Carbon nanotubes (CNTs), which are one-dimensional (1D) molecular conductors, have attracted considerable attention. However, none of the research has reported on superconductivity (SC) in carrier-doped CNTs. Here, we report on SC with the world's highest transition temperature (T c) of 12 K in highly uniform thin films of boron-doped single-walled CNTs (B-SWNTs). We clarify correlation of SC with Fermi level tuning with van Hove singularities (VHS) in electronic density of states (DOS) in the SWNT. Moreover, we show fabrication of paper-like thin films consisting of a pseudo two-dimensional network of weakly coupled B-SWNTs (called the Buckypaper) and show an enhancement of the onset T c up to 19 K by applying only a small pressure. The present observations will shed light on the high feasibility of using CNTs as a 1D superconductor and also on the research of 1D electron correlation.
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