Manipulating of resonances in conductance of an electron waveguide with antidots

The purpose of this paper is to study the interference of the narrow group states with the continuum. The model we have adopted as the basis of our analysis consists of two or three antidots in the waveguide. We extend our previous method (Kim et al., 1999 and 2002) and analyze the evaluation of scattering amplitude with repulsive potentials. We shall study a new scenario when decaying (quasi-bound) states can interfere with the continuum. In a waveguide with two antidots we have observed interesting phenomena: the interference between one subband of the quasi-bound states and background second-subband, and the interference of resonant group states of different subbands. In this case, zero of Fano resonance is shifted in the complex plane and the coupling parameter q becomes complex. The degeneration of two quasi-bound states takes place in the waveguide with three antidots, where interference of the degenerate states may be considered. The Fano-interference of two almost degenerate resonances may bring full suppression of pair resonances in the transmission. This can be explained by parities of quasi-bound states. Our results show that the zero of Fano resonance due to interference between the quasi-bound states and the continuum is generally placed in the complex plane. It gives an additional possibility to manipulate conductance resonances in a waveguide by changing the antidots parameters.