Magnetic-field-induced non-linear effects of Josephson coupled superconductor Bi2Sr2CaCu2O8+δ

The dc current-voltage (I-V) relation along the c-axis of single crystalline Bi₂Sr₂CaCu₂O_8+δ has been measured in magnetic fields parallel and perpendicular to the c-axis. In zero field a clear and sharp jump with large hysteresis in theI-V curve was observed, indicative of the dc-Josephson effect. In magnetic field below a characteristic fieldB ^*≈0.4 T (at T=0 K) parallel to the c-axis the magnetic field suppresses the hysteresis and reduces the critical currentI _c drastically, whereas aboveB ^* theI-V curve becomes broad and featureless behavior. The characteristic field scaleB ^* can be interpreted as an energy scale of the Josephson coupling between superconducting layers in Bi₂Sr₂CaCu₂O_8+δ and is argued with emphasis on the correlation length of pancake vortices in this system.