Kondo effect and transport of electrons in coupled quantum dots and in a two-level dot

Chung-hou Chung

Universität Karlsruhe

We study the Kondo effect and charge transport in two coupled parallel quantum dots and in a two-level quantum dot. Via numerical renormalization group (NRG) technique, we calculate the transmission probability and the linear conductance associated with the electronic transport through the above systems. In the coupled-dot setup with RKKY spin exchange interaction between the dots, we find a quantum phase transition at zero temperature between the Kondo phase with the zero-biased conductance peak and a spin-singlet phase where the Knodo peak is splited. In the spin-singlet phase, We find that the Kondo peak can be restored by either increasing temperature or applying a magnetic field. In the two-level dot, we find a singlet-triplet crossover as either the level spacing or a magnetic field is tuned. Relevance of our results to the experiments is disscussed.