THERMOELECTRIC-POWER OF INHOMOGENEOUS SUPERCONDUCTORS - EFFECTS OF FIELD-INDUCED INTRAGRAIN GRANULARITY

The temperature, magnetic-field, and oxygen-deficiency dependence of t he thermoelectric power (TEP), S, of an inhomogeneous superconductor w ith field-induced intragrain granularity is considered via the superco nductive-glass model. Below the phase-locking (grain-decoupling) tempe rature T(g), which defines the coherent properties of a Josephson-junc tion network, the TEP follows a linear T dependence, while above T(g) (but below the single-superconducting-grain-depairing temperature T(c) ), S shows a semiconductorlike 1/T behavior. The model predicts the ex istence of a maximum of S near T(g) that increases with the applied ma gnetic field and changes its sign above some threshold value of the ox ygen-deficiency parameter. Attributing the intragrain granularity to c lusters of oxygen defects (in the CuO plane), the calculated TEP behav ior is found to be in qualitative agreement with the experimentally ob served (below T(c)) anomalous peak of the magneto-TEP in oxygen-defici ent high-T(c) superconductors.