Magnetic field dependence of the thermoelectric power of superconducting Bi-Sr-Ca-Cu-O

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Abstract
Measurements of the temperature and magnetic field dependence of the thermopower S(B,T) are presented for a polycrystalline sample of the T∼85 K phase of Bi-Sr-Ca-Cu-O. Between 90 and 140 K, S(B,T) is positive and shows a small decrease with increasing temperature. In this temperature interval the application of an external magnetic field does not influence S(B,T). Below 90 K, S(0,T) drops sharply at the superconducting transition temperature. The magnetic field B causes a suppression of the transition temperature similar to the effect observed in resistivity data. The field data are interpreted in terms of the Abrikosov vortex lattice for the mixed state of the type-II superconductor. Relating the thermopower to the transport entropy of the vortex motion due to the temperature gradient across the sample, we find that the sign of the charge carriers is positive, and the principal unit ħ/2m of the particle flux is within 13% of its tabulated value.