Scanning tunnelling spectroscopy measurements of the gap properties of both ceramic MgB2 and c-axis oriented epitaxial MgB2 thin films were reported. Both exhibited a temperature dependent zero bias conductance peak and evidence for 2 superconducting gaps. Tunnelling spectroscopy was applied to superconductor–insulator–superconductor (S-I-S) junctions formed in 2 ways, as well as to normal metal–insulator–superconductor (N-I-S) junctions. A gap, Δ, of 2.2 to 2.8meV was find, with spectral features and temperature dependence that were consistent between S-I-S junction types. In addition, evidence was found for a second, larger gap of 7.2meV which was consistent with a proposed 2-band model.

MgB2 Energy Gap Determination by Scanning Tunnelling Spectroscopy. T.W.Heitmann, S.D.Bu, D.M.Kim, J.H.Choi, J.Giencke, C.B.Eom, K.A.Regan, N.Rogado, M.A.Hayward, T.He, J.S.Slusky, P.Khalifah, M.Haas, R.J.Cava, D.C.Larbalestier, M.S.Rzchowski: Superconductor Science and Technology, 2004, 17, 237-42