Triplet superconducting proximity effect in inhomogeneous magnetic materials

Abstract

We show that quantum spin fluctuations in inhomogeneous conducting ferromagnets drastically affect the Andreev reflection of electrons and holes at a ferromagnet–superconductor interface. As a result, a strong long-range proximity effect appears, associated with electron–hole spin triplet correlations and persisting on a length scale typical for nonmagnetic materials but anomalously large for ferromagnets. For applications, an important consequence is that this long-range proximity effect permits the creation of superconducting quantum interference devices with magnetic Josephson junctions of anomalously large length.