We consider a T-shaped, one-dimensional quantum waveguide containing an attractive or repulsive impurity in the lateral stub, and study how the resonance poles move in the complex k-plane when the strength or the position of the defect changes. Similarities and differences with respect to...

We have studied the behavior of the S–matrix poles near threshold for quantum waveguides coupled to a cavity with a defect. We emphasize the occurrence of both dominant and shadow poles on the various sheets of the energy Riemann surface, and show that the changes of the total conductivity...

We consider T–shaped, two–dimensional quantum waveguides containing attractive or repulsive impurities with a smooth, realistic shape, and study how the resonance behavior of the total conductance depends upon the strength of the defect potential and the geometry of the device. The resonance...