Comment on "Fluctuation-Driven First-Order Transition in Pauli-Limited dd-Wave Superconductors"

This is a Comment on a recent Letter (Phys.Rev.Lett.93, 247002 (2004)) written by Dalidovich and Yang. It is pointed out that any Pauli-limited approach neglecting the vortices is inapplicable to describing the FFLO state in CeCoIn5.Comment: 1 page, no figure. To appear in Physical Review Letter

Modulated Vortex Lattice in High Fields and Gap Nodes

The mean field vortex phase diagram of a quasi two dimensional superconductor with a nodal d-wave pairing and with strong Pauli spin depairing is examined in the parallel field case in order to examine an effect of gap nodes (or minima) on the stability of a FFLO-like vortex lattice. We find through a heuristic argument and a model calculation with a four-fold anisotropic Fermi velocity that the FFLO-like state is relatively suppressed as the field approaches a nodal direction. When taking account of a couple of experimental results altogether, the present result strongly suggests that a node or gap minimum of the pairing function of CeCoIn$_5$ is located along the [100]-direction.Comment: 5 pages, 2 figures, References were added. To appear in Phys. Rev.