Evidence for two superconducting energy gaps in MgB2 by point-contact spectroscopy - art. no. 137005

Experimental support is found for the multiband model of the superconductiv ity in the recently discovered system MgB2 with the transition temperature T-c = 39 K. By means of Andreev reflection, evidence is obtained for two di stinct superconducting energy gaps. The sizes of the two gap. (Delta (S) = 2.8 meV and Delta (L) = 7 meV) are, respectively, smaller and larger than t he expected weak coupling value. Because of the temperature smearing of the spectra the two gap, are hardly distinguishable at elevated temperatures, but when a magnetic field is applied the presence of two gap, can be demons trated close to the bulk T-c in the raw data.