Coherent states in a multi-junction superconducting loop

Abstract
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 eff in the loop. The stability analysis using the method of Floquet exponents shows the highest stability for the state with eff = 1/2. In this state, the MSL behaves like an oscillating magnetic dipole. The optimum stability is reached for the normalised bias current ib 2.5 and the McCumber parameter βC 0.5.