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

The absorption of surface acoustic waves (SAWs) by an array of quantum dots in which the mean level spacing Δ is larger than the sound frequency ω, the temperature T, and the phase breaking rate τ^-1_φ is considered. The direct and the intra-level (Debye) contributions to the SAW attenuation coefficient Γ 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, Δ < τ^-1_φ. It is argued that the non-invasive measurement of Γ represents a new tool for the investigation of the temperature dependence of the energy relaxation rate, τ^-1_∈, and the phase breaking rate, τ^-1_φ, of isolated electronic systems.