Anisotropic surface acoustic wave scattering in quantum-wire arrays

We have investigated anisotropic surface-acoustic-wave (SAW) scattering from quantum-wire arrays as a function of electron concentration and magnetic field. With the SAW's propagating perpendicular to the wires, when one naively expects no interaction classically, we observe strong oscillations in the transmitted intensity reflecting the magnetic depopulation of one-dimensional subbands as described by a full quantum-mechanical description of the SAW-electron interaction. With the SAW parallel to the wires we observe suppression of SAW-electron scattering rates at low electron concentrations in narrow wires as predicted on the basis of phase-space arguments. Surprisingly, at high electron concentrations, the SAW attenuation increases sharply to where it is three times larger than the maximum possible in the unstructured two-dimensional electron gas. We speculate that this could possibly be due to the excitation of intraband two-dimensional plasmonlike modes.