Evidence for Dirac Fermions in a honeycomb lattice based on silicon

TL;DR

This study provides experimental evidence for Dirac fermions in silicene, a silicon-based honeycomb lattice, through STM and spectroscopy revealing linear dispersion and quasi-particle interference patterns.

Contribution

It demonstrates the existence of Dirac fermions in silicene on Ag(111), supported by direct STM and spectroscopy measurements showing linear dispersion.

Findings

Observation of a $\sqrt{3} imes \sqrt{3}$ reconstruction in silicene

Detection of quasi-particle interference patterns indicating Dirac fermions

Derivation of linear energy-momentum dispersion and high Fermi velocity

Abstract

Silicene, a sheet of silicon atoms in a honeycomb lattice, was proposed to be a new Dirac-type electron system similar as graphene. We performed scanning tunneling microscopy and spectroscopy studies on the atomic and electronic properties of silicene on Ag(111). An unexpected $\sqrt{3}\times \sqrt{3}$ reconstruction was found, which is explained by an extra-buckling model. Pronounced quasi-particle interferences (QPI) patterns, originating from both the intervalley and intravalley scattering, were observed. From the QPI patterns we derived a linear energy-momentum dispersion and a large Fermi velocity, which prove the existence of Dirac Fermions in silicene.