Stochastic mean-field theory for the disordered Bose-Hubbard modelU. Bissbort and W. Hofstetter
Institut für Theoretische Physik, Johann Wolfgang Goethe-Universität - 60438 Frankfurt/Main, Germany, EU
received 19 March 2009; accepted in final form 27 May 2009; published June 2009
published online 23 June 2009
We investigate the effect of diagonal disorder on bosons in an optical lattice described by an Anderson-Hubbard model at zero temperature. It is known that within Gutzwiller mean-field theory spatially resolved calculations suffer particularly from finite system sizes in the disordered case, while arithmetic averaging of the order parameter cannot describe the Bose glass phase for finite hopping J > 0. Here we present and apply a new stochastic mean-field theory which captures localization due to disorder, includes non-trivial dimensional effects beyond the mean-field scaling level and is applicable in the thermodynamic limit. In contrast to fermionic systems, we find the existence of a critical hopping strength, above which the system remains superfluid for arbitrarily strong disorder.
03.75.Lm - Tunneling, Josephson effect, Bose–Einstein condensates in periodic potentials, solitons, vortices, and topological excitations.
72.15.Rn - Localization effects (Anderson or weak localization).
67.85.Hj - Bose-Einstein condensates in optical potentials.
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