Interplay of Tomonaga-Luttinger liquids and superconductive phase in carbon nanotubes

Abstract

We report the observation of the interplay between repulsive and superconducting correlations in boron-doped multi-walled carbon nanotubes (MWNTs) with a small number of conductance channels. NMR measurements ascertain the presence of substitutional boron doping with the optimum concentration for superconductivity (SC) in the MWNTs. We find that a gradual transition from Tomonaga-Luttinger-liquid (TLL) states to a SC regime can start only from low (eV /kT) values at low temperatures, while keeping a constant Luttinger parameter at high eV values, but the development of the SC enhances the regime to a high-(eV /kT) region. The phase diagram obtained from low-energy theory reveals that such a transition is actually possible depending on van Hove singularity in one-dimensional electronic states.