Mobility of Electrons at Liquid Helium Surface under Overheating

Mobility of surface electrons (SE) on liquid helium at low temperatures (T≃0.52 K) is studied as a function of the driving electric field E _∥ in the range 1–25 mV/cm. The experimental conditions correspond approximately to effective electron temperatures T _e ≃1–12 K. The measurements are performed for SE with the surface electron density n _s =1.46×10⁸ cm⁻² at different holding electric fields E _⊥ =200–1400 V/cm. The mobility is observed to be an increasing function of the driving field. The function depends strongly on the holding electric field applied. The experimental results are in reasonable agreement with theoretical curves calculated using the force-balance equation method expressing the mobility in terms of the dynamical structure factor of SE.