Oscillatory superconducting transition temperature in superconductor/antiferromagnet heterostructures

TL;DR

This paper predicts that the critical temperature in antiferromagnet/superconductor heterostructures oscillates with AF layer thickness due to proximity-induced triplet correlations, extending known effects from ferromagnet/superconductor systems.

Contribution

It introduces the novel prediction of oscillating critical temperature in AF/S bilayers caused by Neel-type triplet correlations, without macroscopic exchange fields.

Findings

Critical temperature oscillates with AF layer thickness.

Proximity-induced triplet correlations cause finite pair momentum.

Explanation for recent experimental observations.

Abstract

One of the most famous proximity effects at ferromagnet/superconductor (F/S) interfaces is partial conversion of singlet superconductivity to triplet pairing correlations. Due to the presence of macroscopic exchange field in the ferromagnet the Cooper pairs penetrating into the ferromagnet from the superconductor acquire a finite momentum there. The finite-momentum pairing manifests itself, in particular, as a nonmonotonic dependence of the critical temperature of the bilayer on the thickness of the F layer. Here we predict that despite the absence of the macroscopic exchange field the critical temperature of the antiferromagnet/superconductor (AF/S) bilayers also exhibit nonmonotonic (oscillating) dependence on the AF layer thickness. It is a manifestation of the proximity-induced Neel-type triplet correlations, which acquire finite total pair momentum and oscillate in the AF layer due to the Umklapp electron scattering processes at the AF/S interface. Our prediction can provide a possible explanation for a number of recently published experimental observations of the critical temperature of AF/S bilayers.