The results of the first directional point-contact spectroscopy experiments on high-quality MgB2 single crystals were presented here. Because of the directionality of the current injection into the samples, the application of a magnetic field permitted the separation of the contributions of the σ and π bands to the total conductance of the point contacts. By using this technique, it was possible to obtain the temperature dependence of each gap; independently of the other. The consequent, strong reduction of the error on the value of the gap amplitude as a function of temperature allowed a stricter test to be made of the predictions of the 2-band model for MgB2.

Direct Evidence for Two-Band Superconductivity in MgB2 Single Crystals from Directional Point-Contact Spectroscopy in Magnetic Fields. R.S.Gonnelli, D.Daghero, G.A.Ummarino, V.A.Stepanov, J.Jun, S.M.Kazakov, J.Karpinski: Physical Review Letters, 2002, 89[24], 247004 (3pp)