Observation of Dirac Cone Warping and Chirality Effects in Silicene

Abstract

We performed low temperature scanning tunneling microscopy (STM) and spectroscopy (STS) studies on the electronic properties of (√3 × √3)R30° phase of silicene on Ag(111) surface. We found the existence of Dirac Fermion chirality through the observation of -1.5 and -1.0 power law decay of quasiparticle interference (QPI) patterns. Moreover, in contrast to the trigonal warping of Dirac cone in graphene, we found that the Dirac cone of silicene is hexagonally warped, which is further confirmed by density functional calculations and explained by the unique superstructure of silicene. Our results demonstrate that the (√3 × √3)R30° phase is an ideal system to investigate the unique Dirac Fermion properties of silicene.

Dirac fermions in silicene on Pb(111) surface

“…[13][14][15][16][17] Also no Landau-level quantization has been observed in scanning tunneling spectroscopy (STS) in a magnetic field, 18 which clearly indicates absence of Dirac fermions, and even a two-dimensional character of the system. At the same time linear band dispersion has been confirmed experimentally for the ffiffi ffi 11,19,20 which however is expected to be a bilayer of silicene. 12,21,22 Possible loss of the linear dispersion was ascribed to the breaking of symmetry between the up and down out-of-plane atomic displacement.…”

Silicene on Ag(111): Geometric and electronic structures of a new honeycomb material of Si

“…One is bilayer silicene and the other the structure consisting of Ag atoms on the diamond-like Si layers. In addition, there remain intriguing puzzles to be resolved for the 4= ffiffiffi 3 p  4= ffiffiffi 3 p structure such as linear vs parabolic bands [89,91], the Fermi surface warping [92] and superconductivity [93].…”

Silicon Growth at the Two-Dimensional Limit on Ag(111)

“…Early experiments also report evidence for Dirac fermion charge carriers 20,21,23 and superconductivity 24 in this phase.…”