Microwave power dependence of YBa2Cu3O7 thin-film Josephson edge junctions

Using a stripline resonator technique, we measured the dependence on microwave current of the impedance of fabricated superconductor/normal-metal/superconductor Josephson junctions in YBa2Cu3O7 thin films. The results are compared with predictions of a resistively shunted junction model that yields good agreement at low and intermediate values of the microwave current. At high currents deviations from the model predictions are observed, which we propose are due to flux penetration into the junction. The results are consistent with previously proposed explanations of the rf power dependence of the high-Tc materials.