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

P. Szabo (1) , P. Samuely , J. Kacmarcik , Thierry Klein (1) , J. Marcus (1) , Daniel Fruchart (2) , Salvatore Miraglia (2) , C. Marcenat (3) , A. G. M. Jansen (4)

1 LEPES - Laboratoire d'Etudes des Propriétés Electroniques des Solides
2 Laboratoire de Cristallographie
3 SPSMS - UMR 9001 - Service de Physique Statistique, Magnétisme et Supraconductivité
4 GHMFL - Grenoble High Magnetic Field Laboratory

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.

Domaines: Supraconductivité [cond-mat.supr-con]

P. Szabo, P. Samuely, J. Kacmarcik, Thierry Klein, J. Marcus, et al.. Evidence for two superconducting energy gaps in MgB2 by point-contact spectroscopy. Physical Review Letters, 2001, 87, pp.137005. ⟨hal-00122051⟩