Nonequilibrium Microwave Emission from DC-Biased High T_c YBa₂Cu₃O_7-y Junctions

Abstract

We report the observation of microwave emission from dc-biased high T c Au/insulator/YBa 2 Cu 3 O 7- y junctions, which provides a novel method of generating broad-band microwaves. The microwave intensity is typically of the order of subpicowatts, and increases almost linearly with the increase of junction current and vanishes as the bath temperature approaches T c . The observed effect is not similar to the Josephson effect and may be interpreted in terms of the nonequilibrium dynamics involving Cooper pairs and quasiparticles.