Density of Localized States near the Band Edge of Disordered Systems

The band-tail density of states for the tight-binding model with Gaussian distribution of site energies is calculated numerically in one, two, and three dimensions by use of the recursive transformation method. Our results confirm the band-tail scaling properties as predicted by the Halperin-Lax theory but indicate that in 3D, the near-tail behavior displayed by the model is qualitatively distinct from the simple exponential as deduced from experimental data. Implications are discussed.