Formation of gaps in the two-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,{ω}) for the two-dimensional half-filled Hubbard Model. We present results for U/t=4 from lattices ranging from 4×{}4 to 16×{}16, and for inverse temperatures ranging from {β}=2 to {β}=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.