An Aharonov-Bohm interferometer for determining Bloch band topology

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L. Duca, T. Li, M. Reitter, I. Bloch, M. Schleier-Smith, U. Schneider Science 347, 288 (2015), published online Science Express (Dec. 2014)

The geometric structure of a single-particle energy band in a solid is fundamental for a wide range of many- body phenomena and is uniquely characterized by the distribution of Berry curvature over the Brillouin zone.

In their work, Duca and co-workers realize an atomic interferometer to measure Berry flux in momentum space, in analogy to an Aharonov-Bohm interferometer that measures magnetic flux in real space. They demonstrate the interferometer for a graphene-type hexagonal optical lattice loaded with bosonic atoms. By detecting the singular pi Berry flux localized at each Dirac point, they establish the high momentum resolution of this interferometric technique. The experiment forms the basis for a general framework to fully characterize topological band structures.