title: Self-Assembled Si(111) Surface States: 2D Dirac Material for THz Plasmonics.
abstract: Graphene, the first discovered 2D Dirac material, has had a profound impact on science and technology. In the last decade, we have witnessed huge advances in graphene related fundamental and applied research. Here, based on first-principles calculations, we propose a new 2D Dirac band on the Si(111) surface with 1/3 monolayer halogen coverage. The sp(3) dangling bonds form a honeycomb superstructure on the Si(111) surface that results in an anisotropic Dirac band with a group velocity (∼10(6)  m/s) comparable to that in graphene. Most remarkably, the Si-based surface Dirac band can be used to excite a tunable THz plasmon through electron-hole doping. Our results demonstrate a new way to design Dirac states on a traditional semiconductor surface, so as to make them directly compatible with Si technology. We envision this new type of Dirac material to be generalized to other semiconductor surfaces with broad applications.
authors.affiliation: Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026, China.|Department of Materials Science and Engineering, University of Utah, Salt Lake City, Utah 84112, USA.
authors.forename: Z F
authors.initials: ZF
authors.lastname: Wang
authors.affiliation: Department of Materials Science and Engineering, University of Utah, Salt Lake City, Utah 84112, USA.|Collaborative Innovation Center of Quantum Matter, Beijing 100084, China.
authors.forename: Feng
authors.initials: F
authors.lastname: Liu