Expansion dynamics of interacting Bose gases in an optical lattice

Predicting the nonequilibrium dynamics of interacting bosons in optical lattices has remained a challenging topic in many-body physics. While accurate numerical studies are still under development, ultracold quantum gases provide a convenient platform to study nonequilibrium dynamics, where the systems can be driven out of equilibrium via engineered quenches and the subsequent dynamics can be monitored through direct density imaging. For example, nontrivial expansion dynamics of interacting bosons were observed in optical lattices, such as bimodal expansion and self-trapping. Although the suppressed expansion rate in a 2D lattice has been measured and attributed to the interaction-induced diffusion, a detailed characterization of the expansion scaling behavior across the superfluid and the Mott-insulating phases has remained unexplored. In this talk, we will present our measurement of the quench-induced expansion dynamics of uniform cesium Bose gases prepared in a 2D lattice with controllable parameters. Furthermore, we show our investigation on the expansion of particle- and hole-type density defects on top of a uniform background. Our work could provide insight into the many-body expansion dynamics in an optical lattice.