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M. R. Eskildsen, M. Kugler, S. Tanaka, J. Jun, S. M. Kazakov, J. Karpinski, and O. Fischer We report scanning tunneling spectroscopy imaging of the vortex lattice in single crystalline MgB2. By tunneling parallel to the c axis, a single superconducting gap (ƒ¢=2.2 meV) associated with the ƒÎ band is observed. The vortices in the ƒÎ band have a large core size compared to estimates based on Hc2 and show an absence of localized states in the core. Furthermore, superconductivity between the vortices is rapidly suppressed by an applied field. These results suggest that superconductivity in the ƒÎ band is, at least partially, induced by the intrinsically superconducting ƒÐ band.
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