Sudden disappearance of c-axis dissipation in single-crystalline Bi2Sr2CaCu2O8+delta

High-precision resistivity measurements with a wide range of currents have been performed for the c-axis of single-crystalline B2Sr2CaCu2O8+delta in magnetic fields in order to study the vortex dynamics in the vortex liquid phase. It is observed that the resistivity below about 80 mT has a pronounced non-linear behavior and shows a stepwise drop at T-D at the foot region (rho(c)(T-D)/rho(c)(T-c(+))less than or equal to 2 x 10(-4)). The anomaly lies al considerably higher temperature than the vortex line lattice melting (VLLM) transition temperature, T-M. Since the Lorentz force is not active on the vortex line in this case, the appearance of the non-linear resistivity can be attributed to the non-linear Josephson coupling effect between pancake vortices. The sudden drop in rho(c) at T-D is also understood by considering the sharp development of the long-range phase correlation along the c-axis, which strongly suggests a first-order decoupling phase transition.