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three-dimensional imaging of samples. Here we present a confocal setup
for fluorescence lifetime measurements using up-conversion technique
in the femtosecond time range. The promising abilities of the method
Q 21 Poster Quantengase
are shown by investigations of the ultrafast S2 relaxation dynamics of
solutions of the dye malachite green (about 250 fs).
Zeit: Dienstag 14:00–16:00 Raum: Schellingstr. 3
Q 21.1 Di 14:00 Schellingstr. 3
Degenerate fermionic potassium in an optical lattice —
•Henning Moritz, Thilo Stöferle, Christian Schori, Michael
Köhl, and Tilman Esslinger — Institut für Quantenelektronik,
ETH Zürich, CH-8093 Zürich
For quantum degenerate fermions a variety of fascinating quantum
phenomena, such as BCS-type superfluidity, are theoretically predicted
to occur. The BCS-transition temperature in a lattice is expected to be
significantly higher than in an harmonic trap due to the increased interaction
at the individual lattice sites [1].
In our recent experiments with Rubidium in an optical lattice we have
realised the first truly one-dimensional Bose-Gas [2] and studied the transition
from a strongly interacting superfluid to a Mott insulator in one
dimension [3]. We have managed to sympathetically cool fermionic Potassium
40 to quantum degeneracy in the same machine. The poster will
report on the experiments with these atoms in the optical lattice.
[1] W. Hofstetter et al., Phys. Rev. Lett. 89, 220407 (2002)
[2] H. Moritz et al., Phys. Rev. Lett. in press
[3] T. Stöferle et al., preprint 2003
Q 21.2 Di 14:00 Schellingstr. 3
Mixtures of Rubidium and Lithium in the degenerate Regime
— •Tobias Donner, Christian Silber, Sebastian Günther,
and Claus Zimmermann — Physikalisches Institut der Universität
Tübingen, Auf der Morgenstelle 14, 72076 Tübingen
We prepare an experiment with mixtures of Lithium and Rubidium
quantum gases. Rubidium is used as cooling agent for both Lithium isotopes.
Heteronuclear photoassociation will be studied for 6Li-87Rb, 7Li-
87Rb, and 6Li-7Li [1] in the degenerate regime. Another topic will be
molecule formation schemes with two photon Raman spectroscopy [2].
The mixture is stored in a new type of a miniaturized magnetic trap that
allows for studying dimensionality effects for Bose gases as well as for
Fermi gases. We describe the apparatus and its experimental perspectives.
[1] U. Schlöder, C. Silber, T. Deuschle, and C. Zimmermann, Phys.
Rev. A 66, 061403 (R) (2002)
[2] U. Schlöder, T. Deuschle, C. Silber, and C. Zimmermann, accepted
for publication in Phys. Rev. A
Q 21.3 Di 14:00 Schellingstr. 3
An Experiment on Quantum-Degenerate Fermi-Bose Mixtures
in 3D Optical Lattices — •Silke Ospelkaus-Schwarzer, Christian
Ospelkaus, Ralf Dinter, Jürgen Fuchs, Marlon Nakat,
Klaus Sengstock, and Kai Bongs — Institut für Laser-Physik, Universität
Hamburg
We present an experiment on a quantum-degenerate mixture of
Fermionic 40 K and Bosonic 87 Rb atoms which is currently being set up in
Hamburg. The apparatus is based on a two-species 2D-/3D-MOT setup
and an optimized Ioffe-type magnetic trap. Our setup is designed for experiments
in deep three-dimensional optical lattices and promise to be
a versatile model system for solid state theories. Projected experiments
cover single-particle and collective excitations, fermion correlations and
investigations on the possibility of observing a BCS-type phase transition
in a 3D-optical lattice. We present first experimental results and discuss
the planned experiments.
Q 21.4 Di 14:00 Schellingstr. 3
Atomic Bose-Fermi mixtures in an optical lattice — •Fehrmann
Henning, Maciej Lewenstein, Luis Santos und Mikhail Baranov
— ITP Uni Hannover
A mixture of ultra-cold bosons and fermions placed in an optical lattice
constitutes a novel kind of quantum gas and leads to phenomena, which
so far have been discussed neither in atomic physics nor in condensed
matter physics.
We discuss the phase diagram at low temperatures, and in the limit of
strong atom-atom interactions. We predict the existence of quantum pha-
99
ses that involve pairing of fermions with one or more bosons, or bosonic
holes respectively. The resulting composite fermions may form, depending
on the system parameters, a normal Fermi liquid, a density wave, a
super-fluid liquid, or an insulator with fermionic domains.
Furthermore we obtain the analytic form of the phase boundaries separating
these composite fermion phases from the bosonic super-fluid which
coexists with a Fermi liquid.
We compare the results with numerical simulations and discuss their
validity and relevance for current experiments.
Q 21.5 Di 14:00 Schellingstr. 3
Matter wave optics with Bose-Einstein condensates on atom
chips — •Stephan Wildermuth 1 , Peter Krüger 1 , Sebastian
Hofferberth 1 , Mauritz Andersson 1 , Sönke Groth 1,2 , Elmar
Haller 1 , Leonardo Della Pietra 1 , Mihael Brajdic 1 , Israel
Bar-Joseph 2 , and Jörg Schmiedmayer 1 — 1 Physikalisches Institut,
Universität Heidelberg, 69120 Heidelberg — 2 Weizmann Institut, Rehovot,
Israel
Atom chips are built by structuring a conducting layer evaporated on
a substrate. By charging theses structures and/or by passing currents
through them, micropotentials for neutral atoms are formed that can be
used for the controlled manipulation of ultra-cold atomic clouds.
On this poster, we present a selection of possible trapping and guiding
geometries. The flexibility of the atom chip is demonstrated by cooling
atoms to the Bose-condensed phase (BEC) in very different traps.
We have integrated matter wave beam splitters and interferometers on
our atom chip in order to investigate the coherence properties of various
atom-optical tools. Recent progress in the experiments will be reported
as well as future steps towards the realization of 1 and 2-qubit manipulation.
Q 21.6 Di 14:00 Schellingstr. 3
Miniaturisierte Atomuhren und Interferometer in Mikrochip-
Fallen — •Philipp Treutlein 1 , Tilo Steinmetz 1 , Peter
Hommelhoff 1,2 , Theodor W. Hänsch 1 und Jakob Reichel 1
— 1 Max-Planck-Institut für Quantenoptik und Sektion Physik der
Ludwig-Maximilians-Universität, Schellingstr. 4, 80799 München,
Germany — 2 Present address: Varian Physics 220, Stanford University,
Stanford, CA 94305, U.S.A.
Interne Zustände von neutralen Atomen in magnetischen Mikrochip-
Fallen weisen lange Kohärenzzeiten auf [1]. Dies ermöglicht die Realisierung
einer Atomuhr mit Atomen in der Mikrofalle. Dazu erzeugen
wir Superpositionen der Hyperfeinzustände |F = 1, mF = −1〉
und |F = 2, mF = 1〉 des Grundzustands von 87 Rb. Mittels Ramsey-
Spektroskopie messen wir die Stabilität der Übergangsfrequenz zwischen
diesen Zuständen. Unsere Messungen zeigen, daß eine portable, miniaturisierte
Atomuhr mit einer relativen Stabilität von ∼ 10 −13 τ −1/2 / √ Hz
realisierbar ist.
In einem zweiten Experiment untersuchen wir kohärente
Überlagerungen von externen Zuständen der Atome in der Mikrofalle.
Dazu wird ein Bose-Einstein Kondensat in einem magnetischen
Doppelmuldenpotential präpariert. Durch eine Barriere variabler Höhe
zwischen den beiden Potentialmulden soll das Kondensat kohärent
aufgespalten und wieder vereinigt werden. Wir präsentieren den
aktuellen Stand dieses Experiments zur Interferometrie mit gefangenen
Atomen.
[1] Vortrag von Philipp Treutlein
Q 21.7 Di 14:00 Schellingstr. 3
Tunnelkontakte für Bose-Einstein-Kondensate in Mikrofallen
— •Christian Trück, Andreas Günther, Sebastian Kraft,
Claus Zimmermann und József Fortágh — Physikalisches Institut
der Universität Tübingen, Auf der Morgenstelle 14, 72076 Tübingen
Tunnelexperimente mit Bose-Einstein-Kondensaten erfordern eine
präzise Kontrolle von dünnen Potentialbarrieren. Dies ist entweder mit
optischen Gittern möglich oder mit Hilfe von elektrischen und magneti-