Thermopower and fluctuation effects in HTSC crystals of Bismuth cuprates

Thermopower, conductivity and magnetic susceptibility of HTSC bismuth cur pate crystals with the same stoichiometry Bi2 Sr2 Ca Cu2 Ox are investigated. In the vicinity of the superconducting transition temperature (∼ 10% Tc in width) the thermopower temperature dependence turns out to have a peak-shaped peculiarity as well as different behaviours for various samples beyond the peak. These features are closely associated with the defect (impurity) content in the samples. We explain the observed phenomena using ideas of thermodynamic Gauss fluctuations of the two-component order parameter, 2D/0D crossover for two-band superconductor with a narrow band near the Fermi level overlapping a wide band