Welcome to the Quantum gases group at the Eindhoven University of Technology.
Below you find some highlights of our past research.
Magical
Trios
Disentangled
- March
2011
The
weekly journal Cursor of Eindhoven University of Technology devoted an
article to our work on Universal Efimov Physics. It can be found here
(in dutch).Universal
Efimov Physics - January 2011
We
observed the existence of a
universal regime for Efimov trimers through three-body recombination
loss in the vicinity of a Feshbach resonance, for ultracold Li-7 atoms.
We characterize two broad Feshbach resonances in different spin
states by fitting the binding energies of weakly bound molecules,
created by radio-frequency association, by making use of a
theoretical coupled channels analysis. This gives rise to a very
precise determination of the absolute positions of the Feshbach
resonances, and to very precise values of the singlet and triplet
scattering length that characterize the molecular potentials of
lithium. N Gross et al, C.
R. Physique 12, 4 (2011)
Asymptotic
Bound state Model - October 2010
It
took some time, but now we have written up an overview paper on the
Asymptotic Bound state Model, T.
Tiecke et al, Phys.
Rev. A 82, 042712 (2010), an
easy to use model to study weakly-bound states of an ultracold two-body
system, and predict the positions of Feshbach resonances. This model is
already used by several experimental and theoretical groups, in
particular for ultracold mixtures where no precise interaction
potentials are known. In
the same issue of Phys. Rev. A, we also
applied this model to study Feshbach
resonances in 3He*-4He* mixtures:
M. Goosen et al, Phys.
Rev. A 82, 042713 (2010)
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Figure (left): Energies of coupled bound states for Li-40 K with total spin MF = ±3. The black solid line indicates the threshold energy of the entrance channel The gray area represents the scattering continuum and the (colored) lines indicate the coupled bound states. Feshbach resonances occur when a bound state crosses the threshold energy. The color scheme indicates the admixture of singlet and triplet contributions in the bound states. Figure (right): Threshold behavior in a two-channel version of the dressed ABM. The threshold behavior is determined by the coupling between the least bound level in the open channel in P space and the resonant bound level in Q space. The uncoupled levels are shown as the blue (P) and red (Q) dash-dotted lines, with Q crossing the threshold at B0. The solid black lines represent the dressed levels, with the upper branch crossing the threshold at B0 . Near the threshold, the dressed level shows the
characteristic quadratic dependence on (B − B0 ) (see inset). For pure ABM levels (dotted gray) no threshold effects occur and the coupled bound state crosses the threshold at B0.
Nuclear-Spin-Independent
Short-Range
Three-Body Physics in
Ultracold Atoms - September (2010)
We investigate three-body recombination loss across a Feshbach resonance in a gas of ultracold 7Li atoms prepared in the absolute ground state and perform a comparison with previously reported results of a different nuclear-spin state [N. Gross et al., Phys. Rev. Lett. 103, 163202 (2009)]. We extend the previously reported universality in three-body recombination loss across a Feshbach resonance to the absolute ground state. We show that the positions and widths of recombination minima and Efimov resonances are identical for both states which indicates that the short-range physics is nuclear-spin independent.
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Figure: Experimentally measured three-body loss coefficient K3 as a function of scattering length (in units of Bohr radius a0 ) for the mF=1 state (red solid circles) and the mF=0 state (blue open diamonts). The solid lines represent fits to the analytical expressions of universal theory.
Nuclear-Spin-Independent Short-Range Three-Body Physics in Ultracold Atoms
Noam Gross, Zav Shotan, Servaas Kokkelmans, and Lev Khaykovich,
Phys. Rev. Lett. 105, 103203 (2010)
Search for broad Feshbach resonances in the 6Li-40K mixture - August (2009)
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
Interspecies
Feshbach Resonances in a Fermi-Fermi Mixture - February (2008)
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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Figure: Feshbach spectroscopy data of Li and K in one combination of spin states. In total, over 15000 data points with four different spin states have been taken during many weeks.
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)
Links
German press release from IQOQI: press release (german)
Latest News:
Creation
of Rydberg Crystals
Ultracold
atomic gases have been used extensively in recent years to realize
textbook examples of condensed matter phenomena. Recently, phase
transitions to ordered structures have been predicted for gases of
highly excited, 'frozen' Rydberg atoms. Such Rydberg crystals are a
model for dilute metallic solids with tunable lattice parameters, and
provide access to a wide variety of fundamental phenomena. We
investigate theoretically how such structures can be created in four
distinct cold atomic systems, by using tailored laser-excitation in the
presence of strong Rydberg-Rydberg interactions. We study in detail the
experimental requirements and limitations for these systems, and
characterize the basic properties of small crystalline Rydberg
structures in one, two and three dimensions:
arXiv:1103.2096
Collapsing Bose-Einstein Condensates
We describe a model of dynamic Bose-Einstein condensates near a Feshbach resonance that is computationally feasible under assumptions of spherical or cylindrical symmetry. Simulations in spherical symmetry approximate the experimentally measured time to collapse of an unstably attractive condensate, suggesting that the quantum fluctuations and atom-molecule pairing included in the model are the dominant mechanisms during collapse. Simulations of condensates with repulsive interactions find some quantitative disagreement, suggesting that pairing and quantum fluctuations are not the only significant factors for condensate loss or burst formation. Inclusion of three-body recombination was found to be inconsequential in all of our simulations: arXiv:1102.2104Efimov Trimers in a Harmonic Potential
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