Antiferromagnetic Order in Pauli Limited Unconventional Superconductors

TL;DR

This paper presents a theory explaining the coexistence of superconductivity and antiferromagnetism in CeCoIn5, highlighting how Zeeman pair-breaking induces incommensurate AFM and predicting a new magnetic phase, aligning with experimental observations.

Contribution

It introduces a theoretical model for SC and AFM coexistence in Pauli-limited superconductors, predicting a novel double-Q magnetic phase.

Findings

Incommensurate AFM arises from quasi-particle nesting.

Phase diagram shows first order transition to normal state.

Coexistence of SC and AFM occurs at high magnetic fields.

Abstract

We develop a theory of the coexistence of superconductivity (SC) and antiferromagnetism (AFM) in CeCoIn5. We show that in Pauli-limited nodal superconductors the nesting of the quasi-particle pockets induced by Zeeman pair-breaking leads to incommensurate AFM with the moment normal to the field. We compute the phase diagram and find a first order transition to the normal state at low temperatures, absence of normal state AFM, and coexistence of SC and AFM at high fields, in agreement with experiments. We also predict the existence of a new double-Q magnetic phase.