Perturbative corrections to the Gutzwiller mean-field solution
of the Mott-Hubbard model
Christian Schroll
C. Schroll, F. Marquardt, and C. Bruder
Department für Physik, Universität Basel, CH-4056 Basel, Switzerland
We study the Mott-insulator transition of bosonic atoms in optical
lattices. Using perturbation theory, we analyze the deviations from
the mean-field Gutzwiller ansatz, which become appreciable for
intermediate values of the ratio between hopping amplitude and
interaction energy. We discuss corrections to number fluctuations,
order parameter, and compressibility. In particular, we improve the
description of the short-range correlations in the one-particle
density matrix. These corrections are important for experimentally observed
expansion patterns, both for bulk lattices and in a confining trap
potential.
|