Relaxation dynamics of a two-dimensional Bose gas

Quantum many-body systems out of equilibrium are notoriously hard to treat theoretically. In past years it has been suggested that in certain scenarios the relaxation dynamics of such isolated many-body systems exhibit self-similar spatiotemporal scaling as they approach a non-thermal fixed point. So far, self-similar relaxation dynamics were observed with quasi-1D gases and with 3D gases; here we report the first such observation in a box-trapped 2D Bose gas.

We prepare a non-interacting 2D gas in a far-from-equilibrium state with a non-thermal momentum distribution that features a sharp UV cutoff and reduced occupation of low-momentum states. To initiate the relaxation dynamics we suddenly turn on the interactions. We observe bidirectional particle and energy conserving relaxation dynamics with self-similar spatiotemporal scaling revealed in the momentum distribution of the cloud.