Dephasing of Strong-Field-Driven Floquet States Revealed by Time- and Spectrum-Resolved Quantum-Path Interferometry

TL;DR

This paper investigates how strong terahertz fields cause exciton dephasing and dissociation, revealing mechanisms and conditions for maintaining coherence in quantum materials under intense fields.

Contribution

It introduces a time- and spectrum-resolved interferometry method to study exciton dephasing, uncovering the primary role of dissociation at high field strengths.

Findings

Dephasing rate increases sharply beyond a threshold field.

Exciton dissociation is identified as the main dephasing mechanism.

Long dephasing times are observed for strong-field-dressed excitons.

Abstract

Floquet engineering, while a powerful tool for ultrafast quantum-state manipulation, faces challenges under strong-field conditions, as recent high harmonic generation studies unveil exceptionally short dephasing times. In this study, using time- and spectrum-resolved quantum-path interferometry, we investigate the dephasing mechanisms of terahertz-driven excitons. Our results reveal a dramatic increase in exciton dephasing rate beyond a threshold field strength, indicating exciton dissociation as the primary dephasing mechanism. Importantly, we demonstrate long dephasing times of strong-field-dressed excitons, supporting coherent strong-field manipulation of quantum materials.