Macroscopic quantum tunneling and quasiparticle-tunneling blockade effect in s -wave/d -wave hybrid junctions

We have theoretically investigated macroscopic quantum tunneling (MQT) and the influence of nodal quasiparticles and zero energy bound states (ZESs) on MQT in s -wave/ d -wave hybrid Josephson junctions. In contrast to d -wave/ d -wave junctions, the low-energy quasiparticle dissipation resulting from nodal quasiparticles and ZESs is suppressed due to a quasiparticle-tunneling blockade effect in an isotropic s -wave superconductor. Therefore, the inherent dissipation in these junctions is found to be weak. We have also investigated MQT in a realistic s -wave/d -wave (Nb Au YBCO) junction in which Ohmic dissipation in a shunt resistance is stronger than the inherent dissipation and find that MQT is observable within the current experimental technology. This result suggests the high potential of s -wave/ d -wave hybrid junctions for applications in quantum information devices. © 2007 The American Physical Society.