  By performing exact quantum Monte Carlo simulations of a model of interacting
Dirac Fermions with staggered potential, we reveal a novel intermediate phase
where the electronic correlations drive a band insulator metallic, and at a
larger interaction, drive the metal to Mott insulator. We also show that the
Mott insulating phase is antiferromagnetic. A complete phase diagram is
achieved by studying the phase transitions at large staggered potential and
interaction strengths, which shows that the intermediate state is robust and
occupies a large part of the phase diagram and that it should be more feasible
to be detected experimentally.
