Absence of a Dirac cone in silicene on Ag(111): First-principles density functional calculations with a modified effective band structure technique

We investigate the currently debated issue of the existence of the Dirac cone in silicene on an Ag(111) surface, using first-principles calculations based on density functional theory to obtain the band structure. By unfolding the band structure in the Brillouin zone of a supercell to that of a primitive cell, followed by projecting onto Ag and silicene subsystems, we demonstrate that the Dirac cone in silicene on Ag(111) is destroyed. Our results clearly indicate that the linear dispersions observed in both angular-resolved photoemission spectroscopy [P. Vogt et al., Phys. Rev. Lett. 108, 155501 (2012)] and scanning tunneling spectroscopy [L. Chen et al., Phys. Rev. Lett. 109, 056804 (2012)] come from the Ag substrate and not from silicene.