Reentrant superconductivity in a Josephson junction array

Reentrant superconductivity has been observed in various systems, highlighting the interplay between superconductivity and different states of matter. It has been predicted in Josephson junction arrays, which provide a convenient platform for studying various quantum effects. Despite successful efforts to tune arrays near the superconductor-insulator transition (SIT), only quasi-reentrant behavior has been experimentally verified, and a clear demonstration of this effect remains elusive. Here, we investigate the naturally occurring inter-grain Josephson array in granular aluminum and employ a new approach for tuning its parameters. By adjusting the Josephson coupling with RF current, we reveal various regimes across the SIT and observe reentrant superconductivity as a function of temperature and magnetic field. Our findings emphasize the potential of using granular superconductors as controlled platforms for developing new superconducting devices and exploring emerging quantum phenomena in strongly correlated systems.