Insulator-metal transition in the one- and two-dimensional hubbard models

We use quantum Monte Carlo methods to determine T = 0 Green functions, G((r) over right arrow,omega), on lattices up to 16 x 16 for the 2D Hubbard model at U/t = 4. For chemical potentials mu within the Hubbard gap \mu\ < mu(c) and at long distances (r) over right arrow, G((r) over right arrow, omega = mu) similar to e(-\(r) over right arrow\/xi l) with critical behavior xi(l) similar to \mu - mu(c)\(-nu), nu = 0.26 +/- 0.05. This result stands in agreement with the assumption of hyperscaling with correlation exponent nu = 1/4 and dynamical exponent z = 4. In contrast, the generic band insulator as well as the metal-insulator transition in the 1D Hubbard model are characterized by nu = 1/2 and z = 2.