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TT: Fachverband Tiefe Temperaturen

TT 7: Matter at Low Temperature: Poster Session

TT 7.14: Poster

Montag, 25. Februar 2008, 14:00–18:00, Poster B

Hardcore Bosons on a Square Lattice with Nearest- and Next Nearest Neighbour Interactions — •Ansgar Kalz, Andreas Honecker, Sebastian Fuchs, and Thomas Pruschke — Institut für Theoretische Physik, Georg-August-Universität Göttingen

The behaviour of hardcore bosons on a square lattice with competing nearest- and next nearest neighbour interactions is an interesting subject because of the application of the model to cold atoms on an optical lattice.

In the static limit the model maps onto a classical Ising system, which has Néel- and collinear ordered phases, separated by a critical point where the competing interactions yield a degeneracy of the groundstate. We calculate structure factors, specific heat and other quantities. We use Monte-Carlo simulations with parallel tempering and line flip algorithms to avoid freezing problems near the critical point.

We present the resulting phase diagram for the classical model and give an outlook for the case with quantum mechanical hopping terms.