Darmstadt 2008 – wissenschaftliches Programm
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Q: Fachverband Quantenoptik und Photonik
Q 15: Quantengase (Gitter I)
Q 15.6: Vortrag
Dienstag, 11. März 2008, 15:15–15:30, 1C
Quantum Corrections of Mean-Field Phase Diagram for Bosons in Lattices — •Francisco Ednilson Alves dos Santos1 and Axel Pelster2 — 1Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany — 2Fachbereich Physik, Universität Duisburg-Essen, Lotharstraße 1, 47048 Duisburg, Germany
We improve the zero-temperature mean-field calculations for bosons in optical lattices by systematically working out the effect of quantum corrections. To this end we decompose the underlying nonlocal Bose-Hubbard Hamiltonian into the local mean-field Hamiltonian and treat the difference between them perturbatively. Using a diagrammatic technique, we calculate the ground-state energy up to second order in the quantum corrections. Therein, we interpret the order parameter ψ as a variational parameter, which is determined from optimizing the ground-state energy. With this analytical approach we obtain for arbitrary spatial dimension an improved boundary between Mott insulator and superfluid phase in accordance with previous high-precision results from quantum Monte-Carlo simulations.