G-wave pairing and density-dependent gauge field in a Bose-Einstein condensate

In our first work, we report the observation of BECs of spinning Cs2 molecules by inducing pairing interactions in an atomic condensate near a g−wave Feshbach resonance in a two-dimensional, flat-bottomed trap. A large suppression of collision loss of the molecules due to the low temperature and trap geometry permits thermal equilibrium. From our measurement of the equation of state, we determine the molecular scattering length to be +220(30) Bohr. We also investigate the unpairing dynamics within the molecular condensate near the resonance and confirm the dynamics are consistent with the unitarity limit. Our work confirms the transition between atomic and molecular condensate, the bosonic analog of the BEC-BCS (Bardeen-Cooper-Schrieffer superfluid) crossover in a Fermi gas. 

 

In our second work, we investigate the equilibrium and dynamical properties of a BEC with a density-dependent gauge field. Using Floquet engineering, we create a gauge field that takes one of two values depending on the density.  Atoms condensed at different momenta form domains, separated by domain walls. Our scheme allows for a large change of the gauge field over a small range of the density. Furthermore, the low loss and heating of this scheme allows us to investigate the equilibrium and dynamics of the system over hundreds of milliseconds. We observe formation of domains and study the dynamics of the domain wall in response to a time dependent gauge field.