1,721,150 research outputs found
Energy dependence of the normal density of states and of electron-phonon spectral function in the quasiparticle tunneling in high-Tc superconductors
No full textDetermination of the tunneling electron-phonon spectral function in high-T-c superconductors with energy dependence of the normal density of states
No full textEliashberg equations, pair symmetry and tunneling density of states in high-Tc layered superconductors
No full textReproducible tunneling determination of the electron-phonon spectral function in optimally-doped Bi-2212 single crystal break-junctions
No full textTemperature dependence of the Josephson critical current in Bi2Sr2CaCu2O8+x break junctions
No full textIntrinsic surface depression of the order parameter under mixed (s+id)-wave pair symmetry and its effect on the critical current of high-Tc SIS Josephson junctions
No full textJosephson effect and Andreev reflection measurements in MgB2 break- junction and point- contact heterostructures
No full textWe present the first observation of a nonhysteretic dc and ac Josephson effect in break junctions obtained at 4.2 K in high-quality, high-density polycrystalline metallic MgB2 samples recently reported by us (1). Shapiro steps spaced by the ideal dV value were observed by microwave irradiation and we obtained the temperature dependence of the dc Josephson current as well as the dependence on microwave power of the step heights. Besides giving direct proof of the existence of pairs with charge 2e in MgB2 and of the SNS long weak-link character of these junctions, these results provide information on the energy gap. Josephson data are consistent with a dirty-limit gap Delta~4 meV with Tc~27 K in agreement with the two-band model of superconductivity in MgB2.
In different experiments we studied the behaviour in voltage and temperature of the dynamic conductance of normal metal-MgB2 junctions obtained either by using the point-contact technique (with Au and Pt tips) or by making a spot of Ag paint on the sample surface. The conductance curves presented clear Andreev reflection features and were fitted with the generalized BTK model giving evidence of pure s-wave gap symmetry and of a temperature dependency of the gap in dirty limit which follows the standard BCS curve. Out-of-plane, high-pressure point-contact junctions showed almost ideal Andreev reflection characteristics from which the small 3D gap in the clean limit Delta3D = 2.6 ± 0.2 meV and its temperature dependency were obtained, once more in agreement with the two-band model for MgB2.
(1) R.S. Gonnelli et al., Phys.Rev. Lett. 87, 097001 (2001
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Influence of a surface-depressed order parameter on the Josephson critical current in Bi2Sr2CaCu2O8+x nonhysteretic break junctions
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