Comparison of Josephson radiation properties of different YBa2Cu3O7 thin film junctions

摘要

Abstract: We have investigated the Josephson radiation from different types of YBa$-2$/Cu$-3$/O$-7$/ (YBCO) thin film junctions: step-edge (SEJ), biepitaxial, and superconductor-normal conductor- superconductor (SNS) with N=Au and PrBa$-2$/Cu$-3$/O$-7$/. The radiation was detected using a nonresonant radiometer system with a receiving frequency of 11-12 GHz. The current-voltage characteristics were measured simultaneously with the radiation spectra in the temperature range from 4.2 to 90 K. All junctions exhibited a large emission peak at a voltage which was related to the frequency through the second Josephson relation. Typically, for high temperatures, and, therefore, small critical currents, the experimental data of the radiation linewidth agreed well with the theoretical predictions of the RSJ model. At lower temperatures the experimental linewidths deviated from the theoretical values due to additional noise sources in the junctions. Some of the SEJs showed a nonmonotonic dependence of the linewidth on temperature. Such SEJ data will be discussed in terms of a model which treats the SEJ as an interferometer consisting of a parallel array of Josephson junctions. !14