Electron correlation effects on tunneling through a two-level quantum dot

The possibility of detection of the Kondo effect by means of the measurement of Bohm-Aharonov oscillations of the current going through a quantum dot embedded in one of the arms of a mesoscopic ring connected to two leads is demonstrated. The ring is threaded by a magnetic flux and the dot is subjected to a gate voltage V-0 which controls its charge content. Whenever the dot has an odd number of electrons and, as a consequence, a net spin the system is in the Kondo regime. Thus, the Kondo effect can be turned on and off as the two dot levels and their associate Coulomb blockade peaks are tuned to the Fermi level by changing V-0. Since the Kondo resonance provides a new channel for the electrons to tunnel through the dot it allows the flowing of current along the arm of the ring which contains the dot even though the dot levels are out of resonance. The interference between the waves going along the upper and lower arms of the ring gives rise to the Bohm-Aharonov oscillations of the current and is a clear sign of the Kondo effect. (C) 2000 American Institute of Physics. [S0021-8979(00)05005-2].