Effects of signs in tunneling matrix elements on transmission zeros and phase

The effect of the signs in the tunneling matrix elements on the transmission zeros and the transmission phase in transport through a quantum dot is studied. The existence of the transmission zeros is determined by both the relative signs and the strength of the tunneling matrix elements for two neighboring energy levels of a dot. The experimentally observed oscillating behavior of the transmission phase over several Coulomb peaks can be explained by the uniform distribution of the relative signs. Based on the simple model of a quantum dot, we present a possible scenario which can give the uniform signs over several conductance peaks. We suggest that the location of the transmission zeros can be identified by inspecting the Fano interference pattern in the linear response conductance of the Aharonov-Bohm (AB) interferometer with an embedded quantum as a function of the number of electrons in a dot and the AB flux.Comment: 9 pages, 6 figures. Accepted for publication in Phys. Rev.

Mesoscopic Fano Effect in a Quantum Dot Embedded in an Aharonov-Bohm Ring

The Fano effect, which occurs through the quantum-mechanical cooperation between resonance and interference, can be observed in electron transport through a hybrid system of a quantum dot and an Aharonov-Bohm ring. While a clear correlation appears between the height of the Coulomb peak and the real asymmetric parameter $q$ for the corresponding Fano lineshape, we need to introduce a complex $q$ to describe the variation of the lineshape by the magnetic and electrostatic fields. The present analysis demonstrates that the Fano effect with complex asymmetric parameters provides a good probe to detect a quantum-mechanical phase of traversing electrons.Comment: REVTEX, 9 pages including 8 figure