An Aharonov-Bohm-type interferometer for determining Bloch band topology using ultracold atoms (L. Duca) / Rotational cooling of trapped polyatomic molecules (R. Glöckner)

An Aharonov-Bohm-type interferometer for determining Bloch band topology using ultracold atoms (L. Duca)
The geometric structure of an energy band in a solid is fundamental for a wide range of many-body phenomena in condensed matter and is uniquely characterized by the distribution of Berry curvature over the Brillouin zone. Here I will describe an atomic interferometer to measure Berry flux in momentum space which is analogous to an Aharonov-Bohm interferometer that measures the magnetic flux penetrating a given area in real space. As a test case, the interferometry is performed in a hexagonal optical lattice, where it has allowed us to directly detect the pi-Berry flux localized at each Dirac point. I will present our experimental results which demonstrate the capability of the Aharonov-Bohm type interferometer to determine the distribution of Berry curvature in the Brillouin zone with high momentum resolution.

Rotational cooling of trapped polyatomic molecules (R. Glöckner)
Due to their anisotropic long range interaction and many internal states, cold or ultracold polar molecular ensembles offer manifold possibilities for studying many-body physics and quantum information or quantum controlled collisions and chemistry. A prerequisite for all applications in quantum optics is thereby to gain and maintain control over the internal and external degrees of freedom.

In this talk, I present rotational state cooling of trapped polyatomic molecules via optical pumping. Our rotational state cooling scheme integrates seamlessly with our motional cooling [1,2]. With this combination we were able to produce a trapped and cold (30mK) ensemble of CH₃F molecules with more than 70% of all molecules populating the same single rotational state. We expect this method to be applicable to a wide variety of molecular species thus opening a route for quantum controlled experiments with polyatomic molecules.

References:
[1] M. Zeppenfeld  et. al., Phys. Rev. A  80, 041401 (2009).
[2] M. Zeppenfeld et al., Nature 491, 570-573 (2012).