  We study superfluidity of strongly repulsive fermionic atoms in optical
lattices. The atoms are paired up through a correlated tunneling mechanism,
which induces superfluidity when repulsive nearest-neighbor interactions are
included in the Hubbard model. This paired superfluid is a metastable state
which persists for a long time as the pair-broken process is severely
suppressed. The mean-field phase diagram and low energy excitations are
investigated in a square lattice system. Intriguingly, spontaneous superflows
may appear in the ground state of a triangular optical lattice system due to
antiferromagnetic frustration.
