EXPLORING DISORDERED QUANTUM WIRES WITH NONEQUILIBRIUM ACOUSTIC PHONONS

We examine the results of a recent experiment in which non-equilibrium acoustic phonons were used to probe an electron gas confined to a spl it-gate GaAs/AlGaAs quantum wire. The results showed a resistance decr ease following the onset of the interaction between the confined elect ron gas and incident phonon beam and also peaks in resistance decrease versus gate voltage which approximately coincided with the conductanc e step edges. We obtain qualitative agreement with experiment using a model which assumes electron heating due to phonon absorption, togethe r with a wire resistance temperature dependence arising from either (i ) impurity scattering in the presence of electron-electron interaction sla, or (ii) weak localization with phase relaxation due to electron-e lectron scattering. Magnetoconductance measurements will be needed in order to determine which of these two gives the dominant temperature d ependence. A third possible mechanism, the energy dependence of Coulom b scattering from remote donor impurities, gives rise to a resistance increase and is thus ruled out. Taking into account phonon focusing, w e estimate the electron temperature increase for the heater geometry a nd heater temperature of the experiment and find that it is much small er than the experimental estimate. Several possible explanations are g iven for this discrepancy.