Low temperature transport measurements on carbon nanotubes: superconducting proximity effect and intrinsic superconductivity in carbon nanotubes

Mathieu Kociak

I will present low temperature transport measurements on individual single walled carbon nanotubes (SWNT) and on individual ropes of carbon nanotubes. I will first describe the method that allows to solder contacts to carbon nanotubes. Due to the quality of the contacts, I will show that we were able to obtain ohmic contacts even at temperatures down to 50 mK. By avoiding Coulomb blockade, this permits the study of low-temperature transport in carbon nanotubes. I will then present a first set of experiments in which individual SWNT and ropes are connected to superconducting pads. In this case, a clear superconducting transition appears, as deduced by resistance versus temperature and magnetic field and voltage versus intensity measurements. I will interpret this transition as a proximity effect, and discuss the peculiarity of its one-dimensionnality. Finally, I will discuss a second set of experiment on ropes of carbon nanotubes contacted to non-superconducting (normal metals) electrodes. In such a case, huge superconducting fluctuations are evidenced both in the linear and non-linear transport measurements. I will discuss this result in details, focusing again on the one-dimensionnal features of the ropes of carbon nanotubes.