Interlayer spin-singlet pairing induced by magnetic interactions in an antiferromagnetic superconductor

TL;DR

This paper proposes a mechanism where magnetic interactions induce interlayer spin-singlet pairing in antiferromagnetic superconductors, allowing coexistence of magnetism and superconductivity with unique properties.

Contribution

It introduces a novel magnetic interaction-driven pairing mechanism in layered antiferromagnetic metals, explaining coexistence of antiferromagnetism and superconductivity.

Findings

Superconductivity coexists with antiferromagnetic order at low temperatures.

The exchange field does not affect the superconducting state.

The superconducting gap has a horizontal line node and is isotropic in spin space.

Abstract

It is shown that interlayer spin-singlet Cooper pairing is induced by magnetic interactions in a metallic antiferromagnet of stacked conductive layers in which each layer is ferromagnetically polarized and they order antiferromagnetically in stacking direction. As a result, the antiferromagnetic long-range order and superconductivity coexist at low temperatures. It is shown that T_AF > T_c except for in a very limited parameter region unless T_AF = 0, where T_AF and T_c denote the antiferromagnetic and superconducting transition temperatures, respectively. It is found that the exchange field caused by the spontaneous staggered magnetization does not affect superconductivity at all, even if it is very large. The resultant superconducting order parameter has a horizontal line node, and is isotropic in spin space in spite of the anisotropy of the background magnetic order. We discuss the possible relevance of the present mechanism to the antiferromagnetic heavy fermion superconductors UPd_2Al_3 and CePt_3Si.