Enhanced Superconductivity in (Cu0.5Tl0.25Cs0.25)Ba2Ca2Cu3O10−δ by Cs Doping

Abstract

The self doping of carriers in CuO2 planes (accomplished through post annealing in air, N2 and O2 atmospheres in previous studies) is replaced by a more efficient alkali metal dopant such as Cs. The doping of Cs in the Cu0.5Tl0.5Ba2O4−δ charge reservoir of Cu0.5Tl0.5Ba2Ca2Cu3O10−δ superconductors has been found to enhance its superconducting properties. Enhanced superconductivity parameters, such as Tc, Hc and Jc, most likely arise from the enhanced doping efficiency of Cu0.5Tl0.25Cs0.25Ba2O4−δ charge reservoir layer; since the alkali metals are known to lose their outermost “s-orbital” electron, which could be supplied to conducting CuO2 planes. The distance between efficiently doped CuO2 planes is reduced by Be and Mg doping at the Ca Sites. The quantity of diamagnetism and zero resistivity critical temperature [Tc(R=0)] are suppressed by these substitutions. The post-annealing of the Cs doped samples further enhances their superconducting properties; oxygen doping most likely promotes the optimum holes concentration in the superconducting state in the Cs doped samples. These observations have also shown that the free carrier density plays a significant role in the mechanism of superconductivity which was accomplished by synthesizing (Cu0.5Tl0.25Cs0.25)Ba2Ca2Cu3O10−δ superconductors.