Hamburg 2009 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 11: Quantengase: Bosonen im Gitter II

Q 11.1: Talk

Monday, March 2, 2009, 16:30–16:45, VMP 6 HS-A

Bragg Spectroscopy in Optical Lattices — •Philipp T. Ernst, Sören Götze, Jasper S. Krauser, Karsten Pyka, and Klaus Sengstock — Insitut für Laser-Physik, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany

Physics with quantum gases in optical lattices is a dynamically evolving field of fundamental research and particularly well suited to provide an experimental interface between quantum optics and solid state physics. Many novel quantum phases have been predicted in these systems. However, their detection and analysis, especially the characterization of their excitation spectrum, still remains challenging.

Here we report on high resolution momentum-resolved spectroscopy of the excitation spectrum of an ultracold bosonic gas in an optical lattice for the first time. Using Bragg diffraction in 2D and 3D lattice geometries, we show systematic measurements of the dispersion relation of the first and second band over the whole first Brillouin zone varying the lattice depth. The results clearly show the influence of interaction on the excitation spectrum as well as the sensitivity to density and particle numbers. Changing pulse area and probing time provides an insight into the dynamics of these systems.

Our measurements demonstrate high resolution Bragg spectroscopy in optical lattices to be a powerful technique which offers a wide range of applications, from perspectives on detecting new phases to the preparation of specific momentum states as a starting point for further investigations.