Andreev tunneling in quantum dots: A slave-boson approach

We study a strongly interacting quantum dot connected to a normal and to a superconducting lead. By means of the slave-boson technique we investigate the low-temperature regime and discuss electrical transport through the dot. At the level of mean-field approximation we are able to discuss both limits of small and large $\Delta {/T}_K,$ where $\Delta$ is the superconducting gap and $T_K$ is the Kondo temperature. We also find that the zero-bias anomaly in the current-voltage characteristics, which is associated with the occurrence of the Kondo resonance in the quantum dot, is enhanced in the presence of superconductivity, due to resonant Andreev scattering.