Gate-Tunable Critical Current of the Three-Dimensional Niobium Nano-Bridge Josephson Junction

TL;DR

This paper demonstrates a 3D niobium nano-bridge Josephson junction with a gate voltage that can tune the critical current to zero, enabling potential high-integration superconducting circuits.

Contribution

It introduces a novel gate-tunable 3D niobium nano-bridge Josephson junction with controllable critical current and flux modulation capabilities.

Findings

Critical current can be tuned to zero with gate voltage.

Flux modulation is also controllable via gate voltage.

Potential for high-density superconducting circuits.

Abstract

Recent studies have shown that the critical currents of several metallic superconducting nanowires and Dayem bridges can be locally tuned using a gate voltage {V_g}. Here, we report a gate-tunable Josephson junction structure constructed from a three-dimensional (3D) niobium nano-bridge junction (NBJ) with a voltage gate on top. Measurements up to 6 K showed that the critical current of this structure can be tuned to zero by increasing {V_g}. The critical gate voltage Vgc was reduced to 16 V and may possibly be reduced further by reducing the thickness of the insulation layer between the gate and the NBJ. Furthermore, the flux modulation generated by Josephson interference of two parallel 3D NBJs can also be tuned using {V_g} in a similar manner. Therefore, we believe that this gate-tunable Josephson junction structure is promising for superconducting circuit fabrication at high integration levels.