Evidence for Two Superconducting Energy Gaps in MgB2 by Point-Contact Spectroscopy

P. Szabo (1, 2) , P. Samuely (1) , J. Kacmarcík (1) , Thierry Klein (2) , J. Marcus (2) , D. Fruchart (3) , S. Miraglia (3) , C. Marcenat (4) , A. G. M. Jansen (5)

1 CLTP IEP - Centre of Low Temperature Physics
2 LEPES - Laboratoire d'Etudes des Propriétés Electroniques des Solides
3 Laboratoire de Cristallographie
4 SPSMS - UMR 9001 - Service de Physique Statistique, Magnétisme et Supraconductivité
5 LNCMI-G - Laboratoire national des champs magnétiques intenses - Grenoble

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.

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

P. Szabo, P. Samuely, J. Kacmarcík, 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. ⟨10.1103/PhysRevLett.87.137005⟩. ⟨hal-00959105⟩