Correlation between incoherent phase fluctuations and disorder in Y1−xPrxBa2Cu3O7−δ epitaxial films from Nernst effect measurements

Measurements of Nernst effect, resistivity and Hall angle on epitaxial films of ${\mathrm{Y}}_{1\ensuremath{-}x}{\mathrm{Pr}}_{x}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}\ensuremath{\delta}}$ (Pr-YBCO, $0\ensuremath{\leqslant}x\ensuremath{\leqslant}0.4$) 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 YBCO family of cuprates, which suggests a ${T}_{c}\ensuremath{\approx}110\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ for disorder-free $\mathrm{Y}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}\ensuremath{\delta}}$.