Many-electron magnetoconductivity of 2D electrons on liquid helium

The magnetoconductivity sigma(B) of 2D electrons on liquid helium was measured from 0.25 K to 1.30 K in the electron fluid phase in magnetic fields B less than or equal to 8 Tesla. In low fields the Drude model holds even for mu B >> 1. At higher fields sigma(B) becomes density dependent. The Drude behaviour and the density dependence are due to many-electron effects where cyclotron orbit diffusion is controlled by internal electric fields. The density and temperature dependence of these internal fields derived from experiments are in good agreement with Monte Carlo simulations.