Fractional Flux Periodicity in Doped Carbon Nanotubes
  An anomalous magnetic flux periodicity of the ground state is predicted in two-dimensional cylindrical surface composed of square and honeycomb lattice. The ground state and persistent currents exhibit an approximate fractional period of the flux quantum for a specific Fermi energy. The period depends on the aspect ratio of the cylinder and on the lattice structure around the axis. We discuss possibility of this nontrivial periodicity in a heavily doped armchair carbon nanotube. 
K. Sasaki, S. Murakami and R. Saito