We investigate the effects of environmental dielectric screening on the electronic dispersion and the band gap in the atomically-thin, quasi two-dimensional (2D) semiconductor WS2 using correlative angle-resolved photoemission and optical spectroscopies, along with first-principles calculations. We find the main effect of increased environmental screening to be a reduction of the band gap, with little change to the electronic dispersion of the band structure. These essentially rigid shifts of the bands results from the special spatial structure of the changes in the Coulomb potential induced by the dielectric environment in the 2D limit. Our results suggest dielectric engineering as a non-invasive method of tailoring the band structure of 2D semiconductors and provide guidance for understanding the electronic properties of 2D materials embedded in multilayer heterostructures.
@article{arxiv.1907.05535,
title = {Rigid band shifts in two-dimensional semiconductors through environmental screening},
author = {Lutz Waldecker and Archana Raja and Malte Rösner and Christina Steinke and Aaron Bostwick and Roland J. Koch and Chris Jozwiak and Takashi Taniguchi and Kenji Watanabe and Eli Rotenberg and Tim O. Wehling and Tony F. Heinz},
journal= {arXiv preprint arXiv:1907.05535},
year = {2019}
}