Analysis realized by means of unitary transformations of the Kondo Hamiltonian of the different phases in the Kondo lattices

Abstract

I analyze the possibilities of the Kondo lattice scenario for the different quantum phases appearing in strongly correlated systems. I use in this analysis a formulation of the Kondo Hamiltonian in terms of a renormalized set of canonical operators and the construction of strongly correlated modes involving soft electrons (or holes) and a kind of spin wave. These strongly correlated modes approximately diagonalize the resulting transformed Hamiltonian. The quantum phases arise, in this model, only varying the Kondo J coupling and the density of states at ${E}_{F}$ of the noninteracting system ${(D}_{F}).$ For small values of ${D}_{F}$ and sufficient large values of J, the resulting systems are weak antiferromagnetic insulators. For increasing ${D}_{F}$ values and decreasing J couplings, the pattern corresponds to conducting materials which are candidates, in certain conditions, to be heavy-fermion metals. For determined conditions of ${D}_{F}$ and J values, there is an interval of the J parameter ${(J}_{c}<~J<~{J}_{\mathrm{top}}),$ in which an intriguing ground state appears. The properties of this ground state are close to a gapless and low-temperature zero-resistance system whose energy condensation does not require the existence of electronic pair coupling.