The aim of this project is to study the super current transport in S-N-S structures (Superconductor - Normal metal - Superconductor), where the role of the normal metal is played by a metallic carbon nanotube. Carbon nanotubes are quasi-one dimensional molecules with either semiconducting or metallic properties, depending on their chirality and diameter. The combination of their macroscopic length, nm scale diameter and the perfection of their atomic structure, makes them ideal candidates to study the transport in one-dimensional systems, where only few conductive channels are allowed. Recent experiments have demonstrated that a single wall metallic nanotube can support a supercurrent between two bulk superconductors and that ropes of single wall nanotubes are superconductive at very low temperature. We propose to fabricate and study multi-terminal S-N-S devices with additional contacts attached to a nanotube in order to influence its electronic system. The realisation of this devices make possible the study of S-N-S systems in the ballistic regime, a situation not yet realised in conventional SNS structures.
Moreover the one-dimensional character of the current transport in carbon nanotubes promises a more efficient control of the supercurrent by external gates. Experiments in this direction will provide both a better understanding of electronic structure of carbon nanotubes, and the possible interplay between intrinsic superconductive fluctuation and proximity effect in the supercurrent transport. The applicant will obtain training in all aspects of production and characterization of carbon nanotubes She will also have full access to and training in the use of the state-of-the-art nanolithography facilities at the new MC2 clean room available at the host institute and to a wide range of standard nanotube characterization techniques such as SEM/EM, AFM, Raman spectroscopy. All this aspects in combination with her existing background in high temperature superconductivity, will place her in an excellent position for pursuing research into nanoscale superconductivity. The host institute will benefit of the applicant experience in different aspects of superconductivity, material science and device fabrication which complements in a very interesting way with its existing activities.