PROBING THE COLLECTIVE JOSEPHSON PLASMA RESONANCE IN BI2SR2CACU2O8-BAND-MIXING EXPERIMENTS(Y BY W)

We report on W-band-mixing experiments with mesa structures patterned on top of Bi2Sr2CaCu2O8+y, single crystals. Due to the intrinsic Josep hson effect the mixing process could be observed. There is a steep inc rease of the mixing intensity when the bias current approaches the cri tical current. We show that the mixing response is related to the exci tation of the collective Josephson plasma resonance. In magnetic field s we observed a decrease of the Josephson plasma frequency. From this dependence we were able to estimate the frequency of the Josephson pla sma resonance for zero bias and zero field ranging from 105 to 220 GHz .