Revealing the substrate origin of the linear dispersion of silicene/Ag(111)

The band structure of the recently synthesized (3 × 3) silicene monolayer on (4 × 4) Ag(111) is investigated using density functional theory. A k-projection technique that includes the k⊥-dependence of the surface bands is used to separate the contributions arising from the silicene and the substrate, allowing a consistent comparison between the calculations and the angle-resolved photoemission experiments. Our calculations not only reproduce the observed gap and linear dispersion across the K point of (1 × 1) silicene but also demonstrate that these originate from the k⊥-dependence of Ag(111) substrate states (modified by interactions with the silicene) and not from a Dirac state.