Superconducting bistability in floating Al islands of hybrid Al/InAs nanowires

We investigate a nonequilibrium aspect of the current-driven superconducting-normal phase transition in floating Al islands of epitaxial full-shell Al/InAs nanowires. Within a transition region discontinuous voltage jumps and hysteretic behavior of the $I\text{\ensuremath{-}}V$ characteristics are observed, associated with the destruction and recovery of the superconducting order parameter in the island. The strength of the two features varies strongly in different devices in a mutually correlated way and can be suppressed by a small magnetic field. Numerical calculation explains this behavior in terms of a tiny nonequilibrium correction to the electronic energy distribution at low energies. The experiment demonstrates a critical failure of a two-temperature nonequilibrium model of the superconductor-normal transition in floating islands of hybrid nanowire devices.