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Two Gap Superconductors
MgB2: a two gap superconductor.
When an external field is applied to a type II superconductor the magnetic field penetrates in a regular Abrikosov lattice of flux tubes(fluxons), surrounded by solenoids of supercurrents. We can probe the structure of these supercurrents by implanting muons at random positions. The muon spin precessions measure the distribution of internal fields. This is a well established game. What happends when a superconductor has two nearly independent supercarriers? Muons are again a very important probe which allows to check the models and to extract important parameters of the superconductor, like its penetration depth and its coherence length. See also the highlight.
On this and other aspects of two gap superconductivity we had a MIUR PRIN 2004 project, coordinated nationally by M. Putti and locally by L. RomanÚ, which recetly gave rise to a second successful project, MIUR PRIN 2006, with the same coordinators.