INTEGRABLE ONE-DIMENSIONAL HEAVY-FERMION LATTICE MODEL

We consider a one-dimensional lattice gas of interacting electrons emb edding a finite concentration of magnetic impurities, The host electro ns propagate with nearest neighbor hopping t, constrained by the exclu ded multiple occupancy of the lattice sites, and interact with electro ns on neighboring sites via spin exchange J and a charge interaction ( t-J model). The host is integrable at the supersymmetric point, J = 2t , where charges and spin form a graded FFB superalgebra. Without destr oying the integrability we introduce a finite concentration of mixed-v alent impurities with two magnetic configurations of spin S and (S + 1 /2), respectively, which hybridize with the conduction states of the h ost. We derive the Bethe ansatz equations diagonalizing the correlated host with impurities and discuss the ground-state properties as a fun ction of magnetic field and the Kondo exchange coupling. While for an isolated impurity the ground state is magnetic of effective spin S, a finite concentration of impurities introduces an additional Dirac sea (the impurity band), which gives rise to a singlet ground state. The i mpurities are antiferromagnetically correlated and frustrated in zero- field. As a function of field first the narrow impurity band is spin p olarized. The van Hove singularities of the spin-rapidity bands define critical fields at which the susceptibility diverges. The number of i tinerant electrons and the concentration of impurities can be varied c ontinuously, so that the Kondo problem, the supersymmetric t-J model a nd the antiferromagnetic Heisenberg chain are contained as special lim its. The properties of the model are related to heavy fermion alloys a nd the Kondo lattice. (C) 1998 Elsevier Science B.V.