Tomasz Sowiński, Mateusz Łacki, Omjyoti Dutta, Joanna Pietraszewicz, Piotr Sierant, Mariusz Gajda, Jakub Zakrzewski, Maciej Lewenstein
We show that properties of bosons loaded into the $p$-band of a rectangular optical lattice are substantially affected by the anharmonicity of the lattice potential. Even for very deep lattices, the optical confinement treated as a harmonic potential is highly oversimplified and in the low tunneling limit it leads incorrectly to a degeneracy of the ground state. We show that in this limit the degeneracy is lifted by the anharmonicity. For finite range of larger tunnelings the degeneracy is dynamically restored and the system gains an additional symmetry. This symmetry is, however, spontaneously broken in the thermodynamic limit and the state with non vanishing staggered angular momentum becomes the true ground state of the system.
View original:
http://arxiv.org/abs/1304.6299
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