Antiferromagnetic Order and \pi-triplet Pairing in the Fulde-Ferrell-Larkin-Ovchinnikov State

TL;DR

This paper investigates the coexistence of antiferromagnetic order, -triplet pairing, and FFLO superconductivity, revealing how incommensurate AFM order is stabilized by Andreev bound states and enhanced by -triplet pairing, with implications for CeCoIn_5.

Contribution

It introduces a detailed analysis of the AFM-FFLO state, highlighting the stabilization mechanisms of incommensurate AFM order and the role of -triplet pairing in this complex superconducting phase.

Findings

Incommensurate AFM order is stabilized by Andreev bound states in the FFLO state.

-triplet pairing enhances the AFM-FFLO state.

AFM order can occur even when not stable in normal or BCS states.

Abstract

The antiferromagnetic Fulde-Ferrell-Larkin-Ovchinnikov (AFM-FFLO) state of coexisting d-wave FFLO superconductivity and incommensurate AFM order is studied on the basis of Bogoliubov-de Gennes (BdG) equations. We show that the incommensurate AFM order is stabilized in the FFLO state by the appearance of the Andreev bound state localized around the zeros of the FFLO order parameter. The AFM-FFLO state is further enhanced by the induced \pi-triplet superconductivity (pair density wave). The AFM order occurs in the FFLO state even when it is neither stable in the normal state nor in the BCS state. The order parameters of the AFM order, d-wave superconductivity, and \pi-triplet pairing are investigated by focusing on their spatial structures. Roles of the spin fluctuations beyond the BdG equations are discussed. Their relevance to the high-field superconducting phase of CeCoIn_5 is discussed.