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

Recent studies have shown that the critical currentsof severalmetallic superconducting nanowires and Dayem bridges can be locallytuned by using a gate voltage (V (g)). Here,we report a gate-tunable Josephson junction structure constructedfrom a three-dimensional (3D) niobium nanobridge junction (NBJ) witha voltage gate on top. Measurements up to 6 K showed that the criticalcurrent of this structure can be tuned to zero by increasing V (g). The critical gate voltage was reduced to16 V and may possibly be reduced further by reducing the thicknessof the insulation layer between the gate and the NBJ. Furthermore,the flux modulation generated by Josephson interference of two parallel3D NBJs can also be tuned by using V (g) ina similar manner. Therefore, we believe that this gate-tunable Josephsonjunction structure is promising for superconducting circuit fabricationat high integration levels.