QUASI-PARTICLE INJECTION EFFECT OF A YBA2CU3O7-Y FILM WITH DOUBLE INJECTOR GEOMETRY

We present measurements on quasiparticle injection into a YBa2Cu3O7-y (YBCO) film, with double injector-junction geometry free from the para llel overlapping effect of the currents, fabricated by electron-beam c oevaporation and photolithographic lift off. The observed injection ch aracteristics are quite symmetric with respect to the relative flow di rection between the injection current and the film current, in contras t to previous reports. The film critical current decreases almost line arly with the injection current. The critical current density J(c) can be controlled by injection current density much smaller than J(c), in dicating that quasi particle injection is dominant. The estimated effe ctive quasiparticle recombination time at the critical injection is ab out 2 ns, consistent with previous reports of optical excitation.