Magnetization in the two-dimensional Hubbard model: a numerical study

The Projector Quantum Monte Carlo method is used to study the two-dimensional Hubbard model with generalized boundary conditions at half-filling. The convergence of the algorithm depends strongly on the initial trial state. Spin-density waves provide an excellent trial state for the case of weak and of strong correlations. This choice of a trial state with broken symmetry allows us to calculate directly the staggered (or sublattice) magnetization m ₀ as a function of the on-site repulsion U. The use of general boundary conditions strongly reduces finite size effects in m ₀.