Microwave-induced current steps in intrinsic Josephson junctions patternedon Bi2Sr2CaCu2O8 single crystal

With a 10 mu mx10 mu m mesa patterned on Bi2Sr2CaCu2O8 single crystals, we measure the current-voltage (I-V) curves of a stack of intrinsic Josephson junctions. Current steps are observed at an equal voltage spacing of 4 mV w hen the sample is subjected to microwave radiation at around 7 GHz. With in crease of the microwave power, more steps occur while the spacing between n eighboring steps does not seem to change. The magnitude of each step depend s on the microwave power in an oscillating way. Tuning the microwave freque ncy causes such steps to occur over separate frequency ranges, and each ran ge is quite narrow. A temperature rise from 4.2 to 14.3 K completely quench es the step structures. Possible explanations for the step structures, base d on resonances excited by microwave or geometric resonances in the junctio n cavity, are discussed. (c) 1999 American Institute of Physics. [S0003-695 1(99)04024-3].