Carbon nanotubes: Ballistic transport or room-temperature superconductivity?
We theoretically estimate the electron-phonon coupling constant lambda for metallic single-walled carbon nanotubes with a diameter of 1.4 nm. The partial electron-phonon coupling constant for the hardest phonon mode is estimated to be about 0.0036, in good agreement with that deduced from Raman scattering data assuming superconductivity above room temperature. Assuming no superconductivity, we estimate the room-temperature inelastic mean free path l_ep due to electron-phonon scattering to be about 0.46 micrometer, and the total room-temperature inelastic mean free path l_in to be about 0.16 micrometer. We then argue that the electrical transport data of individual multi-walled nanotubes cannot be explained by ballistic transport at room temperature but provide strong evidence for quasi-one-dimensional superconductivity above room temperature.