Magnetic-field dependence of the critical dynamics of a superconductingYBa2Cu3O7−δdetwinned single crystal

Abstract

The in-plane longitudinal resistivities ${\ensuremath{\rho}}_{\mathrm{aa}}$ and ${\ensuremath{\rho}}_{\mathrm{bb}}$ of a single-crystal of ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$ have been measured as a function of magnetic field $H$ (less than 6.75 T) and temperature $T$ near ${T}_{c}.$ We found that the ${\ensuremath{\rho}}_{\mathrm{aa}}(T,H)$ data in the mixed state collapse into a single curve as a function of ${\ensuremath{\rho}}_{\mathrm{bb}}(T,H).$The extracted fluctuation conductivity exhibits dynamic scaling over a wide range of $T$ and $H:$ assuming that the static universality class is the three-dimensional $\mathrm{XY}$ model yields the observed dynamic critical exponent $z=1.5\ifmmode\pm\else\textpm\fi{}0.1(H>0),$ apparently consistent with the dynamic universality class of superfluid ${}^{4}\mathrm{He}.$ In zero field, the data are inconclusive, and a reliable determination of $z$ is not possible.