Journal
NATURE PHYSICS
Volume 9, Issue 12, Pages 795-800Publisher
NATURE PUBLISHING GROUP
DOI: 10.1038/NPHYS2790
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Funding
- DFG [FOR635, FOR801]
- NIM
- DARPA (OLE program)
- Harvard-MIT CUA
- ARO-MURI on Atomtronics
- ARO MURI Quism program
- Deutsche Telekom Stiftung
- Direct For Mathematical & Physical Scien
- Division Of Physics [1125846] Funding Source: National Science Foundation
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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.
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