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

TL;DR

This study uses density functional theory and a $k$-projection technique to show that the linear dispersion in silicene on Ag(111) originates from substrate states, not intrinsic Dirac states, clarifying the substrate's role.

Contribution

The paper introduces a $k$-projection method including $k_ot$-dependence to distinguish substrate and silicene contributions in band structures.

Findings

Linear dispersion in silicene/Ag(111) is substrate-derived.

The observed gap and dispersion are due to substrate states, not Dirac states.

The method aligns well with photoemission experiments.

Abstract

The band structure of the recently synthesized (3$\times$3) silicene monolayer on (4$\times$4) Ag(111) is investigated using density functional theory. A $k$-projection technique that includes the $k_\bot$-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$\times$1) silicene, but also demonstrate that these originate from the $k_\bot$-dependence of Ag(111) substrate states (modified by interactions with the silicene) and \textit{not} from a Dirac state.