Revealing the Substrate Origin of the Linear Dispersion of Silicene/Ag(111)

The band structure of the recently synthesized (3 x 3) silicene monolayer on (4 x 4) Ag(111) is investigated using density functional theory. A k-projection technique that includes the k(perpendicular to)-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 x 1) silicene but also demonstrate that these originate from the k(i)-dependence of Ag(111) substrate states (modified by interactions with the silicene) and not from a Dirac state.