Electronic structure of helically coiled cage of graphitic carbon

General features of the electronic states of helically coiled cages of graphite layer are studied by simple tight-binding models. The topological structure of the cages, which is determined by the distributions of the 5-membered and 7-membered rings, governs the electronic behavior around the Fermi level. Unlike the carbon nanotubes, some types of them show semimetallic character having a sharp peak at the Fermi level, which might cause interesting properties such as the superconducting ones.