摘要： The effect of the inner radius of an annular Josephson junetion on the excitation 0f circularly symmetric soliton states is explored by direct numerical simulation. In a circularly symmetric annular Josephson junction (CSAJJ hereafter), the phase difference in the order parameters Φ across the junction bar-rier obeys the modified sine-Gordon equation (SGE) in which there is a perturbation term Φ_p/ρ inversely proportional to the radial coordinate ρ. and this term does not appear in the case of a 1D in-line junc-tion. The effect of the Φ_p/ρ term becomes prominent when ρ is small. It turns out that for junctions of grven dissipation and annular width, there is a lower limit of the inner radii for the junctions to support stable soliton motion, while the lower limit depends strongly on the dissipation coefficient α. For example, for a CSAJJ with inner radius 5λ_J, outer radius 10λ_J, no stable soliton states would exist when α=0.01 or α=0.02. However, for 0.06≥α≥0.03, there are ring-shaped solitary wave solutions, presumably because the dissipation suppresses the effect of the Φ_p/ρ term. Finally, the behaviour of the seliton states and the rele-vant I-V characteristics are also disscussed.

Abstract: The effect of the inner radius of an annular Josephson junetion on the excitation of circularly symmetric soliton states is explored by direct numerical simulation. In a circularly symmetric annular Josephson junction (CSAJJ hereafter), the phase difference in the order parameters $\Phi$ across the junction bar-rier obeys the modified sine-Gordon equation (SGE) in which there is a perturbation term $\Phi$_p/$\rho$ inversely proportional to the radial coordinate $\rho$. and this term does not appear in the case of a 1D in-line junc-tion. The effect of the $\Phi$_p/$\rho$ term becomes prominent when $\rho$ is small. It turns out that for junctions of grven dissipation and annular width, there is a lower limit of the inner radii for the junctions to support stable soliton motion, while the lower limit depends strongly on the dissipation coefficient $\alpha$. For example, for a CSAJJ with inner radius 5$\lambda$_J, outer radius 10$\lambda$_J, no stable soliton states would exist when $\alpha$=0.01 or $\alpha$=0.02. However, for 0.06≥$\alpha$≥0.03, there are ring-shaped solitary wave solutions, presumably because the dissipation suppresses the effect of the $\Phi$_p/$\rho$ term. Finally, the behaviour of the seliton states and the rele-vant I-V characteristics are also disscussed.

中图分类号:  (Josephson devices)

• 85.25.Cp

85.25.Am (Superconducting device characterization, design, and modeling) 74.50.+r (Tunneling phenomena; Josephson effects)