach to analyze intraband and interband excitations in strongly correlated Mott insulators under intense laser fields.

Findings

Filling-dependent crossover from intraband to interband-dominated HHG.

Increasing interaction strength suppresses interband contributions.

Distinct emission features linked to quantum trajectories and filling.

Abstract

High-harmonic generation (HHG) in strongly correlated Mott insulators is investigated using exact diagonalization and time-dependent density-matrix propagation of a laser-driven one-dimensional Hubbard chain. By projecting onto equilibrium Hubbard bands, we use the doublon population and its dynamics as a diagnostic to analyze intraband (spin-wave-like) and interband (doublon-holon creation) excitation channels. A filling-dependent crossover emerges: Bloch-like intraband response at dilute filling, mixed dynamics at intermediate filling, and interband-dominated HHG with plateau and cutoff near half filling. In the considered parameter range, increasing interaction strength $U$ strongly suppresses interband contributions through the enlarged Mott gap and correlation-induced localization. Intra- and interband current decomposition reveals opposing flows below the Mott gap (\Delta_{\mathrm{Mott}}) and selective dephasing suppression of interband coherence, enhancing net doublon accumulation. Time-frequency analysis uncovers the filling-dependent features of quantum trajectories, manifesting in distinct below-\Delta_{\mathrm{Mott}} emission. This doublon-based analysis provides a transparent link between equilibrium spin-charge separation and nonequilibrium strong-field response, and clarifies how dephasing modifies interband coherence and doublon accumulation.