2-DIMENSIONAL SUPERCONDUCTING PROPERTIES IN SINGLE CRYSTALLINE BI2SR2CACU2O8+DELTA

High precision measurements of angular dependences of the resistivity in high quality single crystalline Bi2Sr2CaCu2O8+delta have been performed to study unusual vortex dynamics in magnetic fields. The results show evidence of strong superconducting fluctuations, which is in strong contrast with the previous understanding based on the vortex motion driven by the Lorentz force interaction, and which is responsible for the dissipation in the reversible magnetization region. It is also shown that the two dimensionality associated with the inherent layered electronic structure in this system plays an essential role for the origin of the unusual vortex dynamics.