Abstract
We study the ground states of cold atoms in the tight-binding bands built from orbitals on a two dimensional honeycomb optical lattice. The band structure includes two completely flat bands. Exact many-body ground states with on-site repulsion can be found at low particle densities, for both fermions and bosons. We find crystalline order at with a structure breaking a number of discrete lattice symmetries. In fermionic systems, if the repulsion is strong enough, we find the bonding strength becomes dimerized at . Experimental signatures of crystalline order can be detected through the noise correlations in time of flight experiments.
- Received 8 February 2007
DOI:https://doi.org/10.1103/PhysRevLett.99.070401
©2007 American Physical Society