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Temperature and junction-type dependency of Andreev reflection in MgB2 |
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| Authors: | R.S. Gonnelli A. CalzolariD. Daghero G.A. UmmarinoV.A. Stepanov P. FinoG. Giunchi S. CeresaraG. Ripamonti |
| Affiliation: | a Dipartimento di Fisica, INFM, Politecnico di Torino, C.so Duca degli Abruzzi 24, 10129 Torino, Italy b P.N. Lebedev Physical Institute, Russian Academy of Sciences, Moscow 119991, Russia c Dipartimento di Scienza dei Materiali ed Ing. Chimica, Politecnico di Torino, 10129 Torino, Italy d EDISON S.p.A., Foro Buonaparte 31, 20121 Milan, Italy |
| 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). |
| Keywords: | A. Intermetallic compounds A. Superconductors D. Superconductivity |
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