ATTENUATION OF SURFACE ACOUSTIC-WAVES BY QUANTUM DOTS

The attenuation Gamma of surface acoustic waves (SAWs) by an array of quantum dots is considered. The processes contributing to Gamma, direc t and intralevel (Debye) absorption and (elastic) scattering off the d irection of the SAW are discussed for two limiting cases of the energy spectra of the dots: firstly a continuous spectrum, which is realized when the SAW frequency omega is much larger than the mean level spaci ng Delta or when the broadening of the levels is sufficiently strong, Delta < tau(phi)(-1), tau(phi)(-1) being the phase breaking rate; seco ndly a discrete spectrum, obtained for omega, tau(phi)(-1) < Delta. Th e results show that the sensitivity of Gamma to weak-localization effe cts such as magnetic fields, spin-orbit scattering and temperature, ar e considerably enhanced for a discrete spectrum. It is argued that the noninvasive character of the measurement of Gamma makes the SAW exper iments especially suitable for the determination of the temperature de pendence of tau(phi)(-1) and the equilibration rate of the electronica lly isolated dots.