Possible observation of energy level quantization in an intrinsic Josephson junction

Energy level quantization (ELQ) is studied to clarify the macroscopic quantum dynamics of the d-wave Josephson junction (JJ). The influences of the nodal quasiparticles of d-wave superconductivity on the damping effect are numerically evaluated on the basis of a phenomenological model. The calculation, based on realistic parameters for a Bi2Sr2CaCu2O8+d (Bi2212) intrinsic JJ, shows that the observation of ELQ is possible when the sweep rate of the bias current exceeds 10 A/sec. High-sweep- rate measurements (121A/sec) performed on a Bi2212 intrinsic JJ result in the appearance of multiple peaks in the switching current distribution suggesting the realization of ELQ in the d-wave JJ.