Collisional properties and many body effects in ultracold systems. Quantum interferometry.

Krzysztof Jachymski

José Paulo D'Incao, Brett D. Esry

We present a comprehensive collection of ultracold three-body collisions properties near overlapping Feshbach resonances. Our results incorporate variations of all scattering lengths and demonstrate novel collisional behavior, such as atom-molecule interference effects. Taking advantage of the unique ways in which these collisions reflect Efimov physics, new pathways to control atomic and molecular losses open up. Further, we show that overlapping resonances can greatly improve the chances of observing multiple Efimov features in an ultracold quantum gas for nearly any system.

A. C. Wilson, Niels Kjærgaard, Angela S. Mellish

J. S. Krauser, Ulrich Ebling, Nick Fläschner +5 more

Collective behavior in many-body systems is the origin of many fascinating phenomena in nature, ranging from the formation of clouds to magnetic properties of solids. We report on the observation of collective spin dynamics in an ultracold Fermi sea with large spin. As a key result, we observed long-lived and large-amplitude coherent spin oscillations driven by local spin interactions. At ultralow temperatures, Pauli blocking stabilizes the collective behavior, and the Fermi sea behaves as a single entity in spin space. With increasing temperature, we observed a stronger damping associated with particle-hole excitations. Unexpectedly, we found a high-density regime where excited spin configurations are collisionally stabilized. Our results reveal the intriguing interplay between microscopic processes either stimulating or suppressing collective effects in a fermionic many-body system.

Julien Dugué

Brian DeMarco, D. S. Jin

We predict phenomena in the behavior of an ultracold, trapped gas of fermionic atoms. We find that quantum statistics radically changes the collisional properties, spatial profile, and off-resonant light-scattering properties of the atomic fermion system, and we suggest how these effects can be observed.