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Observation of Topological Bloch-State Defects and Their Merging Transition

Matthias Tarnowski, Marlon Nuske, Nick Fläschner, Benno Rem, Dominik Vogel, Lukas Freystatzky, Klaus Sengstock, Ludwig Mathey, and Christof Weitenberg
Phys. Rev. Lett. 118, 240403 – Published 15 June 2017
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Abstract

Topological defects in Bloch bands, such as Dirac points in graphene, and their resulting Berry phases play an important role for the electronic dynamics in solid state crystals. Such defects can arise in systems with a two-atomic basis due to the momentum-dependent coupling of the two sublattice states, which gives rise to a pseudospin texture. The topological defects appear as vortices in the azimuthal phase of this pseudospin texture. Here, we demonstrate a complete measurement of the azimuthal phase in a hexagonal optical lattice employing a versatile method based on time-of-flight imaging after off-resonant lattice modulation. Furthermore, we map out the merging transition of the two Dirac points induced by beam imbalance. Our work paves the way to accessing geometric properties in optical lattices also with spin-orbit coupling and interactions.

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  • Received 8 March 2017

DOI:https://doi.org/10.1103/PhysRevLett.118.240403

© 2017 American Physical Society

Physics Subject Headings (PhySH)

Atomic, Molecular & Optical

Authors & Affiliations

Matthias Tarnowski1,2, Marlon Nuske3, Nick Fläschner1,2, Benno Rem1,2, Dominik Vogel1, Lukas Freystatzky3, Klaus Sengstock1,2,3,*, Ludwig Mathey1,2,3, and Christof Weitenberg1,2

  • 1Institut für Laserphysik, Universität Hamburg, 22761 Hamburg, Germany
  • 2The Hamburg Centre for Ultrafast Imaging, 22761 Hamburg, Germany
  • 3Zentrum für Optische Quantentechnologien, Universität Hamburg, 22761 Hamburg, Germany

  • *klaus.sengstock@physnet.uni-hamburg.de

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Issue

Vol. 118, Iss. 24 — 16 June 2017

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