A study was made of the superconductor MgB2 by point-contact spectroscopy. The first derivative conductance of the current–voltage characteristics dI/dV(V) displays the Andreev reflection features at the superconductor–normal metal interface. The largest gap values were estimated to be Δ(4.2K) = 9–12meV. Clear evidence was also observed for the multiple-gap feature, with a small gap of Δ(4.2K) = 1 to 3meV. These gap values agree with the previous break-junction data. The observed peak positions in the second derivative conductance (d2I/dV2(V)) were consistent with the phonon density of states of inelastic neutron scattering measurements.

Point-Contact Spectroscopy Measurements of Binary Superconductor MgB2. T.Takasaki, T.Ekino, R.A.Ribeiro, T.Muranaka, H.Fujii, J.Akimitsu: Physica C, 2005, 426-431[1], 300-3