| Popis: |
We investigated the effect of a magnetic field on the two gaps of MgB 2 , Δ σ and Δ π , by means of directional point-contact spectroscopy in MgB 2 single crystals. The gaps were given by a fit of the experimental conductance curves with a generalized BTK model. The comparison of the experimental Δ π ( B ) and Δ σ ( B ) curves with the predictions of the two-band model in dirty limit gives a diffusivity ratio ϱ = D σ / D π = 0.2 . This result concurs with various other findings (e.g., from de Haas-van Alphen and STM measurements) in indicating that, even in high-quality crystals, the π band is moderately dirty. Further confirmation comes from the direct evaluation of the scattering parameters γ σ and γ π from DC resistivity. |
