Plaquette Ordering in SU(4) Antiferromagnets
  We use fermion mean field theory to study possible plaquette ordering in the antiferromagnetic SU(4) Heisenberg model. We find the ground state for both the square and triangular lattices to be the disconnected plaquette state. Our mean field theory gives a first order transition for plaquette ordering for the triangular lattice. Our results suggest a large number of low lying states. 
Anup Mishra, Michael Ma, Fu-Chun Zhang