Electronic structure of a single vortex in d-wave superconductor   revisited
  The present work deals with the study of d-wave superconductor in presence of a single vortex placed at the centre of the 2D lattice using the $t-t'-J$ model within the renormalized mean field theory. It is found that the in absence of the vortex the ground state has a d-wave configuration. In presence of the vortex, the superconducting order parameter, above the critical doping, drops to a low non zero value within a few lattice points from the vortex (that is within the the vortex core) and beyond it converges to the constant value in absence of vortex. We observe that above the critical doping things are consistent with the experimental results while there is an anomalous rise in the superconducting order parameter at very low doping within the vortex core. This we feel is because of antiferromagnetic ordering taking place within the vortex core at low doping. 
Sanjay Gupta
cond-mat.str-el cond-mat.supr-con