Stability of $p$-orbital Bose-Einstein condensates in optical   checkerboard and square lattices
  We investigate $p$-orbital Bose-Einstein condensates in both the square and checkerboard lattice by numerically solving the Gross-Pitaevskii equation. The periodic potential for the latter lattice is taken exactly from the recent experiment [Nature Phys. 7, 147 (2011)]. It is confirmed that the staggered orbital-current state is the lowest-energy state in the $p$ band. Our numerical calculation further reveals that for both lattices the staggered $p$-orbital state suffers Landau instability but the situation is remarkably different for dynamical instability. A dynamically stable parameter region is found for the checkerboard lattice, but not for the square. 
Yong Xu, Zhu Chen, Hongwei Xiong, W. Vincent Liu, and Biao Wu
cond-mat.quant-gas