Coherent states in a multi-junction superconducting loop

• Published in: Europhysics letters Vol. 33; no. 1; pp. 41 - 46
• Main Authors: Darula, M, Beuven, S, Siegel, M, Seidel, P, Darulova, A
• Format: Journal Article
• Language: English
• Published: IOP Publishing 01.01.1996; EDP Sciences
• Subjects: 74.50.+r; 84.30.Ng; 85.25.Dq
• ISSN: 0295-5075; 1286-4854
• DOI: 10.1209/epl/i1996-00301-2

The mutual coherent interaction of Josephson junctions in a multi-junction superconducting loop (MSL) in the limit of zero-loop inductance is theoretically investigated. For the loop containing 2M junctions there are M coherent states corresponding to different values of effective flux $\phi_{\rm eff}$ in the loop. The stability analysis using the method of Floquet exponents shows the highest stability for the state with $\phi_{\rm eff}=1/2$. In this state, the MSL behaves like an oscillating magnetic dipole. The optimum stability is reached for the normalised bias current $i_{\rm b}\simeq 2.5$ and the McCumber parameter $\beta_{\rm C}\simeq 0.5$.