Low-temperature mobility of surface electrons and ripplon-phonon interaction in liquid helium

The low-temperature dc mobility of the two-dimensional electron system localized above the surface of superfluid helium is determined by the slowest stage of the longitudinal momentum transfer to the bulk liquid, namely, by the interaction between the surface and volume excitations of liquid helium, which decreases rapidly with the temperature. Thus, the temperature dependence of the low-frequency mobility is mu(dc) a parts per thousand 8.4 x 10(-11) n (e) T (-20/3) cm(4) K(20/3)/(V s), where n (e) is the surface electron density. The relation T (20/3) E (aSyen) (-3) a parts per thousand(a) 2 x 10(-7) between the pressing electric field (in kilovolts per centimeter) and temperature (in Kelvins) and the value omega a parts per thousand(2) 10(8) T (5) K(-5) s(-1) of the driving-field frequency have been obtained, at which the above effect can be observed. In particular, E (aSyen) a parts per thousand integral 1 kV/cm corresponds to T a parts per thousand(2) 70 mK and omega/2 pi a parts per thousand(2) 30 Hz.