Negative thermoelectric power of over-doped Bi2Sr2CaCu2O8 superconductor

Abstract

The thermoelectric power S(T) studies of Bi2Sr2CaCu2O8 (Bi2212) samples, including as-processed Partially Melted (Bi2212-PM) and 800°C O2-annealed (Bi2212-O2) are reported here. While Bi2212-PM sample is near optimum doping regime, Bi2212-O2 is an over-doped sample. TcS=0 values obtained through S(T) data match very well with those deduced from the R(T). Interestingly, S(T) behavior of the optimally-doped Bi2212-PM sample is seen to be positive in whole temperature range, it is found negative for the over-doped Bi2212-O2 sample above TcS=0. The observed negative S(T) dependence of the over-doped Bi2212-O2 is in accord with the recent band structure calculations and is in line with the theoretical investigations on a van Hove singularity in electronic density of states in HTSc compounds.