Pinning effect on critical dynamics in Tl/sub 2/Ba/sub 2/CaCu/sub 2/O/sub 8/ films before and after introducing columnar defects

Abstract

The effect of columnar defects on the critical dynamics of superconducting Tl/sub 2/Ba/sub 2/CaCu/sub 2/O/sub 8/ (Tl-2212) film has been investigated. The Tl-2212 film was irradiated at 0/spl deg/C by 1.3 GeV U-ions along the normal of the film surface. The dose of 6.0/spl times/10/sup 10/ ions/cm/sup 2/ of the U-ion irradiation corresponds to a matching field of 1.2 T. The in-plane longitudinal resistivity of the irradiated Tl-2212 has been measured as a function of magnetic field H and temperature T. The extracted fluctuation part of the conductivity /spl sigma//sub xx/(T, H) of the unirradiated sample exhibits 3D-XY scaling behavior that reveals dynamic critical exponent z=1.8/spl plusmn/0.1 and static critical exponent /spl nu//spl ap/1.338. The results indicate that the weak interlayer coupling along the c-axis of Tl-2212 significantly influences static critical exponent /spl nu/ and does not change dynamical critical exponent. After the irradiation, the fluctuation conductivities are enhanced by the strong pinnings and do not exhibit the same 3D-XY scaling behavior as for the unirradiated Tl-2212. Particularly at the low magnetic field values near the matching field of 1.2 T, the fluctuation conductivities show a clear deviation from the critical dynamics, suggesting that the pinning effect on the critical dynamics is significant.