Carrier transport in quasi-one-dimensional electron systems over liquid helium under strong localization

The carrier conductivity in a quasi-one-dimensional electron system over liquid helium was measured at 0.5-1.9 K in pressing electric fields up to 4 kV/cm at 1.1 MHz. Quasi-one-dimensional channels were realized using an optical diffraction grating with a thin liquid helium coating. The carrier conductivity decreased exponentially with lowering temperature T, the activation energy being of several degrees. This suggests electron localization in the quasi-one-dimensional system. As the thickness of the liquid helium layer on the grating was increased, the exponential dependence changed at T < 0.8 K, which may indicate that quantum effects start to contribute to the electron mobility at these temperatures. From the analysis of the data obtained we can suggest that two branches of the optical plasma mode are possible in quasi-one-dimensional electron systems under localization conditions: a high-frequency branch related to the electron oscillations in potential wells and a low-frequency branch generated by oscillations of the complexes electron-dimple of large effective mass.