Carrier-type-dependent thermoelectric response of the superconductor–normal-metal–superconductor configuration in a C-shaped polycrystalline BixPb1−xSr2CaCu2Oy sample

Abstract

Two cuts were inserted at 90° to each other into a ring-shaped sample of BixPb1−xSr2CaCu2Oy. The first cut lay parallel to the applied 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 be predominantly holelike (an In insert) or electronlike (Ag paste supporting a 70-Å-thick Au strip). The left wing was left as sintered. Thermal voltages resulting from the same temperature gradient acting on both continuous and normal-metal-filled halves of the sample were detected as a function of temperature around the superconducting transition at about 109 K. Comparing the difference between the thermopowers of the two halves, ΔS, we calculate the Fermi energy of our superconducting material. ΔS was found to be positive and negative for the h- and e-type carriers of the normal-metal insert, respectively. Relating ΔS to the transport entropy, Δσ, via the carrier charge, q, by ΔS=Δσ/q, we also account for the carrier-sign dependence of ΔS.

Source-reported materials — not catalogue approval

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