MAGNETIC-FIELD-INDUCED NONLINEAR EFFECTS OF JOSEPHSON-COUPLED SUPERCONDUCTOR BI2SR2CACU2O8+DELTA

The dc current-voltage (I-V) relation along the c-axis of single cryst alline Bi2Sr2CaCu2O8+delta has been measured in magnetic fields parall el and perpendicular to the c-axis. In zero field a clear and sharp ju mp with large hysteresis in the I-V curve was observed, indicative of the dc-dosephson effect. In magnetic field below a characteristic fiel d Bapproximate to 0.4 T (at T = 0 K) parallel to the c-axis the magne tic field suppresses the hysteresis and reduces the critical current I -c drastically, whereas above B the I-V curve becomes broad and featu reless behavior. The characteristic field scale B can be interpreted as an energy scale of the Josephson coupling between superconducting l ayers in Bi2Sr2CaCu2O8+delta and is argued with emphasis on the correl ation length of pancake vortices in this system.