•Jürgen König¹, Herbert Schoeller², Teemu Pohjola² und Gerd Schön^2
1Department of Physics, University of Texas, Austin, USA
²Institut für Theoretische Festkörperphysik, Universität Karlsruhe

We consider electronic transport through quantum dots with large level spacing and charging energy. At low temperature and strong coupling to the leads, quantum fluctuations and the Kondo effect become important. They show up, e.g., as zero-bias anomalies in the current-voltage characteristics.

We use a diagrammatic technique [1] to describe charge and spin fluctuations. The latter give rise to Kondo-assisted enhancement of the current through the dot as seen in experiments. We discuss the effect of a finite Zeeman splitting as well as Kondo physics in quantum dots with two levels and double quantum dots [2]. We, furthermore, employ a recently developed real-time renormalization group method [3] and obtain quantitatively reliable results for the empty-orbital and mixed-valence regime.