Noninteger conductance steps in a gapped double electron waveguide.

Abstract

A gapped double electron waveguide that contains a gap in the hard middle wall between two waveguides is proposed, and transport properties of the gap, which is also an electron waveguide, are analyzed. Noninteger conductance steps are found. Similar to what happens in a quantum point contact, conductance steps are found to arise whenever an additional propagation mode in the gap is excited as its width is increased; however, the contribution of each mode to the conductance is found to be less than 2${\mathit{e}}^{2}$/h due to the current branching at the gap. It has also been found that when the width of the input waveguide is modulated, conductance for the current leaked out of the gap shows strong oscillations lined up with the 2${\mathit{e}}^{2}$/h steps of the input waveguide conductance, which can also be characterized by current spectroscopy of the waveguide as del Alamo and Eugster suggested for a leaky electron waveguide.