Superconducting proximity correction to conductance and magnetoconductance fluctuations in random network carbon nanotubes

We investigated the superconducting proximity effect in carbon nanotubes (CNTs). Reentrant behavior caused by the proximity effect was observed in a sandwich structure of network-like CNTs coupled to NbN electrodes. The proximity effect gives rise to enhanced magnetoconductance fluctuations that are similar to universal conductance fluctuation. The proximity effect correction to the conductance and fluctuation amplitude disappears at low temperature and reaches a maximum value at about 8 K, which corresponds to Thouless energy. This reentrant behavior was also observed in the magnetic field dependance of fluctuation amplitude. We found that a correlation magnetic field of about 3 T induces the dephasing of the interference. This high magnetic field is due to the CNTs with small diameter. We discuss this proximity effect in these quasi-one-dimensional CNTs with random network structure in experiment and theory.