The electronic properties of toroidal carbon nanotubes were studied by using a single π-band tight binding Hamiltonian and adopting real-space renormalization techniques within the Green’s function formalism. The analysis was restricted to the achiral torus, and the dependence of the toroidal energy spectra upon its radius and thickness (tube radius) was deduced from the local density of states. The possibility of a metal-insulating transition occurring in infinite single tubes and toroids was investigated as a function of magnetic and electric fields, applied in distinct configurations. Periodic Aharonov-Bohm oscillations in the local density of states at the Fermi level of the nanostructures were found as a result of the annular symmetry. When substitutional impurities were taken into account, the oscillatory behavior was found to be preserved.

Defects and External Field Effects on the Electronic Properties of a Carbon Nanotube Torus. A.Latgé, C.G.Rocha, L.A.L.Wanderley, M.Pacheco, P.Orellana, Z.Barticevic: Physical Review B, 2003, 67[15], 1554131-7