Attochaos I: The classically chaotic postcursor of high harmonic generation

TL;DR

This paper investigates the presence of classical chaos in high harmonic generation by analyzing a Coulomb potential under a laser field, revealing chaos on longer timescales beyond the simple recollision model.

Contribution

It demonstrates the existence of classical chaotic motion in HHG beyond the simple three-step model using dynamical systems tools.

Findings

Chaos exists on longer timescales than the first recollision.

Lyapunov exponents indicate chaotic behavior.

Stroboscopic maps reveal chaotic dynamics in the Coulomb potential.

Abstract

Attosecond physics provides unique insights into light-matter interaction on ultrafast time scales. Its core phenomenon, High Harmonic Generation (HHG), is often described by a classical recollision model, the simple-man or three-step model, where the atomic potential is disregarded. Many features are already well explained using this model; however, the simplicity of the model does not allow the possibility of classical chaotic motion. We show that beyond this model, classical chaotic motion does exist albeit on timescales that are generally longer than the first recollision time. Chaos is analyzed using tools from the theory of dynamical systems, such as Lyapunov exponents and stroboscopic maps. The calculations are done for a one-dimensional Coulomb potential subjected to a linearly polarized electric field.