QUROPE Quantum Information Processing and Communication in Europe

Orbital physics plays an important in strongly-correlated electron systems, but coupling to other degrees of freedom often obscures its effects. A tunable system for exploring orbital physics alone is provided by ultracold spinless fermionic atoms in the p-band of an optical lattice. Instead of relying on deep optical lattice potentials, which often means experimentally inaccessible low temperature, the strongly-correlated regime can be reached without suffering significant atom loss by using an optical p-wave Feshbach resonance, as recently proposed by Goyal \emph{et al.}\ [PRA 82, 062704 (2010)]. We investigate this system (which is equivalent to a three-color fermion model with color-dependent interaction, and spatially anisotropic and color-dependent tunneling) in strong coupling at 1/3 filling, employing a Gutzwiller ansatz to search for competing orbital orderings. Beside a phase without tunneling and an `orbital N\'eel' phase where $p_x$ and $p_y$ orbitals alternate, we find a novel phase of alternating $p_z$ and $p_x+ip_y$ orbits on the lattice, which breaks spatial and time-reversal symmetry.