In order to understand the properties of Mott insulators with strong ground state orbital fluctuations, we study the zero temperature properties of the SU(4) spin-orbital model on a square lattice. Exact diagonalizations of finite clusters suggest that the ground state is disordered with a singlet-multiplet gap and possibly low-lying SU(4) singlets in the gap. An interpretation in terms of plaquette SU(4) singlets is proposed. The implications for LiNiO_2 are discussed.
@article{arxiv.cond-mat/0001051,
title = {Plaquette Ground State in the Two-dimensional SU(4) Spin-Orbital Model},
author = {Mathias van den Bossche and Fu-Chun Zhang and Frederic Mila},
journal= {arXiv preprint arXiv:cond-mat/0001051},
year = {2009}
}