Evidence for Two Superconducting Energy Gaps in MgB2 by Point-Contact Spectroscopy
Résumé
Experimental support is found for the multiband model of the superconductivity in the recently discovered system MgB2 with the transition temperature Tc 39 K. By means of Andreev reflection, evidence is obtained for two distinct superconducting energy gaps. The sizes of the two gaps (DS 2.8 meV and DL 7 meV) are, respectively, smaller and larger than the expected weak coupling value. Because of the temperature smearing of the spectra the two gaps are hardly distinguishable at elevated temperatures, but when a magnetic field is applied the presence of two gaps can be demonstrated close to the bulk Tc in the raw data.
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