We derive an effective spin Hamiltonian for the one-dimensional half-filled tetramerized ionic-Hubbard model in the limit of strong on-site repulsion. We show that the effective Hamiltonian which describes the low-energy spin sector of the model is a spin S=1/2 Heisenberg Hamiltonian with alternating nearest-neighbour exchange.
@article{arxiv.0801.1290,
title = {Effective Hamiltonian for a half-filled tetramerized ionic-Hubbard chain},
author = {M. Menteshashvili and N. Chachava and G. I. Japaridze},
journal= {arXiv preprint arXiv:0801.1290},
year = {2008}
}