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Q: Quantenoptik

Q 27: Poster: Quantengase

Q 27.14: Poster

Dienstag, 25. März 2003, 16:30–18:30, Lichthof

Bose Einstein Condensation in a Microtrap — •Th. Straßel, Ch. vom Hagen, A. Kasper, M. Rückel, St. Schneider, L. Feenstra, and J. Schmiedmayer — Physikalisches Institut, Universität Heidelberg, Philosophenweg 12, 69120 Heidelberg, Germany

The aim of our work is the manipulation of cold atoms on atom chips, ensembles of surface mounted wire traps, lithographically made in a gold layer on a silicon substrate. The wires withstand current densities up to 10⁷ A/cm². We present the creation of a Bose-Einstein condensate (BEC) of ⁸⁷Rb in a magnetic microtrap, which can be used as a source for the atom chip. The heart of our experimental set up is the atom chip holder consisting of a copper H-shaped structure, with the atom chip on top of it. This two-layered set up allows to implement trap geometries of different sizes. We use a double-MOT setup with a continuous push beam from a vapour cell MOT to load a mirror-MOT in an ultra-high vacuum chamber with ∼10⁹ atoms in 20 s. The chip itself acts as the mirror. To bring the atoms closer to the surface, the quadrupole field of external coils is replaced by that of a U-current in the H-structure. After a subsequent optical molasses the Z-trap (Ioffe-Pritchard type trap) is loaded. Compression and RF-evaporation cooling reduce the temperature in 19 s to ∼600 nK, giving a BEC of typically 3×10⁵ atoms, 250 µm above the surface of the chip. We can transfer the atoms from the copper Z-trap to the atom chip in typically 100 ms.

Acknowledgements: atom chip: R. Folman (design); Weizmann Institute of Science, Israel (fabrication). Funding: DFG (SCHM 1599/2-1), EU (ACQUIRE), A.v.Humboldt Stiftung (LF).