The localization effects of Gadolinium on YBCO superconductor: Thermoelectric power study

Abstract

Even though the euphoria of high Tc superconductors is not that evident in recent times, the lingering taste of the field is still reminiscent. Reason for the same is the fact; the ceramics like YBCO are quite unique that paved a healthy platform for understanding variety of unconventional aspects of materials. The normal state of the YBa2Cu3O7-δ is quite unconventional that display a variety of interesting properties that include dimensionality effects, anisotropy, non-Fermi Liquid, Mott insulator derived metallic states and at times a platform for spin-charge separation and so on. In this presentation, we show results of thermoelectric effect and resistivity of Y1-xGdxBa2Cu3O7-δ that are quite indicative of multi-band effects. While the superconducting transition temperature decreases from 90 K to ∼ 80 K upon Gd substitution the normal state resistivity has increased by three times. However, the results on thermo-electric power (TEP) are quite drastic as one could observe a ten-fold increase in normal state Seebeck coefficient. Temperature dependence of thermoelectric power have been analyzed using two models of Xin and Gottwick. Physically meaningful parameters obtained using such fits include carrier concentration, Fermi energy and position of localized states etc and compared. Results are discussed in the light of evolved scenarios.