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Q: Fachverband Quantenoptik und Photonik

Q 70: Quantum Gases: Bosons VI

Q 70.4: Vortrag

Freitag, 4. März 2016, 15:15–15:30, f342

Topological edge state with ultracold atoms in a spatially variable lattice potential — •Martin Leder¹, Christopher Grossert¹, Till Ockenfels¹, Maximilian Genske², Achim Rosch², and Martin Weitz¹ — ¹Institut für Angewandte Physik, Universität Bonn — ²Institut für Theoretische Physik, Universität zu Koeln

An electronic topological insulator has a bulk energy band gap like an ordinary insulator, but conducting edge states on the surface that are insensitive to material impurities [1]. We report on the observation of a topological edge state located between two spatial regions with different topological phases in an atomic physics experiment. Our experiment is built upon a one-dimensional geometry, and uses four-photon lattice potentials which are realized in an atomic three-level system with two ground states of different spin projections and one spontaneously excited state [2]. Using an additional combination of a magnetic field gradient and a careful momentum preparation of an ultracold rubidium atomic wave packet allows to simulate an effective Dirac equation with a spatially varying mass term. We experimentally observe the trapping of the atoms in a bound state locked to the position of the band crossing between of two spatial regions of different topology in the lattice. Our real space observations give a direct link to the SSH model of the electrical conductance of polyacetylene [3].

[1] M. Z. Hasan and C. L. Kane, Rev. Mod. Phys. 82, 3045 (2010).

[2] G. Ritt et al., Phys. Rev. A 74, 063622 (2006).

[3] W. P. Su et al., Phys. Rev. Lett. 42, 1698 (1979).