Coulomb correlation gap: Finite-size analysis

A semiclassical model with randomly distributed N donor and K x N acceptor sites and with infinite-range Coulomb interaction is investigated by means of computer simulations on two-dimensional samples of different sizes. The shape of the Coulomb correlation gap in the density of one-electron excitat ions g(epsilon) is obtained for different values of K within a wide energy interval around the Fermi energy mu. Using simple scaling arguments we demo nstrate that the true behavior of g(epsilon) in the immediate neighborhood of mu is hidden by the finite-size effects and find that g(epsilon) further away from mu is described by a power-law with an exponent, depending on K and the sign of epsilon - mu. (C) 2001 Published by Elsevier Science B.V.