Josephson phase diffusion in the SQUID ratchet

Abstract

We study diffusion of the Josephson phase in the asymmetric SQUID subjected to a time-periodic current and pierced by an external magnetic flux. We analyze a relation between phase diffusion and quality of transport characterized by the dc voltage across the SQUID and efficiency of the device. In doing so, we concentrate on the previously reported regime [J. Spiechowicz and J. Łuczka, New J. Phys. \textbf{17}, 023054 (2015)] for which efficiency of the SQUID attains a global maximum. For long times, the mean-square displacement of the phase is a linear function of time, meaning that diffusion is normal. Its coefficient is small indicating rather regular phase evolution. However, it can be magnified \emph{several times} by tailoring experimentally accessible parameters like amplitudes of the ac current or external magnetic flux. Finally, we prove that in the deterministic limit this regime is essentially \emph{non-chaotic} and possesses an unexpected simplicity of attractors.

in press in Chaos: An Interdisciplinary Journal of Nonlinear Science

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Cited by in corpus (9)

• Coexistence of absolute negative mobility and anomalous diffusion
• SQUID ratchet: Statistics of transitions in dynamical localization
• Brownian ratchets: How stronger thermal noise can reduce diffusion
• Non-monotonic temperature dependence of chaos-assisted diffusion in driven periodic systems
• Anomalous transport in driven periodic systems: distribution of the absolute negative mobility effect in the parameter space
• Tunable $\phi$ Josephson Junction ratchet
• Paradoxical nature of negative mobility in the weak dissipation regime
• Giant oscillations of diffusion in ac-driven periodic systems
• Inertial frictional ratchets and their load bearing efficiencies