Variable-range hopping in the quantum Hall regime

We examine the scaling behavior of the transition between adjacent quantum Hall plateaus away from the critical point in the regime of variable-range hopping driven conductivity σxx. The measured temperature and frequency dependence is used for a direct evaluation of the localization length ξ. We find scaling behavior ξ∝|δν|−γ up to large filling factor distances |δν| to the critical point. The scaling exponent γ=2.3 agrees with its proposed universal value even for samples which do not show universal behavior within the usual transition-width analysis. This demonstrates the advantage of our variable-range hopping analysis and the robustness of the localization length scaling.