Systematic resistivity study of the pseudogap and critical temperature for ( Hg , Re ) - 1223 superconductors

After a detailed characterization of the (Hg,Re)-1223 polycrystalline samples, the pseudogap temperature T ∗, fluctuation temperature Tscf and the superconducting critical temperature Tc have been systematically studied through electrical resistivity ρ measurements by several different current densities. Performing many set of measurements with different current densities we show that, while low current values are desirable because they are in the linear regime, they are plagued by high noise and, on the other hand, high current values are more stable but they yield non-linear terms. Therefore, we have studied the resistivity ρ(T ) by a large interval of current densities in order to obtain an ideal current for each sample. The appropriate current value allows to determine T ∗, Tscf and the critical temperature Tc for three different oxygen content. This method, developed in detail here, and used to derive the (Hg,Re)-1223 phase diagram can be applied to any high critical temperature superconductor (HTSC).