Quasiparticle injection effect of aYBa2Cu3O7−

Abstract

We present measurements on quasiparticle injection into a YBa 2 Cu 3 O 7Ϫy ͑YBCO͒ film, with double injector-junction geometry free from the parallel overlapping effect of the currents, fabricated by electronbeam coevaporation and photolithographic lift off. The observed injection characteristics are quite symmetric with respect to the relative flow direction between the injection current and the film current, in contrast to previous reports. The film critical current decreases almost linearly with the injection current. The critical current density J c can be controlled by injection current density much smaller than J c , indicating that quasiparticle injection is dominant. The estimated effective quasiparticle recombination time at the critical injection is about 2 ns, consistent with previous reports of optical excitation.