Overscreening in 1D lattice Coulomb gas model of ionic liquids
  Overscreening in the charge distribution of ionic liquids at electrified interfaces is shown to proceed from purely electrostatic and steric interactions in an exactly soluble one dimensional lattice Coulomb gas model. Being not a mean-field effect, our results suggest that even in higher dimensional systems the overscreening could be accounted for by a more accurate treatment of the basic lattice Coulomb gas model, that goes beyond the mean field level of approximation, without any additional interactions. 
Vincent Demery, David S. Dean, Thomas C. Hammant, Ron R. Horgan and   Rudolf Podgornik
cond-mat.stat-mech