A THEORETICAL CALCULATION OF TUNNELING SPECTROSCOPY OF AN ELECTRON WAVE-GUIDE WITH OR WITHOUT A SCATTERER

A theoretical study on the tunneling spectroscopy of an electron waveg uide recently observed by Eugster and del Alamo is presented. A narrow electron waveguide coupled with another much wider one by a thin barr ier between them is taken as a theoretical model for the leaky electro n waveguide implemented by Eugster et al., and the transport propertie s of electrons are studied comprehensively through the wavefunction of the system. The results demonstrate that the conductance for the curr ent tunneling out the barrier oscillates strongly with the width of th e narrow electron waveguide, in line with its conductance steps. The t heory is in good agreement with the experiments and confirm that the o scillations of the tunneling current can be considered as a spectrosco py of the 1D DOS (one dimensional electron density of states) in the e lectron waveguide as proposed by Eugster et al. In order to study the effects of scatterers on the transport properties of the leaky electro n waveguide, a delta-function is used to simulate the scattering poten tial. The results show that the presence of even a single scatterer lo cated in the waveguide will lead to obvious distortion of the shape of conductance steps, and will greatly influence the oscillations of the tunneling current observed in clean waveguides. However the effects o f scatterers located outside the tunneling barrier on either the condu ctance steps or the oscillations of the tunneling current are negligib le.