# Ultra-efficient superconducting Dayem bridge field-effect transistor

## TL;DR

This paper reports the development of Ti-based Dayem bridge superconducting FETs that can fully suppress the critical current with low gate voltages, revealing a possible field-effect control mechanism in metallic superconductors.

## Contribution

It demonstrates a novel fabrication of superconducting Dayem bridge FETs capable of controlling critical current, with insights into the field-effect modulation mechanism in metallic superconductors.

## Key findings

- Complete suppression of critical current at low gate voltages
- Increase in superconducting resistance near critical gate voltage
- High transconductance and tunable Josephson inductance

## Abstract

Superconducting field-effect transitor (SuFET) and Josephson field-effect transistor (JoFET) technologies take advantage of electric field induced control of charge carrier concentration in order to modulate the channel superconducting properties. Despite field-effect is believed to be unaffective for superconducting metals, recent experiments showed electric field dependent modulation of the critical current (IC) in a fully metallic transistor. Yet, the grounding mechanism of this phenomenon is not completely understood. Here, we show the experimental realization of Ti-based Dayem bridge field-effect transistors (DB-FETs) able to control IC of the superconducting channel. Our easy fabrication process DB-FETs show symmetric full suppression of IC for an applied critical gate voltage as low as VCG~+-8V at temperatures reaching about the 85% of the record critical temperature TC~550mK for titanium. The gate-independent TC and normal state resistance (RN) coupled with the increase of resistance in the supercoducting state (RS) for gate voltages close to the critical value (VCG) suggest the creation of field-effect induced metallic puddles in the superconducting sea. Our devices show extremely high values of transconductance (gMAXm~15uA/V at VG~+-6.5V) and variations of Josephson kinetic inductance (LK) with VG of two orders of magnitude. Therefore, the DB-FET appears as an ideal candidate for the realization of superconducting electronics, superconducting qubits, tunable interferometers as well as photon detectors.