Probing of level correlation effects in quantum dots by surface acoustic-waves

The attenuation, Γ, of surface acoustic waves (SAWs) by an array of isolated quantum dots is studied. The limiting cases of continuous and discrete energy spectra of the dots are discussed. The spectra are continuous when the SAW frequency ω is larger than the mean level spacing ∆ or when the levels overlap due to broadening, τ _φ^-1>∆, τ _φ^-1 being the phase breaking rate. Discrete spectra are obtained for ω, τ _φ^-1<∆ . The sensitivity of Γ with respect to the global symmetries (“weak localization effects”) is much more pronounced in the discrete spectrum limit, since level correlation effects are resolved. The measurement of Γ yields the temperature dependence of both τ_φ^-1 and the equilibration rate τ_e^-1.