An ionic Hamiltonian for transition metal atoms: Kondo resonances and tunneling currents

An extended ionic Hamiltonian for d(5)-transition metal atoms, that incorporates both the effect of the first Hund rule and the effect of the orbital degeneracy in the ground state, is presented. We also discuss a Green-function method to analyze that Hamiltonian, solved by means of the Equation of Motion method. Results for different cases in a V-2 and aV(4)-order are given and, in particular, Kondo frequencies are calculated for atoms with an orbital singlet state or with a multi-orbital degeneracy. The effect of the multi-orbital degeneracy is shown to be important.