Direct Measurement of the Zak phase in Topological Bloch Bands

2012/12/03 by Marcos Atala, Monika Aidelsburger, Julio T. Barreiro +4 · 5 citations
Physics and Astronomy · #cond-mat.quant-gas #cond-mat.mes-hall #quant-ph

paper · pdf · doi:10.1038/nphys2790

published as Nature Physics 9, 795-800 (2013)

arxiv created 2012/12/03 · arxiv updated 2015/02/09

Abstract

Geometric phases that characterize the topological properties of Bloch bands play a fundamental role in the modern band theory of solids. Here we report on the direct 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 acquired during an 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 optical lattice, which models polyacetylene, we measure a difference of the Zak phase equal to phi_Zak=0.97(2)pi for the two possible polyacetylene phases with different dimerization. This indicates that the two dimerized phases 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.

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Related

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