Antiferromagnetic ordering induced by paramagnetic depairing in unconventional superconductors

TL;DR

This paper explains how strong Pauli paramagnetic depairing in unconventional superconductors can induce antiferromagnetic ordering, especially in materials with nodal gaps, and accounts for observed phenomena in CeCoIn_5.

Contribution

It demonstrates that field-induced antiferromagnetic order arises from paramagnetic depairing effects in superconductors with nodal gaps, providing a unified explanation for experimental observations.

Findings

Field-induced AFM order linked to strong paramagnetic depairing.

Explanation of vortex lattice anomalies in CeCoIn_5.

Connection between AFM order and FFLO state phenomena.

Abstract

Antiferromagnetic (AFM) (or spin-density wave) quantum critical fluctuation enhanced just below H_c2(0) have been often observed in d-wave superconductors with a strong Pauli paramagnetic depairing (PD) including CeCoIn_5. It is shown here that such a tendency of field-induced AFM ordering is a consequence of strong PD and should appear particularly in superconductors with a gap node along the AFM modulation. Two phenomena seen in CeCoIn_5, the anomalous vortex lattice form factor and the AFM order in the Fulde-Ferrell-Larkin-Ovchinnikov state, are explained based on this peculiar PD effect.