Density of states of disordered systems
van Rossum, Mark
Density of states calculations for the tight-binding model with diagonal disorder are presented. An instanton approach is used to calculate the tails of the spectrum, including all prefactors. It is shown that a Hartree resummation improves the predictions. Furthermore, an effective-medium approximation is used to calculate the density of states in the band. Combining both approaches, a prediction is obtained for all energies. Large numerical simulations have been performed to check the validation of the approach for the Andersson model with Gaussian and with binary disorder on square and simple cubic lattices. The theory agrees well with the simulations.