. . . . . . . . . .    ANM 2010     3rd International Conference on Advanced Nano Materials     12-15 September 2010 - Agadir, Morocco Back    Abstract ANMM174 INTRINSIC SUPERCONDUCTIVITY IN ARRAYS OF 4-ANGSTROM CARBON NANOTUBES EMBEDDED IN AFI ZEOLITE Ping Sheng Department of Physics and William Mong Institute of Nano Science and Technology Hong Kong University of Science and Technology, Clear Water Bay Kowloon, Hong Kong, China . Superconductivity in carbon nanotubes has been controversial because carbon is not known to be a superconducting element, and if there is indeed superconducting tendency in carbon nanotubes, its manifestation could be quenched by thermal fluctuations and by the Peierls distortion that favors an insulating ground state. Thus the earlier report on the Meissner effect in 4-Angstrom carbon nanotube-zeolite composites and the more recent observation of their superconducting specific heat signals have only deepened the mystery on the specific manner in which the nanotube superconductivity comes into being, and on whether there can be a sharp superconducting resistive transition usually characteristic of a superconductor.  In this talk I show that by making surface electrical contacts to the samples that are separated by only 100nm, repeatable observations of the superconducting resistive transition were obtained.  The physical picture which emerges is that of a coupled Josephson array consisting of aligned nanotubes crossing over from an individually fluctuating 1D system to a coherent 3D superconductor, mediated by a Berezinkii-Kosterlitz-Thouless (BKT) transition in the transverse plane perpendicular to the c-axis of the nanotubes.  The transition initiates at 15K with a slow resistance decrease and switches to a sharp drop between 7.5-6.0K. The attainment of global coherence at 5K and below is evidenced by the appearance of a well-defined (differential resistance) supercurrent gap. . © nanoAC . . . . . . . . . .

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