Antiferromagnetic order in Pauli-limited unconventional superconductors

Phys Rev Lett. 2011 Aug 26;107(9):096401. doi: 10.1103/PhysRevLett.107.096401. Epub 2011 Aug 26.

Abstract

We develop a theory of the coexistence of superconductivity (SC) and antiferromagnetism (AFM) in CeCoIn(5). We show that in Pauli-limited nodal superconductors the nesting of the quasiparticle pockets induced by Zeeman pair breaking leads to incommensurate AFM with the magnetic moment normal to the field. We compute the phase diagram and find a first order transition to the normal state at low temperatures, the absence of normal state AFM, and the coexistence of SC and AFM at high fields, in agreement with experiments. We also predict the existence of a new double-Q magnetic phase.