Pinning effect on critical dynamics in Tl₂Ba₂CaCu₂O₈ films before and after introducing columnar defects

The effect of columnar defects on the critical dynamics of superconducting Tl₂Ba₂CaCu₂O₈ (Tl-2212) film has been investigated. The TI-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 σ_xx(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 v ≈ 1.338. The results indicate that the weak interlayer coupling along the c-axis of Tl-2212 significantly influences static critical exponent v 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.