Kondo effect in tunneling through a quantum dot

Systematic calculation of tunneling conductance through a quantum dot, which has a single localized orbital, is carried out by using the numerical renormalization group method. In strongly correlated case, two paired Coulomb oscillation peaks grow without large increase of their width as the temperature decreases. At the same time the peak positions shift to their central side. This behavior corresponds well with the recent experimental data, and then suggests that the Kondo effect takes place at low temperatures in the experiment. Theoretically the conductance in valley region between the two peaks gradually increases, and the peaks merge into a broad single peak as the temperature further decreases. This behavior has not been observed in the experiment. The estimated Kondo temperature for the valley region is still much less than the lowest temperature in the experiment.