We study instabilities of single-species fermionic atoms in the p-orbital
bands in two-dimensional optical lattices at noninteger filling against
interactions. Charge density wave and orbital density wave orders with stripe
or checkerboard patterns are found for attractive and repulsive interactions,
respectively. The superfluid phase, usually expected of attractively
interacting fermions, is strongly suppressed. We also use field theory to
analyze the possible phase-transitions from orbital stripe order to
liquid-crystal phases and obtain the phase diagram. The condition of
nearly-perfect Fermisurface nesting, which is key to the above results, is
shown robustly independent of fermion fillings in such p-orbital systems, and
the (2kF​,±2kF​) momentum of density wave oscillation is highly tunable.
Such remarkable features show the promise of making those exotic orbital
phases, which are of broad interest in condensed-matter physics, experimentally
realizable with optical lattice gases.Comment: final version, 8 pages, 5 figure