Size and dimensionality effect in single-impurity Anderson model

The dimensionality and the size effect on the magnetic properties of the si ngle-impurity symmetric Anderson model in three-, two-, and one-dimensional lattices has been studied using the quantum Monte Carlo method. We have co nsidered clusters with odd number of sites with the impurity placed at the center of the cluster and have employed open boundary conditions. In 3D and 1D lattices, we find that at sufficiently low temperatures, the system can be in either a spin compensated or noncompensated state as the cluster siz e is reduced. On the other hand, in 2D the system is always in a spin-compe nsated state independent of the cluster size. These results imply physics b eyond that contained in the simplest Kondo model and may explain the discre pancy between two recent experimental results. (C) 1998 American Institute of Physics. [S0021-8979(98)30811-7].