Single-layer MoS2 on Au(111): Band gap renormalization and substrate interaction

The electronic structure of epitaxial single-layer MoS2 on Au(111) is investigated by angle-resolved photoemission spectroscopy, scanning tunneling spectroscopy, and first-principles calculations. While the band dispersion of the supported single layer is close to a free-standing layer in the vicinity of the valence-band maximum at (k) over bar and the calculated electronic band gap on Au(111) is similar to that calculated for the free-standing layer, significant modifications to the band structure are observed at other points of the two-dimensional Brillouin zone: at (Gamma) over bar, the valence-band maximum has a significantly higher binding energy than in the free MoS2 layer and the expected spin-degeneracy of the uppermost valence band at the (M) over bar point cannot be observed. These band structure changes are reproduced by the calculations and can be explained by the detailed interaction of the out-of-plane MoS2 orbitals with the substrate.