New diagram technique for periodic Anderson model

Abstract

A new diagram technique, previously proposed for Hubbard Model, was used for the Periodic Anderson Model (PAM). The Hamiltonian of localized electrons H 0 f and of free conduction electrons H 0 c are considered as a main part of the Hamiltonian of PAM and the hybridization term is treated as a perturbation. H 0 f contains on-site Coulomb interaction and is diagonalized in Hubbard operators. This diagram technique is used for Matsubara Green functions and contains apart from the Wick product of free Green functions new contributions equal to on-site cumulants depending of the Coulomb interaction. If such cumulants are ignored we obtaine the so called Hubbard I approximation for PAM with 3 branches of renormalized energy spectrum of quasiparticles. They are investigated in detail and the chemical potential of the system is determined

Interaction of strongly correlated electrons and acoustical phonons

“…This problem has been discussed in detail in Ref. 30 , however, only now we are able to present a solution. In order to obtain this solution, we observe that the twocloud functions determined by Eqs.…”