May 03 2022


17:15 - 18:30

Physikalisches Kolloquium with Jean Dalibard

The Collège de France maintains a partnership with the University of Bonn, which for this purpose has established an “Ernst Robert Curtius-Visiting Professorship”, which is currently held by the physicist Jean Dalibard, holder of the chair of “Atomes et rayonnement” at the Collège de France.

Details of the talk:

When: Tuesday, 03.05.2022, 5pm
IAP, Hörsaal 1. Stock, Bonn
Title: Investigating two-body physics in a Bose gas: The spectroscopic way

Abstract: The thermodynamic equilibrium of any homogeneous fluid is characterized by its equation of state. This equation gives the variations of a thermodynamic potential, e.g. the internal energy E, with
respect to a set of variables such as the number of particles, their temperature and their interaction
strength. Regarding this latter variable, the relevant thermodynamic quantity for an ultra-cold gas is
the so-called Tan’s contact, which unifies many different properties from the momentum distribution
to the spatial two-body correlation function. In this talk, I will explain how one can use a Ramsey
interferometric scheme between the two hyperfine clock states of rubidium atoms to map out the
variations of Tan’s contact in a two-dimensional Bose gas, from the strongly degenerate superfluid
case to the non-degenerate case. I will also show a somewhat surprising result, revealed by this precise
microwave spectroscopy in a two-dimensional fluid: In spite of the fact that each clock state is non-
magnetic, a mixture of the two states still displays a magnetic dipole-dipole interaction comparable to
the one expected for the other (magnetic) Zeeman states.

Zoom link for a remote access can be provided by the office upon request.