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|Type:||Artigo de periódico|
|Title:||Two-dimensional Heisenberg Antiferromagnet: Analytic And Numeric Results|
|Abstract:||An approximate analytic expression for the ground state of the anisotropic S = 1 2 Heisenberg model with antiferromagnetic exchange is studied. Its accuracy is determined for a wide range of the anisotropy parameter α. Restricting ourselves to the special case of the square lattice, we used the analytic ground state to calculate exactly the expectation values of several dynamical variables. The approximate analytic results thus obtained are compared with those given by spin wave theory and reliable numerical data obtained by us and other authors. We conclude that the analytic theory is asymptotically exact for α→0 (Ising limit), is highly accurate for 0 ≤ α ≤ 0.5 (less than 1% uncertainty in all calculations), and is reasonably precise (less than 5% uncertainty) in the range 0.5 < α ≤ 1. (α = 1: isotropic Heisenberg model). In particular, our asymptotic approach gives better results than spin wave theory for 0 ≤ α ≤ 0.9. © 1989.|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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