Frequency Scaling of Microwave Conductivity in the Integer Quantum Hall Effect Minima

We measure the longitudinal conductivity σxx at frequencies 1.246 GHz ≤ f ≤ 10.05 GHz over a range of temperatures 235 mK ≤ T ≤ 4.2 K with particular emphasis on the Quantum Hall plateaus. We find that Re(σxx) scales linearly with frequency for a range of magnetic field around the center of the plateaus, i.e. where σxx(ω) ≫ σ DC xx . The width of this scaling region decreases with higher temperature and vanishes by 1.2 K altogether. Comparison between localization length determined from σxx(ω) and DC measurements on the same wafer show good agreement.