Highly Sensitive Superconducting Quantum-Interference Proximity Transistor

We report the design and implementation of a high-performance superconducting quantum-interference proximity transistor based on aluminum-copper technology. With the adoption of a thin and short copper nanowire, we demonstrate full phase-driven modulation of the proximity-induced minigap in the normal-metal density of states. Under optimal bias, we record unprecedentedly high flux-to-voltage (up to 3 mV/Phi(0)) and flux-to-current (exceeding 100 nA/Phi(0)) transfer function values at subkelvin temperatures, where Phi(0) is the flux quantum. The best magnetic-flux resolution (as low as 500n Phi(0)/root Hz at 240 mK being limited by the room-temperature preamplification stage) is reached under fixed current bias. These figures of merit combined with ultralow power dissipation and micrometer-size dimensions make this mesoscopic interferometer attractive for low-temperature applications such as the investigation of the magnetization of small spin populations.