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Research Training Group 1729/Leibniz Universität Hannover
Logo Leibniz Universität Hannover
Research Training Group 1729/Leibniz Universität Hannover
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Seminar 15.11.2012; 14:00-15:30; Room D 326

Max Kahmann
Fachbereich Quantenoptik und Längeneinheit
Physikalisch-Technische Bundesanstalt

Optical Feshbach Resonances with Ca

Compared to the intensively investigated two valence electron systems Sr and Yb, Ca offers by far the narrowest intercombination line at 657 nm with a natural linewidth of 370 Hz, which allows for precision experiments like atom interferometry and sub-Hz spectroscopy. Continuing our work with quantum degenerate 40Ca we want to employ the narrow line for manipulating the scattering length through optical Feshbach resonances. Here the narrow lines let us expect that the corresponding losses are lower than in the experiments with Yb and Sr, where they have so far limited the possible interaction time. As a first step towards application of optical Feshbach resonances in Ca we have measured the so far unknown positions and strength of the least bound molecular states in the relevant molecular potentials.


Seminar 29.11.2012; 14:00-15:30; Room D 326

Sebastian Greschner
Institute of Theoretical Physics
Leibniz Universität Hannover

Simulation of frustrated magnetism with cold gases

Recent experimental advance in controlling motional degrees of freedom of ultracold bosonic atoms in optical lattices has opened the possibility of simulation of frustrated quantum antiferromagnetism, which presents a rich physics due to the interplay between frustration, induced by lattice geometry and interaction. In this context I discuss basic properties of ultracold atoms in optical lattices, experimental methods of simulating frustrated models and give some details on the various quantum phases of ultracold bosonic atoms in (quasi one-dimensional) triangular lattices.

 

Seminar 20.12.2012; 14:00-15:30; Room D 326

Matthias Gempel
Institute of Quantum Optics
Leibniz Universität Hannover

Molecular dipole moments

Quantum degenerate gases of polar molecules are promising candidates for the realization of strongly correlated quantum many body systems. But - how to obtain molecular dipoles?

Seminar 10.01.2013; 14:00-15:30; Room D 326

Christian Hagemann
Fachbereich Quantenoptik und Längeneinheit
Physikalisch-Technische Bundesanstalt

Ultra-stable laser based on a cryogenic single-crystal silicon cavity

State-of-the-art ultra-stable lasers are limited by the thermal noise of the employed reference resonators. In this talk, a laser system with so far unreached short-term stability will be presented, enabled by the use of a cryogenic reference resonator machined from single-crystal silicon. The required steps for the realization of the silicon cavity laser system will be described in detail, further discussing possible noise sources from the environment that might affect the laser performance. The results of a measurement campaign to determine the frequency instability of this laser system on short and long time-scales will be presented, as well as the outcome of its utilization in the strontium optical lattice clock at PTB.

Seminar 24.01.2013; 14:00-15:30; Room D 326

Jan Mahnke
Institute of Quantum Optics
Leibniz Universität Hannover

 

A high repetition BEC machine on a mesoscopic chip structure

We investigate guiding and trapping of ultracold rubidium atoms on a mesoscopic chip structure. This structure is used to create a quadrupole field for a magneto-optical trap, a magnetic guide and flexible magnetic trapping potentials on both sides of the guide. In our experiments, the guide allows us to transport cold atoms into a region that provides better vacuum conditions and perfect stray light protection. It is therefore particularly well suited for evaporative cooling and the production of a Bose-Einstein condensate. We investigate the use of this structure to parallelize the cooling process and thereby reach a high repetition rate of ultracold ensembles

Seminar 31.01.13; 14:00 - 15:30; Room D 326 CANCELED

Dominika Fim
Institute of Quantum Optics
Leibniz Universität Hannover