Field-Induced Spin-Exciton Condensation in dx2-y2-wave Superconducting CeCoIn5

TL;DR

This paper explores how magnetic fields induce a spin-exciton condensation in the superconducting phase of CeCoIn5, leading to coexistence of superconductivity and spin density wave order through a theoretical model.

Contribution

It introduces a theoretical model explaining field-induced SDW instability within dx2-y2-wave superconductivity in CeCoIn5, linking magnetic tuning to spin correlations.

Findings

Magnetic field enhances transverse spin correlations in the superconducting phase.

The model predicts SDW instability coexisting with superconductivity under certain conditions.

Restrictions on Fermi surface and wave-vector are derived for the instability to occur.

Abstract

The implications of the spin exciton mechanism are exposed in the context of a Spin Density Wave (SDW) instability occurring inside the superconducting phase of a layered heavy electron compound. In this model a magnetic field serves as a tuning parameter bringing the system to the point where the transverse spin correlations are enhanced due to dx2 -y2 -wave superconductivity and induces an instability to a phase with coexisting superconductivity and SDW order. The model considers electrons in a crystal with antiferromagnetic interactions and provides restrictions on the Fermi surface characteristics and on the ordering wave-vector (that can be commensurate or incommensurate close to commensuration). The applications of the model are addressed to the low-temperature/high-magnetic-field phase of CeCoIn5 [M. Kenzelmann et al., Science 321, 1652 (2008), Phys. Rev. Lett. 104, 127001 (2010)].