Vortex states in the mesa-structured Bi2Sr2CaCu2O8+delta single crystals with Josephson current along the c-axis

Vortex states in the mesa-structured Bi2Sr2CaCu2O8+delta single crystals ha ve been studied in presence of the Josephson currents along the c-axis. Cha racteristic features have been observed in the magnetic field (H//c-axis) d ependence of the Josephson critical currents. A sudden change in the Joseph son critical current has been clearly observed at the magnetic field H-d, w hich is lower than the magnetic fields of vortex lattice melting and 2D-3D dimensional-crossover obtained from the magnetization measurements. This ha s been considered as a phase boundary of the vortex states, accompanied wit h the Josephson currents.