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

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.

7 pages incl. 3 figures, final version. accepted for Phys. Rev. Lett

References in corpus (5)

• Boron Isotope Effect in Superconducting MgB${}_2$
• Specific heat in the superconducting and normal state (2-300 K, 0-16 Teslas), and magnetic susceptibility of the 38-K superconductor MgB2: evidence for a multicomponent gap
• The reduced total isotope effect and its implications on the nature of superconductivity in MgB2
• Scanning Tunneling Spectroscopy in MgB2
• Tunneling spectroscopy in small grains of superconducting MgB2

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