Controlled dephasing in single-dot Aharonov-Bohm interferometers

We study the Fano effect and the visibility of the Aharonov-Bohm oscillations for a mesoscopic interferometer with an embedded quantum dot in the presence of a nearby second dot. When the electron-electron interaction between the two dots is considered the nearby dot acts as a charge detector. We compute the currents through the interferometer and detector within the Keldysh formalism and the self-energy of the nonequilibrium Green's functions is found up to the second order in the interaction strength. The current formula contains a correction to the Landauer-Buttiker formula. Its contribution to transport and dephasing is discussed. As the bias applied on the detector is increased, the amplitude of both the Fano resonance and Aharonov-Bohm oscillations are considerably reduced due to controlled dephasing. This result is explained by analyzing the behavior of the imaginary part of the interaction self-energy as a function of energy and bias. We emphasize as well the role of the ring-dot coupling. Our theoretical results are consistent with the experimental observation of Buks [Nature 391, 871 (1998)].