Electron Tunneling Excitation of a Coupled Two Impurity System

Abstract

Kondo effects in individual atoms, molecular magnets or quantum dotshave received a lot of attention. Systems with two units, like double quantum dotsor two atoms, have also attracted some attention due to the interplay between thepossible coupling between the spins of the two components and the Kondo effectof each unit. Moreover, the tunneling spectroscopy across one or several magneticatoms deposited on a metal surface has also been analyzed and shown to presentproperties associated with spin-flip processes and Kondo resonances. In this paper we analyze the electron tunneling excitations created in a dimer case, assuming that each unit (atom or quantum well) has spin 1/2 . In our approach, the basic Hamiltonian includes the spin-metal hybridization as well as the spin-spin interaction; then, its basic properties are analyzed by means of a Greens function formalism combined with an Equation of Motion method. We present results showing the tunneling differential conductance as a function of the different parameters of the problem and the limits for which spin-flip processes and/or Kondo resonances appear.