Physical review. B, Condensed matter
Comparison between linked-cluster expansion methods for the Heisenberg antiferromagnet on the square lattice
Zheng Weihong, J. Oitmaa, Chris J. Hamer
Abstract
Comparisons are made between the results of three different linked cluster expansion methods, as applied to the S=1/2 Heisenberg antiferromagnet on a square lattice at zero temperature. Connected moments of the Hamiltonian are calculated up to 15th order, extending previous results of Lee and Lo, and are used to form a t expansion. The t expansion is found to be less accurate than the coupled cluster expansion, which in turn is less accurate than the standard perturbation expansion for this system.