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Evidence for two superconducting energy gaps in MgB2 by point-contact spectroscopy

P. Szabo·P. Samuely·J. Kacmarcik·Th. Klein·J. Marcus·D. Fruchart·S. Miraglia·C. Marcenat·A. G. M. Jansen
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Abstract

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 (Delta_S = 2.8 meV and Delta_L = 7 meV) are respectively smaller and larger than the expected weak coupling value. Due to 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 T_c in the raw data.

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P. Szabo, P. Samuely, J. Kacmarcik, Th. Klein, J. Marcus, D. Fruchart, S. Miraglia, C. Marcenat, A. G. M. Jansen. 2001-08-20. Evidence for two superconducting energy gaps in MgB2 by point-contact spectroscopy. https://doi.org/10.1103/physrevlett.87.137005

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