Ginzburg-Landau theory of noncentrosymmetric superconductors

The data of temperature-dependent superfluid density n(s)(T) in Li2Pd3B and Li2Pt3B [Yuan , Phys. Rev. Lett. 97, 017006 (2006)] show that a sudden change of the slope of n(s)(T) occurs at a temperature slightly lower than the critical temperature. Motivated by this observation, we microscopically derive the Ginzburg-Landau (GL) equations for noncentrosymmetric superconductors with Rashba-type spin-orbit interaction. Cooper pairing is assumed to occur between electrons which are only in the same spin-split band, and pair scattering is allowed to occur between two spin-split bands. The GL theory of such a system predicts two transition temperatures, the higher of which is the conventional critical temperature T-c while the lower one T-* corresponds to the crossover from a mixed singlet-triplet phase at lower temperatures to only a spin-singlet or spin-triplet (depending on the sign of the interband scattering potential) phase at higher temperatures. As a consequence, n(s)(T) shows a kink at this crossover temperature. We attribute the temperature at which the sudden change of slope occurs in the observed n(s)(T) to the temperature T-*. This may also be associated with the observed kink in the penetration depth data of CePt3Si. We have also estimated the critical field near the critical temperature.