Macroscopic quantum tunneling in a stack of capacitively-coupled intrinsic Josephson junctions

A macroscopic quantum theory for the phase dynamics in capacitively-coupled intrinsic Josephson junctions (IJJ's) is constructed. We quantize the capacitively-coupled IJJ model in terms of the canonical quantization method. The multi-junction effect for the macroscopic quantum tunneling (MQT) to the first resistive branch is clarified. It is shown that the escape rate is greatly enhanced by the capacitive coupling between junctions. We also discuss the origin of the N²-enhancement in the escape rate observed in the uniformly switching in Bi-2212 IJJ's