The phase of Fano resonance in Aharonov-Bohm interferometer with a quantum dot embedded

We study the Fano effect of a closed Aharonov-Bohm mesoscopic interferometer, with a quantum dot embedded in one of the paths, in the presence of dephasing which is introduced by the Büttiker model. An exact analytic formula of conductance including dephasing factor is derived and can be written as an extended Fano form with a complex Fano parameter q. While the total conductance is unitary, the coherent part has broken unitarity due to dephasing, and thus has continuous phase shift. Our results agree with recent experimental measurements.