Microwave response of intrinsic Josephson junctions in BSCCO single crystals

We have studied the microwave response of an array of intrinsic Josephson junctions in the c-axis direction in large Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub 7/ (BSCCO) single crystals indicating multiple resistive branches on the I-V characteristics. Under the 8-10 GHz microwave irradiation, they showed three types of responses depending on its power P. For relatively low P, the Shapiro steps were observed, whose voltage separations were two order magnitude larger than that calculated from /spl Delta/V=hf/2e, indicating that about one hundred intrinsic junctions in the crystal are phase-locked. For high P, two types of RF-induced steps were observed. In the case of resonance mode, the I-V curve showed the pronounced constant voltage step together with subharmonic ones. On the other hand, for off-resonance mode the broad step was observed. The voltages of these steps increased lineally with p/sup 1/2/. These results suggest that the fluxon motions in intrinsic Josephson junctions interact with external RF field.<>