Abstract
In this thesis, we present research concerning both electrical transport in a quasi-one-dimensional system and acoustic transport in a two-dimensional system. We investigated the resonance conductance of a quantum point contact (QPC) defined in a two-dimensional electron gas of a high-mobility GaAs/AlGaAs het- erojunction. The potential profile of the QPC channel can be locally tuned by separately biasing the split gate and a cross gate, which is electrically isolated on the top of the QPC. The conductance, which evolves with the cross-gate voltage, exhibits an oscillatory feature superimposed on the quantized plateau for positive bias voltages and a suppression of the plateau for negative bias voltages. Our investigation suggests that the oscillations on the conductance result from the longitudinal resonance through the channel. The governing parameters of the res- onance are the aspect ratio of the channel and the Fermi wavelength of the incident electrons. Next, we investigated the behavior of the zero-bias anomaly (ZBA) in quan- tum wires embedded with impurities. The linear conductance G can exhibit cusp features that evolve with the positions of the impurities, and these features can be continuously tuned using a combination of split-gate and top-gate voltages. The ZBA is observed regardless of the presence of impurities. The Kondo model is in- adequate to describe the behaviors of both G and the ZBA. Despite the presenceof impurity scattering, various ZBA behaviors resembling those reported in clean quantum wires can be observed. Our results suggest that ZBA is an intrinsic phe- nomenon in a quantum wire, and its temperature and magnetic-field dependence do not pertain to Kondo correlations in the quantum dot system. The last portion of this thesis reports a study of the carrier density dependence of the acoustoelectric effect in graphene and the coupling effect between double two-dimensional electronic systems. We integrated interdigital transducers, chem- ical vapor deposition (CVD) graphene and a GaAs/AlGaAs heterostructure into a hybrid device. Our device has two advantages: the SAW can propagate on the GaAs cap layer, and the 2DEG can operate as a back gate for tuning the Fermi energy in the graphene. We obtained the density dependence of the SAW atten- uation by directly measuring the induced acoustoelectric current in the graphene and obtained a result that differs from the theoretical prediction. Despite this dis- agreement, we believe that the interaction between the SAW and the adjustable carrier density in the graphene is significant. In addition, some data reveal that the acoustoelectric transport property in each 2DES has some correlation with the hybrid system.