In-Plane Paraconductivity of Bi2Sr2CaCu2O8 Single Crystals with Different Resistivity Anisotropies

Possible dominance of the Maki–Thompson process in the fluctuation conductivity of Bi-2212 superconducting whiskers

“…7, together with the measured ∆σ data reported as a function of ǫ. From the point of view of the experimental results, it should be noted that, as far as comparisons are possible, our data show the same qualitative behaviour already reported for Bi-2212 whiskers, 29 single crystals 14,30,31,32 and thin films, 33 and for YBa 2 Cu 2 O 7−δ (YBCO) epitaxial thin films as well. 34 In particular, they share with previous results the order of magnitude of ∆σ near T c 12,14,27,32 , the fact that ∆σ is sample dependent 13,14,22,27,29,30,31,32,34,35 and the same dependence on the cross section already shown in Bi-2212 whiskers.…”

“…From the point of view of the experimental results, it should be noted that, as far as comparisons are possible, our data show the same qualitative behaviour already reported for Bi-2212 whiskers, 29 single crystals 14,30,31,32 and thin films, 33 and for YBa 2 Cu 2 O 7−δ (YBCO) epitaxial thin films as well. 34 In particular, they share with previous results the order of magnitude of ∆σ near T c 12,14,27,32 , the fact that ∆σ is sample dependent 13,14,22,27,29,30,31,32,34,35 and the same dependence on the cross section already shown in Bi-2212 whiskers. 29 From the point of view of the fits, it is apparent that the theory excellently fits the data of both samples in a rather large reduced temperature range: 0.021 ≤ ε ≤ 0.148 for sample WI3B 1 and 0.026 ≤ ε ≤ 0.155 for sample WI3C 1.…”

“…Such values are in general agreement with previous experiments on Bi-2212. 27,30,37,38 Also the Fermi level E F can be estimated in the Drude picture from ρ n a and the microscopic parameters, via the formula E F = 2 2πs/(e 2 τ ρ n a ). This gives 1.4 eV and 1.1 eV for samples WI3B 1 and WI3C 1, respectively, which have to be considered as upper limits of the real values, because of the assumption of a cylindrical Fermi surface underlying the theory.…”

“…As a first attempt to account for the experimental data within the thermodynamical fluctuation theory, we tried to follow the scheme of previous experiments which excluded or neglected the presence of the MT contributions [5,[12][13][14][15][16][17][18][19][20][21][23][24][25]. Therefore we tried to fit the experimental data to the truncated formula,…”

“…As regards the MT terms, during recent years most authors have either explained their data in a framework where the MT contributions were absent or have reported them to be unfit or negligible, both for polycrystalline [5,13,14] and for single crystal samples [15][16][17][18][19][20][21][22]. Also, in the experiments focused on the paraconductivity effects in a magnetic field, the MT terms have often been omitted in the data interpretation due to the fact that they were presumed to be very small or that they proved to be inconsistent with the experimental results [12,18,[23][24][25].…”