Numerical Investigation and Model Approximation for the Hysteretic Current-Voltage Characteristics of Josephson Junctions with Nonlinear Quasiparticle Resistance

We present a model analysis for the current-voltage ( I - V ) characteristics of Josephson junctions having superconductor-insulator-superconductor (SIS) structure. The numerical result for the V m value, which is the product of the maximum supercurrent and the observed subgap resistance, shows a marked decrease with increasing junction critical current 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 quasiparticle resistance restricts the voltage oscillation amplitude to the gap voltage, which results in the rapid decrease of the V m value. In this paper, we introduce a sinusoidal oscillation model for the junction voltage, and derive the approximated expressions for the V m value. The model approximation results agree well with the numerical results.