Static vacancies on a 2D Heisenberg spin-1/2 antiferromagnet

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Abstract
We study static vacancies on a 2D Heisenberg spin-(1/2 lattice at T=0, using linear spin-wave theory (LSW) and exact diagonalizaton. Unexpectedly, quantum fluctuations are reduced on neighbors of an isolated vacancy. Two vacancies are attractive, with lowest energy as nearest neighbors. We find LSW to be surprisingly accurate relative to exact diagonalization, both done on a 4×4 lattice. However, LSW on larger systems gives substantial modification of the 4×4 results for binding and ground-state energies, suggesting the need for larger lattices than previously suspected for reliable numerical estimates.