"Strong effective magnetic fields and Zak-Berry phases in optical lattices."

  • Date: Nov 27, 2012
  • Time: 12:30 PM - 12:30 PM (Local Time Germany)
  • Speaker: Marcos Atala, Max Planck Institut für Quantenoptik, Abt. Quanten-Vielteilchensysteme
  • Room: Herbert Walther Lecture Hall
  • Host: MPQ
"Geometric phases are manifested in many phenomena, like quantum Hall effect, and can characterize the topological properties of Bloch bands. For example in one-dimensional periodic potentials the topological invariant is given by the Zak phase-- the Berry phase acquired during an adiabatic motion of a particle across the Brillouin zone.In this talk I will present two topics, the first one will be about the experimental realization of strong effective magnetic fields in a two-dimensional optical lattice. By use of Raman-assisted atom tunneling we imprint a geometric phase to the atoms which can be interpreted as an Aharonov-Bohm phase. We observe that the effective magnetic field leads to a frustrated ground state and to quantum cyclotron orbits.The second topic will be about the direct measurement of the Zak phase for a dimerized optical lattice, which models polyacetylene. The experimental protocol consists of a combination of Bloch oscillations and Ramsey interferometry. This work establishes a new general approach for probing the topological structure of Bloch bands in optical lattices."
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