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Published Online December 20, 2007
Science DOI: 10.1126/science.1150841

Research Articles

Submitted on September 21, 2007
Accepted on December 6, 2007

Time-Resolved Observation and Control of Superexchange Interactions with Ultracold Atoms in Optical Lattices

S. Trotzky 1{dagger}, P. Cheinet 1{dagger}, S. Fölling 1, M. Feld 2, U. Schnorrberger 1, A. M. Rey 3, A. Polkovnikov 4, E. A. Demler 5, M. D. Lukin 5, I. Bloch 1*

1 Institut für Physik, Johannes Gutenberg-Universität, 55099 Mainz, Germany.
2 Institut für Physik, Johannes Gutenberg-Universität, 55099 Mainz, Germany.; Fachbereich Physik, Technische Universität Kaiserslautern, 67663 Kaiserslautern, Germany.
3 Institute for Theoretical Atomic, Molecular and Optical Physics, Harvard-Smithsonian Center of Astrophysics, Cambridge, MA, 02138, USA.
4 Department of Physics, Boston University, Boston, MA, 02215, USA.
5 Institute for Theoretical Atomic, Molecular and Optical Physics, Harvard-Smithsonian Center of Astrophysics, Cambridge, MA, 02138, USA.; Physics Department, Harvard University, Cambridge, MA, 02138, USA.

* To whom correspondence should be addressed.
I. Bloch , E-mail: bloch{at}uni-mainz.de

{dagger}These authors contributed equally to this work.

Quantum mechanical superexchange interactions form the basis of quantum magnetism in strongly correlated electronic media. We report on the direct measurement of superexchange interactions with ultracold atoms in optical lattices. After preparing a spin-mixture of ultracold atoms in an antiferromagnetically ordered state, we measure a coherent superexchange-mediated spin dynamics with coupling energies from 5 Hz up to 1 kHz. By dynamically modifying the potential bias between neighboring lattice sites, the magnitude and sign of the superexchange interaction can be controlled, thus allowing the system to be switched between antiferromagnetic or ferromagnetic spin interactions. We compare our findings to predictions of a two-site Bose-Hubbard model and find very good agreement, but are also able to identify corrections which can be explained by the inclusion of direct nearest-neighbor interactions.


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Itinerant Ferromagnetism with Ultracold Atoms.
W. Zwerger (2009)
Science 325, 1507-1509
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Quantum Gases.
I. Bloch (2008)
Science 319, 1202-1203
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