Nernst Effect and Superconducting Fluctuations in Zn-doped YBa${}_2$Cu${}_3$O${}_{7-\hat{I}´}$

Abstract

We report the measurements of in-plane resistivity, Hall effect, and Nernst effect in Zn doped YBa${}_2$Cu${}_3$O${}_{7-\hat{I}´}$ epitaxial thin films grown by pulsed laser deposition technique. The pseudogap temperature, $T^{\ast }$, determined from the temperature dependence of resistivity, does not change significantly with Zn doping. Meanwhile the onset temperature ($T^{\hat{I}}½$) of anomalous Nernst signal above $T_{c0}$, which is interpreted as evidence for vortex-like excitations, decreases sharply as the superconducting transition temperature $T_{c0}$ does. A significant decrease in the maximum of vortex Nernst signal in mixed state is also observed, which is consistent with the scenario that Zn impurities cause a decrease in the superfluid density and therefore suppress the superconductivity. The phase diagram of $T^{\ast }$, $T^{\hat{I}}½$, and $T_{c0}$ versus Zn content is presented and discussed.

6 pages, 5 figures, Latex; v2: to be published in PRB