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Q: Fachverband Quantenoptik und Photonik

Q 52: Quantum gases: Fermions

Q 52.4: Talk

Thursday, March 21, 2013, 15:00–15:15, F 342

Observation of Ferromagnetic Spin Correlations in a 1D Fermi System — •Simon Murmann, Andre N. Wenz, Vincent Klinkhamer, Andrea Bergschneider, Gerhard Zürn, Thomas Lompe, and Selim Jochim — Physikalisches Institut der Universität Heidelberg

We have studied spin correlations of quasi 1D spin 1/2 systems. Starting with a ground state system of three to five ultracold ⁶Li atoms, we use a Feshbach resonance to introduce repulsive interactions between the particles. After an adiabatic ramp across the resonance the particles end up in metastable states which have higher energies than states of spin-polarized samples with the same atom number. For systems satisfying this criterion the Stoner model predicts a transition to a ferromagnetic state. As a probe for the spin correlations, one particle is allowed to escape from the trap and the z-component of the total spin, as well as the energy of the remaining atoms is measured.

For weak repulsive interactions no significant fraction of prepared systems end up in a spin-polarized final state. This anticorrelation between the spins decreases with increasing repulsion. When crossing the Feshbach resonance to the metastable branch the number of spin-polarized systems is strongly enhanced, indicating the presence of strong ferromagnetic correlations.