Superconducting-insulator transition in disordered Josephson junctions networks

TL;DR

This paper simulates the superconductor-insulator transition in disordered Josephson junction networks, revealing how parameter fluctuations influence the transition and aligning well with experimental observations of emergent granularity.

Contribution

It introduces a simulation approach for the transition in disordered Josephson networks, accounting for parameter fluctuations and comparing results with experimental data.

Findings

Transition occurs at lower Tc with increased parameter fluctuations.

Simulation results align with experimental observations of phase fluctuations.

Emergent granularity explained by mesoscopic phase fluctuations.

Abstract

The superconducting-insulator transition is simulated in disordered networks of Josephson junctions with thermally activated Arrhenius-like resistive shunt. By solving the conductance matrix of the network, the transition is reproduced in different experimental conditions by tuning thickness, charge density and disorder degree. In particular, on increasing fluctuations of the parameters entering the Josephson coupling and the Coulomb energy of the junctions, the transition occurs for decreasing values of the critical temperature Tc and increasing values of the activation temperature To. The results of the simulation compare well with recent experiments where the mesoscopic fluctuations of the phase have been suggested as the mechanism underlying the phenomenon of emergent granularity in otherwise homogeneous films. The proposed approach is compared with the results obtained on TiN films and nanopatterned arrays of weak-links, where the superconductor-insulator transition is directly stimulated.