Exciton-assisted processes in Kondo scattering

The ground state and the excitation spectrum of semiconducting quantum dot (QD) or chemisorbed molecule with strongly interacting electrons and holes coupled by tunneling interaction with spatially separated metallic continuu m is calculated within an Anderson impurity model generalized for the case of scatterer with electron and hole branches of charge excitations. It is s hown that the new type of excitons with the halved binding energy (mid-gap states) appear in QD due to Kondo-type interaction in excited state when th e Kondo effect is absent in the ground state of the system. (C) 1999 Publis hed by Elsevier Science B.V. All rights reserved.