Abstract
The plaquette expansion of the Lanczos recursion method is applied to the two-dimensional antiferromagnetic Heisenberg model. Connected Hamiltonian moments 〈 are calculated with respect to the Néel state up to n=6. The subsequent plaquette expansion of the Lanczos matrix in the number of plaquettes on the lattice, , is determined to order 1/. Diagonalizing the Lanczos matrix in this form gives a value of the energy density of -0.664 in the limit →∞, in good agreement with existing calculations.
- Received 29 September 1993
DOI:https://doi.org/10.1103/PhysRevB.50.1275
©1994 American Physical Society