Independent determination of the two gaps by directional point-contact spectroscopy in MgB_2 single crystals

TL;DR

This study uses directional point-contact spectroscopy on MgB_2 single crystals to independently measure the two superconducting gaps, reducing experimental uncertainty and confirming theoretical models.

Contribution

First application of directional point-contact spectroscopy to MgB_2 single crystals for independent gap measurement with improved accuracy.

Findings

Successfully separated contributions of sigma and pi bands.

Obtained independent measurements of Delta_sigma and Delta_pi.

Temperature dependence matches two-band superconductor models.

Abstract

Directional point-contact spectroscopy measurements were performed for the first time in state-of-the-art MgB_2 single crystals. The selective suppression of the superconductivity in the "pi" band by means of a suitable magnetic field allowed separating the partial contribution of each band to the total point-contact conductance. By fitting the partial conductance curves sigma_sigma(V) and sigma_pi(V), we got an independent determination of the two gaps, Delta_sigma and Delta_pi, 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 MgB_2.