Evidence for Dirac Fermions in a honeycomb lattice based on silicon

Lan Chen, Cheng-Cheng Liu, Baojie Feng, Xiaoyue He, Peng Cheng, Zijing Ding, Sheng Meng, Yugui Yao, Kehui Wu

Published 2012-04-12, updated 2012-04-13Version 2

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.