Superconducting energy gap distribution of MgB₂ investigated by point-contact spectroscopy

We performed point-contact spectroscopy on the binary superconductor MgB$_2$. The differential conductance shows gap-related structures which vary in width and position from contact to contact. The distribution of energy gaps shows a distinct accumulation around 1.7 and 7 meV which is associated with the occurrence of a small and a large energy gap in MgB$_2$. While with increasing $T$ the structure in $dI/dV$ associated with the small gap is present up to $T_C$, in magnetic field it is suppressed well below $B_{c2}$.