Transport properties of superconducting films and heterostructures

Superconducting materials having nanometric characteristic dimensions represent a huge field of investigation, which became accessible only very recently. Properties of superconducting nanowires (NWs) are only two examples of how rich the physics revealed by these systems can be. In particular, in the last years transport properties of superconducting NWs have been intensively investigated both to address fundamental issues, as well as to find new applications in superconducting electronics.

This work deals with the experimental investigation of the electrical properties of interconnected  networks consisting of Nb ultrathin superconducting nanowires achieved by using Porous Silicon single crystals as template substrates. Quantum fluctuations of the superconducting order parameter were consistently revealed from both R(T) and V(I) measurements. All the data were coherently reproduced in the framework of theoretical models elaborated to describe QPS processes. Moreover, as a consequence of the multiple-connectivity of the system, transport properties in applied magnetic fields also reveal peculiar magnetoresistance oscillations, fingerprint of the presence of a coherent state. These systems offer the unique opportunity of accessing the low dimensional regime using a broadly available fabrication technique based on rigid and robust supports. The proposed systems combine two apparently opposing requests: the access the low dimensional transport regime and the use of robust porous Silicon crystals as stable supports, which overcome complex, expensive and time consuming approach usually used at this purpose. They are rather simple and macroscopically large objects, which, however, reveal fascinating quantum effects.