OBSERVATION OF FINITE-FREQUENCY SCALING IN THE INTEGER QUANTUM HALL-EFFECT

We present microwave measurements of the diagonal conductivity sigma(xx), in the integer quantum Hall regime. Our frequencies f were between 0.2 and 14 GHz, and the temperature T was greater than or similar to 50 mK. Broadband Re(sigma(x)), was measured by a transmission line method. The widths DELTAB of Re(sigma(xx)) peaks between IQHE minima increase with f roughly as (DELTAB) is-proportional-to f0.41 for f greater than or similar to 1 GHz. At lower f the peak width dependence on f saturates. We interpret the increase in DELTAB with f as due to dynamic scaling. The exponent, together with existing estimates of the localization length exponent nu, yields a dynamic exponent z almost-equal-to 1.