FLATLAND · Quantum phases of a two-dimensional Bose gas

The proposed project aims at the experimental study of two-dimensional (2D) quantum degenerate Bose gases. In a first stage we will explore the coherence properties of the gas below the critical temperature of the Kosterlitz-Thouless transition. One of our objectives is to reveal the superfluid character of the gas. For this purpose we will rotate the trapped cloud to excite particular collective modes, which are expected to reveal the quenched moment of inertia. Subsequently, we will investigate the coherence dynamics by interfering two initially phase-coherent 2D gases. The contrast of the interference pattern is expected to decay with a very unusual time dependence, and its observation would unveil the extraordinary character of these systems with a marginal long-range order. In a second stage of the project, we plan to implement a novel method to introduce an effective magnetic field which nucleates vortices in the atomic cloud. An artificial electromagnetic gauge field is created by subjecting the Bose gas to an optical topological potential. This method is a promising alternative to fast rotating gases and may enable us to reach the strongly correlated regime, where the physics becomes reminiscent of the fractional quantum Hall effect.