Fiske steps in intrinsic Bi2Sr2CaCu2O8+x stacked Josephson junctions

Current-voltage characteristics in the c-axis direction were studied experi mentally for small-area Bi2Sr2CaCu2O8+x mesas containing only a few intrins ic stacked Josephson junctions. Fiske steps in such junctions were observed . This is direct evidence for the existence of the ac Josephson effect in i ntrinsic high-T-c Josephson junctions. From observation of a periodic modul ation of Fiske step amplitude as a function of magnetic held we obtain that the spacing between intrinsic Josephson junctions, 15.5 Angstrom, is equal to that given by the crystalline structure of Bi2Sr2CaCu2O8+x. [S0163-1829 (99)04813-4].