BOHM-AHARONOV AND KONDO EFFECTS ON TUNNELING CURRENTS IN A MESOSCOPICRING

We present an analysis of the Kondo effect on the Bohm-Aharonov oscill ations of the tunneling currents in a mesoscopic ring with a quantum d ot inserted in one of its arms. The system is described by an Anderson impurity tight-binding Hamiltonian where the electron-electron intera ction is restricted to the dot. The currents are obtained using nonequ ilibrium Green functions calculated through a cumulant diagrammatic ex pansion in the chain approximation. It is shown that at low temperatur e, even with the system out of resonance, the Kondo peak provides a ch annel for the electron to tunnel through the dot, giving rise to the B ohm-Aharonov oscillations of the current. At high temperature these os cillations are important only if the dot level is aligned to the Fermi level, when the resonance condition is satisfied.