Peak in the temperature dependence of the c-axis Josephson current in Bi2Sr2CaCu2O8+x intrinsic Josephson junctions

Abstract

We have measured the temperature dependence of the c-axis critical current (Ic(T)) in intrinsic Josephson tunnel junctions in single crystal Bi2Sr2CaCu2O8+x. Stacks (10×50 μm2) were fabricated on the surfaces of the single crystals by photolithography and Ar-ion milling. The temperature dependence of the critical current deviates from the Ambegaokar-Baratoff relation. The most striking deviation is a peak inIc(T) at ∼80 K. The peak is suppressed if we apply a small (∼50G) magnetic field along the c-axis. The position of the peak does not change in a magnetic field. At∼60K we observe an increase in the flucuations of the critical current as the temperature is decreased. In some samples we also observe some small features inIc(T) at this temperature.