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Fermionic transport and out-of-equilibrium dynamics in a homogeneous Hubbard model with ultracold atoms

Nature Physics volume 8, pages 213218 (2012) | Download Citation

Abstract

Transport properties are among the defining characteristics of many important phases in condensed-matter physics. In the presence of strong correlations they are difficult to predict, even for model systems such as the Hubbard model. In real materials, additional complications arise owing to impurities, lattice defects or multi-band effects. Ultracold atoms in contrast offer the possibility to study transport and out-of-equilibrium phenomena in a clean and well-controlled environment and can therefore act as a quantum simulator for condensed-matter systems. Here we studied the expansion of an initially confined fermionic quantum gas in the lowest band of a homogeneous optical lattice. For non-interacting atoms, we observe ballistic transport, but even small interactions render the expansion almost bimodal, with a dramatically reduced expansion velocity. The dynamics is independent of the sign of the interaction, revealing a novel, dynamic symmetry of the Hubbard model.

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Acknowledgements

We thank M. Moreno-Cardoner, F. Heidrich-Meisner, D. Pekker and R. Sensarma, B. Kawohl, C. Kiefer, J. Krug and M. Zirnbauer for stimulating and insightful discussions.

This work was supported by the Deutsche Forschungsgemeinschaft (FOR801, SFB TR 12, SFB 608, Gottfried Wilhelm Leibniz Prize), the European Union (Integrated Project SCALA), EuroQUAM (L.H.), the US Defense Advanced Research Projects Agency (Optical Lattice Emulator program), the US Air Force Office of Scientific Research (Quantum Simulation MURI (E.D.)), the National Science Foundation (DMR-07-05472) (E.D.), the Harvard-MIT CUA (E.D.), MATCOR (S.W.), the Gutenberg Akademie (S.W.) and the German National Academic Foundation (S.M.).

Author information

Affiliations

  1. Institut für Physik, Johannes Gutenberg-Universität, 55099 Mainz, Germany

    • Ulrich Schneider
    • , Lucia Hackermüller
    • , Jens Philipp Ronzheimer
    • , Sebastian Will
    • , Simon Braun
    • , Thorsten Best
    •  & Immanuel Bloch
  2. Fakultät für Physik, Ludwig-Maximilians-Universität, 80799 Munich, Germany

    • Ulrich Schneider
    • , Jens Philipp Ronzheimer
    • , Sebastian Will
    • , Simon Braun
    •  & Immanuel Bloch
  3. School of Physics and Astronomy, University of Nottingham, NG7 2RD Nottingham, UK

    • Lucia Hackermüller
  4. Max-Planck-Institut für Quantenoptik, 85748 Garching, Germany

    • Immanuel Bloch
  5. Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA

    • Eugene Demler
  6. Institut für Theoretische Physik, Universität zu Köln, 50937 Cologne, Germany

    • Stephan Mandt
    • , David Rasch
    •  & Achim Rosch

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Contributions

U.S., L.H. and J.P.R. carried out the measurements, U.S. performed the data analysis with contributions from L.H. and J.P.R.. I.B. supervised the measurements. S.M. and D.R. performed the numerical calculations supervised by A.R.. E.D., U.S. and A.R. constructed the analytical proof of the dynamical symmetry. U.S. and A.R. wrote the manuscript with substantial contributions by I.B. and all authors.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Ulrich Schneider.

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DOI

https://doi.org/10.1038/nphys2205

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