Subharmonic gap structures and Josephson effect in MgB2/Nb micro-constrictions

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dc.creatorGiubileo, Filippo
dc.creatorAprili, Marco
dc.creatorBobba, Fabrizio
dc.creatorPiano, Samanta
dc.creatorScarfato, Alessandro
dc.creatorCucolo, Anna Maria
dc.date2005-08-04
dc.date2006-01-30
dc.date.accessioned2026-07-07T06:41:32Z
dc.date.available2026-07-07T06:41:32Z
dc.descriptionSuperconducting micro-constrictions between Nb tips and high quality MgB$_{2}$ pellets have been realized by means of a point-contact inset, driven by a micrometric screw. Measurements of the current-voltage characteristics and of the dynamical conductance versus bias have been performed in the temperature range between 4.2 K and 500 K. Above the Nb critical temperature T$_{C}^{Nb}$, the conductance of the MgB$_2$/normal-metal constrictions behaves as predicted by the BTK model for low resistance contacts while high resistance junctions show quasiparticle tunneling characteristics. Consistently, from the whole set of data we infer the value $Δ_π = 2.5 \pm 0.2$ meV for the three-dimensional gap of MgB$_2$. Below T$_{C}^{Nb}$, low resistance contacts show Josephson current and subharmonic gap structures (SGS), due to multiple Andreev reflections. Simultaneous observations of both features, unambiguously indicate coupling of the 3D band of MgB$_2$ with the Nb superconducting order parameter. We found that the temperature dependence of the Josephson critical current follows the classical Ambegaokar-Baratoff behavior with a value $I_CR_N=(2.1 \pm 0.1)$ meV at low temperatures.
dc.description8 pages, 5 figures. Replaced with published version
dc.identifierhttps://arxiv.org/abs/cond-mat/0508137
dc.identifierhttp://arxiv.org/abs/cond-mat/0508137
dc.identifierPhys. Rev. B 72, 174518 (2005)
dc.identifierdoi:10.1103/PhysRevB.72.174518
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/101697
dc.subjectSuperconductivity
dc.subjectMaterials Science
dc.titleSubharmonic gap structures and Josephson effect in MgB2/Nb micro-constrictions
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