A study of the anisotropic superconductor using a combination of scanning tunneling microscopy and spectroscopy revealed 2 distinct energy gaps at 2.3meV and 7.1meV at 4.2K. Different spectral weights of the partial superconducting density of states were a reflection of different tunneling directions in this multiband system. Temperature evolution of the tunneling spectra follows the BCS scheme with both gaps vanishing at the bulk TC. The data confirm the importance of Fermi-surface sheet dependent superconductivity in MgB2, proposed in the multigap model of Liu et al.

Two-Band Superconductivity in MgB2. M.Iavarone, G.Karapetrov, A.E.Koshelev, W.K.Kwok, G.W.Crabtree, D.G.Hinks, W.N.Kang, E.M.Choi, H.J.Kim, S.I.Lee: Physical Review Letters, 2002, 89[18], 187002 (3pp)