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SIZE EFFECT OF INNER RADIUS ON CIRCULARLY SYMMETRIC SOLITON STATES IN ANNULAR JOSEPHSON JUNCTIONS
XU KUN-MING (徐昆明), LU DAO-FANG (陆道芳), YAO XI-XIAN (姚希贤)
Acta Physica Sinica (Overseas Edition), 1993, 2 (4):
300-310.
DOI: 10.1088/1004-423X/2/4/008
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.
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