  We investigate the insulating phases of a frustrated Hubbard model in its
strong coupling regime at half-filling. We pay special attention to all the
symmetry breaking instabilities that can be described by Dynamical Mean Field
Theory (DMFT) on a square plaquette. We identify several mean-field solutions,
two Neel states breaking the SU(2) symmetry, a dimer phase and a Mott insulator
which doesn't break any symmetry. The singlet to singlet fluctuations soften
dramatically in the latter phase, giving rise to dimerization fluctuations as
well as chiral fluctuations that are both low-lying. We present a simple
picture of the different DMFT states and their evolution with frustration.

Strongly Correlated Electrons