CARRIER-TYPE-DEPENDENT THERMOELECTRIC RESPONSE OF THE SUPERCONDUCTOR NORMAL-METAL SUPERCONDUCTOR CONFIGURATION IN A C-SHAPED POLYCRYSTALLINE BIXPB1-XSR2CACU2OY SAMPLE

Two cuts were inserted at 90-degrees to each other into a ring-shaped sample of BixPb1-xSr2CaCu2Oy. The first cut lay parallel to the applie d temperature gradient serving to define a vertical symmetry axis. The second cut lay in the middle of the right wing, perpendicular to the symmetry axis, completely interrupting the passage of supercurrents in this wing. The passage of any normal component of current density was made possible, however, by filling up the cut with a metal that does not show any superconducting properties in the vicinity of 110 K. The carrier type of this normal-metal insert was alternatively chosen to b e predominantly holelike (an In insert) or electronlike (Ag paste supp orting a 70-angstrom-thick Au strip). The left wing was left as sinter ed. Thermal voltages resulting from the same temperature gradient acti ng on both continuous and normal-metal-filled halves of the sample wer e detected as a function of temperature around the superconducting tra nsition at about 109 K. Comparing the difference between the thermopow ers of the two halves, DELTAS, we calculate the Fermi energy of our su perconducting material. DELTAS was found to be positive and negative f or the h- and e-type carriers of the normal-metal insert, respectively . Relating DELTAS to the transport entropy, DELTAsigma, via the carrie r charge, q, by DELTAS=DELTAsigma/q, we also account for the carrier-s ip dependence of DELTAS.