Two band/two gap superconductivity in carbon-substituted MgB2 evidenced by point-contact spectroscopy

TL;DR

This study uses point-contact spectroscopy to show that two band/two gap superconductivity persists in carbon-substituted MgB2 despite a significant reduction in transition temperature.

Contribution

It provides experimental evidence that two gap superconductivity remains in MgB2 even after carbon substitution, despite Tc suppression.

Findings

Superconducting energy gap is reduced but still present.

Two gap superconductivity persists after carbon substitution.

Transition temperature decreases by 17 K.

Abstract

The Andreev reflection measurements of the superconducting energy gap in the carbon-substituted MgB$_2$ are presented. Despite the strong suppression of the transition temperature by 17 K in comparison with the pure MgB$_2$, the same reduced value of the small superconducting energy gap with $2\Delta/kT_c \approx$ 1.7 has been systematically observed. This indicates that the two band/two gap superconductivity is still preserved here.