Direct Measurement of the Current-Phase Relation of a Superfluid 3 He-B Weak Link

Abstract

Direct measurements of the current-phase relation, Iversus Δφ, for a weak link coupling two reservoirs of B-phase superfluid helium-3 (³He-B) were made over a wide range of temperatures. The weak link consists of a square array of 100-nanometer-diameter apertures. For temperatures T such that T/T _c ≥ 0.6 (whereT _c is the superfluid transition temperature),I ∝ sin(Δφ). At lower temperatures,I(Δφ) approaches a straight line. Several remarkable phenomena heretofore inaccessible to superconducting Josephson junctions, including direct observation of quantum oscillations and continuous knowledge of Δφ, were also observed.