Proximity-induced superconductivity in carbon nanotubes

• Published in: Comptes rendus de l'Académie des sciences. Série IIb, Mécanique, physique, astronomie Vol. 327; no. 9; pp. 933 - 943
• Main Authors: Kasumov, Alebker, Deblock, Richard, Kociak, Mathieu, Reulet, Bertrand, Bouchiat, Hélène, Khodos, Igor, Gorbatov, Yusif, Volkov, Vladimir, Journet, Catherine, Stephan, Odile, Burghard, Marko
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.09.1999
• Subjects: carbon nanotubes; effet de proximité; mesoscopic superconductivity; nanotubes de carbone; proximity effect; supraconductivité mésoscopique; nanotubes de carbone; supraconductivité mésoscopique; carbon nanotubes; proximity effect; mesoscopic superconductivity; effet de proximité
• ISSN: 1287-4620
• DOI: 10.1016/S1287-4620(99)80157-4

Single wall carbon nanotubes (SWNT) are model systems for the study of electronic transport in one-dimensional conductors. They are expected to exhibit strong electronic correlations and non-Fermi liquid behavior as suggested by recent experiments. The possibility to induce supercurrents through such molecular wires is a challenging question both for experimentalists and theoreticians. In this paper we show experimental evidence of induced superconductivity in a SWNT. This proximity effect is observed in a single 1 nm diameter SWNT, in individual cristalline ropes containing about 100 nanotubes and also on multiwalled tubes. These samples are suspended as strings between two superconducting electrodes (double layer Au-Re, Au-Ta or Sn film) at a distance varying between 100 and 2 000 nm. This allows their structural study in a transmission electron microscope. When their resistance is low enough, SWNT become superconducting with surprisingly high critical currents (in the micro-Ampere range for a single tube of normal state resistance 25 kΩ). This critical current, extensively studied as function of temperature and magnetic field, exhibits unusual features which are not observed in conventional Superconducting-Normal-Superconducting junctions and can be related to the strong 1D character of these samples. We also show evidence of a huge sensitivity of dc transport properties of the tubes to electromagnetic radiation in the radio-frequency range. Les nanotubes de carbone sont des systèmes modèles pour l'étude du transport électronique à une dimension. Nous montrons expérimentalement qu'il est possible d'induire de la supraconductivité dans ces fils moléculaires par effet de proximité. Les courants critiques des jonctions ainsi obtenues sont surprenants par leur amplitude, ainsi que leur dépendance en température et en champ magnétique.