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A Thouless quantum pump with ultracold bosonic atoms in an optical superlattice

Nature Physics volume 12, pages 350–354 (2016)Cite this article

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Abstract

Topological charge pumping enables the transport of charge through an adiabatic cyclic evolution of the underlying Hamiltonian. In contrast to classical transport, the transported charge is quantized and purely determined by the topology of the pump cycle, making it robust to perturbations. Here, we report on the realization of such a pump with ultracold bosonic atoms forming a Mott insulator in a dynamically controlled optical superlattice. By taking in situ images of the cloud, we observe a quantized deflection per pump cycle. We reveal the pump’s genuine quantum nature by showing that, in contrast to ground-state particles, a counterintuitive reversed deflection occurs for particles in the first excited band. Furthermore, we directly demonstrate that the system undergoes a controlled topological transition in higher bands when tuning the superlattice parameters. These results open a route to the implementation of more complex pumping schemes, including spin degrees of freedom and higher dimensions.

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Figure 1: Topological charge pumping in an optical superlattice.
Figure 2: Centre-of-mass (COM) position of the atom cloud as a function of the pumping parameter ϕ for the lowest band with Vs = 10.0(3)Er,s and Vl = 20(1)Er,l.
Figure 3: Transition from a quantum sliding lattice to the Wannier tunnelling limit for the lowest band.
Figure 4: Cloud displacement and site occupations for the first excited band with Vs = 10.0(3)Er,s and Vl = 20(1)Er,l.
Figure 5: Topological transition in the first excited band.

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Acknowledgements

We acknowledge insightful discussions with F. Grusdt and S. Kohler. This work was supported by NIM and the EU (UQUAM, SIQS). M.L. was additionally supported by ExQM and O.Z. by the Swiss National Science Foundation.

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Authors and Affiliations

  1. Fakultät für Physik, Ludwig-Maximilians-Universität, Schellingstrasse 4, 80799 München, Germany

    M. Lohse, C. Schweizer, M. Aidelsburger & I. Bloch

  2. Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Strasse 1, 85748 Garching, Germany

    M. Lohse, C. Schweizer, M. Aidelsburger & I. Bloch

  3. Institut für Theoretische Physik, ETH Zürich, 8093 Zürich, Switzerland

    O. Zilberberg

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  1. M. Lohse
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Contributions

M.L., C.S. and M.A. performed the experiment and the data analysis. All authors contributed to the theoretical analysis and to the writing of the paper. I.B. supervised the project.

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Correspondence to M. Lohse.

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Lohse, M., Schweizer, C., Zilberberg, O. et al. A Thouless quantum pump with ultracold bosonic atoms in an optical superlattice. Nature Phys 12, 350–354 (2016). https://doi.org/10.1038/nphys3584

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