Electron excitations in doped semiconducting carbon nanotubes

We compute the dispersion of electron excitations of a doped semiconducting carbon nanotube based on a model of a one- dimensional electron gas with Coulomb interaction and two-fold orbital degeneracy. The SU(4) symmetry of the model leads to a rich spectrum with multiple isospin modes in addition to the usual plasmons and spinwaves. A recently developed approximate mapping of the problem in hand onto integrable models enables us to do computation in the most interesting strongly correlated regime of low doping, where velocities of the isospin and plasmon modes become very different. We discuss anomalous transport and tunneling properties that may be observable in this regime.