Coupled k-space structure of $d$-wave superconducting and magnetic orders induced by paramagnetic pair-breaking effect

TL;DR

This paper theoretically explores the k-space structures of coexisting d-wave superconducting and spin-density-wave orders induced by paramagnetic pair-breaking in CeCoIn5, revealing how their mutual enhancement stabilizes their coexistence and affects magnetic properties.

Contribution

It demonstrates the k-space development and mutual enhancement of SC and SDW orders due to sign change in the d-wave gap, providing insights into their coexistence in high field low temperature phases.

Findings

SDW develops near gap nodes where SC is suppressed by PPB

Mutual enhancement of SC and SDW due to sign change stabilizes coexistence

Field dependence of SDW moment influenced by Fermi surface curvature

Abstract

We theoretically investigate k-space structures of $d_{x^2-y^2}$-wave superconducting (SC) and spin-density-wave (SDW) orders in their coexistent phase induced by a paramagnetic pair-breaking (PPB) effect in relation to the high field and low temperature (HFLT) SC phase in CeCoIn$_5$. It is shown that, in k-space, the SDW order develops near the gap nodes where the SC order is suppressed by PPB, and the nesting condition for the SDW ordering is satisfied. By comparing the results in the $d_{x^2-y^2}$-wave SC model and those in an artificial model with no sign change of the gap function in k-space with each other, it is shown that the $d_{x^2-y^2}$-wave SC and SDW orders are enhanced altogether in k-space due to the sign change of the $d_{x^2-y^2}$-wave gap function there, and that this mutual enhancement largely stabilizes the coexistence of these orders in real space. It is also discussed that the field dependence of a SDW moment can be affected by the k-space structure of these orders, which is dependent on the curvature of the Fermi surface.