Dynamic interplay of Berry’s phase and spectral flow in the current-voltage characteristics of a restricted class of large SNS annular Josephson junctions

Abstract

It has been argued that a competition arises between the Berry phase and spectral flow effects in a restricted class of large SNS annular Josephson junctions. A crossover is expected to occur in the junction response at the temperature T* where the superconducting dynamics enters the hydrodynamic limit. For T>T*, spectral flow occurs in the weak link and masks the Berry phase effects; while for T≪T*, spectral flow does not occur allowing Berry phase effects to freely influence junction dynamics. In this paper we focus on temperatures T≲T* where spectral flow masking of Berry phase effects begins to switch off. In the case where a single vortex is present in the weak link, we numerically calculate the I–V curves for a restricted class of annular Josephson junctions in which nonvanishing Berry phase effects are expected to occur. We find that as Berry phase effects strengthen, distinctive shifts appear in the I–V curves which are the signature of the crossover, and provide clear targets for an experimental test of the underlying theory. We estimate T* for a clean junction, summarize the restrictions defining the class of annular junctions in which nonvanishing Berry phase effects are expected to occur, and show how the I–V curve shifts can be understood as a consequence of: (1) a Berry phase contribution to the tunneling current density; (2) the magnetic structure of the vortex core; and (3) Bernoulli’s theorem.

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