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

Abstract

We theoretically investigate k-space structures of dx2−y2-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 SC phase in CeCoIn5. 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 dx2−y2-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 dx2−y2-wave SC and SDW orders are enhanced altogether in k space due to the sign change of the dx2−y2-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.

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