Observation of wave collapse in a two-dimensional Bose gas

Degenerate Bose gases can become unstable for attractive two-body interactions, leading to the process of wave collapse, as described by the nonlinear Schrodinger equation. The stability depends on competition between the kinetic and interaction energies, and on the system's dimensionality. In three dimensions, the gas is always prone to collapse, while in one-dimension, it remains stable and supports soliton solutions.

Here, we study the collapse behaviour in the critical two-dimensional case, for a Bose gas confined in a box potential. We observe collapse if the atom number is larger than the critical value, which, due to scale invariance of the 2D Bose gas, is independent of the system size. Furthermore, we study atom loss dynamics after the collapse event, providing benchmarks for theories of nonlinear wave phenomena.