Multi-walled carbon nanotubes with NbN superconducting electrodes

We fabricated NbN/multi-walled carbon nanotube (MWNT)/Al junctions using MWNTs standing in nano-porous alumina membranes. We observed a reduction in the resistance within the NbN superconducting energy gap voltage caused by Andreev reflection. Moreover, we found that the conductance scales in the form of power laws with respect to temperature and bias voltage, and the power-law exponent α becomes larger when NbN becomes superconductive. These experimental results can be qualitatively explained by the theory of superconductor-Tomonaga–Luttinger liquid hybrid systems.