Critical dynamics of superconducting BSCCO films

We report on a systematic investigation of the critical fluctuations in the complex conductivity of epitaxially-grown Bi${}_2$Sr${}_2$CaCu${}_2$O${}_{8+\delta }$ films for $T\lesssim T_c$ using a two-coil inductive technique at zero applied field. We observe the static 3D-XY critical exponent in the superfluid density near $T_c$. Linear scaling analysis close to the critical temperature yields a dynamic critical exponent of $z=2.0$ for small drive currents, but non-linear effects are seen to be important. At $T_c$, a non-linear scaling analysis also yields a 3D dynamic exponent of $z=2.0$.