LARGE NORMAL RESISTANCE AND THZ ELECTROMAGNETIC-WAVE RESPONSE IN YBACUO STEP-EDGE MICROBRIDGE JOSEPHSON-JUNCTION

A YBaCuO Josephson junction with a large normal resistance (R) was fabricated and characterized. The junction exhibited an extremely sharp transition on the current-voltage curve with R = 10.8 Ohm and I(c)R = 1.8 mV at 15 K. The temperature dependence of critical current (I-c) of the junction was I-c proportional to(1 - T/T-c), while another junction with a smaller R (0.57 Ohm) showed a dependence of I-c proportional to(1 - T/T-c)(2). The difference can be explained by a picture of a grain boundary junction as a parallel array of superconductor-normal-superconductor and superconductor-insulator-superconductor elements. From the results of 110 GHz mixing experiments, it was shown that the present junction could be operative for electromagnetic waves over 2 THz.