FLUX APPROACH TO THE 2D HEISENBERG HAMILTONIAN

The ground state of the spin-1/2 Heisenberg model on a square lattice is studied by the variational Monte Carlo method. We use the variation al wave function which is the Gutzwiller projection on flux-phase stat es of the tight-binding Hamiltonian. The ground state energy has a min imum for the value of the flux through a plaquette PHI = pi. The modif ication of this function by the Kasteleijn-Marshall correlation factor leads to finite sublattice magnetization and S(eff) is 0.328.