Group leader: Servaas Kokkelmans. We are part of: Coherence
and Quantum Technology| Department
of Physics | Eindhoven
University of Technology
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We explore the widths of interspecies Feshbach resonances in a mixture of the fermionic quantum gases 6Li and 40K. Experimentally, we obtain the asymmetric lineshape of the interspecies elastic cross section by measuring the distillation rate of 6Li atoms from an optically-trapped 6Li/40K mixture as a function of magnetic field. This provides us with the first experimental determination of the width of a resonance in this mixture, ΔB=1.5(5) G, being one of the broadest. Our results offer good perspectives for the observation of universal crossover physics in this mixture.
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Figure
(left): The width and
position of all
s-wave
Feshbach
resonances in stable two-component 6Li/40K
mixtures below 500 G as calculated with the Asymptotic Bound-state
Model.
Figure (right): Measurement of the Feshbach resonance width. The red
solid line indicates the best fit obtained for B0=114.47(5)
G and ΔB = 1.5(5) G. The gray shaded area indicates the combined error
in B0 and ΔB.
Broad
Feshbach Resonance
in the 6Li-40K
mixture
T.G. Tiecke, M. Goosen, A. Ludewig, S.D. Gensemer, S. Kraft, S. J. J.
M. F. Kokkelmans, and J.T.M. Walraven,
Physical Review Letters 104 (2010) 053202
The
Fermionic Lithium Potassium
Experiment (FeLiKx)
at the Institute
of Quantum Optics and Quantum Information (IQOQ) has been built to
study a new class of strongly interacting many-body quantum systems. In
our ultracold mixtures of the fermionic atoms Li-6 and K-40 we could
characterize the interactions by measuring 13 heteronuclear Feshbach
resonances. This breaks the ground for fundamental experiments
exploring fermionic mixtures with different atoms.
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In close collaboration between the experimental group in Innsbruck, the theory groups at NIST/Gaithersburg (USA), the Eindhoven University of Technology (The Netherlands) and the University of Amsterdam (The Netherlands) we were able to fully understand the interaction properties of Li-6 K-40 mixtures.
Exploring
an Ultracold Fermi-Fermi Mixture: Interspecies Feshbach Resonances
and Scattering Properties of 6Li and 40K.
E. Wille, F. M.
Spiegelhalder, G. Kerner, D. Naik, A. Trenkwalder, G. Hendl, F.
Schreck, R. Grimm, T. G. Tiecke, J. T. M. Walraven, S. J. J. M. F.
Kokkelmans, E. Tiesinga, and P. S. Julienne.
Phys.
Rev. Lett. 100, 053201 (2008)
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(top, from left to right) Gerhard Hendl, Rudi Grimm, Frederik Spiegelhalder, Eric Wille, Devang Naik, Andreas Trenkwalder, Gabriel Kerner, and Florian Schreck (www.ultracold.at and IQOQI the Innsbruck team)
(bottom, from left to right): Tobias Tiecke and Jook Walraven (Quantum Gases Group Amsterdam), Servaas Kokkelmans (Eindhoven), Eite Tiesinga and Paul Julienne ( Quantum Processes and Metrology Group NIST/USA)
German press release from IQOQI: press release (german)
We study the Efimov effect in a harmonic oscillator in the hyperspherical formulation, and show how a reduced model allows for a description that is a generalization of the Efimov effect in free space and leads to results that are easily interpreted. Efimov physics may be observed by varying the value of the scattering length, since in the regime where the trimers have a mixed harmonic oscillator and Efimov character, the inelastic properties of these states are still manageable. The model also allows for the study of non-universal Efimov trimers by including the effective range scattering parameter. While we find that in a certain regime the effective range parameter can take over the role of the three-body parameter, interestingly, we obtain a numerical relationship between these two parameters different from what was found in other models: arXiv:1101.0696