Helium-film-induced retrapping transition in the two-dimensional electron system above an uneven solid-hydrogen surface

Abstract

A detailed theoretical analysis of the conductivity of surface electrons above a thin liquid-helium film covering an uneven solid-hydrogen surface is presented. The pronounced conductivity anomaly which is observed during the growth of the helium film is shown to originate from a strong coupling of the electrons to the roughness of the underlying hydrogen substrate. The observed conductivity anomalies (dip and peak) can be explained quantitatively by a retrapping structural transition within the disordered system of localized charges. We have measured the effects of varying electron density and discuss the influence of electronic correlation on the conductivity.