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

We performed point-contact spectroscopy on the binary superconductor MgB2. 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 MgB2. While with increasing T the structure in dI/dV associated with the small gap is present up to Tc, in magnetic field it is suppressed well below Bc2.