Collective transport in the insulating state of Josephson junction arrays

TL;DR

This paper studies how groups of Cooper pairs move collectively in Josephson junction arrays in the insulating state, revealing size-dependent activation energies and thresholds influenced by magnetic fields, linked to phase synchronization.

Contribution

It provides an analytical model for collective charge transport in Josephson arrays, connecting Coulomb barriers, size scaling, and magnetic field effects, with implications for disordered superconducting films.

Findings

Activation energy and depinning voltage scale with system size.

Magnetic field causes non-monotonic changes in activation energy.

Phase synchronization influences Coulomb barrier formation.

Abstract

We investigate collective Cooper-pair transport of one- and two-dimensional Josephson junction arrays in the insulating state. We derive an analytical expression for the current-voltage characteristic revealing thermally activated conductivity at small voltages and threshold voltage depinning. The activation energy and the related depinning voltage represent a dynamic Coulomb barrier for collective charge transfer over the whole system and scale with the system size. We show that both quantities are non-monotonic functions of magnetic field. We propose that formation of the dynamic Coulomb barrier as well as the size scaling of the activation energy and the depinning threshold voltage, are consequences of the mutual phase synchronization. We apply the results for interpretation of experimental data in disordered films near the superconductor-insulator transition.