Regensburg 2000 – wissenschaftliches Programm

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SYNA: Carbon Nanotubes

SYNA V: HV V

SYNA V.1: Hauptvortrag

Donnerstag, 30. März 2000, 12:00–12:30, H20

Proximity-induced superconductivity in single-walled carbon nanotubes — •Helène Bouchiat¹, A.Yu. Kasumov^1,2, R. Deblock¹, M. Kociak¹, B. Reulet¹, C. Journet³, and M. Burghard⁴ — ¹LPS, Université Paris-Sud, F-91405 Orsay, France — ²Russian Academy of Sciences, Chernogolowka, Russia — ³LPMC Montpellier, France — ⁴MPI-Stuttgart, Germany

Single wall carbon nanotubes (SWNT) have at most only two conducting modes at low temperature. They are model systems for the study of transport in one-dimensional conductors and are expected to present strong electronic correlations and non-Fermi-liquid behavior as suggested by recent experiments. In this talk we show experimental evidence of induced superconductivity in a SWNT. This proximity effect is observed in a unique 1.4 nm diameter SWNT and also in individual crystalline ropes containing about 100 nanotubes. These samples are suspended as strings between two superconducting electrodes (double layer Au-Re or Au-Ta film) at a distance varying between 100 and 2000 nm, enabling the structural characterization of these samples in a transmission electron microscope. The temperature dependence of the resistance of all measured samples, presents an anomaly at the superconducting transition of the electrodes. This anomaly strongly depends on the value of the resistance R of the different samples. When R is low enough, SWNTs become superconducting with surprisingly high critical currents (in the µAmpere range for a single tube of normal resistance 25 kOhm). This critical current, extensively studied as function of temperature and magnetic field, presents unusual features which are not observed in ordinary Superconducting-Normal-Superconducting junctions and can be related to the strong 1D character of these samples. Carbon nanotubes offer the possibility to fabricate high quality, very long and narrow suspended superconducting junctions whose aspect ratio has not previously been obtained with ordinary materials. They open a wide range of potentialities for both applications and fundamental studies.