Monte Carlo simulation of the ‘‘Kondo necklace’’

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Abstract
The projector Monte Carlo method and finite-size scaling are applied to the solution of the ground-state properties of the ‘‘Kondo necklace’’ Hamiltonian. The energy and various spin-spin correlation functions are calculated for chains up to 16 sites in length. Correlations between the spins on different sites are evaluated, and the nature of the ground-state phase as a function of the ratio of the exchange coupling J to the bandwidth W is examined. Evaluation of the correlation function 〈S→(i)⋅τ→(i)〉 shows that as the coupling between the localized S spins and the τ spin chain increases, the system becomes composed of independent singlets on each site. Contrary to both mean-field and various approximate renormalization-group calculations, we find that our results are consistent with an absence of magnetic order as soon as J is different from 0.