Nonsingular vortices in (s+d)-wave superconductors
  The structure of a single flux line in (s+d)-wave superconductors has been analyzed within the Ginzburg-Landau (GL) model generalized for two order parameter components. The fourfold symmetric singular vortex solution is shown to be unstable in a certain range of the GL parameters with respect to the mutual shift of s- and d- wave unit vortices. The resulting nonsingular vortex structure is studied both analytically and numerically. 
A. S. Mel'nikov, I. M. Nefedov, D. A. Ryzhov, I. A. Shereshevskii, P.   P. Vysheslavtsev