High-energy electron local injection in top-gated metallic superconductor switch

Abstract The gate-tunable superconductivity in metallic superconductors has recently attracted significant attention due to its rich physics and potential applications in next-generation superconducting electronics. Although the operating principles of these devices have been attributed to the small leakage currents of high-energy electrons in recent experiments, the generated phonons can spread over considerable distances in the substrate, which may limit their further applications. Here, we utilize a top gate structure with monocrystalline h-BN as a gate dielectric and demonstrate the gate-adjustable supercurrent in a metallic Nb microbridge. The gate current of the devices perfectly follows the Fowler–Nordheim law of field emission, indicating that the injection of high-energy electrons presumably causes the suppression of the supercurrent. Our devices reduce the distance between the gate and the microbridge to a few nanometers or less, significantly minimizing the generated phonons’ spreading distance and power dissipation in the substrate or surrounding environment. These observations demonstrate that top-gated metallic superconducting switches with local electron injection can improve the device integration density, providing us with more versatile and practical opportunities to explore superconducting circuit architecture.