Anisotropic Dirac cones in monoatomic hexagonal lattices: a DFT study
Departamento de Física, Universidad Nacional de
Colombia, Ciudad Universitaria, 111321
Received in final form: 5 February 2014
Published online: 19 March 2014
In the last few years, the fascinating properties of graphene have been thoroughly investigated. The existence of Dirac cones is the most important characteristic of the electronic band-structure of graphene. In this theoretical paper, hexagonal monolayers of silicon (h-Si) and germanium (h-Ge) are examined using density functional theory, within the generalized gradient approximation. Our numerical results indicate that both h-Si and h-Ge are chemically stable. The lattice parameters, electronic dispersion relations and densities of states for these systems are reported. The electronic dispersion relations display Dirac cones with the symmetry of an equilateral triangle (the group D3) in the vicinity of the K-points. Hence, the Fermi velocity depends on the wave vector direction around K-points. Fermi velocities for holes and electrons are significantly different. The maximum and minimum Fermi velocities are also reported.
Key words: Mesoscopic and Nanoscale Systems
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2014