Some New variational resonating-valence-bond-type wave functions for the spin-1/2 antiferromagnetic heisenberg model on a square lattice

We consider a class of singlet resonanting-valence-bond wave functions on a square lattice, with the bond-length distribution as a variational parameter. This class contains the two limiting cases of the dimer wave function and of the Néel state. We present numerical calculations of the energy and the spin-spin correlation functions up to very large lattice sizes (180×180) both for disordered states with exponentially decaying correlation functions and for ordered states. The energy of a disordered state can be within 0.1% of our best ordered state (-0.3344Jbond).