Hannover 2010 – wissenschaftliches Programm

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Q: Fachverband Quantenoptik und Photonik

Q 55: Poster II

Q 55.8: Poster

Donnerstag, 11. März 2010, 16:00–19:00, Lichthof

Mott insulator phases of spin-3/2 fermions in one-dimensional lattices — Karen Rodriguez, Arturo Arguelles, •Maria Colome-Tatche, Temo Vekua, and Luis Santos — Institut fur Theoretische Physik, Leibniz Universitat Hannover, Appelstr. 2, D-30167, Hannover, Germany

We study the ground state phase diagram of repulsive spin-3/2 fermions at zero magnetization in the presence of quadratic Zeeman effect (QZE). Starting from the Hamiltonian of the 4-component Hubbard model we derive the effective hard-core Hamiltonian, that can be understood as a spin-chain model. This model presents effective coupling constants which show a non-trivial dependence induced by the interplay between QZE and spin-changing collisions. In the absence of QZE the ground state of the system is either in the dimer (spin Peierls) phase or in the spin liquid one. Applying a non-zero QZE the system breaks the degeneracy between 1/2 and 3/2 spin components, resulting in a phase transition into an effective pseudo-spin 1/2 isotropic Heisenberg antiferromagnet for a sufficiently large QZE. We characterize by means of DMRG calculations the ground state properties for the different regimes and determine the boundaries between the different phases. We characterize the transition between dimer phase and effective Heisenberg antiferromagnet by means of exact diagonalization techniques. We shall also discuss, by means of Gutzwiller Ansatz calculations for the particular case of spinor bosons, a resonance occuring between spin-changing collisions and QZE, which may lead to the destruction of the Mott-insulator phase.