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Independent determination of the two gaps by directional point-contact spectroscopy in MgB2 single crystals

R. S. Gonnelli, D. Daghero, G. A. Ummarino, V. A. Stepanov, J. Jun, S. M. Kazakov, J. Karpinski

cond-mat.supr-conarXiv:cond-mat/0209472

Abstract

Directional point-contact spectroscopy measurements were performed for the first time in state-of-the-art MgB2 single crystals. The selective suppression of the superconductivity in the "pi" band by means of a suitable magnetic field allowed separating the partial contribution of each band to the total point-contact conductance. By fitting the partial conductance curves sigmasigma(V) and sigmapi(V), we got an independent determination of the two gaps, Deltasigma and Deltapi, with a strong reduction of the experimental uncertainty. Their temperature dependence was found to agree well with the predictions of the two-band models for MgB2.

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