Metallic supercurrent field-effect transistor

TL;DR

This paper demonstrates the first experimental control of supercurrent in all-metallic superconducting transistors using electrostatic fields, showing a bipolar decay of critical current up to near the critical temperature.

Contribution

It provides the first evidence of field-effect manipulation of supercurrent in metallic superconductors, supported by a phenomenological theory explaining the electric-field-induced perturbation.

Findings

Critical current decays with increasing electrostatic field in titanium and aluminum superconducting films.

Bipolar field effect persists up to 85% of the critical temperature.

Supercurrent can be quenched by electrostatic gating in all-metallic superconducting transistors.

Abstract

In their original formulation of superconductivity, the London brothers predicted the exponential suppression of an $electrostatic$ field inside a superconductor over the so-called London penetration depth, $\lambda_L$. Despite a few experiments indicating hints of perturbation induced by electrostatic fields, no clue has been provided so far on the possibility to manipulate metallic superconductors via field-effect. Here we report field-effect control of the supercurrent in $all$-metallic transistors made of different Bardeen-Cooper-Schrieffer (BCS) superconducting thin films. At low temperature, our field-effect transistors (FETs) show a monotonic decay of the critical current under increasing electrostatic field up to total quenching for gate voltage values as large as $\pm 40$V in titanium-based devices. This $bipolar$ field effect persists up to $\sim 85\%$ of the critical temperature ($\sim 0.41$K), and in the presence of sizable magnetic fields. A similar behavior was observed in aluminum thin film FETs. A phenomenological theory accounts for our observations, and points towards the interpretation in terms of an electric-field-induced perturbation propagating inside the superconducting film. In our understanding, this affects the pairing potential and quenches the supercurrent. These results could represent a groundbreaking asset for the realization of an $all$-metallic superconducting field-effect electronics and leading-edge quantum information architectures.