NUMERICAL INVESTIGATION AND MODEL APPROXIMATION FOR THE HYSTERETIC CURRENT-VOLTAGE CHARACTERISTICS OF JOSEPHSON-JUNCTIONS WITH NONLINEAR QUASI-PARTICLE RESISTANCE

We present a model analysis for the current-voltage (I-V) characterist ics of Josephson junctions having superconductor-insulator-superconduc tor (SIS) structure. The numerical result for the V-m value, which is the product of the maximum supercurrent and the observed subgap resist ance, shows a marked decrease with increasing junction critical curren t density (J(c)). The marked decrease is independent of leak current. Increasing J(c) reduces the junction capacitance C-J and enlarges the amplitude of the junction voltage oscillation. Nonlinearity of the qua siparticle resistance restricts the voltage oscillation amplitude to t he gap voltage, which results in the rapid decrease of the V-m value. In this paper, we introduce a sinusoidal oscillation model for the jun ction voltage, and derive the approximated expressions for the V-m val ue. The model approximation results agree well with the numerical resu lts.