ELECTRON LOCALIZATION IN SOUND-ABSORPTION OSCILLATIONS IN THE QUANTUMHALL-EFFECT REGIME

The absorption coefficient for surface acoustic waves in a piezoelectr ic insulator in contact with a GaAS/Al(0.25)Ga(0.75)AS heterostructure (with two-dimensional electron mobility mu = 1.3 x 10(5) cm(2)/(V.s) at T = 4.2 K) via a small gap has been investigated experimentally as a function of the frequency of the wave, the width of the vacuum gap, the magnetic field, and the temperature. The magnetic field and freque ncy dependences of the high-frequency conductivity (in the region 30-2 10 MHz) are calculated and analyzed. The experimental results can be e xplained if it assumed that there exists a fluctuation potential in wh ich current carrier localization occurs. The absorption of the surface acoustic waves in an interaction with two-dimensional electrons local ized in the energy ''tails'' of Landau levels is discussed. (C) 1997 A merican Institute of Physics.