Many-particle resonances in excited states of semiconductor quantum dots

An Anderson impurity model for semiconductor quantum dots is extended to take into account both particle and hole branches of charge excitations. It is shown that in dots with an even number of electrons where the Kondo effect is absent in the ground state, midgap exciton states emerge in the energy spectrum due to Kondo-type shake-up processes. The relevance of the model to heterostructures doped by transition-metal impurities and to rare-earth ions adsorbed on metallic surfaces is discussed.