The radio-frequency impedance of individual intrinsic Josephson junctions

We have measured the response of an array of Bi2Sr2CaCu2O8+delta intrinsic Josephson junctions to irradiation at 3 GHz. By measuring the dependence of the switching current upon the radio-frequency current for five of the junctions in the array we show quantitatively that the junctions have identical impedances at 3 GHz, this impedance being given by the inverse of the slope of the current-voltage characteristics