Intrinsic Relaxation Dynamics and Cooling in Optical-Lattice Hubbard Models
University of Illinois
Knowledge of relaxation dynamics arising from inter-particle interactions is central to our understanding of phenomena such as resistivity, diffusion, and thermoelectricity. Predicting relaxation timescales is a challenging problem for strongly correlated systems, leaving us with many unresolved questions regarding systems such as Mott-Hubbard materials and a critical need for information from controlled experiments. Understanding intrinsic relaxation and rethermalization is also central to achieving lower entropies and new quantum phases in optical lattice experiments, since trapped quantum gases do not thermalize with a reservoir. In this talk, I will describe how we are addressing these issues using ultracold 87Rb and 40K atoms trapped in optical lattices, which realize the Bose and Fermi-Hubbard models. I will describe new techniques we have developed to drive lattice gases out of equilibrium and measure the resulting relaxation dynamics. I will report measurements of relaxation for thermal bosons in the superfluid (SF) regime of the Bose-Hubbard (BH) model and degenerate fermions in the metallic regime of the Fermi-Hubbard model. In both cases, we find astonishingly fast relaxation timescales and a violation of weakly interacting predictions. These fast relaxation timescales enable a new technique for cooling quasimomentum in an optical lattice, which we demonstrate by cooling bosons in the SF regime of the BH model in a proof-of-principle experiment.
Hosts: Luis Orozco and Jimmy Williams
College Park, MD 20742