Thermodynamic fluctuations and the thermoelectric coefficient in (Bi1.6Pb0.4)Sr2Ca3(Cu1−xAgx)4O12+δ superconductors

Abstract

We present a study of the thermoelectric coefficient L(T) of polycrystalline silver doped (Bi1.6Pb0.4)Sr2Ca3(Cu1−xAgx)4O12+δ samples. L(T) relates the thermopower S(T) with electrical conductivity, σ(T), and gives an indication of the influence of the order parameter fluctuations (OPF) on S(T) in the mean field region (MFR). The results of L(T) indicate that the critical behavior of S(T) above the superconducting transition is driven essentially by σ(T). These results suggest that, in the MFR, L(T) is not affected by thermodynamic fluctuations of the superconducting order parameter (OPF). The OPF effects show a bi-dimensional character in the entire MFR, which is not affected by Ag doping. For low Ag concentrations, the experimental data Δσ/σB fit well to the Lawrence-Doniach model for layered superconductors in the MFR. Furthermore, the behavior of ΔL is nearly temperature independent.

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