Point-Contact Spectroscopy in MgB_2: from Fundamental Physics to Thin-Film Characterization
R.S. Gonnelli, D. Daghero, A. Calzolari, G.A. Ummarino, V. Dellarocca, V.A. Stepanov, S.M. Kazakov, J. Karpinski, C. Portesi, E. Monticone, V. Ferrando, C. Ferdeghini
Abstract
In this paper we highlight the advantages of using point-contact spectroscopy (PCS) in multigap superconductors like MgB_2, 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 MgB_2 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 of MgB_2 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.