# Stuttgart 2012 – wissenschaftliches Programm

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# Q: Fachverband Quantenoptik und Photonik

## Q 21: Quantengase: Optische Gitter 1

### Q 21.3: Vortrag

### Dienstag, 13. März 2012, 11:00–11:15, V53.01

**Klein-Tunneling of a Quasirelativistic Bose-Einstein Condensate in an Optical Lattice** — •Christopher Grossert^{1}, Tobias Salger^{1}, Sebastian Kling^{1}, Dirk Witthaut^{2}, and Martin Weitz^{1} — ^{1}Institut für Angewandte Physik, D- 53115 Bonn — ^{2}Max-Planck-Institute for Dynamics and Self-Organization, D-37073 Göttingen

A proof-of-principle experiment simulating effects predicted by relativistic wave equations with ultracold atoms in a bichromatic optical lattice that allows for a tailoring of the dispersion relation is reported [1]. In this lattice, for specific choices of the relativistic phases and amplitudes of the lattice harmonics the dispersion relation in the region between the first and the second excited band becomes linear, as known for ultrarelativistic particles. We have shown that the dynamics can be described by an effective one-dimensional Dirac equation [2].

We experimentally observe the analog of Klein-Tunneling, the penetration of relativistic particles through a potential barrier without the exponential damping that is characteristic for nonrelativistic quantum tunneling [3]. Both linear (relativistic) and quadratic (nonrelativistic) dispersion relations are investigated, and significant barrier transmission is only observed for the relativistic case.

[1] T. Salger et al.: Phys. Rev. Lett. **107** 240401 (2011)

[2] D. Witthaut et al.: Phys. Rev. A **84** 033601 (2011)

[3] O. Klein: Z.Physik **53** 127 (1929)