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Reentrance effect in macroscopic quantum tunneling and non-adiabatic Josephson dynamics in d-wave junctions

We develop a theoretical description of non-adiabatic Josephson dynamics in superconducting junctions containing low energy quasiparticles. Within this approach we investigate the effects of midgap states in junctions of unconventional d-wave superconductors. We identify a reentrance effect in the transition between thermal activation and macroscopic quantum tunneling, and connect this phenomenon to the experimental observations in Phys. Rev. Lett. 94, 087003 (2005). It is also shown that nonlinear Josephson dynamics can be defined by resonant interaction with midgap states reminiscent to nonlinear optical phenomena in media of two-level atoms.