Hannover 2013 – wissenschaftliches Programm
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Q: Fachverband Quantenoptik und Photonik
Q 56: Poster III
Q 56.37: Poster
Donnerstag, 21. März 2013, 16:00–18:30, Empore Lichthof
Quantum magnetism of ultracold fermions in an optical lattice — •Gregor Jotzu1, Daniel Greif1, Thomas Uehlinger1, Leticia Tarruell1,2, and Tilman Esslinger1 — 1Institute for Quantum Electronics, ETH Zurich, 8093 Zurich, Switzerland — 22 LP2N UMR 5298, Univ. Bordeaux 1, Institut d'Optique and CNRS, 351 cours de la Lib
Interactions between electrons lead to fascinating magnetic phenomena including antiferromagnets, RVB states and spin liquids. However, even simple model hamiltonians for these interactions have proven notoriously difficult to solve. Ultracold fermions in optical lattices have emerged as a new tool to investigate such models, including the the celebrated Fermi-Hubbard hamiltonian. Whilst charge-ordering in systems simulating this models has been successfully investigated, magnetic order could so far not be observed due to the low temperatures required. Here we present the first observation of quantum magnetism of fermions in an optical lattice. Local order appears when loading a low-temperature gas into the lattice and is detected by projecting pairs of neighbouring sites on a singlet or triplet wavefunction. Using a tunable geometry lattice, we create dimerized and anisotropic cubic lattices. There the exchange energy of certain links is stronger, which drastically enhances magnetic correlations between sites they connect. We investigate the dependence of the correlations on the entropy and geometry of the system. In the regime where a second order high-temperature series is still reliable, we find good agreement with theory.