EFFECT OF SUPERIMPOSED ELECTRICAL AND THERMAL-GRADIENTS IN BISMUTH-BASED HIGH-TEMPERATURE SUPERCONDUCTORS

The superconducting analogue of the fountain effect in superfluid liqu id helium is briefly reviewed and experimental evidence is presented f or the existence of the effect in bulk BSCCO 2212 and 2223, in which i t is similar. This effect is usually detected by measurement of a pola rity asymmetry in the I-V response of superconducting weak-links or ju nctions in the presence of superimposed electrical and thermal gradien ts when the applied current direction is reversed. Observation of this effect has recently been reported in a thick film of high T(c) superc onducting YBCO in the microbridge geometry. We show here that the effe ct is observable in other high T(c) systems, where the polycrystalline nature of bulk samples results in intrinsic microbridge-like nature o f the conduction paths. Results are presented showing the temperature dependence of this effect in bulk bismuth-based high temperature super conductors. The study supports the importance of weak-link related eff ects in the thermoelectricity of high T(c) cuprates.