On the dissipation process in Bi2Sr2Ca2Cu3O10 tapes and bulk samples with preferential grain orientation in zero external magnetic field

Current-voltage characteristics of Bi₂Sr₂Ca₂Cu₃O₁₀ tapes and bulk samples with preferentially oriented crystallites have been measured in zero applied magnetic field and for temperatures close to the mean-field critical-temperature,T_c0. It was shown that the power-law dependence,V=AI^a, valid for two-dimensional systems, does not correctly describe the data, which clearly indicate the existence of a finite critical-current density,J_c. The experimentalI-V curves are fitted quite well with the model which attributes the finite critical-current density to the coupling between the CuO₂ double layers. It was found thatJ_c vanishes at a temperature value belowT_c0. This behavior can result from the occurrence of vortex fluctuation-induced layer decoupling and/or from the contribution of entropy to the vortex unbinding process.