Atomic Floquet physics revealed by free electrons

TL;DR

This paper explores how free electrons can probe the nonlinear Floquet dynamics of atoms under intense light, revealing complex energy features and resonances that depend on light parameters.

Contribution

It introduces a quantum-mechanical formalism to analyze free electron interactions with illuminated atoms, uncovering new Floquet-related energy features and resonances.

Findings

Identification of energy features from electron-photon exchanges

Observation of Floquet resonances dependent on light intensity and frequency

Revelation of complex electron-atom interaction effects under strong illumination

Abstract

We theoretically investigate the ability of free electrons to yield information on the nonlinear Floquet dynamics of atomic systems subject to intense external illumination. By applying a quantum-mechanical formalism to describe the atom-electron interaction under the presence of a monochromatic classical light field, we observe multiple energy features that reveal a large departure from non-illumination conditions in two- and three-level illuminated atoms, including the emergence of energy features associated with direct electron-photon exchanges, as well as a varied set of Floquet resonances that strongly depend on the light intensity and frequency. Our results unveil a wealth of effects associated with the interaction between free electrons and optically driven electronic systems.