Frankfurt 2006 – wissenschaftliches Programm
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Q: Quantenoptik und Photonik
Q 8: Quantengase II
Q 8.4: Vortrag
Montag, 13. März 2006, 14:45–15:00, HVI
Stability of a Dilute Ultracold Trapped Gas of Bose and Fermi Atoms — •Steffen Röthel1 and Axel Pelster2 — 1Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany — 2Fachbereich Physik, Universität Duisburg-Essen, Universitätsstraße 5, 45117 Essen, Germany
Considering the grand-canonical partition function of a Bose-Fermi mixture, we integrate out the fermionic field and derive the effective action of the Bose subsystem. Its extremization at zero temperature yields in the Thomas-Fermi limit an algebraic Gross-Pitaevskii equation for the condensate wave function. Within this approximation we determine the density profiles of both components in a 87Rb–40K mixture where the δ-interaction is repulsive between the bosons and attractive between both components.
Furthermore, we investigate the stability of the Bose-Fermi mixture with respect to collapse by evaluating numerically the effective action for a trial Gaussian density profile of the condensate. We find that the instability occurs in the center of the density profile, and that the critical numbers of bosons and fermions are reciprocal to each other. Our results, which strongly depend on the numerical value of the Bose-Fermi s-wave scattering length, are compared with recent experiments on 87Rb–40K mixtures in Florence and Hamburg.