  We obtain the phase-diagram of the half-filled honeycomb Hubbard model with
density matrix embedding theory, to address recent controversy at intermediate
couplings. We use clusters from 2-12 sites and lattices at the thermodynamic
limit. We identify a paramagnetic insulating state, with possible hexagonal
cluster order, competitive with the antiferromagnetic phase at intermediate
coupling. However, its stability is strongly cluster and lattice size
dependent, explaining controver- sies in earlier work. Our results support the
paramagnetic insulator as being a metastable, rather than a true, intermediate
phase, in the thermodynamic limit.
