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

¹  Aoyama Gakuin University - 5-10-1 Fuchinobe, Sagamihara, Kanagawa 229-8558, Japan
²  Institute for Solid State Physics, University of Tokyo - Kashiwanoha 5-1-5, Kashiwa, Chiba 277-8581, Japan
³  JST-CREST - 4-1-8 Hon-machi, Kawaguchi, Saitama 332-0012, Japan
⁴  Instituto de Estructura de la Materia, CSIC - Serrano 123, 28006-Madrid, Spain, EU
⁵  Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca - 20125 Milano, Italy, EU
⁶  The Tokyo University - 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
⁷  Nagoya University - Furo-cho, Chigusa, Nagoya 464-8602, Japan

Corresponding author: J-haru@ee.aoyama.ac.jp

Received: 18 June 2009
Accepted: 21 December 2009

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.