Observation of 2D Polarons and Magnetopolarons on Superfluid Helium Films

We report the observation of the polaronic effect in a 2D electron system on helium films covering a glass substrate. For thin films and for strong holding electric fields we achieved conditions under which the calculated binding energies are larger than kBT, and our mobilities are shown to be in good agreement with the theoretically predicted values for the polaron mobility. In the strong magnetic field regime we show that the longitudinal conductivity data can be interpreted by taking into account the effective collision frequency of the magnetopolaron dimple.