title: Flat bands and Wigner crystallization in the honeycomb optical lattice.
abstract: We study the ground states of cold atoms in the tight-binding bands built from p 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 n=1/6 with a sqrt[3] x sqrt[3] 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 n=1/2. Experimental signatures of crystalline order can be detected through the noise correlations in time of flight experiments.
authors.affiliation: Kavli Institute for Theoretical Physics, University of California, Santa Barbara, California 93106, USA.
authors.forename: Congjun
authors.initials: C
authors.lastname: Wu
authors.forename: Doron
authors.initials: D
authors.lastname: Bergman
authors.forename: Leon
authors.initials: L
authors.lastname: Balents
authors.forename: S
authors.initials: S
authors.lastname: Das Sarma