Instability of square vortex lattice in d-wave superconductors is due to paramagnetic depairing

Phys Rev Lett. 2008 Jul 11;101(2):027001. doi: 10.1103/PhysRevLett.101.027001. Epub 2008 Jul 8.

Abstract

The effects of paramagnetic depairing on structural transitions between vortex lattices of a quasi-two-dimensional d-wave superconductor are examined. We find that, when the Maki parameter alphaM is of order unity, a square lattice induced by a d-wave pairing is destabilized with increasing fields, and that a reentrant rhombic lattice occurs in higher fields. Further, a weak Fermi surface anisotropy competitive with the pairing symmetry induces another structural transition near Hc2. These results are consistent with the structure changes of the vortex lattice in CeCoIn5 in H parallel c determined from recent neutron scattering data.