Correlation effects in carbon nanotubes

We consider the effects of Coulomb interactions on single-wall carbon nanotubes using an on-site Hubbard interaction, u . For the ~N ,N! armchair tubes the low-energy theory is shown to be identical to a two-chain Hubbard model at half-filling, with an effective interaction uN5u/N . Umklapp scattering leads to gaps in the spectrum of charge and spin excitations which are exponentially small for large N . Above the gaps the intrinsic nanotube resistivity due to these scattering processes is linear in temperature, as observed experimentally. The presence of ‘‘d-wave’’ superconductivity in the two-chain Hubbard model away from half-filling suggests that doped armchair nanotubes might exhibit superconductivity with a purely electronic mechanism. @S0163-1829~97!50518-2#