Heidelberg 2015 – wissenschaftliches Programm

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Q: Fachverband Quantenoptik und Photonik

Q 15: Poster: Quantum Optics and Photonics I

Q 15.57: Poster

Montag, 23. März 2015, 17:00–19:00, C/Foyer

Probing Bloch band geometry and topology with ultracold atoms — •Martin Reitter1,2, Lucia Duca1,2, Tracy Li1,2, Sebastian Scherg1,2, Immanuel Bloch1,2, Monika Schleier-Smith3, and Ulrich Schneider1,21Ludwig-Maximilians-Universität, München, DE — 2MPQ, Garching, DE — 3Stanford University, Palo Alto, USA

Topological features lie at the heart of a wide range of many-body phenomena in solid state systems. We have experimentally studied local topological properties of a graphene-like optical lattice, which features two nonequivalent Dirac points in the first Brillouin zone. By performing Ramsey interferometry along closed loops around one of the Dirac points, we are able to directly measure a Berry phase of π and locate the Berry curvature with high momentum resolution. In addition, we will report on the first measurements of multiband topological properties in the presence of a strong gradient. In this regime, the two lowest bands are formally equivalent to the case of two degenerate bands, as described by Wilczek and Zee [1]. By combining Stückelberg interferometry and measurements of the population transfer to the second band, we are able to reconstruct the elements of the Wilson loop matrix that characterizes this two-band model. Future research directions are also presented.

[1]F. Wilczek and A. Zee., Phys. Rev. Lett. 52, 2111 (1984).

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