Spin splitting induced in a superconductor by an antiferromagnetic insulator

TL;DR

This paper demonstrates that antiferromagnetic insulators can induce significant, disorder-resistant spin splitting in superconductors through a microscopic model, avoiding issues associated with ferromagnetic materials.

Contribution

It introduces a microscopic model showing how antiferromagnetic insulators induce spin splitting in superconductors, considering interface disorder effects.

Findings

Antiferromagnetic insulators induce large spin splitting in superconductors.

Disorder effects mimic impurity and spin-flip scattering, but do not significantly affect superconductivity.

The model predicts disorder-resistant spin splitting without detrimental effects.

Abstract

Inspired by recent feats in exchange coupling antiferromagnets to an adjacent material, we demonstrate the possibility of employing them for inducing spin splitting in a superconductor, thereby avoiding the detrimental, parasitic effects of ferromagnets employed to this end. We derive the Gor'kov equation for the matrix Green's function in the superconducting layer, considering a microscopic model for its disordered interface with a two-sublattice magnetic insulator. We find that an antiferromagnetic insulator with effectively uncompensated interface induces a large, disorder-resistant spin splitting in the adjacent superconductor. In addition, we find contributions to the self-energy stemming from the interfacial disorder. Within our model, these mimic impurity and spin-flip scattering, while another breaks the symmetries in particle-hole and spin spaces. The latter contribution, however, drops out in the quasi-classical approximation and thus, does not significantly affect the superconducting state.