SPECTRAL CORRELATIONS IN DISORDERED ELECTRONIC SYSTEMS - CROSSOVER FROM METAL TO INSULATOR REGIME

We use the semiclassical approach combined with the scaling results or the diffusion coefficient to consider the two-level correlation function R for a disordered electron system in the crossover region, characterized by the appearance of a macroscopic correlation or localization length, ξ, that diverges at the metal-insulator transition. We show new critical statistics, characterized by a nontrivial asymptotic behavior of R, to emerge on both sides of the transition at higher energies, and to expand to all energies larger than mean level spacing when ξ exceeds the system size. © 1995 The American Physical Society.