EXACTLY SOLVABLE KONDO-LATTICE MODEL

In this work, we exactly solve a Kondo-lattice model in the thermodynamic limit. The system consists of an electronic conduction band described by unconstrained hopping matrix elements between the lattice sites. The conducting electrons interact with a localized impurity spin at each lattice cell. We have found the exact thermodynamics, the ground-state energies of the system. At T=0, we explicitly demonstrate that the system exhibits a metal-insulator phase transition at half filling. In the limit of strong coupling between the impurity spin and the conduction electrons, J=+, we have solved the system on a lattice of any size L. The ground states are the resonating-valance-bond-type Jastrow product wave functions. Various correlation functions can be computed for the impurity spins, and for the singlets formed by electrons and impurities. © 1995 The American Physical Society.