The comparison between the pseudo gap opening temperatures in different cuprate superconductors with two CuO₂ planes

The pseudo gap temperature T* was determined for some single crystal and polycrystalline superconductors which have two CuO₂ planes by ρ(T) measurement. The experimental results indicate that the normalized pseudo gap temperature, namely T*/T_c^max, decreases with increasing T_cT_c^max, The curves of T*/T_c^max vs. T_c/T_c^max plotted using our experimental data, as well as the other authors' results reported previously, display an identical trend. This identity reveals that the relationship between T*/T_c^max and T_c/T_c^max is intrinsic for high temperature cuprate superconductors with two layers of CuO₂.