Superconducting quantum interference proximitytransistor

Abstract

When a superconductor is placed close to a non-superconducting metal, it can induce superconducting correlations in the metal 1-10 , known as the proximity effect 11 . Such behaviour modifies the density of states (DOS) in the normal metal 12-15 and opens a minigap 12,13,16 with an amplitude that can be controlled by changing the phase of the superconducting order parameter 12,15 . Here, we exploit such behaviour to realize a new type of interferometer, the superconducting quantum interference proximity transistor (SQUIPT), for which the operation relies on the modulation with the magnetic field of the DOS of a proximized metal embedded in a superconducting loop. Even without optimizing its design, this device shows extremely low flux noise, down to ∼10 -5 φ 0 Hz -1/2 (φ 0 ≃2×10 -15 Wb is the flux quantum) and dissipation several orders of magnitude smaller than in conventional superconducting interferometers 17-19 . With optimization, the SQUIPT could significantly increase the sensitivity with which small magnetic moments are detected. © 2010 Macmillan Publishers Limited. All rights reserved.