DC- and AC-scaling of the integer quantum Hall effect in the presence of interactions

The temperature and frequency dependence of the plateau-to-plateau transiti ons in the quantum Hall effect are investigated experimentally for up to 5 Landau bands. Features induced by Coulomb interaction and impurity scatteri ng are identified in different regions of temperature, frequeucy and magnet ic field. For DC, data are consistent with scaling exponents kappa = 0.2, 0 .4, depending on whether or not Landau hands with different spin direction art degenerate. For AC (35 to 52 GHz), frequency-dominated behaviour is obs erved at hf > k(B)T.