A Rotating-Valence-Bond scenario for the 2D Antiferromagnetic Heisenberg   Model
  We propose that the valence bonds forming the ground state of the 2D-AF Heisenberg model on a square lattice may rotate under the effect of the antiferromagnetic background. To test this idea we apply a real space renormalization group approach to construct a rotating-valence-bond ground state anstaz. Our results are analytic and valid for any value of the spin S of the AF-magnet, which allow us to perfom semiclassical expansions of the energy and the staggered magnetization. 
German Sierra and Miguel A. Martin-Delgado