Suppression of electron-electron repulsion and superconductivity in Ultra Small Carbon Nanotubes

TL;DR

This paper investigates the superconductivity observed in ultra-small carbon nanotubes, exploring whether it arises from purely electronic mechanisms using Luttinger and Hubbard models, and predicts a transition temperature consistent with experiments.

Contribution

It compares two theoretical approaches to explain superconductivity in ultra-small carbon nanotubes and predicts a transition temperature aligning with experimental observations.

Findings

Superconductivity observed at T_c ~ 15 K in ultra-small nanotubes.

Hubbard model predicts a transition temperature similar to experimental values.

Electronic mechanisms may explain superconductivity without lattice effects.

Abstract

Recently, ultra-small-diameter Single Wall Nano Tubes with diameter of $ \sim 0.4 nm$ have been produced and many unusual properties were observed, such as superconductivity, leading to a transition temperature $T_c\sim 15^oK$, much larger than that observed in the bundles of larger diameter tubes. By a comparison between two different approaches, we discuss the issue whether a superconducting behavior in these carbon nanotubes can arise by a purely electronic mechanism. The first approach is based on the Luttinger Model while the second one, which emphasizes the role of the lattice and short range interaction, is developed starting from the Hubbard Hamiltonian. By using the latter model we predict a transition temperature of the same order of magnitude as the measured one.