Mapping light-dressed Floquet bands by highly nonlinear optical excitations and valley polarization

TL;DR

This paper demonstrates how Floquet light-dressed states can be used to map nonlinear optical excitations and valley polarization in 2D materials like hBN, providing a new approach for ultrafast spectroscopy.

Contribution

It introduces a theoretical framework showing that Floquet states, rather than undressed states, are essential to understand nonlinear optical phenomena in 2D materials.

Findings

Floquet states reveal band-dressing effects in nonlinear optics.

Elliptically-polarized lasers induce k-resolved charge patterns in hBN.

The work provides a measurable signature for ultrafast valley manipulation.

Abstract

Ultrafast nonlinear optical phenomena in solids have been attracting major interest as novel methodologies for femtosecond spectroscopy of electron dynamics and control of material properties. Here, we theoretically investigate strong-field nonlinear optical transitions in a prototypical two-dimensional material, hBN, and show that the k-resolved conduction band charge occupation patterns induced by an elliptically-polarized laser can be understood in a multi-photon resonant picture; but remarkably, only if using the Floquet light-dressed states instead of the undressed matter states. Consequently, our work establishes a direct measurable signature for band-dressing in nonlinear optical processes in solids, and opens new paths for ultrafast spectroscopy and valley manipulation.