Reduced decay in Josephson coupling across ferromagnetic junctions with spin-orbit coupling layers

TL;DR

This study experimentally demonstrates that spin-orbit coupling layers in ferromagnetic Josephson junctions can reduce the decay of Josephson coupling, suggesting the presence of spin-triplet correlations.

Contribution

First experimental evidence showing reduced decay in Josephson coupling due to spin-orbit layers in ferromagnetic junctions, indicating triplet pairing.

Findings

Reduced decay of Josephson coupling with spin-orbit layers

Possible indication of $S_z=1$ triplet correlations

Magnetization interaction with Meissner effect influences correlations

Abstract

The generation of $S_z=1$ triplet Cooper pairs has been predicted theoretically in superconducting-ferromagnetic hybrid heterostructures in the presence of spin-orbit coupling [F. S. Bergeret and I. V. Tokatly, Phys. Rev. B 89, 134517 (2014) and Jacobsen et al., Sci. Rep. 6, 23926 (2016)]. In this study, we experimentally investigate vertical Josephson junctions where the weak link is formed from a ferromagnetic layer with perpendicular magnetic anisotropy sandwiched by two non-magnetic layers with weak or strong spin-orbit coupling. We find that the decay of the Josephson coupling is reduced in the latter case, possibly indicating the presence of $S_z=1$ spin-triplet correlations. We speculate that the canted magnetization required for these correlations is provided by the interaction of magnetization with Meissner effect in the superconducting layers.