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 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 Γ, 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 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.