Correlation between incoherent phase fluctuations and disorder in Y_1-xPr_xBa₂Cu₃O_7-δ epitaxial films from Nernst effect measurements

Abstract

Measurements of Nernst effect, resistivity and Hall angle on epitaxial films of Y_1-xPr_xBa₂Cu₃O_7-δ (Pr-YBCO, 0δxδ0.4) are reported over a broad range of temperature and magnetic-field strength. While the hall and resistivity data suggest a broad pseudogap regime in accordance with earlier results, these first measurements of the nernst effect on Pr-YBCO show a large signal above the superconducting transition temperature (T_c). This effect is attributed to vortexlike excitations in the phase incoherent condensate existing above T_c. A correlation between disorder and the width of the phase fluctuation regime has been established for the γBCO family of cuprates, which suggests a T_c≈110 k for disorder-free YBa₂Cu₃O_7-δ