The electronic structure of epitaxial single-layer MoS2 on Au(111) is investigated by angle-resolved photoemission spectroscopy. Pristine and potassium-doped layers are studied in order to gain access to the conduction band. The potassium-doped layer is found to have a (1.39±0.05)~eV direct band gap at Kˉ with the valence band top at Γˉ having a significantly higher binding energy than at Kˉ. The moir\'e superstructure of the epitaxial system does not lead to the presence of observable replica bands or minigaps. The degeneracy of the upper valence band at Kˉ is found to be lifted by the spin-orbit interaction, leading to a splitting of (145±4)~meV. This splitting is anisotropic and in excellent agreement with recent calculations. Finally, it is shown that the strength of the potassium doping is k-dependent, leading to the possibility of band structure engineering in single-layers of transition metal dichalcogenides.
@article{arxiv.1410.0615,
title = {Electronic Structure of Epitaxial Single-Layer MoS$_2$},
author = {Jill A. Miwa and Søren Ulstrup and Signe G. Sørensen and Maciej Dendzik and Antonija Grubišić Čabo and Marco Bianchi and Jeppe Vang Lauritsen and Philip Hofmann},
journal= {arXiv preprint arXiv:1410.0615},
year = {2015}
}