Exciton-coherence generation through diabatic and adiabatic dynamics of Floquet state

TL;DR

This paper demonstrates how ultrafast, intense mid-infrared pulses can generate and reveal the dynamics of Floquet states in monolayer WSe2, enabling control of quantum material properties via pulse shaping.

Contribution

It provides the first experimental observation of coherent exciton emissions linked to Floquet state dynamics under non-perturbative driving conditions.

Findings

Coherent exciton emissions observed under intense mid-infrared fields.

Emission reflects diabatic and adiabatic Floquet state dynamics.

Results enable ultrafast control of quantum states through pulse shaping.

Abstract

Floquet engineering of electronic systems is a promising way of controlling quantum material properties on an ultrafast time scale. So far, the energy structure of Floquet states in solids has been observed through time and angle-resolved photoelectron spectroscopy or pump-probe measurement techniques. However, the dynamical aspects of the photon-dressed states under ultrashort pulse driving have not been explored yet. Their dynamics become highly sensitive to the envelope of the driving field when the light-matter interaction enters non-perturbative regime, and thus, understanding of them is crucial for ultrafast manipulation of quantum state. Here, we observed coherent exciton emissions under intense and non-resonant mid-infrared fields in monolayer WSe2 at room temperature, which is unexpected in perturbative nonlinear optics. Together with numerical calculations, our measurements revealed that the coherent exciton emission reflects the diabatic and adiabatic dynamics of Floquet states. Our results provide a new approach to probing the dynamics of the Floquet state and lead to control of quantum materials through pulse shaping of the driving field.