Surface defects characterization in quantum wires by acoustical phonons scattering

We investigate, in the harmonic approximation, the influence of local defects on scattering properties of elastic waves in perturbed quasi-one-dimensional planar waveguide. Our model is based on two infinite quantum wires in which different adsorbed scatterers (or surface defects) are considered. Following the approach of Landauer, we solve the dynamical equation using scattering boundary conditions and applying the matching method formalism. A detailed study of the defect-induced fluctuations in the transmission and conductance spectra is presented for the scattering process for two defect configurations. As in the electronic case, the presence of localized states in the frequency range of propagating states leads to additional structures which can be related with Fano type resonant states and Fabry-Pérot oscillations. The Fano resonance shifts to lower energy for increasing defect mass. Numerical results reveal the intimate relation between transmission spectra and localized impurity states and provide a basis for the understanding of conductance spectroscopy experiments in mesoscopic systems.