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Supercurrents through Carbon Nanotubes

Hélène Bouchiat (June 1999)

CNRS researchers at the Orsay Laboratory of Solid State Physics have observed proximity-induced superconductivity in single-walled carbon nanotubes.

Single-walled carbon nanotubes, with a diameter of 1 nm and a length of the order of a few micrometers, are model systems for the study of one-dimensional electronic transport. According to theoretical predictions, they should be very sensitive to Coulomb repulsion and become insulators at low temperatures. Such electronic properties are in theory incompatible with superconductivity. However, researchers have shown that it is possible to create superconducting junctions with carbon nanotubes connected to superconducting contacts. When the resistance of the nanotube junction is sufficiently low, it becomes superconducting and can carry high supercurrents. This junction exhibits surprising features that are related to its highly one-dimensional character. Such supercurrents are known as Josephson currents, which characterize Josephson tunnel junctions and more generally superconducting weak links made of a small piece of normal metal between superconducting contacts. Suspended carbon nanotubes between superconductor contacts constitute a new type of Josephson junction, which offers interesting potential applications such as very sensitive bolometers, which are thermal detectors of feeble infrared radiation.

Transmission electron microscope image of one singlewall nanotube suspended between two superconducting pads (bilayer Ta/Au electrode).

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