Independent determination of the two gaps by directional point-contact spectroscopy in MgB2 single crystals

Abstract

Directional point-contact spectroscopy measurements were performed for the first time in state-of-the-art MgB2 single crystals. The selective suppression of the superconductivity in the π band by means of a suitable magnetic field allowed separation of the partial contribution of each band to the total point-contact conductance. By fitting the partial conductance curves σσ(V) and σπ(V), we got an independent determination of the two gaps, Δσ and Δπ, with a strong reduction of the experimental uncertainty. Their temperature dependence was found to agree well with the predictions of the two-band models for MgB2.