The superconducting-gap of MgB2 was studied by high-resolution angle-resolved photoemission spectroscopy. The results showed that superconducting gaps with values of 5.5 and 2.2meV open on the σ band and the π band, respectively, but both gaps closed at the bulk transition temperature; providing definitive experimental evidence for 2-band superconductivity with strong interband pairing interaction. The experiments validated the role of k-dependent electron-phonon coupling as being the origin of multiple-gap superconductivity as well as the high transition temperature.

Definitive Experimental Evidence for Two-Band Superconductivity in MgB2. S.Tsuda, T.Yokoya, Y.Takano, H.Kito, A.Matsushita, F.Yin, J.Itoh, H.Harima, S.Shin: Physical Review Letters, 2003, 91[12], 127001 (3pp)