Electric-field effects on Fano resonances and transmission phase through quantum wires

摘要

The effect of a transverse electric field on Fano line shapes in electronic transport through a quantum wire is investigated via a Feshbach three-channel model. The coupling between channels is provided by an attractive short-range scatterer with lateral extent. It is shown that the resonance structure in a particular subband is sensitive on the electric field strength and direction. In particular, collapse of a Fano profile either in the first or the second subband may occur, depending on whether the electric field points in the negative or positive direction, respectively. This is due to the vanishing coupling between the bound states and the conduction ones which, in turn, is a consequence of the electric field-induced shift of the confining potential. This tunability of Fano resonances may prove experimentally useful in ballistic transport through narrow channels. The results in the first subband are compared with those obtained from a two-channel model. A detailed account of the transmission phase is also given, and the abrupt phase shift by π is shown to occur whenever the energy of the transmitted electron crosses the energy of the transmission zero.