Crystal-momentum-resolved contributions to multiple plateaus of high-order harmonic generation from band-gap materials

TL;DR

This study investigates how initial crystal momenta influence high-order harmonic generation in band-gap materials, revealing that electrons away from the Gamma point contribute to higher plateaus, using a novel self-consistent periodic model.

Contribution

The paper introduces a self-consistent periodic approach to simulate HHG in infinite crystals beyond the single-active-electron approximation, linking initial crystal momentum to HHG plateau features.

Findings

Electrons away from Gamma point mainly contribute to higher HHG plateaus.

Electrons near Gamma point are responsible for the first plateau harmonics.

Finite models can effectively mimic infinite crystal HHG spectra.

Abstract

We study the crystal-momentum-resolved contributions to the high-order harmonic generation (HHG) in band-gap materials, and identify the relevant initial crystal momenta for the first and higher plateaus of the HHG spectra. We do so by using a time-dependent density-functional theory model of one-dimensional linear chains. We introduce a self-consistent periodic treatment for the infinitely extended limit of the linear chain model, which provides a convenient way to simulate and discuss the HHG from a perfect crystal beyond the single-active-electron approximation. The multi-plateau spectral feature is elucidated by a semiclassical k-space trajectory analysis with multiple conduction bands taken into account. In the considered laser-interaction regime, the multiple plateaus beyond the first cutoff are found to stem mainly from electrons with initial crystal momenta away from the Gamma point (k = 0), while electrons with initial crystal momenta located around the Gamma point are responsible for the harmonics in the first plateau. We also show that similar findings can be obtained from calculations using a sufficiently large finite model, which proves to mimic the corresponding infinite periodic limit in terms of the band structures and the HHG spectra.