Quantum transport through carbon nanotubes: proximity induced and intrinsic superconductivity

TL;DR

This study demonstrates proximity-induced and intrinsic superconductivity in suspended single-walled carbon nanotubes, revealing attractive interactions that enable superconductivity in one-dimensional systems at very low temperatures.

Contribution

It introduces a new technique for fabricating and characterizing nanotubes, and reports the first observation of intrinsic superconductivity in nanotube ropes with normal contacts.

Findings

Superconductivity observed with large supercurrents in proximity effect.

Intrinsic superconductivity in nanotube ropes with normal contacts.

Samples remain metallic and superconducting down to very low temperatures.

Abstract

We report low temperature transport measurements on suspended single walled carbon nanotubes (both individual tubes and ropes). The technique we have developed, where tubes are soldered on low resistive metallic contacts across a slit, enables a good characterization of the samples by transmission electron microscopy. It is possible to obtain individual tubes with a room temperature resistance smaller than 40 kOhms, which remain metallic down to very low temperatures. When the contact pads are superconducting, nanotubes exhibit proximity induced superconductivity with surprisingly large values of supercurrent. We have also recently observed intrinsic superconductivity in ropes of single walled carbon nanotubes connected to normal contacts, when the distance between the normal electrodes is large enough, since otherwise superconductivity is destroyed by (inverse) proximity effect. These experiments indicate the presence of attractive interactions in carbon nanotubes which overcome Coulomb repulsive interactions at low temperature, and enables investigation of superconductivity in a 1D limit never explored before.