Kinetic properties of surface electrons over liquid helium under strong electron-electron interaction

The mobility μ and lifetime of ground-level electrons τ⊥ are studied experimentally in a two-dimensional electron system at the surface of liquid helium at temperatures of0.4 to1.4 K and charge concentrations of (2.8–12.0) × 108 cm−2. It is shown that for fairly low temperature and high concentration where the frequency of interelectronic collisions is much higher than that of electron-ripplon ones, the so-called complete control condition is realized in the electron system, i.e., when the average drift velocity of electrons and the effective electron temperature can be introduced. This model is found to describe well the kinetic properties of surface electrons in the range of charge concentrations up to 4×108 cm−2, where the one-particle approach is no longer applicable. For the value of parameter Γ=e2(πns)1/2/T=47 that corresponds to a strong electron-electron interaction, the lifetime τ⊥ is found to increase sharply and the short-range order typical of a liquid state appears in the two-dimensional electron layer.