Precursor Superconductivity and Superconducting Fluctuation Regime Revealed by the C-axis Optical Spectra of YBa2(Cu1-xZnx)3Oy

To clarify recent discussions on the precursor superconducting state in high-Tc cuprates, we performed a temperature dependent c- axis optical study on YBa2(Cu1-xZnx)Oy single crystals in the pseudogap region for several different Zn-contents (x = 0, 0.007, 0.012, and 0.04) and doping levels. The superfluid density calculation revealed a third temperature scale (Tp) for a precursor superconducting state in between the superconducting transition temperature, Tc, and the pseudogap opening temperature, T*. We observed the suppression and the disappearance of Tp with increasing Zn-content, which is further evidence of the close relation between the origin of Tc and Tp.