Finite Hubbard clusters with large spin polarization

A generalized Hubbard model can be used to characterize hydrogenic impurities in semiconductors. It has been shown that the ground state spin of such impurity clusters is very sensitive to a cluster's electron number and geometry [1]. An understanding of how these factors affect cluster magnetization is particularly relevant in light of the current ability to position phosphorus donors with nanometer accuracy within bulk silicon [2]. We present numerical results for two-dimensional clusters showing the effect of geometry and electron-hole asymmetry present in real systems of hydrogenic donors. We also consider the robustness of high-spin cluster ground states to perturbations of site position, and discuss the general features of clusters found to possess a high-spin ground state, in particular the fully spin-polarized state.\newline [1] Erik Nielsen and R. N. Bhatt, Phys. Rev. B 76, 161202 (2007). \newline [2] J. L. O'Brien et al., Phys. Rev. B 64, 161401 (2001).