Neel order, ring exchange and charge fluctuations in the half-filled Hubbard model
Abstract
We investigate the ground state properties of the two dimensional half-filled one band Hubbard model in the strong (large-U) to intermediate coupling limit ({\it i.e.} away from the strict Heisenberg limit) using an effective spin-only low-energy theory that includes nearest-neighbor exchange, ring exchange, and all other spin interactions to order t(t/U)^3. We show that the operator for the staggered magnetization, transformed for use in the effective theory, differs from that for the order parameter of the spin model by a renormalization factor accounting for the increased charge fluctuations as t/U is increased from the t/U -> 0 Heisenberg limit. These charge fluctuations lead to an increase of the quantum fluctuations over and above those for an S=1/2 antiferromagnet. The renormalization factor ensures that the zero temperature staggered moment for the Hubbard model is a monotonously decreasing function of t/U, despite the fact that the moment of the spin Hamiltonien, which depends on transverse spin fluctuations only, in an increasing function of t/U. We also comment on quantitative aspects of the t/U and 1/S expansions.
Cite
@article{arxiv.cond-mat/0412033,
title = {Neel order, ring exchange and charge fluctuations in the half-filled Hubbard model},
author = {J. -Y. P. Delannoy and M. J. P. Gingras and P. C. W. Holdsworth and A. -M. S. Tremblay},
journal= {arXiv preprint arXiv:cond-mat/0412033},
year = {2007}
}
Comments
9 pages - 3 figures - References and details to help the reader added