Ultra-Efficient Superconducting Dayem Bridge Field-Effect Transistor

Abstract

Superconducting field-effect transitor (SuFET) and Josephson field-effect transistor (JoFET) technologies take advantage of electric-field-induced control of charge-carrier concentration to modulate the channel superconducting properties. Despite the fact that the field-effect is believed to be ineffective for superconducting metals, recent experiments showed electric-field-dependent modulation of the critical current ( I_C) in a fully metallic transistor. However, 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 the I_C of the superconducting channel. Our easy fabrication process for DB-FETs show symmetric full suppression of I_C for applied critical gate voltages as low as V_G^C ≃ ±8 V at temperatures reaching about the 85% of the record critical temperature, T_C ≃ 550 mK, for titanium. The gate-independent T_C and normal-state resistance ( R_N) coupled with the increase of resistance in the superconducting state ( R_S) for gate voltages close to the critical value ( V_G^C) suggest the creation of field-effect induced metallic puddles in the superconducting sea. Our devices show extremely high values of transconductance (| g_m^MAX| ≃ 15 μA/V at V_G ≃ ±6.5 V) and variations of Josephson kinetic inductance ( L_K) with V_G of 2 orders of magnitude. Therefore, the DB-FET appears as an ideal candidate for the realization of superconducting electronics, superconducting qubits, and tunable interferometers as well as photon detectors.

Keywords: Josephson effect; field effect; superconductivity; transistor.