Pair and quasiparticle tunneling characteristics of small-sized intrinsic Josephson junctions in Bi 2Sr 2CaCu 2O y

Abstract

Tunneling properties of small-sized intrinsic Josephson junctions in Bi 2Sr 2CaCu 2O y single crystals have been investigated in order to understand their inherent properties. We have successfully fabricated mesas with lateral dimensions ranging from sub-μm 2 to several tens μm 2 on the same crystal. As a result, a clear gap structure and the normal resistance region could be observed without significant overheating together with typical multiple branches. The gap value, 2 Δ, was about 60 meV at 4.2 K, while the I c R n product was about 2.4 mV. Additionally, we observed that the temperature dependence of I c slightly deviates from the Ambegaoker–Baratoff relation for the s-wave superconductor. This is interpreted as evidence of the d-wave symmetry of the order parameter and coherent interlayer tunneling. We also found that from the simultaneous observation of the superconducting gap and the pseudogap, the pseudogap may be different from the precursor of superconductivity.