Physics of high-T_c josephson junctions and SQUIDs

Effects of magnetic fields and microwave radiation on I-V characteristics of YBa₂Cu₃O_y high-T_c Josephson junctions, SQUIDs and Josephson arrays were reported in this experiment, with special emphasis focused on the effects of microwave radiation. In addition to the ordinary constant-voltage steps resulting from the ac Josephson effect, noninteger constant voltage steps are occasionally observed under microwave radiation. We attribute these noninteger constant-voltage steps to the flux coupled to junctions or SQUIDs. Resistive SQUIDs disclose V - Φ modulation without a biased current. The peak to peak value ΔV of a V - Φ curve is enhanced by microwave radiation.