Reentrant behavior and universality in the Anderson transition

The three-dimensional Anderson model with a rectangular distribution of site disorder displays two distinct localization-delocalization transitions, against varying disorder intensity, for a relatively narrow range of Fermi energies. Such transitions are studied through the calculation of localization lengths of quasi-one-dimensional systems by transfer-matrix methods, and their analysis by finite-size scaling techniques. For the transition at higher disorder we find the localization-length exponent ν=1.60(5) and the limiting scaled localization-length amplitude Λ₀=0.57(1), strongly suggesting universality with the transition at the band center, for which currently accepted values are ν=1.57(2) and Λ₀=0.576(2). For the lower (reentrant) transition, we estimate ν=1.55(15) and Λ₀=0.55(5), still compatible with universality but much less precise, partly owing to significant finite-size corrections.