Microscopic theory of equilibrium properties of F/S/F trilayers with weak ferromagnets

TL;DR

This paper presents a microscopic theory explaining the non-monotonic temperature dependence of the superconducting gap in F/S/F trilayers with weak ferromagnets, highlighting the role of Andreev bound states and various physical parameters.

Contribution

It introduces a detailed microscopic model and recursive algorithm to analyze how Andreev bound states influence the superconducting gap in weak ferromagnet trilayers.

Findings

Non-monotonic temperature dependence of the superconducting gap explained

Andreev bound states compete with minigap formation

Parameter effects on gap behavior detailed

Abstract

The aim of this paper is to explain the non monotonic temperature dependence of the self-consistent superconducting gap of ferromagnet/superconductor/ferromagnet (F/S/F) trilayers with weak ferromagnets in the parallel alignment (equivalent to F/S bilayers). We show that this is due to Andreev bound states that compete with the formation of a minigap. Using a recursive algorithm we discuss in detail the roles of various parameters (thicknesses of the superconductor and ferromagnets, relative spin orientation of the ferromagnets, exchange field, temperature, disorder, interface transparencies).