Probing the Kondo density of states in a three-terminal quantum ring
  We have measured the Kondo effect in a quantum ring connected to three terminals. In this configuration non-linear transport measurements allow to check which lead contributes to the Kondo density of states (DOS) and which does not. When the ring is connected to two strongly and one weakly coupled leads, the measurement of the differential conductance through the weakly coupled lead allows to probe directly the Kondo DOS. In addition, by applying a bias between the two strongly coupled leads, we show the splitting of the out-of-equilibrium DOS. 
R. Leturcq, L. Schmid, K. Ensslin, Y. Meir, D. C. Driscoll, A. C.   Gossard