Lattice instability and superconductivity in electron doped (3, 3) carbon nanotubes

We investigated the effect of electron doping on the phonon dispersion and electron-phonon coupling of a small diameter (3, 3) carbon nanotube using first principles density functional perturbation theory. Electron doping increases the number of nesting features in the electronic band structure, which is reflected in a wealth of phonon anomalies. We found that the overall electron-phonon coupling is substantially enhanced with respect to the pristine tube, which improves superconductivity. At the same time, the intrinsic Peierls instability remains similar, but the Peierls temperature still remains larger than the superconducting transition temperature.