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 WS2 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 WS2 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 WS2 and extrinsic substrate contributions to the transient band structure of monolayer WS2. 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.
@article{arxiv.2405.01371,
title = {k-resolved ultrafast light-induced band renormalization in monolayer WS$_2$ on graphene},
author = {Niklas Hofmann and Alexander Steinhoff and Razvan Krause and Neeraj Mishra and Giorgio Orlandini and Stiven Forti and Camilla Coletti and Tim O. Wehling and Isabella Gierz},
journal= {arXiv preprint arXiv:2405.01371},
year = {2025}
}