Normal-state Nernst coefficient in high-temperature superconductors of the Y-Ba-Cu-O system

Abstract

A comparative experimental study of the normal-state Nernst coefficient, Q, in high- temperature superconductors of the YBa2Cu3Oy system with different types of deviations from the stoichiometry was performed. The peculiarities of the Q(T) dependences characteristic of Y-based HTSC, as well as the specific features of the influence of different types of doping on the absolute Q value were revealed. The obtained Q(T) dependences were analyzed on the basis of a narrow-band model together with the thermopower temperature dependences measured on the same samples. It is shown that the developed approach allows one to describe quantitatively all the experimental Nernst results and to determine from their analysis the values of the charge-carrier mobility and the degree of the dispersion law asymmetry. The data on the variation of these parameters under influence of different types of doping are obtained and discussed with respect to the modification of the energy spectrum structure induced by studied dopants.