Electronic Structures of Carbon-Based Kagomé Lattices

A structurally stable two-dimensional carbon allotrope of graphene is studied theoretically based on the first-principles calculations. This allotrope can be formed by inserting acetylene and diacetylene fragments into β-graphyne. The calculations on structure and electronic energy spectra show that the carbon Kagomé lattice is a structurally stable semimetal with the Dirac cones below the Fermi surface, in contrast to the Dirac points at the Fermi surface in intrinsic graphene.