Electron localization in anisotropic systems

We generalize the scaling theory of localization to anisotropic systems, using both a diagrammatic analysis and deriving the effective action for the corresponding field theory. We find that the effects of anisotropy near the weak coupling (metallic) fixed point can be completely absorbed into an anisotropic diffusion coefficient. Implications for both two- and three-dimensional systems are discussed, and excellent agreement is obtained with experimental results on the former by Bishop, Dynes, Lin, and Tsui.