Hessam Habibian, Simone Paganelli, Giovanna Morigi
We determine the quantum ground-state properties of ultracold bosonic atoms interacting with the mode of a high-finesse resonator, when the atoms are confined by an external optical lattice whose period is incommensurate with the cavity mode wave length. In a pump-probe experiment where the atoms are transversally pumped by a laser resonant with the cavity, one expects no coherent scattering into the cavity mode because of destructive interference. For sufficiently large laser intensities, however, cavity back-action amplifies small quantum fluctuations that in turn support scattering into the cavity mode. We derive a Bose-Hubbard model for this system and find that the coefficients due to the cavity potential depend on the atomic density at all lattice sites. For large parameter regions cavity back-action forces the quantum gas in a phase with vanishing order parameter and finite compressibility, a Bose glass, that maximizes scattering into the cavity mode. This system constitutes a novel setting where quantum fluctuations can give rise to effects usually associated with disorder.
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http://arxiv.org/abs/1206.5175
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