Stuttgart 2012 – wissenschaftliches Programm
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Q: Fachverband Quantenoptik und Photonik
Q 35: Poster 2
Q 35.11: Poster
Mittwoch, 14. März 2012, 16:30–19:00, Poster.I+II
Quantum magnetism of bosons in hexagonal optical lattices — •Eva-Maria Richter1, Dirk-Sören Lühmann2, and Daniela Pfannkuche1 — 1I. Institut für Theoretische Physik, Universität Hamburg, Germany — 2Institut für Laser-Physik, Universität Hamburg, Germany
Ultracold quantum gases in optical lattices open many new perspectives for the investigation of quantum behaviour in condensed-matter physics under ideal circumstances. Our concern is directed to the effects of finite-size systems. Starting from the Bose-Hubbard-Hamiltonian and within the framework of exact diagonalization for finite systems with periodic boundary conditions we investigate the magnetic phases in a hexagonal optical lattice with triangular sublattice structure. We study the finite-size effects of different sized unit cells in the case of a two-component Bose mixture in the deep Mott phase. For our model an effective spin-Hamiltonian can be derived in second order pertubation theory by a Schrieffer-Wolff-transformation in the limit of U>>J. The investigation of next-neighbour correlation functions within our two-component system therefore unravels ferro- or antiferromagnetic ordering in the according isospin hamiltonian. A ferro-antiferromagnetic transitions is investigated for different parameters and different unit cells, exhibiting the influence of finite sample sizes. We also implement an additional rotating magnetic field in the plane of the lattice to investigate spin transport.