Magnetic excitations of carbon nanotubes in chiral model of graphene

Abstract

Within the scope of the chiral model of graphene in 8-spinor realization, suggested earlier [1, 2], the combined spinor field Ψ is used as a new order parameter, which contains information on spin and quasispin excitations in graphene (8-spinor part) and also that on sp-hybridization effect of carbon valence electrons [SU(2)-matrix part]. This model admits two kinds of configurations describing, in the long-wave approximation, the graphene mono-atomic plane and the carbon nanotube respectively. The first one is given by the domain-wall (or kink-like) solution and the second one is described by the hedgehog ansatz with large topological charge (winding number n). We consider the infinite carbon nanotube in a static external magnetic field oriented along the tube and analyze the structure of the magnetic intensity on the outside. The diamagnetic behavior of the material is shown by the perturbation method which proves to be self-consistent for n ≫ 1.