Photoemission results of intermetallic superconductors: Nb3Al and MgB2 Original Research Article

We study the superconducting electronic structures of Nb3Al and MgB2 using high-resolution spectroscopy. The obtained spectrum of Nb3Al measured below Tc shows clear opening of the superconducting gap with a sharp pile up in the density of states and a shift of the leading edge. In addition, the spectrum shows a peak–dip–hump line shape expected from the strong-coupling theory. On the other hand, for MgB2, the superconducting-state spectrum measured at 5.4 K shows a coherent peak with a shoulder structure, in sharp contrast to that expected from a single isotropic gap. The superconducting spectral shape of MgB2 can be explained in terms of a multicomponent gap.