Pinning effect on critical dynamics inTl2Ba2CaCu2O8 films beforeand after introducing columnar defects

摘要

The effect of columnar defects on the critical dynamics of superconducting Tl2Ba2CaCu2O8 (Tl-2212) film has been investigated. The Tl-2212 film was irradiated at 0°C by 1.3 GeV U-ions along the normal of the film surface. The dose of 6.0×1010 ions/cm2 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 σxx(T, H) of the unirradiated sample exhibits 3D-XY scaling behavior that reveals dynamic critical exponent z=1.8±0.1 and static critical exponent ν≈1.338. The results indicate that the weak interlayer coupling along the c-axis of Tl-2212 significantly influences static critical exponent ν 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