Large Enhancement of Critical Current in Superconducting Devices by Gate Voltage

The gate-voltage-induced suppression of critical currents in metallic superconductors observed recently [De Simoni et al., Nat. Nanotechnol. 13, 802 (2018)] has raised crucial questions regarding the nature and mechanism of the electric field effect in these systems. Here, we demonstrate an enhancement of up to 30 % in critical current in the type II superconductor NbN, micro- and nano superconducting bridges, tunable via a back-gate voltage. Our suggested plausible mechanism of this enhancement in critical current based on surface nucleation and pinning of Abrikosov vortices is consistent with expectations and observations for type-II superconductor films with thicknesses comparable to their coherence length. Furthermore we demonstrate infinite electroresistance and a hysteretic resistance dependence on the applied electric field which could lead to logic and memory applications in a superconductors-based low-dissipation digital computing paradigm. Our work thus provides the first demonstration of an electric field enhancement in the superconducting property in metallic superconductors, constituting a crucial step towards understanding of electric field-effects on the fundamental properties of a superconductor and its exploitation for future technologies.