Kondo resonances in split-gate quantum dots

The Kondo resonances observed in quantum dots are studied as a function of the tunnel coupling to the leads. It is observed that a Kondo resonance develops in one Coulomb-blockade region as the coupling is increased. This is taken as an indication that there is a degeneracy on the dot for this electron number, which is a prerequisite of the Anderson impurity model predicting the Kondo resonances. The nature of this degeneracy is studied in tilted magnetic fields and the generally accepted picture, that a spin degeneracy is responsible for the Kondo resonance, is confirmed.