Interaction effects on electronic Floquet spectra: Excitonic effects

TL;DR

This paper investigates how many-body excitonic interactions influence the Floquet spectra of semiconductors under light, revealing significant corrections even with virtual exciton excitation, using perturbative analysis and specific material examples.

Contribution

It introduces a perturbative approach to incorporate excitonic effects into Floquet spectra analysis in non-equilibrium conditions, providing analytical and computational insights.

Findings

Excitonic effects cause significant modifications to Floquet spectra.

Perturbative expansion effectively captures many-body interaction impacts.

Results are demonstrated in phosphorene and MoS₂ for experimental relevance.

Abstract

Floquet engineering of electronic states by light is a central topic in modern experiments. However, the impact of many-body interactions on the single-electron properties remains unclear in this non-equilibrium situation. We propose that interaction effects could be reasonably understood by performing perturbative expansion in both the pump field and the electron-electron interaction when computing physical quantities. As an example, we apply this approach to semiconductors and show analytically that excitonic effects, i.e., effects of electron-hole interaction, lead to dramatic corrections to the single-electron Floquet spectra even when the excitons are only virtually excited by the pump light. We compute these effects in phosphorene and monolayer MoS$_2$ for time- and angle-resolved photoemission spectroscopy and ultrafast optical experiments.