Kondo resonance in a nanotube quantum dot coupled to a normal and a superconducting lead

M. R. Graeber, T. Nussbaumer, W. Belzig, T. Kontos, C. Schoenenberger

Published 2004-06-25Version 1

We report on electrical transport measurements through a carbon nanotube quantum dot coupled to a normal and a superconducting lead. The ratio of Kondo temperature and superconducting gap $T_{K}/\Delta$ is identified to govern the transport properties of the system. In the case of $T_{K}<\Delta$ the conductance resonance splits into two resonances at $\pm \Delta$. For the opposite scenario $T_{K}>\Delta$ the conductance resonance persists, however the conductance is not enhanced compared to the normal state due to a relative asymmetry of the lead-dot couplings. Within this limit the data is in agreement with a simple model of a resonant SN-interface.