Title: Experiments with 2D Bose gases

Speaker: Christof Weitenberg, Universität Hamburg

Time and place: 1520-616 at 14:15

Abstract:

The appearance of degeneracy in a 2D Bose gas is fundamentally different from the 3D case, in particular due to the absence of continuous symmetry breaking in such systems for short-range interactions. I will present different experiments with 2D Bose gases that we performed in the group of Jean Dalibard in Paris.

The equation of state (EoS) of the 2D Bose gas is of particular interest due to its scale invariance that stems from the dimensionless coupling constant. It can be extracted from the measurement of the density distribution in a smoothly varying confining potential. We apply the fit-free data analysis introduced by Zwierlein and coworkers, which does not rely on thermometry of individual images. The method leads to a strong reduction of the noise level and we find excellent agreement with the prediction from Monte Carlo calculations.

Box-shaped potentials are interesting, because they avoid the average over different densities that are present in a gas in a harmonic trap and therefore allow a more direct comparison with the predictions for the thermodynamic limit. A Bose gas in a combination of several such traps (e.g. two rectangles or a ring around a disk) will lead to interference fringes in time-of-flight, which can be used to study the phase coherence in the system and to detect thermally activated vortices.

Coffee, tea and cake will be served at 14:05