Pairing symmetry reflected in vortex lattice structure of noncentrosymmetric superconductors

A novel type of modulated vortex states to be realized in Rashba noncentrosymmetric superconductors (NCSs) in parallel fields are studied by examining spatial distributions of the gauge-invariant phase of the order parameter Delta. It is found that a modulated structure reflecting a relative shift of the Fermi surfaces is not due to a single type of nodal lines but rather to rows of vortex-antivortex pairs, and that coalescence of these vortex pairs results in a square vortex lattice separated from the familiar triangular lattice via a first order structural transition. Such a structure supported by rows of vortex pairs is also the origin of striped structures in higher odd LL vortex lattices realizable in centrosymmetric systems with a strong paramagnetic depairing. (C) 2009 Elsevier B.V. All rights reserved.