Hannover 2013 – scientific programme
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Q: Fachverband Quantenoptik und Photonik
Q 59: Quantum gases: Optical lattices III
Q 59.5: Talk
Friday, March 22, 2013, 12:00–12:15, F 342
Quantum magnetism of ultracold fermions in an optical lattice — •Thomas Uehlinger1, Daniel Greif1, Gregor Jotzu1, Leticia Tarruell1,2, and Tilman Esslinger1 — 1Institute for Quantum Electronics, ETH Zurich, 8093 Zurich, Switzerland — 2LP2N UMR 5298, Univ. Bordeaux 1, Institut d'Optique and CNRS, 351 cours de la Libération, 33405 Talence, France
Quantum magnetism is a fundamental phenomenon in condensed matter physics, which manifests itself for example in antiferromagnets or spin-liquids and is believed to play a crucial role in high-temperature superconductivity. Remarkably, even simple models of the underlying many-body physics are often intractable with state-of-the-art theoretical methods. While ultracold atoms in optical lattices have been successfully used to investigate simple condensed matter model systems, the regime of quantum magnetism could so far not be accessed due to the low temperatures required.
We report on the first observation of quantum magnetism of a Fermi gas in an optical lattice. The key to obtaining and detecting the short-range magnetic order is a tunable geometry optical lattice set to either a dimerized or an anisotropic simple cubic geometry. For a low-temperature gas we find magnetic correlations on neighbouring sites, which manifest as an excess number of singlets as compared to triplets consisting of two atoms with opposite spins. For the anisotropic lattice, we determine the transverse spin correlator from the singlet-triplet imbalance and observe antiferromagnetic correlations along one spatial axis.