Direct measurement of the Zak phase in topological Bloch bands

作者：Atala, Marcos; Aidel**urger, Monika; Barreiro, Julio T.; Abanin, Dmitry; Kitagawa, Takuya; Demler, Eugene; Bloch, Immanuel^*

来源：Nature Physics, 2013, 9(12): 795-800.

DOI：10.1038/NPHYS2790

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• SOLITONS
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Geometric phases that characterize the topological properties of Bloch bands play a fundamental role in the band theory of solids. Here we report on the measurement of the geometric phase acquired by cold atoms moving in one-dimensional optical lattices. Using a combination of Bloch oscillations and Ramsey interferometry, we extract the Zak phase-the Berry phase gained during the adiabatic motion of a particle across the Brillouin zone-which can be viewed as an invariant characterizing the topological properties of the band. For a dimerized lattice, which models polyacetylene, we measure a difference of the Zak phase delta phi(Zak) = 0.97(2)pi for the two possible polyacetylene phases with different dimerization. The two dimerized phases therefore belong to different topological classes, such that for a filled band, domain walls have fractional quantum numbers. Our work establishes a new general approach for probing the topological structure of Bloch bands in optical lattices.

• 出版日期2013-12