Noise and generation effects in parallel Josephson junction chains

Abstract

We consider mutual effects of soliton dynamics and noise in a chain of Josephson junctions in the framework of the Frenkel-Kontorova model. The investigations are performed by the analysis of experimentally relevant quantities such as oscillation power and spectral linewidth, which both can be derived from the power spectral density of the system as, respectively, its integral and its width. Taking into account both ohmic and surface losses together with bias inhomogeneity, and considering dense soliton chain under the effect of external magnetic field, it is demonstrated that increase of the system discreteness (decrease of coupling between neighboring elements) leads to the oscillation power reduction and spectral linewidth increase, which signals about increase of the total noise in the system. Drastic increase of the linewidth is observed when the distance between elements becomes comparable with the soliton size, which is explained by an increase of stochasticity due to reflections of solitons from the system edges and noise.