High Frequency Conductivity in the Quantum Hall Regime (original) (raw)

We have measured the complex conductivity σxx of a two-dimensional electron system in the quantum Hall regime up to frequencies of 6 GHz at electron temperatures below 100 mK. Using both its imaginary and real part we show that σxx can be scaled to a single function for different frequencies and for all investigated transitions between plateaus in the quantum Hall effect. Additionally, the conductivity in the variable-range hopping regime is used for a direct evaluation of the localization length ξ. Even for large filing factor distances δν from the critical point we find ξ ∝ δν −γ with a scaling exponent γ = 2.3.