Some results on the phase diagram of the 2D Hubbard model using an analytic Lanczos method

Aspects of the ground state phase diagram of the two-dimensional Hubbard mo del have been determined using a new non-perturbative method based on an an alytic formulation of the Lanczos algorithm. The ground state energy for ar bitrary repulsion U/t and density n has been calculated using a number of t rial states which are expected to be qualitatively correct in certain regim es of this model - the paramagnetic Fermi sea and the Hartree-Fock spin den sity wave state. We find large corrections to the mean-held result that shi ft the paramagnetic-ferromagnetic transition to higher values of U/t and cl oser to half-filling. (C) 1999 Elsevier Science B.V. All rights reserved.