Overdoped High Current Density Bi_2-xPb_xSr₂CaCu₂O_8+δ Intrinsic Josephson Junction Mesas and Their Switching Current Distributions

Small and thin mesa structures of intrinsic Josephson junctions 1-2 μm on a side and 1.5-7.5 nm in thickness are fabricated from single crystals of Bi2-xPbxSr2CaCu2O8+δ with a nominal Pb content x from 0.2 to 0.5. The Josephson critical current density jc is found to be pronouncedly large, ranging from 10 to 50 kA/cm2. Switching current probability measurements for these mesa samples show an indication of a crossover to the macroscopic quantum tunneling region.