Figure 2: The subtle gap peak structure is not caused by Pb.
From: Momentum-dependent multiple gaps in magnesium diboride probed by electron tunnelling spectroscopy
(a) Tunnelling spectrum of a Pb/PbO/Pb junction at T=4.2 K. (inset) The single peak at about −2.6 mV corresponds to twice the average superconducting gap of Pb. The experimental data (squares) are fit by a Gaussian function (line). (b) The tunnelling spectra of a MgB2/native oxide/Pb junction at T=4.2, 5.0, 5.5, 6.0, 6.5 and 7.0 K (curves from bottom to top). The curves are shifted vertically for clarity with horizontal bars indicating zero conductance.
