NONEQUILIBRIUM MICROWAVE EMISSION FROM DC-BIASED HIGH T-C YBA2CU3O7-YJUNCTIONS

We report the observation of microwave emission from de-biased high T- c Au/insulator/YBa2Cu3O7-y junctions, which provides a novel method of generating broad-band microwaves. The microwave intensity is typicall y of the order of subpicowatts, and increases almost linearly with the increase of junction current and vanishes as the bath temperature app roaches T-c. The observed effect is not similar to the Josephson effec t and may be interpreted in terms of the nonequilibrium dynamics invol ving Cooper pairs and quasiparticles.