Abstract
An electron gas in a one-dimensional periodic potential can be transported even in the absence of a voltage bias if the potential is slowly and periodically modulated in time. Remarkably, the transferred charge per cycle is sensitive only to the topology of the path in parameter space. Although this so-called Thouless charge pump was first proposed more than thirty years ago1, it has not yet been realized. Here we report the demonstration of topological Thouless pumping using ultracold fermionic atoms in a dynamically controlled optical superlattice. We observe a shift of the atomic cloud as a result of pumping, and extract the topological invariance of the pumping process from this shift. We demonstrate the topological nature of the Thouless pump by varying the topology of the pumping path and verify that the topological pump indeed works in the quantum regime by varying the speed and temperature.
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Acknowledgements
We thank N. Kawakami, S. Fujimoto, J. Ozaki, T. Fukui, I. Maruyama, Y. Hatsugai and S. Nakamura for valuable discussions and A. Sawada for experimental assistance. This work was supported by the Grant-in-Aid for Scientific Research of JSPS (No. 25220711, No. 26247064, No. 24-1698), and the Impulsing Paradigm Change through Disruptive Technologies (ImPACT) Program. L.W. and M.T. were supported by ERC Advanced Grant SIMCOFE and by the Swiss National Science Foundation through the National Center of Competence in Research Quantum Science and Technology QSIT. L.W. and M.T. acknowledge X. Dai for collaborations on the related topic.
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S.N. and T.T. carried out experiments and the data analysis. S.T. conceived the experimental techniques for the superlattice. T.I. and H.O. contributed to building the superlattice set-up. L.W. carried out the theoretical calculations. Y.T. conducted the whole experiment. All the authors contributed to the writing of the manuscript.
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Nakajima, S., Tomita, T., Taie, S. et al. Topological Thouless pumping of ultracold fermions. Nature Phys 12, 296–300 (2016). https://doi.org/10.1038/nphys3622
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DOI: https://doi.org/10.1038/nphys3622
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