Thursday, April 18, 2013

1304.4826 (John F. Dawson et al.)

Leading-Order Auxiliary Field Theory of the Bose-Hubbard Model    [PDF]

John F. Dawson, Fred Cooper, Chih-Chun Chien, Bogdan Mihaila
We discuss the phase diagram of the Bose-Hubbard model in the leading-order auxiliary field (LOAF) theory. LOAF is a conserving non-perturbative approximation that treats on equal footing the normal and anomalous density condensates. We find two possible mean-field solutions of LOAF: a first-order phase transition solution that leads to a quantum phase transition in ultracold Bose atomic gases confined on a three-dimensional lattice, and a second-order phase transition solution that predicts the correct order of the transition in continuum Bose gases. For both solutions, a superfluid state is tied to the presence of an anomalous-density related diatom condensate in the system. As such, LOAF offers a possible representation for the superfluid to Mott insulator transition in bosonic systems that compares qualitatively well with existing experimental data and results of ab initio Monte Carlo simulations.
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