Detailed measurements of both the Nernst coefficient, Ne, and the current vs. voltage characteristics were carried out in a YBCO film by varying systematically the flux density, B, and the temperature, T. The Nernst coefficient was observed over the temperature region of a fairly wide superconducting vs. normal resistive transition under the applied flux density, B. The transport entropy of a fluxoid, Sφ estimated directly from the present measurements showed a small tail decreasing exponentially with increasing temperature, even above the mean-field critical temperature, Tc(B), whereas the existing theory predicted Sφ to become zero above Tc(B). Then the expression for Sφ above Tc(B) was derived. The expression for the resistivity around the temperatures of the resistive transition was also derived, including the resistivity due to the flux flow. With the aid of these expressions, the observed Nernst coefficient was explained quantitatively by the present theory.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Energy Engineering and Power Technology
- Electrical and Electronic Engineering