Charge-tunable Cooper-pair diode

Superconducting diodes, devices that allow Cooper-pair currents to flow more easily in one direction than the other, are set to become key building blocks for dissipationless electronics. Existing realizations, however, rely on magnetic fields, ferromagnets, or complex heterostructures that hinder integration and scalability. Here we demonstrate a diode effect for Cooper-pairs that arises solely from electron-electron interactions in nanoscale superconducting lead islands. When these islands are driven into the Coulomb blockade regime, Cooper-pair transport occurs through resonant charge states. By tuning the island's electrostatic environment, we controllably break particle-hole symmetry and induce nonreciprocal supercurrents, thereby achieving a gate-switchable superconducting diode without any external magnetic field. Our approach enables robust rectification of superconducting currents and microwave photoresponse, providing a scalable strategy to superconducting logic devices.