Many-body effects in finite metallic carbon nanotubes

The nonhomogeneity of the charge distribution in a carbon nanotube leads to the formation of an excitonic resonance, in a way similar to the one observed in x-ray absorption in metals. As a result, a positive anomaly at low bias appears in the tunneling density of states. This effect depends on the screening of the electron-electron interactions by metallic gates, and it modifies the coupling of the nanotube to normal and superconducting electrodes.