Author/Authors :
R.S. Gonnelli، نويسنده , , A. Calzolari، نويسنده , , D. Daghero، نويسنده , , G.A. Ummarino، نويسنده , , V.A. Stepanov، نويسنده , , P. Fino، نويسنده , , G. Giunchi، نويسنده , , S. Ceresara، نويسنده , , G. Ripamonti، نويسنده ,
Abstract :
We studied the voltage and temperature dependency of the dynamic conductance of normal metal–MgB2 junctions obtained either with the point-contact technique (with Au and Pt tips) or by making Ag-paint spots on the surface of MgB2 samples. The fit of the conductance curves with the generalized BTK model gives evidence of pure s-wave gap symmetry. The temperature dependency of the gap, measured in Ag-paint junctions (dirty limit), follows the standard BCS curve with 2Δ/kBTc=3.3. In out-of-plane, high-pressure point-contacts we obtained almost ideal Andreev reflection characteristics showing a single small s-wave gap Δ=2.6±0.2 meV (clean limit).
