Multiband dynamics of extended harmonic generation in solids under ultraviolet injection

TL;DR

This study explores the multiband electron dynamics in solids during high harmonic generation using ultraviolet injection, revealing new insights into the emission mechanisms and potential applications in attosecond science.

Contribution

It introduces an extended three-step model validated for multiband harmonic emission and analyzes chirp characteristics related to electron trajectories in solids.

Findings

Harmonics in the second plateau are dominated by the extended three-step model.

Different electron trajectories (short, long, general) influence harmonic chirp characteristics.

Insights may advance attosecond science and band structure reconstruction.

Abstract

Using one-dimensional semiconductor Bloch equations, we investigate the multiband dynamics of electrons in a cutoff extension scheme employing an infrared pulse with additional UV injection. An extended three-step model is firstly validated to play a dominant role in emitting harmonics in the second plateau. Surprisingly, further analysis employing the acceleration theorem shows that though harmonics in both the primary and secondary present positive and negative chirps, the positive (negative) chirp in the first region is related to the so-called short (long) trajectory, while that in the second region is emitted through `general' trajectory, where electrons tunnelling earlier and recombining earlier contribute significantly. The novel characteristics deepen the understanding of high harmonic generation in solids and may have great significance in attosecond science and reconstruction of band dispersion beyond the band edge.