I-Vcharacteristics of a circularly symmetric annular Josephson junction

The I-V characteristics of a circularly symmetric annular Josephson junction are investigated numerically in this paper. By assuming a soliton solution in the junction initially, we found that in the absence of both an applied magnetic field and a feeding current there exists a quasisoliton solution for the equation ${\mathrm{\phi }}_{\mathrm{\rho }\mathrm{\rho }}$+${\mathrm{\rho }}^{\mathrm{-}1}$ ${\mathrm{\phi }}_{\mathrm{\rho }}$-${\mathrm{\phi }}_{\mathit{t}\mathit{t}}$-α${\mathrm{\phi }}_{\mathit{t}}$=sinφ so long as dissipative effects are excluded (i.e., α=0). In the presence of the dissipative term (α≠0), such a quasisoliton solution does not exist. When a dc feeding current is introduced but the applied magnetic field is zero, the I-V characteristics show no evidence of zero-field steps. There does exist an Ohmic relationship in the I-V curve and a simple analytical treatment for this Ohmic behavior is made by assuming a rotary periodic solution for the equation. However, when a large external magnetic field is applied, the boundary conditions of this equation become asymmetric, which allows fluxon resonant propagation to occur within the junction. Hence we obtain a step-shaped I-V curve and these are considered to be Fiske steps. Finally, when the applied external magnetic field is small, we found no Fiske steps in the I-V curves.