Fluctuation conductivity in the superconducting compound Bi1.7Pb0.3Sr2Ca2Cu3Oy

A study of how the partial substitution of Bi with Pb impacts the mechanism of excess conductivity in a Bi-Sr-Ca-Cu-O system. It is found that such a substitution leads to an increase in the critical temperature of the Bi1.7Pb0.3Sr2Ca2Cu3Oy(B2) sample, in comparison to Bi2Sr2CaCu2Ox (B1) [T-c (B2) = 100.09 K and T-c (B1) = 90.5 K, respectively]. At the same time, the resistivity rho of the sample B2 in the normal phase decreases by almost 1.5 times in comparison to B1. The mechanism responsible for the generation of excess conductivity in cuprate HTSCs Bi2Sr2CaCu2Ox and Bi1.7Pb0.3Sr2Ca2Cu3Oy is examined using the local pair model with consideration of the Aslamazov-Larkin theory, near T-c. The temperature T-0 of the transition from the 2D fluctuation region to the 3D (i.e., the temperature of the 2D-3D crossover), is also determined. The coherence length xi(c)(0) along the c axis of fluctuation Cooper pairs is calculated. It is shown that the partial substitution of Bi with Pb in the Bi-Sr-Ca-Cu-O system leads to a decrease in xi(c)(0) by a factor of 1.3 (4.205 and 3.254 angstrom, respectively), and that there is a narrowing of both the region of pseudogap existence and the region of superconducting fluctuations near T-c. The temperature dependence of the pseudogap Delta*(T) and the value Delta*(T-c) are determined, and the temperatures T-m, which correspond to the maximum of the pseudogap as a function of temperature in these materials, are estimated. The pseudogap maxima in samples B1 and B2 are found to be 61.06 and 38.18 meV, respectively. Published by AIP Publishing.