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arXiv:1205.6161 · New Journal of Physics

Scattering and absorption of ultracold atoms by nanotubes

B. Jetter, J. Märkle, Philipp Schneeweiß, M. Gierling, Stefan Scheel, Andreas Günther, József Fortágh, T. E. Judd

Published Jul 2, 2013• 9 citations
arXivHTMLPDF

Abstract

We investigate theoretically how cold atoms, including Bose–Einstein condensates, are scattered from, or absorbed by, nanotubes with a view to analysing recent experiments. In particular, we consider the role of potential strength, quantum reflection, atomic interactions and tube vibrations on atom loss rates. Lifshitz theory calculations deliver a significantly stronger scattering potential than that found in experiment and we discuss possible reasons for this. We found that the scattering potential for dielectric tubes can be calculated to a good approximation using a modified pairwise summation approach, which is efficient and easily extendable to arbitrary geometries. Quantum reflection of atoms from a nanotube may become a significant factor at low temperatures, especially for non-metallic tubes. Interatomic interactions are shown to increase the rate at which atoms are lost to the nanotube and lead to non-trivial dynamics. Thermal nanotube vibrations do not significantly increase loss rates or reduce condensate fractions, but lower frequency oscillations can dramatically heat the cloud.

DOI
10.1088/1367-2630/15/7/073009

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We investigate the sympathetic relaxation of a free-standing, vibrating carbon nanotube that is mounted on an atom chip and is immersed in a cloud of ultracold atoms. Gas atoms colliding with the nanotube excite phonons via a Casimir-Polder potential. We use Fermi's golden rule to estimate the relaxation rates for relevant experimental parameters and develop a fully dynamic theory of relaxation for the multimode phononic field embedded in a thermal atomic reservoir. Based on currently available experimental data, we identify the relaxation rates as a function of atom density and temperature that are required for sympathetic ground-state cooling of carbon nanotubes.
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