Effect of superimposed electrical and thermal gradients in bismuth-based high temperature superconductors

Abstract

The superconducting analogue of the fountain effect in superfluid liquid helium is briefly reviewed and experimental evidence is presented for the existence of the effect in bulk BSCCO 2212 and 2223, in which it is similar. This effect is usually detected by measurement of a polarity asymmetry in the I - V response of superconducting weak-links or junctions in the presence of superimposed electrical and thermal gradients when the applied current direction is reversed. Observation of this effect has recently been reported in a thick film of high T c superconducting YBCO in the microbridge geometry. We show here that the effect is observable in other high T c systems, where the polycrystalline nature of bulk samples results in intrinsic microbridge-like nature of the conduction paths. Results are presented showing the temperature dependence of this effect in bulk bismuth-based high temperature superconductors. The study supports the importance of weak-link related effects in the thermoelectricity of high T c cuprates.