THE EFFECT OF RESONANCE ON THE GROUND-STATE ENERGY OF THE HEISENBERG HAMILTONIAN

The ground-state properties of a chain of squares, with at every corne r of a square an s = 1/2 particle and doped with two holes, have been studied in the antiferromagnetic Heisenberg model. The ground-state en ergies, staggered magnetisations and spin-spin correlations are given, using different basis sets. These data have been analyzed in terms of a magnetic contribution to the interaction of the two holes. An attra ctive interaction between the holes has been found and ascribed to res onance. This resonance has been quantified in terms of sizes of subset s of the basis set, classified by the number of singlet bonds along an exchange interaction.