Stuttgart 2012 – wissenschaftliches Programm
Q 35.12: Poster
Mittwoch, 14. März 2012, 16:30–19:00, Poster.I+II
An optical lattice of tunable topology for ultracold fermions — •Thomas Uehlinger, Leticia Tarruell, Daniel Greif, Gregor Jotzu, and Tilman Esslinger — Institute for Quantum Electronics, ETH Zurich, 8093 Zurich, Switzerland
Ultracold Fermi gases have emerged as a versatile tool to simulate condensed matter phenomena. For example, the control of interactions in optical lattices has lead to the observation of Mott insulating phases. However, the topology of the lattice is equally important for the properties of a solid. A prime example is the honeycomb lattice of graphene, where the presence of topological defects in momentum space - the Dirac points - leads to extraordinary transport properties.
We report on the observation of Dirac points of a quantum degenerate Fermi gas of 40K atoms confined in the honeycomb structure of an optical lattice with tunable topology. The lattice is created by superimposing a square lattice with an interfering superlattice, which can be continuously adjusted to create square, triangular, dimer und honeycomb structures. We change the effective mass of the fermions by breaking the lattice inversion symmetry. As we adjust the lattice anisotropy we move the Dirac points in the Brillouin zone and observe the topological transition to a lattice structure without Dirac points. We also report on recent progress on the investigation of this novel lattice.