Ballistic transport in ferromagnet-superconductor-ferromagnet trilayers with arbitrary orientation of magnetizations

TL;DR

This paper theoretically investigates ballistic transport in ferromagnet-superconductor-ferromagnet trilayers with arbitrary magnetization orientations, revealing how conductance and spin-triplet correlations depend on magnetic alignment and interface properties.

Contribution

It provides generalized scattering expressions and analyzes size, coherence, and magnetization effects on conductance and triplet correlations in clean FSF heterostructures.

Findings

Conductance spectra depend monotonically on magnetization misorientation angle.

Both singlet and triplet pair correlations oscillate and decay as power-laws in clean FSF structures.

Magnetoresistance varies smoothly from parallel to antiparallel magnetization configurations.

Abstract

Transport phenomena in clean ferromagnet-superconductor-ferromagnet (FSF) trilayers are studied theoretically for a general case of arbitrary orientation of in-plane magnetizations and interface transparencies. Generalized expressions for scattering probabilities are derived and the differential conductance is computed using solutions of the Bogoliubov-de Gennes equation. We focus on size and coherence effects that characterize ballistic transport, in particular on the subgap transmission and geometrical oscillations of the conductance. We find a monotonic dependence of conductance spectra and magnetoresistance on the angle of misorientation of magnetizations as their alignment is changed from parallel to antiparallel. Spin-triplet pair correlations in FSF heterostructures induced by non-collinearity of magnetizations are investigated by solving the Gor'kov equations in the clean limit. Unlike diffusive FSF junctions, where the triplet correlations have a long-range monotonic decay, we show that in clean ferromagnet-superconductor hybrids both singlet and triplet pair correlations induced in the F layers are oscillating and power-law decaying with the distance from the S-F interfaces.