Point-contact spectroscopy in MgB2: from fundamental physics to thin-film characterization

In this paper we highlight the advantages of using point-contact spectroscopy (PCS) in multigap superconductors like MgB2, both as a fundamental research tool and as a non-destructive diagnostic technique for the optimization of thin-film characteristics. We first present some results of crucial fundamental interest obtained by directional PCS in MgB2 single crystals, for example the temperature dependence of the gaps and of the critical fields, and the effect of a magnetic field on the gap amplitudes. Then, we show how PCS can provide useful information about the surface properties ofMgB2 thin films (e.g., Tc, gap amplitude(s), clean- or dirty-limit conditions) in view of their optimization for the fabrication of tunnel and Josephson junctions for applications in superconducting electronics.