Influence of the pseudogap on the Nernst coefficient of Y0.9Ca0.1Ba2Cu3Oy
We have studied the Nernst coefficient, v(T), of epitaxial thin films of the superconductor Y1-xCaxBa2Cu3Oy with x =0.05 and x = 0.1. The x = 0.1 sample has been measured at three different values of y, in the over- (OV), optimally- (OP), and under-doped (UD) states. As the doping level is reduced, v(T) starts to fall linearly with T at the temperature (T*) where we expect to see the influence of the pseudogap. The onset temperature of the superconducting fluctuation contribution to v(T) was found to vary slowly with the hole concentration (p) between p = 0.118 and 0.197. For the OP and UD samples, v(T>T*) is unusually large, being comparable with |S tan(Theta)| where S is the Seebeck coefficient and Theta the Hall angle.