# Josephson Field-Effect Transistors Based on All-Metallic Al/Cu/Al Proximity Nanojunctions

## TL;DR

This paper reports the first all-metallic SNS Josephson transistors controlled by electric fields, demonstrating significant critical current suppression and high transconductance, expanding the potential for all-metallic superconducting electronics.

## Contribution

It introduces all-metallic SNS-FETs with electric field control, showing their full characterization and fundamental physics implications for proximity-induced superconductors.

## Key findings

- Electric field suppresses critical current by about one third.
- High transconductance of up to 100 nA/V at 100 mK.
- Suppression mechanism does not require true pairing potential.

## Abstract

We demonstrate the first \textit{all-metallic} mesoscopic superconductor-normal metal-superconductor (SNS) field-effect controlled Josephson transistors (SNS-FETs) and show their full characterization from the critical temperature $T_c$ down to 50 mK in the presence of both electric and magnetic field. The ability of a static electric field -applied by mean of a lateral gate electrode- to suppress the critical current $I_s$ in a proximity-induced superconductor is proven for both positive and negative gate voltage values. $I_s$ suppression reached typically about one third of its initial value, saturating at high gate voltages. The transconductance of our SNS-FETs obtains values as high as 100 nA/V at 100 mK. On the fundamental physics side, our results suggest that the mechanism at the basis of the observed phenomenon is quite general and does not rely on the existence of a true pairing potential, but rather the presence of superconducting correlations is enough for the effect to occur. On the technological side, our findings widen the family of materials available for the implementation of all-metallic field-effect transistors to \textit{synthetic} proximity-induced superconductors.