Absorption of surface acoustic waves by quantum dots: Discrete spectrum limit

The absorption of surface acoustic waves (SAW's) by an array of quantum dots in which the mean level spacing Delta is larger than the sound frequency omega, the temperature T, and the phase breaking rate tau⁻¹_phi is considered. The direct and the intra-level (Debye) contributions to the SAW attenuation coefficient Gamma are evaluated, and it is shown that the sensitivity to weak magnetic fields and spin-orbit scattering (``weak localization effects'') is dramatically enhanced as compared to the case of a continuous spectrum, Delta < tau⁻¹_phi. It is argued that the non-invasive measurement of Gamma represents a new tool for the investigation of the temperature dependence of the energy relaxation rate, tau⁻¹_epsilon, and the phase breaking rate, tau⁻¹_phi$, of isolated electronic systems.