Ginzburg-Landau Analysis for the Antiferromagnetic Order in the Fulde-Ferrell-Larkin-Ovchinnikov Superconductor

TL;DR

This paper uses Ginzburg-Landau theory to analyze incommensurate antiferromagnetic order in FFLO superconductors, revealing complex phase diagrams and proposing experimental methods for future validation.

Contribution

It formulates a two-component Ginzburg-Landau model to describe AFM states in FFLO superconductors with broken translation symmetry, providing new insights into their phase structure.

Findings

Multiple phase diagram with single-q and double-q phases.

Comparison of magnetic properties with neutron scattering and NMR data.

Proposal of ultrasonic measurement for experimental identification.

Abstract

Incommensurate antiferromangetic (AFM) order in the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) superconductor is investigated on the basis of the Ginzburg-Landau theory. We formulate the two component Ginzburg-Landau model to discuss two degenerate incommensurate AFM states in the tetragonal crystal structure. Owing to the broken translation symmetry in the FFLO state, a multiple phase diagram of single-q phase and double-q phase is obtained under the magnetic field along [100] or [010] direction. Magnetic properties in each phase are investigated and compared with the neutron scattering and NMR measurements for a heavy fermion superconductor CeCoIn_5. An ultrasonic measurement is proposed for a future experimental study to identify the AFM-FFLO state. The field orientation dependence of the AFM order in CeCoIn_5 is discussed.