Kondo effect in quantum dot systems - Numerical renormalization group study

We review recent theoretical studies on the Kondo effect in tunneling through quantum dots. The calculation is carried out using the numerical renormalization group method. It is shown that two Coulomb peaks merge into a plateau for the case of an odd number of electrons in the dot. The anomaly of tunneling conductance in an even number of electrons with local spin singlet-triplet degeneracy is studied. The two-impurity Kondo effect, in which a competition between the Kondo coupling and two localized spins coupling occurs, causes a conductance peak in the double quantum dot. The Aharonov-Bohm (AB) oscillation in the conductance of a quantum dot embedded in an AB circuit is also Studied.