Temperature dependences of jump voltage in Bi2Sr2CaCu2Ox intrinsic Josephson junctions

The basic experimental features of voltage jump V-J, between two adjacent branches in stacked Bi2Sr2CaCu2Ox intrinsic Josephson junctions (IJJs) are discussed. The temperature dependence of the V-J normalized to its value at 4.2 K, V-J(T)/V-J(4.2K), exhibited a downward deviation from a BCS temperature dependence of gap voltage. In this study, we assume that the critical current I-c, much smaller than that expected from the Ambegaokar-Baratoff (AB) theory is the intrinsic feature for IJJs. To interpret the V-J(T) characteristics, the linear approximation for the subgap quasiparticle current is also examined and a linear subgap resistance model is proposed as follows: R-J,R-sg(T)=R-J,R-sg(0)/[1+exp(k(o)(T-T-c/2)], where k(o) is constant. Under these assumptions, the voltage jump is given by V-J(T)=R-J,R-sg(T) x I-c(T). The normalized V-J(T)/V-J(4.2) characteristics for all samples with different V-J and I-c values are well explained using this model. (C) 2012 Published by Elsevier B.V. Selection and/or peer-review under responsibility of the Guest Editors.