The transport of spin in an ultracold gas can demonstrate how microscopic interactions lead to macroscopic dissipative and coherent effects. Subtle properties of individual two-atom interactions can dramatically alter behavior in bulk ensembles. Understanding these microscopic-macroscopic connections shows the importance of quantum mechanical processes and may lead to development of atom-based “spintronic” devices.
In this talk, I will describe how we use the flow of atomic spin in a weakly interacting gas to study out-of-equilibrium dynamics in a quantum fluid. In particular, we are interested in how the gas transitions from classical to quantum behavior near the critical temperature for superfluidity. This seemingly-simple system exhibits remarkably rich transport behavior, including non-classical diffusion, spin waves, long-lived domain walls, and spin instabilities in this quantum regime – all tunable by negligible changes in energy.