k-resolved ultrafast light-induced band renormalization in monolayer WS$_2$ on graphene

TL;DR

This study uses time-resolved photoemission spectroscopy to reveal how resonant light excitation causes significant, transient changes in the electronic band structure of monolayer WS$_2$ on graphene, aligning with ab initio predictions.

Contribution

It provides the first detailed experimental and theoretical analysis of k-resolved ultrafast band renormalization in monolayer WS$_2$ on graphene after exciton resonance.

Findings

Significant transient band gap reduction observed.

Band structure renormalization agrees with ab initio calculations.

Insights into substrate and intrinsic effects on electronic dynamics.

Abstract

Understanding and controlling the electronic properties of two-dimensional materials is crucial for their potential applications in nano- and optoelectronics. Monolayer transition metal dichalcogenides such as WS$_2$ have garnered significant interest due to their strong light-matter interaction and extreme sensitivity of the band structure to the presence of photogenerated electron-hole pairs. In this study, we investigate the transient electronic structure of monolayer WS$_2$ on a graphene substrate after resonant excitation of the A-exciton using time- and angle-resolved photoemission spectroscopy. We observe a pronounced band structure renormalization including a substantial reduction of the transient band gap that is in good quantitative agreement with our {\it ab initio} theory that reveals the importance of both intrinsic WS$_2$ and extrinsic substrate contributions to the transient band structure of monolayer WS$_2$. Our findings not only deepen the fundamental understanding of band structure dynamics in two-dimensional materials but also offer valuable insights for the development of novel electronic and optoelectronic devices based on monolayer TMDs and their heterostructures with graphene.