Theory of Andreev bound states in S-F-S junctions and S-F proximity devices

Andreev bound states are an expression of quantum coherence between particles and holes in hybrid structures composed of superconducting and non- superconducting metallic parts. Their spectrum carries important information on the nature of the pairing, and determines the current in Josephson devices. Here I focus on Andreev bound states in systems involving superconductors and ferromagnets with strong spin- polarization. I provide a general framework for non- local Andreev phenomena in such structures in terms of coherence functions, and show how the latter cross- link wave-function and Green-function theories.