Dresden 2009 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 41: Matter at Low Temperature: Quantum Liquids, Bose-Einstein-Condensates, Ultra-cold Atoms

TT 41.14: Vortrag

Donnerstag, 26. März 2009, 17:45–18:00, HSZ 105

Meissner effect in atom chips containing superconducting microstructures — •Daniel Cano, Brian Kasch, Helge Hattermann, Reinhold Kleiner, Claus Zimmermann, Dieter Koelle, and József Fortágh — Physikalisches Institut & Center for CollectiveQuantum Phenomena, Universität Tübingen, Germany

Superconducting microstructures for trapping and manipulating ultracold quantum gases are expected to provide intriguing physical scenarios in which atomic physics and superconductor science converge. In this study, we investigate the impact of the Meissner effect on magnetic microtraps generated by superconducting microstructures. Both numerical simulations and experiments demonstrate that the Meissner effect shortens the distance between the microtrap and the superconducting surface, reduces the radial magnetic-field gradients and lowers the trap depth. Simulations based on the London theory have been carried out to calculate the supercurrent densities in thin-film microstructures. Experiments were done in a recently-built apparatus that loads ultracold ⁸⁷Rb atomic clouds into a magnetic microtrap generated by a superconducting Nb wire with circular cross section. By monitoring the position of the atomic cloud, we observe how the Meissner effect changes the microtrap parameters. Measurements of the trap position reveal a complete exclusion of the magnetic field from the superconducting wire for T<6 K. For higher T, the magnetic field partially penetrates the superconducting wire and the microtrap parameters become more similar to those expected for a normal-conducting wire.

[1] D. Cano et al., Phys. Rev. Lett. 101, 183006 (2008)