QUANTUM TRANSPORT OF SURFACE ELECTRONS OVER LIQUID-HELIUM IN MAGNETIC-FIELD

The magnetoconductivity sigma(xx) of surface electrons over liquid hel ium at electron densities (1-9) x 10(8) cm-2 is measured at temperatur es down to 0.5 K and magnetic fields H up to 25 kOe. Sigma(xx) is show n to decrease with increasing H. For rather high temperatures and low magnetic fields dependence sigma(xx)-1 on H displays a classical behav ior, but as the temperature is reduced or H is increased, a transition to the quantum magnetotransport regime occurs. It is shown that sigma (xx) decreases at lowering temperature, passes through a minimum and t hen slightly increases in the region of electron-ripplon scattering. T he measured data are in good agreement with the theoretical results ta king into account the preferable contribution of electron scattering o n ripplons with wavelength near magnetic length. At the region of elec tron crystal sigma(xx) is weakly dependent on T. At low magnetic field sigma(xx)-1 increases with H linearly and, at H > 17 kOe, sigma(xx)-1 approximately H1.5.