FORMATION OF GAPS IN THE 2-DIMENSIONAL HALF-FILLED HUBBARD-MODEL

Using a combination of quantum Monte Carlo and the maximum-entropy method, we have studied the formation of gaps and pseudogaps in the single-particle spectral weight function A(p, omega) for the two-dimensional half-filled Hubbard Model. We present results for U/t = 4 from lattices ranging from 4 X 4 to 16 X 16, and for inverse temperatures ranging from beta = 2 to beta = 12. We find that a pseudogap appears only when the spin-spin correlations are comparable to the size of the lattice. Since the spin-spin correlation length is known to diverge only at T = 0, the implication is that in an infinite lattice there is no pseudogap except at T = 0 for U/t = 4.