CHARGE-TRANSFER GAP FROM A MONTE-CARLO SIMULATION OF THE 3-BAND HUBBARD-MODEL

We have studied a three-band Hubbard model describing the CuO2 layers in the high-Tc superconductors via Quantum Monte Carlo simulations. For a Hubbard interaction Ud = 6 on the copper sites (in units of the Cu-O hybridization tCu−O), we see the formation of a correlation gap depending on the size of the charge-transfer energy Δ = εp − εd. For inverse temperatures as low as β = 10 we study the behavior of the charge-transfer gap as a function of the parameters Δ, Up and of the O-O hopping matrix element to-o. © 1990, Elsevier Science Publishers B.V. (North-Holland). All rights reserved.