CARRIER TRANSPORT IN QUASI-ONE-DIMENSIONAL ELECTRON-SYSTEMS OVER LIQUID-HELIUM UNDER STRONG LOCALIZATION CONDITIONS

The conductivity of carriers in a quasi-one-dimensional electron syste m over liquid helium is measured in the temperature interval 0.5-1.9 K in confining electric fields up to 4 kV/cm at a frequency of 1.1 MHz. Quasi-one-dimensional channels were created by using an optical diffr action grating covered with a thin helium layer. The carrier conductiv ity decreases exponentially with temperature T, and the activation ene rgy is of the order of a few degrees, thus pointing towards localizati on of electrons in a quasi-one-dimensional electron system. As the thi ckness of the helium layer covering the grating is increased, a depart ure from a mono exponential dependence is observed at T<0.8 K, which i ndicates that quantum effects begin to play an active role in electron mobility at these temperatures. An analysis of the obtained results l eads to the assumption that under localization conditions, quasi-one-d imensional electron systems may contain two branches of the optical mo de of plasma oscillations, viz., a high-frequency branch associated wi th electron oscillations in potential wells, and a low-frequency branc h associated with the oscillations of the electron-dimple complex with a large effective mass. (C) 1997 American Institute of Physics. [S106 3-777X(97)00311-3].