Pseudogap Phenomenon in Single Phase Hg-1223 Cuprate Superconductors

The single phase Hg-1223 cuprate superconductors have been successfully fabricated. The postannealing treatment under oxygen (O₂) gas and argon (Ar) gas with different annealing time was performed in order to obtain various hole density samples. These samples were used to study the pseudogap phenomenon in the normal phase. With the plot of ln[1/(T) – 1/_N(T)] against 1/T, three characteristic temperatures T*, T_S, and T_F were obtained, which describe the role of the pseudogap phenomenon. The magnitudes of the pseudogap were extracted from the slope of the stated plots. It is found that the three characteristic temperatures T*, T_S, and T_F change with the hole density linearly. The relationship between T* and T_C goes within T* = T*_op+₀ (1–T_C/T^max_C), where T*_op and T_C^max are the pseudogap opening temperature and the critical temperature for the optimal sample. It is also found that the pseudogap phenomenon only exists below the optimal regime in the hole doping phase diagram.