The role of canting and depleted-triplet minima in superconducting spin valve structures

TL;DR

This paper investigates how canting angles affect pair correlations and Josephson currents in superconducting spin valves, revealing a depleted-triplet minimum phenomenon linked to triplet correlations and sign changes in Gor'kov functions.

Contribution

It demonstrates the distinct effects of canting on trilayer and pentalayer spin valves and introduces a toy model to clarify the behavior of Gor'kov functions in these systems.

Findings

Depleted-triplet minimum observed in trilayer spin valves.

Triplet correlations are weakly affected by canting in trilayers.

Sign change of Gor'kov functions correlates with the depleted-triplet minimum.

Abstract

The trilayer and pentalayer spin valve structures are revisited to determine the behavior of pair correlations and Josephson current when the magnetic layers are canted at arbitrary angle. The two systems display markedly different behaviors in the center magnetic layer. While the trilayer generates a triplet component that is weakly affected by canting, the pentalayer tunes in singlet pair correlations depending heavily on canting. We also show that a minimum with depleted $m=\pm1$ triplet components, rather than a $0-\pi$ transition, may be observed in the current profile $I_c(d_F)$ of a trilayer spin valve. The depleted-triplet minimum (DTM) is directly attributable to a decrease of $m=\pm1$ triplet correlations with increased thickness of the central ferromagnet, accompanied by a hidden, simultaneous sign change of the Gor'kov functions contributed from the left and right superconductors. We introduce a toy model for superconducting-magnetic proximity systems to better illuminate the behavior of individual components of the Gor'kov function and compare with a full numerical calculation.