SUPERCONDUCTING FLUCTUATION EFFECTS ON THE THERMOELECTRIC COEFFICIENT ABOVE THE TRANSITION-TEMPERATURE

The quantum kinetic-equation method is applied to calculate the response of a metal to a temperature gradient above the superconducting transition temperature T(c). It is shown that the fluctuation correction to the thermoelectric coefficient of a three-dimensional superconductor is nonsingular near T(c). The fluctuation correction is more important in low-dimensional systems: it diverges as ln(T-T(c)) in a thin film and as (T - T(c))1/2 in a filament. Applying the linear-response method, we confirm these results and prove microscopically the Onsager relation for this problem. We also demonstrate how more singular terms obtained in earlier papers are canceled out by other terms representing the corrections to the heat current operator. The universal relation, independent on the electron mean free path, between the electric and heat current operators for the fluctuating order parameter is obtained.