Fluctuation and Order of Antiferromagnetism induced by Paramagnetic Pair-Breaking in Superconducting Vortex Lattice

TL;DR

This paper theoretically investigates how strong Pauli-paramagnetic pair-breaking influences antiferromagnetic order and vortex lattice structure in d-wave superconductors, revealing spatially modulated AFM order coexisting with superconductivity.

Contribution

It demonstrates the role of PPB-induced AFM fluctuations and ordering in modifying vortex lattice form factors and spatial magnetic structures in superconductors.

Findings

PPB-induced AFM fluctuations enhance vortex lattice form factor.

AFM order is spatially modulated and coexists with superconductivity.

Results relate to observed phenomena in CeCoIn5, including vortex form factor anomalies and AFM order.

Abstract

Effects of the strong Pauli-paramagnetic pair-breaking (PPB) on the vortex lattice in d-wave superconductors are theoretically studied by putting emphasis on consequences of the PPB-induced antiferromagnetic (AFM) ordering in the spatial modulation in the vortex lattice. It is shown that the PPB-induced AFM fluctuation in the superconducting state leads to an enhancement of the vortex lattice form factor which is a measure of spatial variations of the internal magnetic field and that the enhancement becomes more remarkable as an AFM instability is approached. It is also demonstrated that the PPB-induced AFM ordering is assisted by the vortex-lattice modulation, and thus, that the resulting AFM order is spatially modulated, while it is not localized in the vortex cores but coexistent with the nonvanishing superconducting order parameter. These results are discussed in connection with two phenomena observed in CeCoIn5, the anomalous field dependence of the vortex lattice form factor and the AFM order appearing inside the high-field and low-temperature superconducting phase.