Atomic-scale imaging of laser-driven electron dynamics in solids using subcycle-resolved x-ray-optical wave mixing

TL;DR

This paper introduces a novel subcycle-resolved x-ray-optical wave mixing technique to image and analyze laser-driven electron dynamics in solids at the atomic scale, revealing symmetry effects and enabling reconstruction of charge distributions.

Contribution

The work develops a new method for reconstructing microscopic charge distributions and electron currents from x-ray-optical wave mixing spectra, advancing atomic-scale imaging of electron dynamics.

Findings

Reconstruction of Fourier components of charge distributions from spectra.

Identification of symmetry effects on wave mixing signals.

Visualization of microscopic electron currents and their phases.

Abstract

We investigate laser-driven electron dynamics in solids on the atomic scale and in real space within Floquet formalism, and develop a method based on subcycle-resolved x-ray-optical wave mixing to reconstruct those dynamics. We analyze how time-reversal and inversion symmetries influence properties of optically-induced charge distributions and microscopic electron currents. Several examples for the $\mu$th-order microscopic optical response of band-gap crystals are shown and compared for cases when there is either a considerable or a vanishing $\mu$th-order macroscopic response. We then analyze the consequence of crystal symmetries on subcycle-resolved x-ray-optical wave mixing, a process in which an x-ray pulse of a duration shorter than the optical cycle of the driving pulse interacts with a laser-dressed crystal. Based on this analysis, we develop a method to reconstruct amplitudes and phases of Fourier components of optically-induced charge distributions from momentum and delay dependence of x-ray-optical wave-mixing spectra. Subcycle-resolved x-ray-optical wave mixing also reveals phases of temporal oscillations of microscopic optical response and some properties of microscopic laser-driven electron currents.