Physical review. B, Condensed matter
Generalized spin-wave theory for the Hubbard model at half filling
Xin-Zhong Yan
Abstract
By taking into account the contribution of transverse spin fluctuations deviating from the mean-field approximation, we develop a generalized spin-wave theory for the square-lattice Hubbard model at half filling. The present theory reproduces very accurately the ground-state energy of Lieb and Wu for the one-dimensional case; the discrepancy is typically 1%. In the very-strong-coupling limit, it reduces exactly to Anderson's spin-wave theory for the antiferromagnetic Heisenberg model.